Improving soil water dynamics and crop productivity through conservation tillage in arid regions

Abstract

Exploring the impact of different tillage practices on soil moisture retention and crop yield in dryland winter wheat- spring maize rotation on the Loess Plateau is crucial for enhancing rainfall utilization and advancing tillage systems in arid agricultural regions. A long-term field experiment was conducted from 2019 to 2021 in the Weibei dryland area of the Loess Plateau to investigate the effects of conservation tillage. Continuous tillage (CC) was used as the control, with three alternative methods: no-tillage (NN), subsoiling (SS), and a combination of no-tillage and subsoiling (NS). The study assessed the impact of these tillage practices on soil water retention, bulk density, relative chlorophyll content, crop yield, and water use efficiency during both the fallow period and the growing seasons of winter wheat and spring maize. The results revealed the following: (1) All treatments effectively reduced soil bulk density in the 0–60 cm soil layer relative to pre-experiment levels and increased soil porosity. Among the treatments, NS was the most effective, reducing the average bulk density in the 0–60 cm layer by 0.1–0.2 g cm⁻³ and increasing porosity by 2.0-5.5% compared to the other treatments. (2) During the fallow period, tillage treatments significantly enhanced soil water content and storage compared to CC, with NN and NS treatments showing superior water retention effects. (3) In the winter wheat growing season, the average soil water content in the 0–200 cm layer for the NN, SS, and NS treatments was 4.8%, 5.4%, and 3.5% higher than that of CC, respectively. During the spring maize growing season, the increases were 49.3 mm, 17.7 mm, and 36.3 mm, respectively. All tillage treatments resulted in higher soil water storage in the 0–200 cm layer compared to CC, with NN being the most effective during the winter wheat season and SS during the spring maize season. (4) Compared to CC, all tillage treatments improved SPAD values, with NS showing the most significant effect. (5) All treatments increased the yields of both winter wheat and spring maize compared to the control, with increases of 5.4-10.0% for winter wheat and 7.3-18.7% for spring maize. Notably, NS significantly boosted crop yields. Water use efficiency improved by 1.2-6.0% for winter wheat and 5.5-31.3% for spring maize, with SS improving water use efficiency for winter wheat and NS for spring maize. In conclusion, the combination of no-tillage and subsoiling significantly improves soil quality, crop yield, and water use efficiency in the drylands of the Loess Plateau. This makes it a promising tillage practice for the sustainable development of dryland agriculture.

Introduction

The Loess Plateau is a representative dryland agricultural region in China, where the predominant cropping system is characterized by monocultures of winter wheat and spring maize. Agricultural productivity in this region remains relatively low, with soil conditions that are neither highly productive nor stable. Additionally, the prolonged use of intensive traditional tillage practices has led to inefficient utilization of water and soil resources, increasing the risk of economic losses. These challenges have imposed significant constraints on the sustainable development of regional agriculture¹. As a result, improving soil fertility and water use efficiency to achieve high and stable crop yields has become an urgent priority for the region’s agricultural development.

Tillage is a direct method for altering the physical, chemical, and biological properties of soil, which in turn affects nutrient cycling within farmland ecosystems. Conservation tillage practices can improve soil structure, enhance water retention capacity, and increase crop yields, thereby facilitating nutrient and water uptake by crop roots and promoting sustainable agricultural development^2,3. Techniques such as no-tillage and subsoiling, when combined with straw return, help reduce surface exposure, suppress soil evaporation, increase the infiltration of local precipitation, and optimize soil conditions. These practices contribute to improved crop yields and water use efficiency. Straw return not only improves soil moisture conditions on the surface but also enhances crop water use efficiency, stimulating crop growth and development, ultimately leading to higher yields⁴. Sonme research demonstrated that conservation tillage significantly increased soil moisture levels during the wheat growth period compared to conventional tillage, under various tillage methods combined with straw retention, soil water storage during the maize growth period increased by 4.8% with no-tillage and 1.2% with subsoiling relative to traditional tillage^5,6. In Northeast China’s black soil, no-tillage has been shown to enhance soil organic matter content and moisture, which in turn improves nitrogen transformation processes⁷. Similarly, practices such as no-tillage or subsoiling combined with straw mulching have been found to improve soil moisture conditions during potato growth, optimize water use, and increase both yield and water use efficiency⁸. Tillage practices that incorporate straw return have also been observed to increase soil water content, yield, and water use efficiency during the maize seedling stage by 1.9%, 12.2%, and 5.4%, respectively⁹. Reduced tillage has been associated with improvements in maize grain number, 100-grain weight, and overall yield¹⁰. Additionally, while conservation tillage may reduce maize emergence rates, it does not appear to negatively affect final yield¹¹.

