Skip to main content
NCBI home page
Frontiers in Plant Science logoLink to Frontiers in Plant Science
. 2022 Jun 23;13:754232. doi: 10.3389/fpls.2022.754232

Nitrogen and Chemical Control Management Improve Yield and Quality in High-Density Planting of Maize by Promoting Root-Bleeding Sap and Nutrient Absorption

Xiaoming Liu 1, Liguo Zhang 2, Yang Yu 3, Chunrong Qian 3, Congfeng Li 4, Shi Wei 1, Caifeng Li 1,*, Wanrong Gu 1,*
PMCID: PMC9260249  PMID: 35812983

Abstract

High-density planting aggravates competition among plants and has a negative impact on plant growth and productivity. Nitrogen application and chemical control can improve plant growth and increase grain yield in high-density planting. Our experiment explored the effects of nitrogen fertilizer and plant growth regulators on maize root-bleeding sap, phosphorus (P) and potassium (K) accumulation and translocation, and grain yield and quality in high-density planting. We established a field study during the 2017 and 2018 growing seasons, with three nitrogen levels of N100 (100 kg ha−1), N200 (200 kg ha−1), and N300 (300 kg ha−1) at high-density planting (90,000 plants ha−1), and applied Yuhuangjin (a plant growth regulator mixture of 3% DTA-6 and 27% ethephon) at the 7th leaf. Our results showed that N200 application combined with chemical control could regulate amino acid and mineral nutrient concentration delivery rates in root-bleeding sap and improve its sap rate. Also, the treated plant exhibited higher P and K uptake and translocation ability. Furthermore, chemical control and N200 treatment maintained a high level of ribulose-1,5-bisphosphate carboxylase (RuBPCase), phosphoenolpyruvate carboxylase (PEPCase), nitrate reductase (NR), and glutamine synthetase (GS) enzymatic activities in leaves. In addition, plant growth regulator and nitrogen application improved the enzymatic activities of GS, glutamate dehydrogenase (GDH), and glutamic pyruvic transaminase (GPT) and the contents of crude protein, lysine, sucrose, and soluble sugar in grain and ultimately increased maize yield. This study suggests that N200 application in combination with chemical control promotes root vitality and nutrient accumulation and could improve grain yield and quality in high-density planting.

Keywords: nitrogen fertilizer, chemical control, root bleeding sap, nutrient absorption, maize

Introduction

The root is an essential absorption system, and its function is to maintain the supply of nutrients and soil moisture for crop growth and development (Xu et al., 2009; Fan et al., 2021). The root system of crops greatly influences the above-ground growth and biomass yield, which play an important role in yield formation (Yang et al., 2004; Chen et al., 2022). The capacity for nutrient and soil moisture uptake by crops is directly influenced by root development and root activity strength (Li et al., 2019). Well-developed root systems are always accompanied by vigorous above-ground growth and high yields. Root-bleeding sap is a sign of root pressure, and its change is consistent with root activity (Xu et al., 2016). The root-bleeding sap is directly correlated to the uptake of nutrients and water and reflects the root system's potential for plant growth and root activity (Ansari et al., 2004; Noguchi et al., 2005). The concentration of nutrients in root-bleeding sap represents the nutritional status and reflects root absorption and translocation rates in crops (Noguchi et al., 2005; Nishanth and Biswas, 2008). Hence, an appropriate rate of root-bleeding sap is vital to optimizing maize yield and directly influencing maize growth and development.

Nutrient absorption and translocation in crops are the physiological basis for dry matter accumulation and yield formation, influencing crop growth and development (Wu et al., 2018; Li et al., 2021). The difference in biomass yield is closely correlated to the plant's nutrient uptake and utilization characteristics. It is generally believed that obtaining a higher yield requires crops to absorb a large amount of nutrients from the soil (Wu et al., 2015; Zhan et al., 2016). Phosphorus promotes carbohydrate and starch synthesis in stems and leaves and increases the nutrient transport to the grains, thereby improving grain weight and quality (Wang and Ning, 2019). Potassium can stimulate the synthesis and transport of carbohydrates and promote the growth of maize ear (Shahzad et al., 2017). Phosphorus and potassium are nutrient elements in great demand for maize. Adequate P and K supply promotes root development and dry matter accumulation and enhances maize's resistance to stress (Xie et al., 2011; Iqbal et al., 2020). Furthermore, maize's adequate P and K contents promote the grain development process and help in obtaining a relatively high grain number per ear and weight (Liu et al., 2011). Therefore, the absorption and translocation of P and K play an important role in maize growth and yield potential in the process of yield formation.

Maize (Zea mays L.) is one of the most essential cereal feeds worldwide and occupies a prominent place in global food security and sustainable development (Palacios-Rojas et al., 2020). Since the mid-1990s, with the improvement of the economy and dietary structure in China, the consumption of animal-derived foods, such as meat, milk, and eggs, has increased, which rapidly increased the demand for maize. Maize is the most widely cultivated crop in China, and its production reflects people's need (Liu S. Q. et al., 2021). Northeast China is a major maize producing region, and its planting area and yield account for 31 and 34%, respectively, of the total maize production in China (Liu and Ye, 2020). The current maize planting density in Northeast China is relatively low, resulting in fewer grain yields (Luo et al., 2020). Maize yield in this region has only reached 50% of its yield potential, which offers an excellent opportunity for increasing yield. It is generally accepted that relying on high-density planting to enhance population productivity is one of the most important measures to increase yield potential (Tang et al., 2018). However, high-density planting increases resource competition among maize plants, leading to a decline in individual plant productivity and negatively affecting yield potential (Rossini et al., 2011). This inevitably intensifies the competition betwen the root systems as it is an important organ for maize to obtain environmental resources. Increased planting density leads to decreased row spacing, resulting in increased nutrients, water, and space competition between maize plants. It also severely limits the spatial distribution of the root system and restricts the capacity of nutrient absorption and utilization, ultimately leading to a decline in root quality and grain yield (Gao et al., 2021). According to Shao et al. (2018), root length and root number per plant decrease significantly as planting density increases. The increase in planting density not only inhibits the growth, quantity, and quality of maize roots but also reduces nutrient absorption and translocation in maize (Li et al., 2020; Gao et al., 2021). Therefore, enhancing root physiological characteristics and nutrient absorption capacity in high-density planting for optimal maize growth and high yield has become a significant problem in maize production.

A sufficient supply of nutrients has become essential to achieving high crop yield under high-density planting. Nitrogen, one of the most critical nutrient elements during the maize growing period, greatly affects the root morphological characteristics and physiological activities (Li et al., 2019). It is reported that nitrogen application could significantly increase the total length, volume, and effective absorption area of roots, thereby improving root nutrient absorption capacity (Liu et al., 2017). Furthermore, nitrogen fertilizer plays an important role in the crop's nutrient accumulation and transport activity. Appropriate nitrogen application can increase the grain yield by increasing nutrient accumulation post-anthesis and nutrient translocation to grains (Zhang et al., 2021). Chemical control is one of the efficient cultivation measures, which regulates plant growth and development process, enhances nutrient utilization capacity and environment adaptability, and improves grain yield and quality (Hutsch and Schubert, 2017; Stutts et al., 2018). The application of plant growth regulators can enhance the capacity of crops to absorb nutrients and soil moisture by improving their root growth characteristics (Lin et al., 2019; Nawaz et al., 2020). Yuhuangjin is a type of plant growth regulator that is widely used in maize production in China. The main component is ethephon and diethyl aminoethyl hexanoate DTA-6, which improves plant growth, enhances lodging resistance, optimizes yield component, and increases yield (Zhang et al., 2014). Therefore, we hypothesized that chemical control and nitrogen fertilizer could improve root growth, increase nutrient absorption, and promote yield formation in maize. To prove this hypothesis, this study investigated the effects of chemical control and nitrogen fertilizers on root-bleeding sap characteristics, P and K accumulation and translocation, and grain yield and quality in high plant density. This study aimed to provide a theoretical basis for increasing maize yield and quality in future high-density planting management practices.

Materials and Methods

Site Description

The experiment was conducted from April to September in 2017 and 2018 at the experimental station of Northeast Agricultural University, Harbin, Heilongjiang Province, China (126°54′E, 45°46′N). The region has a typical warm temperate monsoon climate with an annual mean temperature of 4.5°C and annual mean precipitation of 569 mm. The crop rotation system is continuous maize cropping, and the soil type at the experimental site is chernozem. The physical and chemical characteristics of tillage layer soil were pH 6.85; organic matter 25.25 g kg−1; total nitrogen 1.70 g kg−1; available phosphorus 65.34 mg kg−1; and available potassium 179.35 mg kg−1. Temperature and rainfall during the growth stage of spring maize in 2017 and 2018 are shown in Figure 1.

Figure 1.

Figure 1

Open in a new tab

Monthly rainfall distribution and mean temperature during spring maize growing stage in 2017 and 2018.

Experimental Design and Field Management

The experiment was laid out as a split-plot design with three replicates. Two chemical treatments (Y, Yuhuangjin; Control (CK), water) were used as the main plots, and three nitrogen fertilizer levels were used as the subplots: 100 kg ha−1 (N100), 200 kg ha−1 (N200), and 300 kg ha−1 (N300). The plant growth regulator Yuhuangjin (the mixture of 3% DTA-6 and 27% ethephon) was provided by Haolun Co., Ltd., Fujian, China. About 0.83 mL L−1 of Yuhuangjin solution was sprayed on the foliar surface at the seven-leaf stage in the afternoons between 16:00 and 18:00 h. Yuhuangjin was applied at 450 L ha−1, and the same volume of water was applied to the control plants. Spring maize Longyu 365, a high-yielding variety in Heilongjiang province, was sown manually at 90,000 plants ha−1 on 30 April and harvested on 25 September in 2017 and 2018. The size of each plot was 5.2 × 8 m with 0.65 m row spacing. All plots were supplied with 100 kg ha−1 P2O5 and 100 kg ha−1 K2O. The total phosphorus and potassium and half of the nitrogen (urea, 46% N) were applied at the sowing. The balance half of the nitrogen was applied at the jointing stage. No irrigation was applied during the maize growing season. Pests, weeds, and diseases were controlled in a timely manner, and tillage management was conducted according to local farmer management.

Collection of Root-Bleeding Sap

Three representative plants were sampled from each plot at jointing, tasseling, early grain filling, and milking stages. The plants were cut at the third basal internode using lopping shears at 19:00 h. The incision was washed with distilled water, covered with a centrifuge tube containing degreasing cotton (≈2/3 of the centrifugal tube volume), and secured with plastic wrap to collect the root-bleeding sap. The centrifuge tubes were collected at 6:00 h the next day, and the weight was measured (Wang H. et al., 2019). The bleeding sap rate was calculated as the weight increase of the centrifuge tube per hour per plant (g h−1 plant−1).

