Optimizing boron and zinc supplementation for cane growth and its residual effect on the ratoon crop

Abstract

Sugarcane (Saccharum officinarum L.), as a long-duration and nutrient-intensive crop, is particularly susceptible to micronutrient depletion, especially under intensive cultivation. Despite the essential roles of zinc (Zn) and boron (B) in plant growth and metabolism, their management is often neglected, and their residual effects on ratoon crops remain underexplored. The present study aims to optimize Zn and B supplementation to enhance yield and quality in plant cane while assessing their carry-over effects on ratoon productivity for improved and sustainable micronutrient management in tropical agroecosystems. Field experiments were conducted at three sites on the College Farm, NAU, Navsari during the winter seasons from 2017 to 18 to 2019–20 for plant cane and from 2018 to 19 to 2020–21 for ratoon cane, to evaluate the direct effects of B and Zn application on plant sugarcane and their residual effects on ratoon sugarcane. The treatments included four levels of boron (0, 1.0, 2.0, and 3.0 kg ha⁻¹) and four levels of zinc (0, 5.0, 7.5, and 10.0 kg ha⁻¹), applied along with the recommended dose of fertilizers. The experiment was laid out in a factorial randomized block design with three replications, and the data were subjected to pooled analysis of variance over the years. Significant individual effects of boron and zinc on sugarcane growth and yield was observed. Millable cane height, weight, and the yield of cane and green trash were significantly higher with a B application of 3 kg ha^-1 and a Zn application of 10 kg ha^-1. Nutrient application influenced the chemical composition of sugarcane, increasing brix (%), sucrose (%), and commercial cane yield (%), particularly at the same application rates. Nutrient content and uptake in sugarcane, specifically nitrogen (N), phosphorus (P₂O₅), potassium (K₂O), boron (B), and zinc (Zn) increased significantly with the application of boron at 3 kg ha^-1 and zinc at 10 kg ha^-1. No noticeable interaction effect was observed between B and Zn on the yield and quality parameters of both the sugarcane and its ratoon.

Supplementary Information

The online version contains supplementary material available at 10.1038/s41598-025-29338-y.

Introduction

Sugarcane is a globally important cash crop, valued for its economic, industrial, and nutritional significance ^1,2. It contributes approximately 21% of global crop production (2000–2022 average). In India, where it is the primary source of sugar, it supports the livelihoods of over 2.8 lakh farmers and more than 11 lakh individuals through direct and indirect employment ^3,4. With an annual production of 439.93 million metric tons over 5.883 million hectares⁵, India is the world’s second-largest sugarcane producer and largest consumer. Despite its economic prominence, sugarcane productivity in India remains suboptimal, constrained by biotic and abiotic factors, among which soil fertility and micronutrient availability are critical limiting factors.

Micronutrient deficiencies, especially of zinc (Zn) and boron (B), are widespread in intensively cultivated regions, including the tropical and subtropical soils of India^6,7. In South Gujarat’s black soil zones, factors such as high soil pH, calcareousness, and clay content further restrict Zn and B bioavailability^8,9. Zinc deficiency is particularly prevalent due to its strong adsorption to clay colloids, while boron deficiency is exacerbated by leaching losses and a narrow threshold between deficiency and toxicity. Over 40% of sugarcane fields in Gujarat show micronutrient limitations, with Zn and B among the most critical.

Zinc is a structural and catalytic component of numerous enzymes involved in protein and carbohydrate metabolism, photosynthesis (e.g., pyruvic carboxylase), auxin biosynthesis (tryptophan synthetase), and carbon fixation (carbonic anhydrase)^10–12. It enhances photosynthetic efficiency and sugar accumulation, particularly under Zn-deficient conditions in sugarcane¹³. Field studies have shown that Zn application improves yield, nutrient use efficiency, and physiological performance of sugarcane under tropical conditions¹⁴. Boron, on the other hand, plays vital roles in cell wall formation, sugar transport, carbohydrate metabolism, membrane stability, and cell division^15–17. In sugarcane, boron deficiency impairs sugar translocation and weakens structural integrity, leading to impaired growth and reduced productivity ¹⁸. Recent studies emphasize the critical role of B in sustaining yield, improving nutrient uptake, and supporting soil fertility in intensively cultivated soils ⁸.