While numerous studies have explored the effects of conservation tillage on soil physicochemical properties and crop monocultures, limited research has focused on how different tillage patterns and rotation systems can synergistically optimize soil water status and crop growth characteristics in the Weibei dry farming region^5–12. Most existing studies are restricted to single-crop systems and fail to investigate the vertical distribution of soil water and its variation patterns at different growth stages. This gap in research makes it difficult to fully understand the long-term impacts of diverse tillage practices on crop yield and resource use efficiency. This study uniquely integrates multiple conservation tillage measures to systematically evaluate soil water dynamics across different soil layers at various growth stages under the wheat-maize rotation system. It also examines their effects on crop biological traits and yield. By doing so, this work fills a crucial gap in optimizing tillage models in the Weibei dry farming region and provides more targeted technical approaches and theoretical foundations for the sustainable development of regional agriculture.

Materials and methods

Overview of the experimental area

The experiment was conducted at the Fuping Experimental Base, located in Chuyuan Village, Ducun Town, Fuping County, Weinan City, Shaanxi Province (109°11′N, 34°42′E) (Fig. 1). The region is characterized by a warm temperate semi-humid climate, with an average annual rainfall of 473 mm. Rainfall exhibits significant variability both interannually and seasonally, with 49% of the total annual precipitation occurring between July and September. Annual evaporation rates range from 1,000 to 1,300 mm, and the average annual temperature is 13 °C, creating favorable conditions for crop growth. These climatic conditions align well with the primary growing period of spring maize. Long-term precipitation data is provided in Table 1. The soil type is the commonly found dark loessial soils in the region, which has excellent water retention and nutrient preservation properties¹³. The cropping system used in this experiment is a winter wheat-spring maize rotation over three ymaizes with two crops. The contents of sand, silt and clay in the topsoil were 26.8%, 42.0% and 21.0%, respectively. The contents of sand, silt and clay in plough bottom were 33.6%, 39.0% and 25.7%, respectively.

Fig. 1.

Location of the Experimental Area. Through the utilization of a three-dimensional map (V10.3.0, available at https://www.ovital.com/download/), satellite image data was accessed (provided by Map World Co., Ltd., with authorization number GS (2024) 0568). Subsequently, the data was processed using ArcGIS 10.3 software (accessible via https://www1.bjsdxd.cn/tem.html?soft=gis-jb61d), resulting in the generation of a figure rendered with a satellite image map effect.

Table 1.

Monthly rainfall from 2019 to 2021.

Ymaize	Month
	1	2	3	4	5	6	7	8	9	10	11	12
2019	28.8	8.0	12.7	31.4	23.2	95.4	54.1	123.2	64.9	19.3	13.4	0.0
2020	2.4	25.0	18.4	14.7	131.5	48.2	48.5	85.2	54.5	31	33.8	4.1
2021	0.0	18.7	12.4	38.1	26.0	38.8	145.2	131.1	66.5	34.2	1.2	0.0
Average	5.5	15.4	20.2	22.4	46.7	50.1	98.9	102.8	85.8	42.8	25.6	2.8

Experiment design

The experiment was conducted from September 2019 to September 2021 under a winter wheat-spring maize rotation system. Soil parameters measured prior to 2019 served as the pre-treatment baselines. A completely randomized block design was used, consisting of three replications (blocks) for each of the four tillage treatments, resulting in a total of 12 experimental plots (each 25 m × 4 m = 100 m²). Blocks were arranged to account for spatial variability, and treatments were randomly assigned within each block. Tillage treatments were applied as fixed factors to evaluate their deterministic impact on soil properties (Table 2). Blocks were treated as a random effect to account for variability among replicates, while time was modeled as a repeated-measures random factor to address temporal autocorrelation in the measurements. Prior to the experiment (2019), all plots were uniformly managed under conventional plowing (Fig. 2). After harvest, straw was shredded and returned to the field, followed immediately by the application of one of three conservation tillage treatments (Table 2).

Table 2.

Different tillage treatments.

Tillage treatments	Methods
no-tillage: NN	Each year, after the crop harvest, all straw was shredded and spread over the soil surface without any additional measures, maintaining straw cover on the soil surface throughout the fallow period.
subsoiling tillage: SS	Each year, after the crop harvest, all straw was shredded and spread over the soil surface. Single deep loosening was performed with a plowing depth of 30–35 cm and a width of 40–60 cm, maintaining straw cover on the soil surface throughout the fallow period.
no-tillage- subsoiling tillage: NS	After crop harvest, a no-till treatment and deep loosening treatment were alternated annually (One year no tillage, one year subsoiling).
continuous tillage: CC	Each ymaize, after crop harvest, all straw was shredded and spread over the soil surface. A single plowshare was used to completely invert the soil to a depth of 20–25 cm, burying all straw, with the soil surface left bare throughout the fallow period.