Analysis of Root-Bleeding Sap Components

Concentrations of serine (Ser), glutamic acid (Glu), glycine (Gly), alanine (Ala), valine (Val), lysine (Lys), methionine (Met), arginine (Arg), and leucine (Leu) in the root-bleeding sap were measured using high-performance liquid chromatography with pre-column derivatization (Li H. W. et al., 2012). Concentrations of P, K, Ca, Mg, Fe and Zn were measured using inductively coupled plasma optical emission spectroscopy (ICP-AES, OPTIMA 3300 DV, Perkin-Elmer, USA).

Determination of Photosynthesis and N Metabolism Enzyme Activities in Ear Leaf

Approximately 0.5 g of fresh ear leaf was homogenized with an extraction medium (pH 8.4, 0.1 mmol L−1 Tricine-HCl, 10 mmol L−1 MgCl2, 1 mmol L−1 EDTA, 7 mmol L−1 β-mercaptoethanol, 5% glycerol (v/v) and 1% PVP) in an ice-cold mortar with a pestle. The homogenate was centrifuged at 15,000 × g for 10 min at 4°C. The supernatant was used for the RuBPCase and PEPCase assays following the methods of Lilley and Walker (1974) and Arnozis et al. (1988), respectively.

Approximately 1 g of fresh ear leaf was homogenized with the extraction medium (pH 7.5, 0.1 mol L−1 Tris-NaOH, 5 mmol L−1 MgCl2 and 1 mmol L−1 DTT) precooled in ice, followed by centrifugation at 20,000 × g for 15 min at 4°C. The supernatant was used for enzyme assays. Nitrate reductase (NR) activity was determined by the method of Lewis et al. (1982), and glutamine synthetase (GS) activity was determined by the method of Canovas et al. (1991).

Determination of N Metabolism Enzyme Activity in Grain

Three ears per plot were randomly sampled at 10, 15, 20, 25, and 30 days after silking. Approximately 100 grains in the middle of the ear were collected and frozen in liquid N2 and stored at −80°C for enzyme assays. About 0.5 g of frozen grain was homogenized with phosphate buffer (pH 7.2), followed by centrifugation at 10,000 × g for 20 min. The supernatant was used for enzyme assays of GS and glutamate dehydrogenase (NADH-GDH and NAD-GDH) activities following the method of Wang et al. (2016).

About 0.2 g of frozen grain was homogenized with Tris-HCl extraction buffer (pH 7.2, 50 mmol L−1 trihydroxymethyl aminomethane) precooled in ice, followed by centrifugation at 20,000 × g for 20 min at 4°C. The supernatant was used for the glutamic-pyruvic transaminase (GPT) assay following the method of Wang et al. (2016).

Analysis of Nutrients Concentration in Grain

The grains were sampled and oven-dried at 40°C for 24 h and ground to powder at harvest. The resulting grain powder was passed through a 0.25 mm mesh and stored at 4°C for analysis. Crude protein in grain was assayed by the micro-Kjeldahl method described by the Association of Official Agricultural Chemists AOAC (1975). Crude fat was assayed following the method of AOAC (1984). Starch was assayed by the colorimetric method described by Boros et al. (2004). Lysine was assayed using the colorimetric method described by Reddy et al. (2013).

Approximately 1 g of fresh grain was ground in a mortar with liquid nitrogen, and 10 ml of distilled water was added to the sample and incubated in boiling water for 60 min. The mixture was centrifuged at 12,000 × g for 20 min at 4°C. The supernatant was used for soluble sugar and sucrose measures. Soluble sugar was measured by the anthrone colorimetric method described by Liu et al. (2007). Sucrose was measured by the anthrone method described by Van (1968).

Determination of P and K Accumulation and Translocation

Three plants were sampled from each plot and separated into stems, leaves, and grains during harvest. The samples were dried in an oven at 105°C for 30 min and afterward at 80°C to a constant weight. Dried samples were weighed and ground to pass through a 1-mm sieve and digested by an H2SO4-H2O2 mixture (Wolf, 1982). The P concentration was determined by the ammonium molybdate ascorbic acid reduction method (Murphy and Riley, 1962). The K concentration was determined by the flame photometer method. Nutrient (P or K) accumulation was calculated based on the sum of the dry matter and P or K concentration in plant parts.

Nutrient (P or K) translocation amount of pre-silking (TAE, kg ha−1) = vegetative organ nutrient (P or K) content at silking—vegetative organ nutrient (P or K) content at maturity.

Nutrient (P or K) translocation rate of pre-silking (TRE, %) = TAE/vegetative organ nutrient (P or K) content at silking × 100.

Contribution rate of nutrient (P or K) translocation amount of pre-silking (CTAE, %) = TAE/grain nutrient (P or K) content at maturity × 100.

Nutrient (P or K) accumulation amount of post-silking (AAT, kg ha−1) = plant nutrient (P or K) content at maturity – plant nutrient (P or K) content at silking.

Contribution rate of nutrient (P or K) accumulation amount of post-silking (CAAT, %) = AAT/grain nutrient (P or K) content at maturity × 100.

Statistical Analysis

The data were summarized to calculate the mean value and standard error (SE). The mean value was compared by the analysis of variance (ANOVA) to analyze the significant differences between samples with different treatments (P < 0.05). All statistical analyses were performed by SPSS 19.0 procedures (SPSS Inc., Chicago, IL, USA). Microsoft Excel 2010 was used to draw tables.

Results

Root-Bleeding Sap and Nutrients Composition Delivery Rate

The chemical control and nitrogen fertilization exhibited a significant influence on the rate of root-bleeding sap during the maize growing period in 2017 and 2018 (Table 1). At the same N levels, chemical control increased root-bleeding sap rate with an average augment of 12.26, 15.99, 14.21, 8.97, and 18.46% from the jointing stage to the maturing stage compared with water treatment. Root-bleeding sap rate first increased and then decreased with the increase of nitrogen application under the same chemical treatment, and the highest value was measured under N200 treatment. The results show that a high N level inhibited the increase of root-bleeding. An analysis of the synthetic effect revealed that the highest root-bleeding sap rate was obtained from N200 application under chemical control.

Table 1.

Effects of chemical control and nitrogen fertilizers on root-bleeding sap rate (μg h−1 plant−1) during the maize growing period in 2017 and 2018.

Year Treatment Jointing stage Tasseling stage Early filling stage Milk stage Maturing stage
2017 N100+CK 1.42d 1.75d 1.99d 2.75cd 0.76d
N200+CK 1.56c 1.96c 2.17c 2.79c 0.86c
N300+CK 1.47d 1.85cd 2.08cd 2.71d 0.82c
N100+Y 1.58c 2.07b 2.31b 2.99b 0.92b
N200+Y 1.77a 2.26a 2.49a 3.10a 1.03a
N300+Y 1.67b 2.20a 2.38b 2.98b 0.98a
2018 N100+CK 1.36c 1.65c 2.03d 2.50c 0.70c
N200+CK 1.49b 1.87b 2.24bc 2.64b 0.80b
N300+CK 1.47b 1.75c 2.15c 2.56c 0.77b
N100+Y 1.53b 1.95b 2.32b 2.70b 0.82b
N200+Y 1.67a 2.10a 2.50a 2.85a 0.91a
N300+Y 1.61ab 1.98b 2.45a 2.77ab 0.90a
Open in a new tab

N100+CK, N200+CK, and N300+CK indicate nitrogen applied levels at 100, 200, and 300 kg ha−1 under water treatment, respectively; N100+Y, N200+Y, and N300+Y indicate nitrogen applied levels at 100, 200, and 300 kg ha−1 under chemical control, respectively. Means within a column for the same year followed by the different letters indicate a significant difference at P < 0.05.

The delivery rate of free amino acids in root-bleeding sap was influenced by chemical control and nitrogen fertilizer, which decreased after the jointing stage in maize (Table 2). At the same N levels, chemical control increased the delivery rate of Ser, Glu, Gly, Ala, Val, Lys, Met, Arg, and Leu with an average augment of ≈11.45–19.04% than water treatment at the tasseling stage in both years, which was consistent at different growth stages. Under the same chemical treatment, the free amino acid delivery rate obtained the highest value under N200 treatment, which showed an average augment of 6.54–15.04% and of 4.15–6.97% compared with N100 and N300 nitrogen rates in both years. From the analysis of synthetic effect, the delivery rate of free amino acids in root-bleeding sap was optimal in N200 application under chemical control.

Table 2.

Effects of chemical control and nitrogen fertilizers on amino acids concentrations (μg h−1 plant−1) in root-bleeding sap during the maize growing period in 2017 and 2018.

Growth stage Treatment 2017 2018
Ser Glu Gly Ala Val Lys Met Arg Leu Ser Glu Gly Ala Val Lys Met Arg Leu
Jointing stage N100+CK 479.35d 284.97d 1.34d 13.91d 57.59d 92.92e 5.46c 85.15d 17.88e 468.15d 279.68d 1.27d 13.39d 54.58d 89.06d 4.95d 83.29d 16.63d
N200+CK 506.23c 310.99c 1.44c 15.38c 62.68bc 101.63cd 5.87b 95.36b 19.47cd 495.77bc 303.61c 1.38c 14.56bc 59.63bc 96.43c 5.26c 90.14c 18.15c
N300+CK 496.70cd 307.06c 1.40cd 14.26d 59.52cd 96.61de 5.30c 89.93c 18.36de 482.89cd 295.27c 1.31d 14.07c 57.71c 91.45d 5.13cd 87.15cd 17.36cd
N100+Y 539.22b 334.64b 1.56b 16.01bc 66.32b 105.60bc 6.00b 99.17b 20.86bc 516.74b 327.46b 1.45b 15.22b 62.46b 101.54b 5.59b 94.82b 19.43b
N200+Y 568.89a 359.67a 1.65a 17.53a 71.86a 116.71a 6.48a 105.17a 22.92a 543.23a 346.84a 1.57a 16.24a 66.87a 109.18a 6.11a 100.48a 21.32a
N300+Y 544.89ab 339.95b 1.56b 16.51ab 67.04ab 108.43b 6.17ab 99.18b 21.74ab 525.28ab 335.29ab 1.49b 15.48ab 63.52b 104.77ab 5.78b 96.57ab 20.08b
Tasseling stage N100+CK 377.14d 227.46d 1.13d 11.69d 49.83d 73.17d 4.37d 74.47e 13.91c 365.26d 212.76d 1.04d 11.24d 45.62d 70.33d 4.05d 69.02d 13.34d
N200+CK 403.18c 242.68c 1.22c 12.64c 53.64cd 82.09c 4.72c 80.27cd 15.97b 386.53c 230.53c 1.12c 12.29c 50.57c 78.05c 4.48bc 75.24bc 15.36b
N300+CK 383.42d 226.22d 1.13d 11.74d 49.96d 73.17d 4.28d 76.75de 14.39c 370.72cd 218.42d 1.07cd 11.73cd 47.45d 72.48d 4.29c 72.65c 14.21c
N100+Y 424.42b 255.84b 1.26bc 13.55b 55.78bc 86.38b 5.07b 83.34bc 17.40a 409.58b 245.84b 1.19b 13.26b 52.63c 82.09b 4.66b 78.73b 16.02b
N200+Y 453.42a 278.94a 1.36a 14.70a 61.24a 94.45a 5.33a 89.53a 18.28a 435.21a 264.39a 1.30a 14.02a 59.29a 88.84a 5.03a 85.82a 17.27a
N300+Y 438.67ab 265.77b 1.31ab 14.05ab 58.21ab 89.34b 4.97b 85.13b 17.02ab 422.47ab 254.56ab 1.23b 13.68ab 56.34b 84.27b 4.83ab 80.56b 16.29b
Early filling stage N100+CK 318.24c 173.80c 0.71c 9.88e 44.29c 61.05e 3.99d 66.60c 7.71c 302.85c 169.82d 0.69d 9.43d 40.03d 60.61d 3.68d 62.14d 7.06d
N200+CK 342.15bc 197.32b 0.77b 11.05cd 48.62b 69.74c 4.31c 72.01b 9.14b 333.52b 185.35c 0.74c 10.24c 44.67c 66.44c 4.04bc 70.47b 8.23c
N300+CK 329.59bc 184.54c 0.71c 10.36de 44.05c 65.30d 4.01d 66.90c 7.75c 315.62c 177.47cd 0.70d 9.77cd 42.98c 63.25d 3.89c 66.44c 7.32d
N100+Y 367.79ab 209.01b 0.88a 11.59bc 51.53a 72.88c 4.42bc 74.67b 9.47b 345.07b 198.09b 0.83b 10.88b 47.44b 72.96b 4.21b 73.92ab 8.98b
N200+Y 383.05a 230.34a 0.90a 12.86a 54.37a 83.57a 4.90a 79.70a 10.80a 367.26a 221.53a 0.88a 12.02a 51.85a 78.37a 4.65a 77.25a 9.75a
N300+Y 365.08ab 222.42a 0.87a 12.25ab 52.57a 77.77b 4.61b 78.99a 9.84ab 351.63ab 207.04b 0.85ab 11.34b 48.62b 76.72a 4.36b 75.34a 9.52a
Milk stage N100+CK 147.14d 108.01e 0.50e 6.00d 23.39d 39.69d 2.02cd 29.19c 3.86c 148.53d 110.84d 0.55e 5.89d 22.08e 39.82d 1.78d 27.14e 4.14e
N200+CK 169.19c 123.96cd 0.69c 7.08c 29.31b 47.88c 2.17c 36.59b 4.99b 163.29c 120.06c 0.64c 6.78c 25.31c 45.47c 1.92c 32.19c 5.05c
N300+CK 162.04c 119.80de 0.63d 6.68c 26.81c 44.55c 1.95d 31.15c 4.25c 157.24c 114.26d 0.59d 6.14d 23.86d 41.19d 1.83cd 30.18d 4.63d
N100+Y 183.75b 134.16bc 0.71bc 8.04b 30.24b 52.28b 2.51b 39.02b 5.33b 179.08b 130.32b 0.70b 7.66b 28.75b 50.95b 2.27b 34.63b 5.51b
N200+Y 209.35a 148.63a 0.82a 8.89a 33.84a 60.34a 2.77a 45.58a 6.46a 192.41a 142.89a 0.76a 8.25a 31.87a 56.21a 2.49a 40.52a 6.11a
N300+Y 190.15b 144.44ab 0.75b 8.14b 32.59a 55.58b 2.46b 39.37b 6.07a 184.47ab 136.93a 0.72b 7.62b 29.24b 53.02b 2.35b 35.79b 5.78b
Open in a new tab

N100+CK, N200+CK, and N300+CK indicate nitrogen applied levels at 100, 200, and 300 kg ha−1 under water treatment, respectively; N100+Y, N200+Y, and N300+Y indicate nitrogen applied levels at 100, 200, and 300 kg ha−1 under chemical control, respectively. Means within a column for the same growth stage followed by the different letters indicate a significant difference at P < 0.05.

A similar change trend was observed in the mineral nutrient concentrations in bleeding sap during the maize growing period in 2017 and 2018 (Table 3). The mineral nutrient concentrations were significantly affected by chemical control and nitrogen fertilizer. The delivery rate of mineral nutrients first increased and then decreased with the increase of nitrogen application under the same chemical treatment. At the same N levels, chemical control obviously increased the delivery rate of mineral nutrients at different growth stages. From the analysis of synthetic effect, the delivery rate of mineral nutrients in root-bleeding sap was optimal in N200 application under chemical control.

Table 3.

Effects of chemical control and nitrogen fertilizers on mineral nutrients concentrations (μg h−1 plant−1) in root-bleeding sap during the maize growing period in 2017 and 2018.

Growth period Treatment 2017 2018
Fe Mn Cu Zn Ca Mg Mo K P B Si Fe Mn Cu Zn Ca Mg Mo K P B Si
Jointing stage N100+CK 1.62d 4.37d 0.046c 10.93c 318.23c 299.46cd 0.057d 1747.53e 113.76c 1.14cd 50.45c 1.55d 4.15d 0.043d 10.08d 302.98d 259.46d 0.051d 1682.49d 104.07d 1.01d 44.37d
N200+CK 1.80c 4.75c 0.050bc 11.55bc 347.74b 314.76bc 0.064c 1920.50cd 123.26bc 1.21c 53.66b 1.79c 4.62c 0.049c 11.39bc 332.63bc 290.56c 0.058c 1801.37c 115.48c 1.11c 48.62c
N300+CK 1.87c 4.80c 0.051bc 11.66b 339.26b 284.37d 0.055d 1833.47de 118.52c 1.07d 53.96b 1.77c 4.51c 0.047c 10.92c 320.06c 278.85c 0.056c 1754.88cd 110.75c 1.04d 45.89d
N100+Y 2.06b 5.22b 0.056ab 12.43a 350.32b 332.33ab 0.070b 1998.30bc 134.01ab 1.37b 55.22b 1.96b 5.07b 0.053b 11.85b 346.45b 307.82b 0.064b 1895.03b 122.62b 1.26b 51.84b
N200+Y 2.17a 5.50ab 0.060a 12.82a 383.02a 345.53a 0.075a 2124.70a 142.78a 1.49a 58.39a 2.12a 5.43a 0.058a 12.77a 370.82a 333.13a 0.071a 2093.27a 136.59a 1.39a 56.25a
N300+Y 2.20a 5.57a 0.062a 13.05a 374.64a 328.45ab 0.068b 2087.37ab 138.60a 1.37b 58.97a 2.08a 5.39a 0.057a 12.64a 362.17ab 316.28b 0.066b 1956.36b 127.94b 1.28b 53.08b
Tasseling stage N100+CK 0.49d 4.29d 0.063e 9.26d 300.46e 292.80d 0.062d 1538.44d 110.49c 1.09d 44.41d 0.52e 4.05d 0.58d 8.98d 282.94d 267.25d 0.059d 1496.05d 98.72c 1.00d 42.67d
N200+CK 0.65c 4.73c 0.069d 9.97c 320.38cd 310.57bc 0.075c 1671.27c 118.37bc 1.18c 46.93c 0.62c 4.52bc 0.64c 9.53c 303.39c 285.03bc 0.069c 1602.88c 109.46b 1.10c 45.42c
N300+CK 0.71c 4.90c 0.071cd 9.92c 307.73de 297.60cd 0.071c 1608.97cd 110.54c 1.09d 45.82cd 0.58d 4.37c 0.62c 9.39cd 287.33d 276.29cd 0.066c 1579.14c 102.78c 1.06c 44.68cd
N100+Y 0.77b 5.04bc 0.074bc 10.93b 344.16ab 328.07a 0.086b 1760.22b 123.53b 1.28b 49.99b 0.74b 4.68b 0.69b 10.21b 320.17b 297.42b 0.077b 1693.49b 112.53b 1.17b 48.39b
N200+Y 0.90a 5.40ab 0.078ab 11.48a 359.44a 335.49a 0.094a 1874.43a 135.76a 1.39a 53.39a 0.86a 5.23a 0.76a 11.15a 343.48a 325.28a 0.086a 1819.53a 125.85a 1.31a 52.05a
N300+Y 0.92a 5.55a 0.079a 11.74a 335.66bc 323.83ab 0.088b 1822.54ab 126.88ab 1.29b 54.78a 0.83a 5.06a 0.74a 10.92a 325.84b 316.17a 0.084a 1786.67a 117.09b 1.22b 50.83a
Early filling stage N100+CK 1.55c 5.87d 0.039c 4.85d 456.81c 361.88d 0.095e 1036.46c 143.64c 0.96d 25.91d 1.47d 5.79d 0.34d 5.17d 450.24e 333.92d 0.088d 1087.65d 128.95d 0.90d 22.07e
N200+CK 1.68b 6.65c 0.045bc 5.83c 486.52b 377.28c 0.103cd 1251.03b 155.73bc 1.07c 28.92c 1.63c 6.27c 0.38c 5.59c 477.91cd 354.38c 0.096c 1174.59c 141.63c 0.99c 28.58c
N300+CK 1.73b 6.75c 0.044bc 5.95c 475.80b 358.97d 0.098de 1167.03b 151.38bc 1.03c 30.43c 1.59c 6.05cd 0.37c 5.42cd 468.17de 340.03cd 0.093c 1106.27d 134.07d 0.93d 24.94d
N100+Y 1.77b 7.30b 0.044bc 6.73b 524.52a 392.79b 0.109bc 1248.27b 163.15ab 1.16b 34.17b 1.75b 6.91b 0.41b 6.58b 496.87bc 377.49b 0.104b 1256.76b 152.19b 1.06b 32.31b
N200+Y 1.94a 7.98a 0.050ab 7.12a 537.46a 411.63a 0.122a 1396.47a 173.51a 1.22a 37.13a 1.85a 7.64a 0.46a 6.94a 525.75a 403.67a 0.115a 1362.09a 169.72a 1.14a 35.85a
N300+Y 1.98a 7.91a 0.051a 7.28a 525.22a 399.12ab 0.113b 1380.29a 165.35ab 1.16b 37.88a 1.81ab 7.38a 0.45a 6.85ab 520.33ab 396.54a 0.108b 1283.15b 157.94b 1.12a 33.67b
Milk stage N100+CK 0.37d 1.26d 0.021c 2.64d 117.79c 20.18d 0.067d 481.15d 41.52d 0.17d 15.89c 0.35d 1.31d 0.23d 3.42d 113.06d 24.31e 0.065d 493.17d 42.35d 0.20d 13.77d
N200+CK 0.46c 1.66c 0.026bc 3.26c 130.83b 30.82c 0.076c 560.38c 48.58c 0.25c 16.56c 0.43c 1.62c 0.26c 3.89c 126.74c 31.38d 0.073c 545.39c 46.88c 0.24c 15.85c
N300+CK 0.48c 1.80bc 0.028bc 3.54c 129.95b 32.04c 0.069d 539.03c 46.93cd 0.25c 17.03c 0.41c 1.57c 0.24d 3.57d 118.38d 25.47e 0.068d 516.28d 44.27d 0.21d 14.42d
N100+Y 0.59b 1.92b 0.026b 4.31b 155.06a 38.73b 0.085b 622.59b 57.07b 033a 20.97b 0.56b 1.85b 0.30b 4.36b 139.02b 36.79c 0.079b 603.05b 52.53b 0.29b 20.51b
N200+Y 0.68a 2.33a 0.031ab 4.65ab 167.65a 49.55a 0.091a 712.55a 64.38a 0.35a 24.25a 0.64a 2.26a 0.33a 4.73a 158.85a 45.32a 0.088a 684.91a 57.96a 0.32a 22.69a
N300+Y 0.69a 2.44a 0.034a 4.97a 162.60a 46.57a 0.089ab 676.37a 58.75ab 0.27b 25.50a 0.62a 2.18a 0.31b 4.48b 152.37a 42.68b 0.085a 627.56b 54.19b 0.30b 21.18b
Open in a new tab