Fig. 2.

The details of the different tillages in this experiments. (a) no-tillage, (b) subsoiling tillage, (c) no-tillage- subsoiling tillage, (d) continuous tillage.

In this experiment, spring maize was sown in mid-April, with the test maize variety being Jincheng 508, at a sowing rate of 75 kg/ha. The row spacing for spring maize was 60 cm, with a planting density of 67,500 plants/ha. Fertilizer was applied manually before sowing, with application rates of N 150 kg/ha, P₂O₅ 120 kg/ha, and K₂O 90 kg/ha. The test winter wheat variety was Jinmai 47, sown at a rate of 300 kg/ha, with a row spacing of 40 cm and a planting density of 67,500 plants/ha. Fertilizer application before sowing was the same as for spring maize.

Soil bulk density measurement

Using the ring knife method, soil bulk density (BD) was measured after the harvest of spring maize. Soil samples were collected from each plot at depths of 0–60 cm, which represents the main depth affected by tillage and fertilization treatments. Sampling intervals were set at 0–20 cm, 20–40 cm, and 40–60 cm to reveal differences in soil bulk density influenced by tillage practices and crop root growth across different soil layers. Five sampling points were established using the diagonal method, based on the shape of the experimental plots. At each sampling point, intact soil samples were collected from three different depth levels, sealed, and transported to the laboratory. The soil samples were then dried at 105 °C for 24 h and weighed to determine soil bulk density.

1

In the equation, BD represents soil bulk density in g/cm³; WS represents the combined mass of the ring knife and the dried soil sample in grams (g); W represents the mass of the ring knife in grams (g); V represents the volume of the ring knife in cubic centimeters (cm³).

Soil porosity measurement

Soil porosity (SP), also known as soil porosity, is generally not directly measured, but can be calculated according to soil bulk density and specific gravity.

2

In the equation, SP represents soil porosity (%), BD represents soil bulk density (g/cm³), SG represents the specific gravity of the soil, and its average value is generally 2.65 g/cm³.

Soil moisture measurement

During the critical growth stages following crop sowing and throughout the winter fallow period, soil moisture within the 0–200 cm soil layer was determined using the soil drilling and drying methods. Soil samples were collected at 20 cm intervals, with one sampling point established per plot. Based on these measurements, soil water storage and water use efficiency were subsequently estimated.

3

In the equation, SW represents soil moisture content in percentage (%); M1 represents the mass of wet soil in grams (g); M2 represents the mass of dried soil in grams (g).

4

In the equation, W represents soil water storage in millimeters (mm); SWi represents the moisture content of the i-th soil layer in percentage (%); Pi represents the bulk density of the i-th soil layer in grams per cubic centimeter (g/cm³); Hi represents the thickness of the i-th soil layer in centimeters (cm).

Relative chlorophyll content measurement

During the main growth stages of the crops, the relative chlorophyll content of the maize leaves was measured using a SPAD-502 chlorophyll meter. For each plot, 30 maize leaves with similar growth conditions and orientation were selected for measurement.

Yield and water use efficiency

Winter Wheat: At the harvest stage, 2 m² from each experimental plot was sampled to measure traits such as the number of grains per spike and thousand-grain weight. This was repeated three times. The samples were manually threshed, dried, and weighed to calculate the yield.

Spring Maize: At maturity, the diagonal method was used to select three sampling points in each experimental plot, with 20 plants sampled at each point, totaling 60 plants. Thirty of these plants were selected for agronomic trait investigation and the number of grains per maize was measured. The samples were then manually threshed, dried, and the hundred-grain weight was determined to calculate the yield.

Water Use Efficiency (WUE): WUE is defined as the ratio of the economic yield per unit area to the water consumption (mm) during the growing period.

5

Where: WUE is the yield water use efficiency, kg/(hm²·mm); GY is the grain yield, kg/hm²; and ET is the crop water consumption, mm.

6

In the equation, ET represents crop water consumption in millimeters (mm); R2 represents precipitation during the crop growing period in millimeters (mm); ΔW represents the change in soil water storage during the calculation period in millimeters (mm).