N100+CK, N200+CK, and N300+CK indicate nitrogen applied levels at 100, 200, and 300 kg ha−1 under water treatment, respectively; N100+Y, N200+Y, and N300+Y indicate nitrogen applied levels at 100, 200, and 300 kg ha−1 under chemical control, respectively. Means within a column for the same growth stage followed by the different letters indicate a significant difference at P < 0.05.

P and K Accumulation and Translocation

Changes between the P and K accumulation in maize plants followed similar trends; both P and K increased gradually from the jointing stage to thewe maturing stage (Table 4). Chemical control and N fertilization level exhibited a marked influence on P and K accumulation amount during the maize growing period in both years. At the same N levels, chemical control increased P accumulation amount with an average augment of 4.48, 15.34, 22.07, 23.52, and 24.32% and K accumulation amount with an average augment of 6.30, 14.43, 17.60, 18.94, and 19.55% from the jointing stage to the maturing stage in 2017 and 2018. Under both water and chemical control conditions, P and K accumulation amount increased by increasing the N level from N100 to N300, but there was no significant difference between N200 and N300 treatments in both years. Compared with N100, N200 and N300 treatments increased P and K accumulation amount with an average augment of 22.41 and 24.26%, respectively.

Table 4.

Effects of chemical control and nitrogen fertilizers on P and K accumulation (kg ha−1) during the maize growing period in 2017 and 2018.

Nutrient Treatment 2017 2018
Jointing stage Tasseling stage Early filling stage Milk stage Maturing stage Jointing stage Tasseling stage Early filling stage Milk stage Maturing stage
P N100+CK 9.88c 22.02c 26.96c 29.08d 30.31d 9.55c 20.78c 25.81c 27.82c 28.95c
N200+CK 10.26bc 25.55b 32.52b 36.78bc 39.09bc 10.02bc 23.74b 30.64b 34.35b 36.37b
N300+CK 10.45b 26.32b 33.57b 37.83b 39.85b 10.38b 24.66b 31.89b 35.77b 37.81b
N100+Y 10.20b 25.48b 32.78b 36.03c 38.01c 10.04b 23.62b 31.16b 34.29b 36.13b
N200+Y 10.76a 29.85a 40.08a 45.65a 48.64a 10.61a 27.81a 38.27a 43.43a 46.18a
N300+Y 10.96a 30.10a 40.37a 45.86a 48.65a 10.68a 28.17a 38.75a 43.77a 46.38a
K N100+CK 37.0.88c 72.56c 93.49c 105.01d 114.71d 37.49c 70.15c 89.64c 100.87c 109.61c
N200+CK 39.53bc 81.61b 107.64b 123.89bc 137.60bc 39.36bc 77.42b 101.27b 114.92b 125.88b
N300+CK 41.21b 85.18b 112.92b 129.75c 143.62c 39.91b 78.79b 103.25b 117.38b 128.53b
N100+Y 39.95b 82.01b 107.51b 122.60b 134.81b 38.67bc 76.04b 99.21b 112.45b 123.04b
N200+Y 42.89a 96.47a 130.70a 152.04a 169.10a 42.52a 89.88a 120.96a 139.24a 153.72a
N300+Y 43.05a 97.22a 133.48a 154.80a 172.73a 43.13a 91.37a 123.52a 141.91a 156.29a
Open in a new tab

N100+CK, N200+CK, and N300+CK indicate nitrogen applied levels at 100, 200, and 300 kg ha−1 under water treatment, respectively; N100+Y, N200+Y, and N300+Y indicate nitrogen applied levels at 100, 200, and 300 kg ha−1 under chemical control, respectively. Means within a column for the same nutrient followed by the different letters indicate a significant difference at P < 0.05.

Changes in the proportion of P and K accumulation in maize plants during various growth stages seemed to follow similar trends (Table 5). Proportions of P and K accumulation had a higher value at emerging (VE) —jointing (JT) and JT—tasseling (TS) stages and decreased gradually from TS—early-filling (EF) to milk (MK)—maturing (MT) stage. The proportions of P and K accumulation were significantly affected by chemical control and N fertilization level. At the same N levels, chemical control increased the proportions of P and K accumulation at TS-EF, EF-MK, and MK-MT stages, while the proportions decreased at the VE-JT stage and remained relatively constant at the JT-TS stage in 2017 and 2018. Under both water and chemical control conditions, N supply significantly increased the proportions of P and K accumulation. However, there was no significant difference between N200 and N300 treatments, and the highest proportions were obtained under N200 treatment at EF-MK and MK-MT stages in both years.

Table 5.

Effects of chemical control and nitrogen fertilizers on the proportion of P and K accumulation (%) at different maize growing stages in 2017 and 2018.

Nutrient Treatment 2017 2018
VE-JT JT-TS TS-EF EF-MK MK-MT VE-JT JT-TS TS-EF EF-MK MK-MT
P N100+CK 32.60a 40.04a 16.31d 6.98d 4.07d 32.99a 38.79a 17.37d 6.94d 3.90d
N200+CK 26.25b 39.12a 17.82c 10.91b 5.90b 27.55b 37.72a 18.97c 10.20b 5.55b
N300+CK 26.23b 39.83a 18.19c 10.69b 5.05c 27.45b 37.77a 19.12c 10.26b 5.40b
N100+Y 26.85b 40.19a 19.21b 8.55c 5.21c 27.79b 37.59a 20.87b 8.66c 5.09c
N200+Y 22.12c 39.26a 21.02a 11.46a 6.14a 22.98c 37.25a 22.65a 11.17a 5.96a
N300+Y 22.54c 39.34a 21.11a 11.28a 5.73b 23.03c 37.71a 22.81a 10.82a 5.63b
K N100+CK 33.02a 30.23a 18.25d 10.04c 8.46d 34.20a 29.80a 17.78c 10.25c 7.97c
N200+CK 28.73b 30.58a 18.92cd 11.81b 9.96c 31.27b 30.24a 18.95b 10.84b 8.71b
N300+CK 28.69b 30.62a 19.31bc 11.72b 9.66c 31.05b 30.25a 19.03b 10.99b 8.68b
N100+Y 29.63b 31.20a 18.92cd 11.19b 9.06b 31.43b 30.37a 18.83b 10.76b 8.61b
N200+Y 25.36c 31.69a 20.24ab 12.62a 10.09a 27.66c 30.81a 20.22a 11.89a 9.42a
N300+Y 25.07c 31.54a 21.12a 12.41a 9.86a 27.60c 30.87a 20.57a 11.77a 9.20a
Open in a new tab

VE, emerging stage; JT, jointing stage; TS, tasseling stage; EF, Early filling stage; MK, milk stage; MT, maturing stage. N100+CK, N200+CK, and N300+CK indicate nitrogen applied levels at 100, 200, and 300 kg ha−1 under water treatment, respectively; N100+Y, N200+Y, and N300+Y indicate nitrogen applied levels at 100, 200, and 300 kg ha−1 under chemical control, respectively. Means within a column for the same nutrient followed by the different letters indicate a significant difference at P < 0.05.

Chemical control and nitrogen fertilizer significantly influenced the nutrient (P and K) translocation and contribution, including the vegetative organ nutrient content at the silking stage (VCS), the vegetative organ nutrient content at the maturing stage (VCM), and the grain nutrient content at the maturing stage (GCM), the nutrient translocation amount of pre-silking (TAE), the nutrient translocation rate of pre-silking (TRE), the contribution rate of nutrient translocation amount of pre-silking (CTAE), the nutrient accumulation amount of post-silking (AAT), and the contribution rate of nutrient accumulation amount of post-silking (CAAT) (Table 6). At the same N levels, VCS, VCM, GCM, TAE, AAT, and CAAT of P and K in maize plants under chemical control were markedly higher than those under water treatment. In contrast, TRE and CTAE of P and K in maize plants under chemical control were markedly lower than those under water treatment. Under both water and chemical control conditions, VCS, VCM, GCM, and TAE of P and K in maize plants were significantly increased by increasing N levels; however, TRE and CTAE were decreased. While N supply in general significantly increased AAT and CAAT of P and K in maize plants, there is no significant difference between N200 and N300 treatments, and the highest values were obtained under N200 treatment in both years.

Table 6.

Effects of chemical control and nitrogen fertilizers on maize nutrient (P and K) translocation and contribution during the maize growing period 2017 and 2018.

Nutrient Treatment 2017 2018
VCS (kg ha−1) VCM (kg ha−1) GCM (kg ha−1) TAE (kg ha−1) TRE (%) CTAE (%) AAT (kg ha−1) CAAT (%) VCS (kg ha−1) VCM (kg ha−1) GCM (kg ha−1) TAE (kg ha−1) TRE (%) CTAE (%) AAT (kg ha−1) CAAT (%)
P N100+CK 21.19d 7.54e 22.27c 13.64d 64.40a 61.27a 8.62c 38.73d 20.37c 7.03d 21.02c 13.35d 65.51a 63.49a 7.68c 36.51c
N200+CK 26.33c 10.26c 28.63b 16.07c 61.04b 56.13c 12.56b 43.87b 24.60b 9.52bc 25.73b 15.09c 61.32b 58.63b 10.65b 41.37b
N300+CK 27.82b 11.05b 28.80b 16.77b 60.27b 58.24b 12.03b 41.76c 25.49b 9.97b 26.01b 15.52bc 60.90b 59.69b 10.48b 40.31b
N100+Y 26.08c 9.17d 29.13b 16.91b 64.84a 58.05b 12.22b 41.95c 25.10b 9.07c 26.83b 16.03b 63.87a 59.77b 10.79b 40.23b
N200+Y 32.16a 13.50a 34.94a 18.66a 58.01c 53.39d 16.29a 46.61a 31.29a 12.92a 33.24a 18.38a 58.73b 55.29c 14.86a 44.71a
N300+Y 32.24a 13.72a 34.11a 18.52a 57.43c 54.29d 15.59a 45.71a 31.46a 12.89a 33.35a 18.58a 59.04b 55.69c 14.78a 44.31a
K N100+CK 82.58e 35.07d 78.64e 47.51e 57.53b 60.41a 31.13d 39.59d 79.59d 30.88d 76.73c 48.70c 61.20a 63.48a 28.02d 36.52d
N200+CK 96.39c 44.87b 94.73d 51.51d 53.44d 54.38c 43.21c 45.62b 89.70bc 39.76b 88.12b 49.94bc 55.67b 56.68c 38.18b 43.32b
N300+CK 100.76b 44.26b 103.36b 56.50b 56.08c 54.67bc 46.86b 45.33bc 92.03b 40.56b 89.97b 51.47b 55.93b 57.21c 38.50b 42.79b
N100+Y 91.77d 37.38c 97.43c 54.39c 59.27a 55.82b 43.04c 44.18c 87.11c 35.31c 86.13b 51.80b 59.46a 60.14b 34.33c 39.86c
N200+Y 111.62a 52.11a 118.51a 59.51a 53.31d 50.22d 59.00a 49.78a 103.24a 46.12a 107.60a 57.12a 55.33b 53.08d 50.48a 46.92a
N300+Y 112.83a 51.85a 121.03a 60.98a 54.05c 50.38d 60.05a 49.62a 105.96a 46.89a 109.40a 59.08a 55.75b 54.00d 50.33a 46.00a
Open in a new tab

VCS, vegetative organ nutrient (P or K) content at silking stage; VCM, vegetative organ nutrient (P or K) content at maturing stage; GCM, grain nutrient (P or K) content at maturing stage; TAE, nutrient (P or K) translocation amount of pre-silking; TRE, nutrient (P or K) translocation rate of pre-silking; CTAE, contribution rate of nutrient (P or K) translocation amount of pre-silking; AAT, nutrient (P or K) accumulation amount of post-silking; and CAAT, contribution rate of nutrient (P or K) accumulation amount of post-silking. N100+CK, N200+CK, and N300+CK indicate nitrogen applied levels at 100, 200, and 300 kg ha−1 under water treatment, respectively; N100+Y, N200+Y, and N300+Y indicate nitrogen applied levels at 100, 200, and 300 kg ha−1 under Yuhuangjin treatment, respectively. Means within a column for the same nutrient followed by the different letters indicate a significant difference at P < 0.05.

RuBPCase and PEPCase Activities in Leaf

Chemical control and N fertilization level exhibited a marked influence on RuBPCase activity in leaves during the maize growing period in 2017 and 2018 (Figure 2). At the same N levels, chemical control increased RuBPCase activity with an average augment of 12.45, 12.91, 11.03, and 13.02% from the jointing stage to the milk stage in 2017 and 2018, respectively. Under both water and chemical control conditions, RuBPCase activity increased with an average augment of 6.78% by increasing the N supply level from N100 to N200 in both years, but further increasing the N supply level from N200 to N300 decreased RuBPCase activity at different stages. From the analysis of synthetic effect, RuBPCase activity in maize leaf was optimal in N200 application under chemical control.

Figure 2.

Figure 2

Open in a new tab

Effects of chemical control and nitrogen fertilizers on RuBPCase and PEPCase activities in ear leaf during the maize growing period in 2017 and 2018. N100+CK, N200+CK, and N300+CK indicate nitrogen applied levels at 100, 200, and 300 kg ha−1 under water treatment, respectively; N100+Y, N200+Y, and N300+Y indicate nitrogen applied levels at 100, 200, and 300 kg ha−1 under chemical control, respectively. Error bars indicate the value of standard error. Different letters within a growth stage indicate a significant difference at P < 0.05.

A similar trend was also observed for PEPCase activity in maize leaf, and the activity was significantly affected by chemical control and N fertilization levels (Figure 2). At the same N levels, chemical control increased PEPCase activity with an average augment of 15.46, 11.98, 15.13, and 17.43% from the jointing stage to the milk stage in 2017 and 2018, respectively. Under both water and chemical control conditions, PEPCase activity under N200 treatment was higher than those under N100 and N300 treatments, with an average augment of 7.87 and 4.46% at different stages, respectively. From the analysis of synthetic effect, PEPCase activity in maize leaf was optimal in N200 application under chemical control.

NR and GS Activities in Leaf

Chemical control and N fertilization level exhibited a marked influence on NR and GS activities in leaves during the maize growing period in 2017 and 2018 (Figure 3). At the same N levels, chemical control increased NR activity with an average augment of 18.23, 17.11, 14.32, and 14.71% and increased GS activity with an average augment of 20.28, 24.12, 17.41, and 25.69% from the jointing stage to the milk stage in both years, respectively. Under water and chemical control conditions, NR and GS activities were significantly increased by increasing the N level from N100 to N200, but further increasing the N supply level from N200 to N300 caused a decrease in NR and GS activities at different stages. From the analysis of synthetical effect, NR and GS activities in maize leaf were optimal in N200 application under chemical control.

Figure 3.

Figure 3

Open in a new tab

Effects of chemical control and nitrogen fertilizers on NR and GS activities in ear leaf during the maize growing period in 2017 and 2018. N100+CK, N200+CK, and N300+CK indicate nitrogen applied levels at 100, 200, and 300 kg ha−1 under water treatment, respectively; N100+Y, N200+Y, and N300+Y indicate nitrogen applied levels at 100, 200, and 300 kg ha−1 under chemical control, respectively. Error bars indicate the value of standard error. Different letters within a growth stage indicate a significant difference at P < 0.05.

N Metabolism Enzyme Activity in Grain

Chemical control and N fertilization level exerted a marked effect on grain GS, GDH, and GPT activities from 10 to 30 days after silking in 2017 and 2018 (Figure 4). Of these, GS and GDH activities increased between 10 and 20 days after silking and then decreased until 30 days after silking. However, GPT activity fluctuated with grain growth, which was highest and lowest at 25 and 30 days after silking, respectively. At the same N levels, chemical control increased GS, GDH, and GPT activities with an average augment of 15.22, 12.76, and 14.21% from 10 to 30 days after silking in both years, respectively. Under both water and chemical control conditions, GS, GDH, and GPT activities in grain were significantly increased by increasing the N supply level from N100 to N200 in both years, but further increasing the N supply level from N200 to N300 caused a slight decrease in grain N metabolism enzyme activities. From the analysis of synthetic effect, N metabolism enzyme activities in grain were optimal in N200 application under chemical control.

Figure 4.

Figure 4

Open in a new tab

Effects of chemical control and nitrogen fertilizers on GS, GDH, and GPT activities in grain from 10 to 30 days after silking in 2017 and 2018. N100+CK, N200+CK, and N300+CK indicate nitrogen applied levels at 100, 200, and 300 kg ha−1 under water treatment, respectively; N100+Y, N200+Y, and N300+Y indicate nitrogen applied levels at 100, 200, and 300 kg ha−1 under chemical control, respectively. Error bars indicate the value of standard error. Different letters within a growth stage indicate a significant difference at P < 0.05.

Nutrients Concentrations in Grain

At the same N levels, chemical control significantly increased crude protein, lysine, sucrose, and soluble sugar concentrations of maize compared with water treatment in 2017 and 2018 (Table 7). Crude protein and lysine concentrations were significantly increased by increasing the N supply level from N100 to N200, but further increasing the N supply level from N200 to N300 caused a significant decrease in 2017 and a slight decrease in 2018. Similar trends were also observed for sucrose and soluble sugar concentrations of maize grain. Crude fat and starch concentrations were unaffected by chemical control and N fertilization level. The results show that nutrient concentrations in maize grain were optimal in N200 application under chemical control.

Table 7.

Effects of chemical control and nitrogen fertilizers on grain nutrients concentrations (%) of maize during maize growing period 2017 and 2018.

Year Treatment Crude protein Crude fat Starch Lysine Sucrose Soluble sugar
2017 N100+CK 9.53e 5.16a 71.81a 0.43d 1.02e 1.68d
N200+CK 10.67c 5.20a 73.14a 0.47b 1.11b 1.78b
N300+CK 10.06d 5.16a 72.56a 0.45c 1.07d 1.72cd
N100+Y 10.78c 5.14a 71.69a 0.45c 1.09c 1.74bc
N200+Y 11.78a 5.26a 73.18a 0.49a 1.15a 1.85a
N300+Y 11.33b 5.22a 72.97a 0.47b 1.12b 1.82a
2018 N100+CK 9.05e 5.21a 71.63a 0.42c 1.02c 1.67c
N200+CK 10.12cd 5.28a 73.57a 0.45b 1.14b 1.80b
N300+CK 9.67d 5.23a 72.35a 0.45b 1.09b 1.75bc
N100+Y 10.29bc 5.24a 72.06a 0.45b 1.10b 1.79b
N200+Y 11.18a 5.34a 73.94a 0.49a 1.17a 1.93a
N300+Y 10.74ab 5.29a 72.68a 0.48a 1.11ab 1.88ab
Open in a new tab

N100+CK, N200+CK, and N300+CK indicate nitrogen applied levels at 100, 200, and 300 kg ha−1 under water treatment, respectively; N100+Y, N200+Y, and N300+Y indicate nitrogen applied levels at 100, 200, and 300 kg ha−1 under chemical control, respectively. Means within a column for the same year followed by the different letters indicate a significant difference at P < 0.05.

Yield and Yield Components

Chemical control and N fertilization level exhibited a marked influence on yield and yield components of maize in 2017 and 2018 (Table 8). Chemical control significantly increased the number of grains per ear and 1,000-grain weight compared with maize under water treatment in 2017 and 2018. Grain number per ear and 1,000-grain weight significantly increased by increasing the N supply level from N100 to N200, but further increasing the N supply level from N200 to N300 caused a slight decrease in 2017 and 2018. The highest grain yields were obtained from the N200 application under chemical control in 2017 and 2018.

Table 8.

Effects of chemical control and nitrogen fertilizers on yield and yield components of maize during the maize growing period 2017 and 2018.