Statistical analysis

In this study, a variety of statistical methods were used to analyze soil water dynamics, crop growth characteristics and yield characteristics under different conservation tillage modes. First, Excel was used to analyze the mean value, standard deviation and coefficient of variation of each variable to reveal the basic characteristics of the data. Secondly, SPSS was used to analyze the relationship between soil moisture, crop physiological indicators and yield, and ANOVA and Duncan’s multiple range were used to evaluate the significant effects of different tillage modes on soil and crop growth. The data were analyzed using a mixed-effects model, with tillage treatments as fixed effects and block and year as random effects to account for spatial and temporal variability. Significance was assessed at P < 0.05 via ANOVA, followed by post-hoc tests where applicable. All analyses were performed in SPSS. SPSS was utilized for Path Analysis. Initially, multiple linear regression was employed to construct regression models of the dependent variable with respect to the intermediary variable and the independent variable separately, thereby preliminarily testing the significance of the path relationships. Subsequently, a path diagram was developed in AMOS to specify the direct and indirect effects between variables. Following the execution of the analysis, the standardized path coefficients, significance levels, and goodness-of-fit indices were obtained. Ultimately, the causal mechanisms between variables were elucidated by integrating the path coefficients with the results of effect decomposition.

Results

BD and porosity at different soil depths

After tillage treatments in 2019, the BD of soil in each layer from 0 to 60 cm decreased compared to pre-treatment levels, with reductions ranging from 5.1 to 10.0%, 1.0–9.0%, and 5.3–10.6%, respectively (Fig. 3). From 2019 to 2020, the trends of BD across the 0–20 cm, 20–40 cm, and 40–60 cm layers followed the same pattern for all tillage treatments, with the order being CC > NN > SS > NS. In 2020, significant differences in soil BD between the CC tillage treatment and the other treatments were observed in the 0–60 cm layer (P < 0.05). The increases in BD compared to the CC treatment ranged from 2.4 to 5.6%, 2.22–11.1%, and 2.3–3.2% across the three soil layers, respectively. In 2021, the trends in BD under the various tillage treatments in the 0–20 cm and 40–60 cm layers remained consistent with those in 2019 and 2020. In the 20–40 cm layer, the order was CC > NN > NS > SS, with no significant difference between the CC and NN treatments. When analyzing the average BD of each tillage treatment across the 0–20 cm, 20–40 cm, and 40–60 cm layers over three years, all treatments effectively reduced BD compared to pre-treatment levels. Reductions in BD ranged from 4.7 to 10.8%, 1.8–5.8%, and 4.0–8.7%, respectively. The NS treatment exhibited the lowest average soil porosity in the 0–60 cm layer, with reductions of 6.0%, 4.2%, and 2.7% in porosity compared to the CC, NN, and SS treatments, respectively.

Fig. 3.

Effects of tillage methods on soil bulk density in 2019–2021. Indicated with different lowercase letters, the difference is statistically significant (P < 0.05).

Across different years, the trends of soil porosity under different tillage treatments were consistent with those of BD in various soil layers. From 2019 to 2021, in the 0–20 cm, 20–40 cm, and 40–60 cm layers, soil porosity under each treatment increased by 4.7–1.9%, 2.0–6.6%, and 5.4–11.6%, respectively, compared to pre-treatment levels (Fig. 4). NS exhibited a negative correlation between average soil porosity and BD in the 0–60 cm layer, showing the greatest increase compared to CC, NN, and SS treatments, with increases of 5.45%, 3.59%, and 2.02%, respectively.

Fig. 4.

Effects of tillage methods on soil porosity in 2019–2021. Indicated with different lowercase letters, the difference is statistically significant (P < 0.05).

Soil moisture and water content during fallow periods

Before planting winter wheat, the soil moisture profiles under different treatments exhibited similar trends across the 0–200 cm soil layer. There was a slight increase in moisture from 0 to 60 cm, followed by a decrease from 60 to 140 cm. Across the entire 0–200 cm layer, the average soil moisture content under each tillage treatment followed the order: NS > NN > SS > CC, while the average soil water storage followed the order: NN > NS > SS > CC. Each treatment effectively increased water storage compared to the traditional CC treatment, with increases of 49 mm, 17 mm, and 36 mm, respectively (Fig. 5).

Fig. 5.

Changes of soil moisture and soil water content in 0 ~ 200 cm soil layer of different tillage methods before sowing of crops. (a) for the cultivation of winter wheat and (b) for the cultivation of spring maize.

Before planting spring maize, the soil moisture profiles under different treatments in the 0–200 cm soil layer exhibited a consistent pattern, with a slight increase from 0 to 60 cm, a decrease from 60 to 120 cm, and an increase from 120 to 200 cm. Compared to the traditional CC treatment, the NN and NS treatments significantly increased soil water storage by 3.7% and 1.8%, respectively.