Year Treatment Ears number per ha Grains number per ear 1,000-grain weight (g) Yield (kg ha−1)
2017 N100+CK 81,078a 541c 332b 10511c
N200+CK 81,654a 568b 327b 11548b
N300+CK 81,782a 560b 316c 11053bc
N100+Y 81,657a 571b 340ab 11427b
N200+Y 81,683a 591a 351a 12646a
N300+Y 82,150a 570b 339ab 11921b
2018 N100+CK 80,325a 531c 294c 9840bc
N200+CK 80,793a 550bc 298bc 10430b
N300+CK 78,685b 533c 298bc 9204c
N100+Y 81,052a 556abc 306bc 9990bc
N200+Y 81,184a 581a 327a 11704a
N300+Y 81,167a 566ab 314ab 10732ab
Open in a new tab

N100+CK, N200+CK, and N300+CK indicate nitrogen applied levels at 100, 200, and 300 kg ha−1 under water treatment, respectively; N100+Y, N200+Y, and N300+Y indicate nitrogen applied levels at 100, 200, and 300 kg ha−1 under chemical control, respectively. Means within a column for the same year followed by the different letters indicate a significant difference at P < 0.05.

Correlation Analysis

As shown in Figure 5, correlation analysis indicated that grain yield was positively correlated with the rate of root-bleeding sap, the delivery rate of amino acids and mineral nutrients in the bleeding sap, and CAAT of P and K. Besides, the CAAT of P and K were positively correlated with the rate of root-bleeding sap.

Figure 5.

Figure 5

Open in a new tab

Correlation analysis of root-bleeding sap, nutrient contribution, and grain yield (values are the average in both years). CAAT, contribution rate of nutrient (P or K) accumulation amount post-silking.

Discussion

The root system is an essential source for uptake of water and nutrients, and its physiological activity is closely correlated to the development of the plant's parts above ground and the yield formation of crops (Yang et al., 2004; Fan et al., 2021). Root-bleeding sap reflects the capacity of roots to uptake water and nutrients, and it represents the physiological activity of the root system (Ansari et al., 2004; Wang P. et al., 2019). It has been found that root growth is closely associated with root-bleeding sap rate. The reduction of root quality in high-density planting seriously affects yield formation (Yu et al., 2019; Liu Z. et al., 2021). A balanced application of nitrogen can enhance root activity by supplying nutrients to form a robust root system (Wang H. et al., 2019). Equally, chemical control can optimize root morphological construction and improve the absorption ability of the root system (Lin et al., 2019).

In this study, N200 application in combination with chemical control significantly enhanced the rate of root-bleeding sap to enhance the strength of root activity. The nutrient concentrations in root-bleeding sap are closely associated with the absorption and transformation capacity of the root system, and its variation reflects the interaction intensity of nutrients in the aboveground and underground plant parts (Nishanth and Biswas, 2008). The xylem sap can transport nutrients upward to the aboveground tissues. The nutrient concentrations in root-bleeding sap are generally recognized as indicators of the plant's nutrient status (Ansari et al., 2004). Amino acids are essential for maintaining plant growth and, when contained in root-bleeding sap, promote root growth (Zheng et al., 2020). Mineral nutrient concentration is considered a primary factor for plant growth and grain yield. The delivery rate of mineral nutrients primarily depends on the root physiological activity and the nutrient concentrations across the root zone (Liang et al., 2020). High-density planting reduces root physiological activity and intensifies the depletion of nutrients in the root zone, resulting in the reduction of free amino acids and mineral nutrient concentrations (Yu et al., 2012; Liang et al., 2020). The content of free amino acids varied significantly with different nitrogen nutrient levels. It is believed that the delivery rate of free amino acids in root-bleeding sap increases with an increasing rate of nitrogen application (Li et al., 2009). In the present study, we found that N200 application combined with chemical control increased the delivery rate of amino acids and mineral nutrients in root-bleeding sap. The proper cultivation measure can improve the capacity of roots to absorb, synthesize, and transport carbohydrates, auxin, and other substances, thereby promoting root activity and root growth (Wang H. et al., 2019). The increase in root activity and its capacity for water and nutrients could lay the foundation for the increase in maize yield under high-density planting.

Nutrient absorption and accumulation are the basis of crop yield formation, and it directly affects the growth process of crops (Wu et al., 2018; Gorlach et al., 2021). Nutrient absorption in maize increases with plant growth. Sufficient nutrient supply during the growth period is the key to obtaining a high maize yield (Ray et al., 2020). Phosphorus and potassium are essential macronutrient elements for maize growth, which play an important role in the yield potential (Wu et al., 2015; Zhan et al., 2016). Nitrogen fertilizer is recognized to be an important factor affecting nutrient accumulation and transportation in addition to chemical control, which also impacts plant nutrient absorption capability (Van Oosten et al., 2019; Ray et al., 2020). In the present study, chemical control increased P and K accumulation amounts at different N levels. P and K accumulation amount increased with increasing level of N application, but the differences between N200 and N300 treatments were not significant. The nutrient accumulation by plants during different growth stages may impact crop yield. It is believed that the high nutrient absorption of N, P, and K in the middle growth stage of crops can promote pre-anthesis non-structural carbohydrate (NSC) reserves in the stem and accordingly enhance grain sink strength during grain filling (Fu et al., 2011; Li W. H. et al., 2012). Liu et al. (2019) considered that the P and K nutrient absorption in the late growth stage played an important role in improving maize production. In the present study, chemical control and nitrogen fertilizer greatly influenced the proportion of P and K accumulation during different growth stages in maize plants. Similarly, chemical control significantly increased the proportion of P and K accumulation during different growth stages except for the VE-JT and JT-TS stages. The proportion of P and K accumulation after the tasseling stage was obviously increased with increasing levels of N application. Chemical control and nitrogen fertilizer application substantially improved the CAAT of P and K in maize plants, and the highest CAAT of P and K were recorded under N200 application in combination with chemical control. The above results indicate that chemical control and nitrogen fertilizers can improve nutrient accumulation in maize after tasseling and increase the transfer of nutrients from vegetative organs to grains, consequently providing a material basis for yield formation. This result is similar to the study by Ray et al. (2020), which found that appropriate nutrient accumulation and translocation after silking created good conditions for maintaining the supply of nutrients to the grains, resulting in increased yields.

Carbon and nitrogen metabolism determines the level of crop production and function to provide the main energy and basic nutrients for plants (Cui et al., 2019). RuBPCase, PEPCase, NR, and GS are key enzymes involved in carbon and nitrogen metabolism in plants. In the present study, chemical control combined with N200 treatment increased RuBPCase, PEPCase, NR, and GS activities, leading to more assimilate accumulation and higher grain yield (Cheng et al., 2019; Yang et al., 2020). The plants maintained a high carbon and nitrogen metabolism and nutrient accumulation, which was the basis for assimilate accumulation in the grains. Main enzymes such as GS, GPT, and GDH are involved in the nitrogen metabolism in grains, and their activities directly affect the synthesis of amino acids and protein in grains (Wang et al., 2016). The N200 application, in combination with chemical control, significantly increased amino acid and protein content in grains, which in turn increased GS, GPT, and GDH activities. Chemical control and N200 treatments also increased the sucrose and soluble sugar contents of grains. This may be due to its association with higher sucrose metabolism and key enzyme activities (Kaur et al., 2018).

Increasing planting density is one of the important practices to increase maize yield per unit area in agricultural production (Tang et al., 2018). However, high-density planting intensifies the competition for light, nutrients, moisture, and space between maize plants, which restricts the growth of shoot and root systems, resulting in reduced crop yield (Rossini et al., 2011). The root system is the crop organ responsible for the uptake of nutrients, and a higher root activity enhances the nutrient absorption capacity in the root system (Yang et al., 2004). In the present study, the rate of root-bleeding sap was positively correlated with the contribution rate of nutrient (P or K) accumulation amount post-silking. It showed that the enhancement of root activity might be an effective method to develop the absorption and utilization capacity of P and K. Maintaining a relatively high level of root activity is an important approach to improving maize production. Niu et al. (2020) showed that increased root activity ensured the availability of soil nutrients and boosted photosynthetic capacity and biomass production, which are critical for grain filling and yield formation. In the present study, the grain yield was positively correlated with the rate of root-bleeding sap, the delivery rate of amino acids and mineral nutrients in bleeding sap, and the CAAT of P and K. It further confirmed that maintaining higher root activity and absorption and utilization capacity of P and K are the important approaches to obtaining high yields. Establishing a well-developed root system and efficient plant population can promote photosynthate production and nutrient accumulation and improve phosphorus and potassium distribution ratios after silking. Excessive nutrient transfer after silking usually affects the photosynthesis in leaves at a later growth stage, resulting in acceleration of leaf and root senescence and limiting yield improvement. However, deficient nutrient transfer after silking is harmful to grain filling, making it difficult to achieve a high yield. Therefore, appropriate cultivation methods can coordinate nutrient transfer and nutrient accumulation after silking and optimize the source-sink relationship, which plays an important role in improving yield. Our study on maize cultivation in Northeast China indicated that N200 combined with chemical control could optimize P and K absorption and translocation in the later growth stage by increasing root activity, thereby improving grain yield and quality.

Conclusion

N200 application in combination with chemical control significantly increased the root-bleeding sap rate, amino acid delivery rate, and mineral nutrient delivery rate. It promoted the accumulation and translocation of P and K nutrients after the tasseling stage, and as a result, it provided a material basis for yield formation. Moreover, N200 combined with chemical control obviously enhanced enzyme activities of carbon and nitrogen metabolism in leaves, increased nitrogen metabolism enzyme activities in grains during the early and middle grain filling stage, and improved amino acid and protein content in grains, thereby increasing the grain yield and quality of maize in high-density planting. The schematic representation indicates that nitrogen fertilizers and chemical control increased the grain yield and quality by optimizing root-bleeding sap, nutrient accumulation and transport, photosynthesis, and N metabolism in maize under high-density planting (Figure 6). Therefore, attention should be paid to promoting nitrogen fertilizer and chemical control management in high-density planting of maize in future agricultural production in Northeast China as it plays a crucial role in improving maize yield and quality.

Figure 6.

Figure 6

Open in a new tab

The schematic representation of nitrogen fertilizers and chemical control regulated maize yield. The red arrows (↑) and the blue arrows (↓) represent the positive and passive roles of treatment, respectively.

Data Availability Statement

The original contributions presented in the study are included in the article/supplementary material, further inquiries can be directed to the corresponding author/s.

Author Contributions

XL and LZ collected and analyzed the samples and wrote the manuscript. YY, CQ, and CoL contributed to the writing and editing of the manuscript. SW, CaL, and WG contributed to the design of the work and analysis and revised the manuscript. All authors read and approved the article.

Funding

This study was financially supported by the National Key Research and Development Program of China (2016YFD0300103) and the National Modern Agriculture Industry Technology System (CARS-02-12).

Conflict of Interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Publisher's Note

All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.

References

  1. Ansari T. H., Yamamoto Y., Yoshida T., Sakagami K., Miyazaki A. (2004). Relation between bleeding rate during panicle formation stage and sink size in rice plant. Soil Sci. Plant Nutr. 50, 57–66. 10.1080/00380768.2004.10408452 [DOI] [Google Scholar]
  2. AOAC (1975). Official Methods of Analysis, 12th Edn. Washington, DC: Association of Official Agricultural Chemists. [Google Scholar]
  3. AOAC (1984). Official Methods of Analysis, 14th Edn. Arlington, VA: Association of Official Analytical Chemists. [Google Scholar]
  4. Arnozis P. A., Nelemans J. A., Findenegg G. R. (1988). Phosphoenolpyruvate carboxylase activity in plants grown with either NO3- or NH4+ as inorganic nitrogen source. J. Plant Physiol. 132, 23–27. 10.1016/S0176-1617(88)80177-9 [DOI] [Google Scholar]
  5. Boros D., Slominski B. A., Guenter W., Campbell L. D., Jones O. (2004). Wheat by-products in poultry nutrition. Part II. Nutritive value of wheat screenings, bakery by-products and wheat mill run and their improved utilization by enzyme supplementation. Can. J. Anim. Sci. 84, 429–435. 10.4141/A03-113 [DOI] [Google Scholar]
  6. Canovas F. M., Canton F. R., Gallardo F., Garciagutierrez A., Devicente A. (1991). Accumulation of glutamine-synthetase during early development of maritime pine (Pinus pinaster) seedlings. Planta 185, 372–378. 10.1007/BF00201059 [DOI] [PubMed] [Google Scholar]
  7. Chen P. P., Gu X. B., Li Y. N., Qiao L. R., Li Y. P., Fang H., et al. (2022). Effects of residual film on maize root distribution, yield and water use efficiency in Northwest China. Agric. Water Manag. 260, 107289. 10.1016/j.agwat.2021.107289 [DOI] [Google Scholar]
  8. Cheng Y. Y., Wang Y., Han Y. L., Li D. Y., Zhang Z. K., Zhu X. Q., et al. (2019). The stimulatory effects of nanochitin whisker on carbon and nitrogen metabolism and on the enhancement of grain yield and crude protein of winter wheat. Molecules 24, 1752. 10.3390/molecules24091752 [DOI] [PMC free article] [PubMed] [Google Scholar]
  9. Cui G. C., Zhang Y., Zhang W. J., Lang D. Y., Zhang X. J., Li Z. X., et al. (2019). Response of carbon and nitrogen metabolism and secondary metabolites to drought stress and salt stress in plants. J. Plant Biol. 62, 387–399. 10.1007/s12374-019-0257-1 [DOI] [Google Scholar]
  10. Fan Y. F., Gao J. L., Sun J. Y., Liu J., Su Z. J., Wang Z. G., et al. (2021). Effects of straw returning and potassium fertilizer application on root characteristics and yield of spring maize in China inner Mongolia. Agron. J. 113, 4369–4385. 10.1002/agj2.20742 [DOI] [Google Scholar]
  11. Fu J., Huang Z. H., Wang Z. Q., Yang J. C., Zhang J. H. (2011). Pre-anthesis non-structural carbohydrate reserve in the stem enhances the sink strength of inferior spikelets during grain filling of rice. Field Crops Res. 123, 170–182. 10.1016/j.fcr.2011.05.015 [DOI] [Google Scholar]
  12. Gao J., Lei M., Yang L. J., Wang P., Tao H. B., Huang S. B. (2021). Reduced row spacing improved yield by optimizing root distribution in maize. Eur. J. Agron. 127, 126291. 10.1016/j.eja.2021.126291 [DOI] [Google Scholar]
  13. Gorlach B. M., Henningsen J. N., Mackens J. T., Muhling K. H. (2021). Evaluation of maize growth following early season foliar P supply of various fertilizer formulations and in relation to nutritional status. Agronomy 11, 727. 10.3390/agronomy11040727 [DOI] [Google Scholar]
  14. Hutsch B. W., Schubert S. (2017). Maize harvest index and water use efficiency can be improved by inhibition of gibberellin biosynthesis. J. Agron. Crop Sci. 204, 209–218. 10.1111/jac.12250 [DOI] [Google Scholar]
  15. Iqbal S., Akhtar J., Naz T., Riaz U., Hussain S., Mazhar Z., et al. (2020). Root morphological adjustments of crops to improve nutrient use efficiency in limited environments. Commun. Soil Sci. Plan. 51, 2452–2465. 10.1080/00103624.2020.1836199 [DOI] [Google Scholar]
  16. Kaur M., Sharma S., Singh D. (2018). Influence of selenium on carbohydrate accumulation in developing wheat grains. Commun. Soil Sci. Plan. 49, 1650–1659. 10.1080/00103624.2018.1474903 [DOI] [Google Scholar]
  17. Lewis O. A. M., Watson E. F., Hewitt E. J. (1982). Determination of nitrate reductase activity in barley leaves and roots. Ann. Bot. 49, 31–37. 10.1093/oxfordjournals.aob.a086227 [DOI] [Google Scholar]
  18. Li G. H., Cheng Q., Li L., Lu D. L., Lu W. P. (2021). N, P and K use efficiency and maize yield responses to fertilization modes and densities. J. Integr. Agric. 20, 78–86. 10.1016/S2095-3119(20)63214-2 [DOI] [Google Scholar]
  19. Li G. H., Wang L. F., Li L., Lu D. L., Lu W. P. (2020). Effects of fertilizer management strategies on maize yield and nitrogen use efficiencies under different densities. Agron. J. 112, 368–381. 10.1002/agj2.20075 [DOI] [Google Scholar]
  20. Li G. H., Zhao B., Dong S. T., Zhang J. W., Liu P., Ren B. Z., et al. (2019). Morphological and physiological characteristics of maize roots in response to controlled-release urea under different soil moisture conditions. Agron. J. 111, 1849–1864. 10.2134/agronj2018.08.0508 [DOI] [Google Scholar]
  21. Li H. W., Liu L. J., Wang Z. Q., Yang J. C., Zhang J. H. (2012). Agronomic and physiological performance of high-yielding wheat and rice in the lower reaches of Yangtze River of China. Field Crops Res. 133, 119–129. 10.1016/j.fcr.2012.04.005 [DOI] [Google Scholar]
  22. Li S. X., Wang Z. H., Malhi S. S., Li S. Q., Gao Y. J., Tian X. H. (2009). Nutrient and water management effects on crop production: and nutrient and water use efficiency in dryland areas of China. Adv. Agron. 102, 223–265. 10.1016/S0065-2113(09)01007-4 [DOI] [Google Scholar]
  23. Li W. H., Hou M. J., Cao Y. S., Song H., Shi T. Y., Gao X. W., et al. (2012). Determination of 20 free amino acids in asparagus tin by high-performance liquid chromatographic method after pre-column derivatization. Food Anal. Methods 5, 62–68. 10.1007/s12161-011-9197-1 [DOI] [Google Scholar]
  24. Liang X. Y., Guo F., Feng Y., Zhang J. L., Yang S., Meng J. J., et al. (2020). Single-seed sowing increased pod yield at a reduced seeding rate by improving root physiological state of Arachis hypogaea. J. Integr. Agric. 19, 1019–1032. 10.1016/S2095-3119(19)62712-7 [DOI] [Google Scholar]
  25. Lilley R. M., Walker D. A. (1974). An improved spectrophotometric assay for ribulosebisphosphate carboxylase. BBA-Enzymology 358, 226–229. 10.1016/0005-2744(74)90274-5 [DOI] [PubMed] [Google Scholar]
  26. Lin Y. R., Watts D. B., Kloepper J. W., Feng Y. C., Torbert H. A. (2019). Influence of plant growth-promoting rhizobacteria on corn growth under drought stress. Commun. Soil Sci. Plan. 51, 250–264. 10.1080/00103624.2019.170532933083600 [DOI] [Google Scholar]
  27. Liu A. H., Ye Z. C. (2020). “China Agriculture Yearbook” in China Statistical Yearbook (Beijing: China Agriculture Press; ), 373–402. (in Chinese). [Google Scholar]
  28. Liu H. R., Song H. X., Liu D. P., Guan C. Y., Liu Q., Chen S. Y. (2007). Dynamics changes of soluble sugar and free amino acid contents in stem and leaf of different oilseed rape varieties (in Chinese with English abstract). Acta Agri Boreali-occidentalis Sin. 16, 123–126. 10.3969/j.issn.1004-1389.2007.01.029 [DOI] [Google Scholar]
  29. Liu K., Ma B. L., Luan L. M., Li C. H. (2011). Nitrogen, phosphorus, and potassium nutrient effects on grain filling and yield of high-yielding summer corn. J. Plant Nutr. 34, 1516–1531. 10.1080/01904167.2011.585208 [DOI] [Google Scholar]
  30. Liu M. L., Wang C., Wang F. Y., Xie Y. J. (2019). Maize (Zea mays) growth and nutrient uptake following integrated improvement of vermicompost and humic acid fertilizer on coastal saline soil. Appl. Soil Ecol. 142, 147–154. 10.1016/j.apsoil.2019.04.024 [DOI] [Google Scholar]
  31. Liu S. Q., Jian S. L., Li X. N., Wang Y. (2021). Wide-narrow row planting pattern increases root lodging resistance by adjusting root architecture and root physiological activity in maize (Zea mays L.) in Northeast China. Agriculture 11, 517. 10.3390/agriculture11060517 [DOI] [Google Scholar]
  32. Liu Z., Ying H., Chen M., Liu Z. T., Ying H., Chen M. Y., et al. (2021). Optimization of China's maize and soy production can ensure feed sufficiency at lower nitrogen and carbon footprints. Nat. Food 2, 426–433. 10.1038/s43016-021-00300-1 [DOI] [PubMed] [Google Scholar]
  33. Liu Z., Zhu K. L., Dong S. T., Liu P., Zhao B., Zhang J. W. (2017). Effects of integrated agronomic practices management on root growth and development of summer maize. Eur. J. Agron. 84, 140–151. 10.1016/j.eja.2016.12.006 [DOI] [Google Scholar]
  34. Luo N., Wang X. Y., Hou J. M., Wang Y. Y., Wang P., Meng Q. F. (2020). Agronomic optimal plant density for yield improvement in the major maize regions of China. Crop Sci. 60, 1580–1590. 10.1002/csc2.20000 [DOI] [Google Scholar]
  35. Murphy J., Riley J. P. (1962). A modified single solution method for the determination of phosphate in natural waters. Anal. Chim. Acta 27, 31–36. 10.1016/S0003-2670(00)88444-5 [DOI] [Google Scholar]
  36. Nawaz M., Ishaq S., Ishaq H., Khan N., Iqbal N., Ali S., et al. (2020). Salicylic acid improves boron toxicity tolerance by modulating the physio-biochemical characteristics of maize (Zea mays L.) at an early growth stage. Agronomy 10, 2013. 10.3390/agronomy10122013 [DOI] [Google Scholar]