Soil moisture during key growth stages

During the winter wheat grain filling stage, soil moisture content displayed consistent trends across the various growth stages under different tillage treatments. Throughout all six growth stages, soil moisture content decreased in the 140–200 cm soil layer, with the lowest moisture levels observed during the wheat filling stage. In the 0–200 cm soil layer, the average soil moisture content under the NN, SS, and NS treatments was 4.8%, 5.4%, and 3.5% higher, respectively, compared to the traditional CC treatment (Fig. 6).

Fig. 6.

Changes of soil moisture in 0–200 cm soil layer of different tillage methods during at various growth stages of crops. (a) for the cultivation of winter wheat and (b) for the cultivation of spring maize.

During the spring maize planting period, soil moisture content gradually decreased as the growth stages progressed under each tillage treatment. The reduction in soil moisture content from the seeding stage to the maturity stage ranged from 20.6 to 32.3%. In the 0–200 cm soil layer, the NN, NS, and SS treatments increased soil moisture content by 7.6%, 10.7%, and 10.0%, respectively, compared to the CC treatment.

Soil water content during growth periods

During the planting periods of winter wheat and spring maize, soil water storage in the 0–200 cm soil layer under each tillage treatment was higher than that under the traditional CC treatment. During the winter wheat planting period, compared to the CC treatment, each treatment increased soil water storage by 2.0 to 12.0%, 2.1 to 6.4%, 0.5 to 5.4%, 8.0 to 15.4%, 7.4 to 15.4%, and 3.3 to 11.4% in the six key growth stages, respectively (Fig. 7). The order of average soil water storage in the 0–200 cm soil layer throughout the growth period was NN> SS> NS> CC, with the NN treatment effectively increasing soil water storage compared to other treatments by 3.9 to 9.6%.

Fig. 7.

Changes of soil water content in 0 ~ 200 cm soil layer of different tillage methods during at various growth stages of crops. (a) for the cultivation of winter wheat and (b) for the cultivation of spring maize.

During the spring maize planting period, compared to the CC treatment, each treatment increased soil water storage by 16.0–17.9%, 2.9–7.4%, 5.1–12.4%, 1.5–4.7%, and 12.9–21.8% in five key growth stages (except for the tassel stage), respectively. The order of average soil water storage in the 0–200 cm soil layer throughout the growth period was SS > NN > NS > CC, with the SS treatment increasing soil water storage by 8.2 mm, 10.7 mm, and 46.9 mm compared to other treatments.

Relative chlorophyll content of crops during growth periods

During the heading and booting stages, the SPAD values of winter wheat under each treatment followed a consistent trend, with the order NS > NN > SS > CC, showing significant differences between treatments (P < 0.05) (Fig. 8). The NS treatment exhibited higher SPAD values compared to the NN, SS, and CC treatments during the heading, booting, and grain filling stages, with increases of 14.9%, 32.4%, and 62.6%; 4.4%, 15.7%, and 27.7%; and 12.1%, 7.2%, and 11.1%, respectively. Throughout the key growth stages of winter wheat, SPAD values under the NS, NN, and SS treatments were higher than those under the CC treatment, with average SPAD values over the growth period being 34.6%, 22.8%, and 12.6% higher, respectively.

Fig. 8.

Effects of tillage methods on SPAD at various growth stages of winter wheat and spring maize. Indicated with different lowercase letters, the difference is statistically significant (P < 0.0). (a) for the cultivation of winter wheat and (b) for the cultivation of spring maize.

Under different tillage treatments, the SPAD values of spring maize showed a gradual increase as the growth period progressed, reaching their peak during the grain filling stage. The trends in SPAD values during the tasseling and grain filling stages were consistent across treatments, following the order: NS > SS > NN > CC. During the three major growth stages, the NN, SS, and NS treatments increased SPAD values compared to the CC treatment by 4.4–7.1%, 2.2–4.9%, and 1.8–7.6%, respectively, with significant differences observed between CC and each treatment (P < 0.05). Throughout the entire growth period of spring maize, the NS treatment exhibited the highest SPAD values, increasing by 3.4%, 0.9%, and 6.1% compared to the NN, SS, and CC treatments, respectively.