  37. Nishanth D., Biswas D. R. (2008). Kinetics of phosphorus and potassium release from rock phosphate and waste mica enriched compost and their effect on yield and nutrient uptake by wheat (Triticum aestivum). Bioresour. Technol. 99, 3342–3353. 10.1016/j.biortech.2007.08.025 [DOI] [PubMed] [Google Scholar]
  38. Niu L., Yan Y. Y., Hou P., Bai W. B., Zhao R. L., Wang Y. H., et al. (2020). Influence of plastic film mulching and planting density on yield, leaf anatomy, and root characteristics of maize on the Loess Plateau. Crop J. 8, 548–564. 10.1016/j.cj.2019.12.002 [DOI] [Google Scholar]
  39. Noguchi A., Kageyama M., Shinmachi F., Schmidhalter U., Hasegawa I. (2005). Potential for using plant xylem sap to evaluate inorganic nutrient availability in soil—I. Influence of inorganic nutrients present in the rhizosphere on those in the xylem sap of Luffa cylindrica Roem. Soil Sci. Plant Nutr. 51, 333–341. 10.1111/j.1747-0765.2005.tb00038.x [DOI] [Google Scholar]
  40. Palacios-Rojas N., McCulley L., Kaeppler M., Titcomb T. J., Gunaratna N. S., Lopez-Ridaura S., et al. (2020). Mining maize diversity and improving its nutritional aspects within agro-food systems. Compr. Rev. Food Sci. Food Sci. Food Saf. 19, 1809–1834. 10.1111/1541-4337.12552 [DOI] [PubMed] [Google Scholar]
  41. Ray K., Banerjee H., Dutta S., Sarkar S., Murrell T. S., Singh V. K., et al. (2020). Macronutrient management effects on nutrient accumulation, partitioning, remobilization, and yield of hybrid maize cultivars. Front. Plant Sci. 11:1307. 10.3389/fpls.2020.01307 [DOI] [PMC free article] [PubMed] [Google Scholar]
  42. Reddy Y. R., Ravi D., Reddy C. R., Prasad K. V. S. V., Zaidi P. H., Vinayan M. T., et al. (2013). A note on the correlations between maize grain and maize stover quantitative and qualitative traits and the implications for whole maize plant optimization. Field Crops Res. 153, 63–69. 10.1016/j.fcr.2013.06.013 [DOI] [Google Scholar]
  43. Rossini M. A., Maddonni G. A., Otegui M. E. (2011). Inter-plant competition for resources in maize crops grown under contrasting nitrogen supply and density: variability in plant and ear growth. Field Crops Res. 121, 373–380. 10.1016/j.fcr.2011.01.003 [DOI] [Google Scholar]
  44. Shahzad A. N., Fatima A., Sarwar N., Bashir S., Rizwan M., Qayyum M. F., et al. (2017). Foliar application of potassium sulfate partially alleviates pre-anthesis drought-induced kernel abortion in maize. Int. J. Agric. Biol. 19, 495–501. 10.17957/IJAB/15.0317 [DOI] [Google Scholar]
  45. Shao H., Xia T. T., Wu D. L., Chen F. J., Mi G. H. (2018). Root growth and root system architecture of field-grown maize in response to high planting density. Plant Soil 430, 395–411. 10.1007/s11104-018-3720-8 [DOI] [Google Scholar]
  46. Stutts L., Wang Y., Stapleton A. E. (2018). Plant growth regulators ameliorate or exacerbate abiotic, biotic and combined stress interaction effects on Zea mays kernel weight with inbred-specific patterns. Environ. Exp. Bot. 147, 179–188. 10.1016/j.envexpbot.2017.12.012 [DOI] [Google Scholar]
  47. Tang L. Y., Ma W., Noor M. A., Li L. L., Hou H. P., Zhang X. Y., et al. (2018). Density resistance evaluation of maize varieties through new “Density-Yield Model” and quantification of varietal response to gradual planting density pressure. Sci. Rep. 8:17281. 10.1038/s41598-018-35275-w [DOI] [PMC free article] [PubMed] [Google Scholar]
  48. Van Oosten M. J., Dell'Aversana E., Ruggiero A., Cirillo V., Gibon Y., Woodrow P., et al. (2019). Omeprazole treatment enhances nitrogen use efficiency through increased nitrogen uptake and assimilation in corn. Front. Plant Sci. 10:1507. 10.3389/fpls.2019.01507 [DOI] [PMC free article] [PubMed] [Google Scholar]
  49. Van H. E. (1968). Direct microdetermination of sucrose. Anal. Biochem. 22, 280–283. 10.1016/0003-2697(68)90317-5 [DOI] [PubMed] [Google Scholar]
  50. Wang C., Ning P. (2019). Post-silking phosphorus recycling and carbon partitioning in maize under low to high phosphorus inputs and their effects on grain yield. Front. Plant Sci. 10:784. 10.3389/fpls.2019.00784 [DOI] [PMC free article] [PubMed] [Google Scholar]
  51. Wang F., Gao J. W., Liu Y., Tian Z. W., Muhammad A., Zhang Y. X., et al. (2016). Higher ammonium transamination capacity can alleviate glutamate inhibition on winter wheat (Triticum aestivum L.) root growth under high ammonium stress. PLoS ONE 11:e0160997. 10.1371/journal.pone.0160997 [DOI] [PMC free article] [PubMed] [Google Scholar]
  52. Wang H., Xu R. R., Li Y., Yang L. Y., Shi W., Liu Y. J., et al. (2019). Enhance root-bleeding sap flow and root lodging resistance of maize under a combination of nitrogen strategies and farming practices. Agric. Water Manag. 224, 105742. 10.1016/j.agwat.2019.105742 [DOI] [Google Scholar]
  53. Wang P., Wang Z. K., Pan Q. C., Sun X. C., Chen H., Chen F. J., et al. (2019). Increased biomass accumulation in maize grown in mixed nitrogen supply is mediated by auxin synthesis. J. Exp. Bot. 70, 1859–1873. 10.1093/jxb/erz047 [DOI] [PMC free article] [PubMed] [Google Scholar]
  54. Wolf B. (1982). A comprehensive systems of leaf analysis and its use for diagnosing crop nutrients status. Commun. Soil Sci. Plant. 13, 1035–1059. 10.1080/00103628209367332 [DOI] [Google Scholar]
  55. Wu H., Xiang J., Zhang Y. P., Zhang Y. K., Peng S. B., Chen H. Z., et al. (2018). Effects ofpost-anthesis nitrogen uptake and translocation on photosynthetic production and rice yield. Sci. Rep. 8, 12891. 10.1038/s41598-018-31267-y [DOI] [PMC free article] [PubMed] [Google Scholar]
  56. Wu L. Q., Cui Z. L., Chen X. P., Yue S. C., Sun Y. X., Zhao R. F., et al. (2015). Change in phosphorus requirement with increasing grain yield for Chinese maize production. Field Crops Res. 180, 216–220. 10.1016/j.fcr.2015.06.001 [DOI] [Google Scholar]
  57. Xie W. J., Wang H. Y., Xia J. B., Yao Z. G. (2011). Influence of N, P, and K application on Zea mays L. growth and Cu and Pb accumulation. Plant Soil Environ. 57, 128–134. 10.17221/225/2010-PSE [DOI] [Google Scholar]
  58. Xu C. L., Tao H. B., Tian B. J., Gao Y. B., Ren J. H., Wang P. (2016). Limited-irrigation improves water use efficiency and soil reservoir capacity through regulating root and canopy growth of winter wheat. Field Crops Res. 196, 268–275. 10.1016/j.fcr.2016.07.009 [DOI] [Google Scholar]
  59. Xu L. Z., Niu J. F., Li C. J., Zhang F. S. (2009). Growth, nitrogen uptake and flow in maize plants affected by root growth restriction. J. Integr. Plant Biol. 51, 689–697. 10.1111/j.1744-7909.2009.00843.x [DOI] [PubMed] [Google Scholar]
  60. Yang C. M., Yang L. Z., Yang Y. X., Zhu O. Y. (2004). Rice root growth and nutrient uptake as influenced by organic manure in continuously and alternately flooded paddy soils. Agric. Water Manag. 70, 67–81. 10.1016/j.agwat.2004.05.003 [DOI] [Google Scholar]
  61. Yang H., Gu X. T., Ding M. Q., Lu W. P., Lu D. L. (2020). Weakened carbon and nitrogen metabolisms under post-silking heat stress reduce the yield and dry matter accumulation in waxy maize. J. Integr. Agric. 19, 78–88. 10.1016/S2095-3119(19)62622-5 [DOI] [Google Scholar]
  62. Yu X. F., Zhang Q., Gao J. L., Wang Z. G., Borjigin Q., Hu S. P., et al. (2019). Planting density tolerance of high-yielding maize and the mechanisms underlying yield improvement with subsoiling and increased planting density. Agronomy 9, 370. 10.3390/agronomy9070370 [DOI] [Google Scholar]
  63. Yu X. M., Wang B., Zhang C. X., Xu W. P., He J. J. (2012). Effect of root restriction on nitrogen levels and glutamine synthetase activity in “Kyoho” grapevines. Sci. Hortic. 137, 156–163. 10.1016/j.scienta.2012.01.025 [DOI] [Google Scholar]
  64. Zhan A., Zou C. Q., Ye Y. L., Liu Z. H., Cui Z. L., Chen X. P. (2016). Estimating on-farm wheat yield response to potassium and potassium uptake requirement in China. Field Crops Res. 191, 13–19. 10.1016/j.fcr.2016.04.001 [DOI] [Google Scholar]
  65. Zhang Q., Zhang L. Z., Evers J., Werf W. V. D., Zhang W. Q., Duan L. S. (2014). Maize yield and quality in response to plant density and application of a novel plant growth regulator. Field Crops Res. 164, 82–89. 10.1016/j.fcr.2014.06.006 [DOI] [Google Scholar]
  66. Zhang Z., Yu Z. W., Zhang Y. L., Shi Y. (2021). Optimized nitrogen fertilizer application strategies under supplementary irrigation improved winter wheat (Triticum aestivum L.) yield and grain protein yield. PeerJ 9, e11467. 10.7717/peerj.11467 [DOI] [PMC free article] [PubMed] [Google Scholar]
  67. Zheng T., Haider M. S., Zhang K. K., Jia H. F., Fang J. G. (2020). Biological and functional properties of xylem sap extracted from grapevine (cv. Rosario Bianco). Sci. Hortic. 272, 109563. 10.1016/j.scienta.2020.109563 [DOI] [Google Scholar]

Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Data Availability Statement

The original contributions presented in the study are included in the article/supplementary material, further inquiries can be directed to the corresponding author/s.

Articles from Frontiers in Plant Science are provided here courtesy of Frontiers Media SA

RESOURCES