Yield and water use efficiency

Under different tillage treatments, the order of spikelet number in winter wheat was NS > NN > SS > CC, while for spring maize, it followed the order SS > NS > CC > NN, with significant differences observed between treatments (P < 0.05). The thousand-grain weight of winter wheat under the NN, SS, and NS treatments was 3.2%, 5.1%, and 3.9% higher, respectively, compared to the traditional CC treatment (Table 3). Similarly, the hundred-grain weight of spring maize under each treatment showed an increase ranging from 1.4 to 6.9% compared to winter wheat, with significant differences between treatments (P < 0.05). All tillage treatments increased the yield of both winter wheat and spring maize compared to the traditional CC treatment, with yield increases ranging from 5.4 to 10.0% for winter wheat and 7.3–18.7% for spring maize. The NS treatment resulted in the highest yield increase for both crops, with increases of 0.6%, 4.3%, and 10.6% for winter wheat and 2.5% for spring maize, compared to the NN and SS treatments, with significant differences between treatments (P < 0.05). During the planting periods of winter wheat and spring maize, water use efficiency (WUE) under each treatment was higher than that under the traditional CC treatment, with increases ranging from 1.2 to 6.0% for winter wheat and 5.5–31.3% for spring maize. For winter wheat, the order of WUE under each treatment was SS > NN > NS > CC, while for spring maize, it was NS > SS > NN > CC.

Table 3.

Effects of tillage methods on crop yield and WUE of winter wheat and spring maize.

Crop	Treament	Grain (Partical Size)	1000-grain)/ 100-grain wt(g)	Yield (kg/hm2)	Water consumption (mm)	WUE (kg/mm·hm2)
Winter wheat	NN	26.53 ± 0.94ab	41.67 ± 0.76a	4965.87 ± 23.21ab	338.53 ± 7.31b	14.67 ± 0.83ab
	SS	26.15 ± 0.54ab	42.45 ± 1.03a	4789.35 ± 8.98b	316.90 ± 9.24b	15.11 ± 0.54a
	NS	27.65 ± 1.21a	41.95 ± 0.91a	4997.03 ± 12.65a	346.44 ± 2.45a	14.42 ± 0.69ab
	CC	25.78 ± 0.79b	40.39 ± 1.31b	4543.95 ± 13.65c	318.72 ± 9.68b	14.26 ± 1.21b
Spring maize	NN	437.77 ± 7.98c	33.34 ± 1.98a	7314.87 ± 22.12ab	383.34 ± 3.24a	19.08 ± 0.69ab
	SS	461.77 ± 10.21a	34.58 ± 0.95a	7894.40 ± 19.45b	340.51 ± 2.54b	23.18 ± 0.78a
	NS	451.10 ± 6.35b	35.14 ± 1.21a	8091.54 ± 23.65a	340.81 ± 3.63b	23.74 ± 0.56a
	CC	444.73 ± 3.69ab	32.87 ± 1.42b	6816.34 ± 15.21c	377.06 ± 1.05ab	18.08 ± 1.02b

The data in the table are the average data of three years, SD ± standard deviation, lowercase letters indicate the significant difference between different treatments (P < 0.05).

Path analysis

A path analysis was conducted to examine the effects of various factors—including soil bulk density (BD), porosity, soil moisture content, water storage, relative chlorophyll content, water consumption, crop yield, and water use efficiency—on crop yield. The analysis revealed that conservation tillage explained 93% of the total variation in crop yield. Throughout both the winter wheat and spring maize growing seasons, soil physical properties were found to influence crop yield, with BD negatively correlated with yield. Both water use efficiency and crop yield had a positive effect, with standardized path coefficients of 0.93** and 0.975*, respectively (Fig. 9).

Fig. 9.

A path analysis of treatment effects on kernel number per plant (KNP), 100-kernel weight (KW), ET and grain yield (GY). The number near the arrow indicates the standardized path coefficient. The thickness of the line indicates the size of the coefficient. The thicker the line, the larger the path coefficient. The red line, blue line and dotted line represent the positive, negative and nonsignificant path coefficient, respectively(*P < 0.05, **P < 0.01, ***P < 0.001 ). (a) for the cultivation of winter wheat and (b) for the cultivation of spring maize.

During the winter wheat growing season, soil porosity was positively correlated with the relative chlorophyll content in crops. In the spring maize growing season, porosity, hundred-grain weight, and water use efficiency all positively influenced yield. The positive impact of water use efficiency on yield was primarily mediated through its effect on hundred-grain weight, with a standardized path coefficient of 0.99*. Environmental factors notably affect BD through structural changes induced by tillage practices. This study underscores the importance of optimizing soil BD and porosity, maintaining adequate soil moisture, enhancing crop chlorophyll content, reducing water consumption, and improving water use efficiency. Together, these factors enhance crop yield components and ultimately increase grain productivity.

Discussion

BD and soil porosity

The BD serves as a critical indicator of soil physical properties. Variations in BD are influenced by a combination of environmental factors, including long-term and relatively stable climatic conditions, inherent soil characteristics, and anthropogenic factors such as mechanical tillage and management practices. Among these factors, tillage practices exert the most substantial influence^14–17. A 12-year study on conservation tillage in rain-fed farmland on the Loess Plateau indicated that conservation tillage significantly reduced soil bulk density compared to traditional tillage practices^18–21. However, other experimental results have shown that long-term no-tillage treatment can lead to a shallower plow layer, increased soil compaction, and increased soil bulk density^22,23. Some scholars believe that no-tillage reduces soil bulk density²⁴. These findings align with the results of this study, which demonstrated that different tillage combinations effectively reduced BD compared to pre-experiment levels while enhancing soil porosity. Among the treatments, the no-tillage combined with subsoiling approach had the most pronounced effect, reducing the average BD in the 0–60 cm soil layer by 5.99%, 4.2%, and 2.6% compared to the CC, NN, and SS treatments, respectively. This improvement is primarily attributed to the limitations of traditional tillage, where continuous plowing and prolonged mechanical operations lead to increased soil compaction, while insufficient plowing depth fails to disrupt the plow pan, restricting root penetration and water infiltration^14,19. While the no-tillage combination reduces soil disturbance, it does not effectively loosen the soil layers, leading to some degree of soil compaction. The combination of subsoiling and no-tillage effectively reduces soil disturbance and breaks the plow pan. The study also found that the impact of tillage methods on soil BD was greater in the 40 cm soil layer than in the 20 cm layer. This is because surface soil is more susceptible to mechanical compaction and rainfall erosion, which diminish the effectiveness of tillage measures. This finding aligns with studies conducted in the arid regions of southern Ningxia, where different conservation practices have been shown to significantly influence soil physical properties²⁵. Different tillage measures can effectively reduce soil BD and increase soil porosity, with the combination of no-tillage and subsoiling being the most effective, followed by continuous subsoiling. The combination of subsoiling and no-tillage is crucial because it not only minimizes soil disturbance (preserving soil structure and organic matter) but also actively breaks up compacted plow pans through deep loosening, whereas no-tillage alone fails to address subsurface compaction^19–23. This dual approach enhances root penetration, water infiltration, and nutrient cycling while maintaining surface residue cover for erosion control and moisture retention, making it superior for sustainable soil management.

Soil moisture during fallow periods

Conservation tillage effectively controls soil erosion by employing reduced or no-tillage methods different from traditional cultivation practices, while maximizing straw cover to increase soil water content and improve soil structure^26,27. In this study, before planting spring maize, the trends in soil moisture content and water storage under each treatment closely resembled those observed for winter wheat. The NN and NS treatments increased soil water storage by 3.7% and 1.8%, respectively, compared to the traditional CC treatment. This may be attributed to long-term no-tillage practices, which can lead to soil compaction in deeper layers, thereby affecting water infiltration and retention^28,29. Before planting spring maize, water storage in the 100–200 cm soil layer showed an increasing trend, which can be attributed to the different tillage methods applied during fallow periods. The combination of no-tillage and deep loosening, along with crop straw cover, effectively reduces surface evaporation during fallow periods, promoting rainfall infiltration into deeper soil layers³⁰. In contrast, traditional plowing leads to higher surface evaporation, which hinders water retention and soil moisture conservation, consistent with previous research findings³¹. Continuous no-tillage and the no-tillage with deep loosening combination reduce soil disturbance, decrease soil evaporation during fallow periods, and improve soil moisture conditions necessary for crop growth. These findings highlight the critical role of conservation tillage combined with subsoiling in enhancing soil water storage and moisture retention during fallow periods, providing a sustainable solution to improve water-use efficiency and crop productivity in arid and semi-arid agricultural systems.

Soil water variation during the crop growth season

Research on the impact of conservation tillage on soil moisture and thermal conditions in the black soil of Northeast China’s cold regions has shown significant increases in soil moisture during the maize growing season, with studies also demonstrating that combined tillage practices and straw cover can increase soil moisture content in the plow layer by 9.6–11.7%^32–35. The results of this study are highly consistent with these findings. No-tillage reduces soil disturbance, maximizes water retention under straw cover, and deep loosening effectively preserves moisture in deeper layers due to mechanical actions, although it may promote soil moisture evaporation. However, the improved soil infiltration rate facilitates timely storage of rainfall^36,37. As the crop growth stages progress, soil moisture content gradually decreases due to crop water consumption and uneven regional precipitation patterns³⁸. This study found that under different tillage treatments during the wheat-maize growing season, soil water storage gradually decreased as the growth stages advanced³⁹. The differences in soil water storage within the 0–60 cm soil layer were significant across different growth stages, whereas variations in deeper soil layers were less pronounced^40–44. During the winter wheat growing season, soil water storage increased by 0.5–15.4% compared to traditional tillage at key growth stages, while during the maize growing season, the increase ranged from 1.5 to 21.8%. For the winter wheat planting period, the NN treatment showed the greatest increase, followed by SS, while for the spring maize planting period, the SS treatment was most effective, followed by NN. The study revealed that conservation tillage significantly improved soil moisture retention in the 0–60 cm layer during crop growth, with more pronounced effects in shallow depths, while deeper soil layers (below 60 cm) showed relatively stable moisture levels with less variation across treatments and growth stages.

The effect of tillage on the relative chlorophyll content of crops

Research in the Jiaodong area and the hilly dry regions of western Henan has found that conservation tillage practices increased post-anthesis photosynthetic rates in winter wheat, significantly impacting wheat photosynthetic performance^45–48. The results of this study indicate that during the winter wheat growing season, SPAD values under different tillage treatments initially increase and then decrease as the growth stages progress, with average SPAD values rising by 12.6–34.6% compared to conventional tillage. During the spring maize planting season, SPAD values gradually increase as the growth stages advance, with NN, SS, and NS treatments showing increases of 4.4–7.1%, 2.2–4.9%, and 1.8–7.6%, respectively, compared to the CC treatment. This trend aligns with the findings of Wang Yuling, demonstrating that conservation tillage effectively enhances photosynthesis and relative chlorophyll content during the main growth stages of winter wheat and spring maize, with increases ranging from 2.2 to 33.3% and 2.4–23.0%, respectively^49–51. Under the winter wheat-spring maize cropping system in semi-arid regions of the Loess Plateau, applying a combination of no-tillage and deep loosening delays leaf senescence and chlorophyll degradation, optimizing photosynthetic performance in a coordinated manner compared to traditional tillage methods.

Effects of tillage on crop yield, water use efficiency and pathways

The results of this study indicate that different tillage treatments significantly increased the yields of winter wheat and spring maize compared to traditional tillage, with increases ranging from 5.4 to 10.0% and 7.3–18.7%, respectively. The combination of no-tillage and deep loosening showed the greatest yield increases for both winter wheat and spring maize, with improvements of 0.6%, 4.3%, 10.6%, and 2.5%, respectively, compared to continuous no-tillage and continuous deep loosening treatments. This can primarily be attributed to no-tillage reducing soil disturbance, effectively decreasing soil water evaporation, and maintaining soil moisture^52–56. Deep loosening increases the depth of the tillage layer, enhances the capacity of deep soil to accumulate water, improves soil structure, and promotes crop root growth^30,57. Additionally, straw mulching increases surface roughness, enhances rainfall infiltration, improves soil water storage, and suppresses inter-row evaporation, all of which contribute to higher crop yields^58,59. During the winter wheat and spring maize planting seasons, all treatments demonstrated higher water use efficiency compared to traditional tillage, with increases ranging from 1.2 to 6.0% and 5.5–31.3%, respectively. Research in typical black soil areas and dryland fields of the Loess Plateau has consistently shown that tillage practices contribute 90% and 99%, respectively, to yield improvements, aligning with the findings of this study^60–62. The long-term adoption of conservation tillage (particularly no-tillage with deep loosening) demonstrates a synergistic effect: while no-tillage maintains surface moisture through straw retention, deep loosening progressively improves subsoil water storage and root penetration over successive years, with the most significant yield and WUE benefits observed in the critical 0–40 cm root zone where water and nutrient uptake predominantly occur. This highlights how tillage depth and duration interact to optimize the soil-plant-water continuum.

Conclusion

Tillage practices and straw mulching have positive effects on soil quality, water storage, and crop yield in dryland agriculture. Specifically, deep loosening and no-tillage treatments improve soil bulk density, increase porosity, and enhance soil moisture compared to traditional plowing. The combination of no-tillage with deep loosening is particularly effective in increasing water storage during fallow periods and improving soil water retention during crop growth. This combination also boosts crop relative chlorophyll content and yields, outperforming other treatments in both winter wheat and spring maize planting seasons. Notably, the no-tillage with deep loosening combination enhances water use efficiency, making it a promising model for sustainable dryland agriculture in the Loess Plateau. Further long-term field studies are needed to explore the relationship between agricultural inputs and economic outcomes under various tillage systems.

Author contributions

The manuscript was reviewed and approved for publication by all authors. J.L conceived and designed the experiments. J.L performed the experiments, analyzed the data, drew the figures and wrote the paper.Z.N and Z.G and J.B and S.Y and D.H revised the paper.

Data availability

All data generated or analyzed during this study are included in this published article.

Declarations

Competing interests

The authors declare no competing interests.