However, the use of micronutrients in sugarcane cultivation remains relatively limited in regions like South Gujarat. The introduction of high-yielding sugarcane varieties necessitates revised nutrient management strategies tailored to site-specific micronutrient needs. Studies by^19–21 demonstrated that targeted Zn and B application significantly improved cane yield and sugar recovery. Additionally, balanced and site-specific micronutrient application not only improves plant growth and quality but may also provide residual benefits to the succeeding ratoon crop-a component often neglected in existing research.

Therefore, this study was undertaken to evaluate the direct effects of boron and zinc levels on the growth, yield, quality, and the content and uptake of major and micronutrients by plant crop sugarcane (CoN 5071), as well as their residual effects on the succeeding ratoon crop.

Materials and methods

Experimental site

A field experiment was conducted at the College Farm of Navsari Agricultural University (20^o 37’ N latitude and 72^o 54’ E longitude) during the winter season over multiple years: from 2017–18 to 2019–20 for the plant sugarcane crop and from 2018–19 to 2020–21 for the ratoon sugarcane crop. The study site falls under the ‘Am’ category (tropical monsoon climate) of the Köppen climate classification system, characterized by high humidity, heavy seasonal rainfall, and mean annual temperatures above 24 °C. The monsoon season is warm and humid with significant rainfall and starts during the third week of June with an average annual rainfall of 1633 mm. The total number of rainy days is around 59 (the average of the last ten years). In general, rainfall does not occur in the winter and summer seasons. The overall meteorological data, including monthly temperature, rainfall, and relative humidity (RH) recorded during the experimental period (2017–2022), are presented in the supplementary material (supplementary table S1). The data revealed that the weather conditions were normal and conducive for the adequate growth and development of sugarcane over the period of study. The soil of the experimental location is classified under the order “Inceptisols” according to the 7th Approximation, which includes members of the fine, montmorillonitic, isohyperthermic great soil group of Vertic Ustrochrepts and Jalapore series. According to the USDA soil taxonomy, the soil texture is classified as clay. Locally, these soils are referred to as “deep black soils.” Dry soil is a dark brown, clay-like substance. When the earth is dry, it develops extensive cracks and gets quite hard; when it’s moist, it gets plastic and sticky.

Field experiment

The study aimed to evaluate the effects of micronutrient fertilization specifically B and Zn on the sugarcane variety CoN-5071. A two-factorial randomized block design (FRBD) with three replications was employed, comprising four levels of boron (0, 1.0, 2.0, and 3.0 kg ha⁻¹) and four levels of zinc (0, 5.0, 7.5, and 10.0 kg ha⁻¹), resulting in sixteen treatment combinations. The selection Zn and B application rates were guided by soil test-based recommendations and supported by previous regional research. Initial soil analysis indicated marginal to deficient levels of available Zn and B (Table 1). The chosen rates span a range from low to high doses that are agronomically safe and widely studied in tropical sugarcane systems^19,20. This design enabled evaluation of both the immediate effects on plant crop performance and the residual impacts on ratoon productivity, while remaining within practical fertilization limits followed by farmers.

Table 1.

Details on planting time, irrigation frequency and intercultural operations.

	Plant Sugarcane			Ratoon Sugarcane
Year	2017-18	2018-19	2019-20	2018-19	2019-20	2020-21
Site	F 4(B)	B−5	F-11	F 4(B)	B−5	F-11
Sowing date	24/01/18	27/12/18	07/01/20	16/01/19	02/03/20	02/01/21
Harvesting date	15/01/19	29/02/20	01/01/21	11/02/20	04/03/21	25/01/22
Number of irrigations (Year-wise)	11	12	11	9	9	10
Number of weeding	2	2	1	2	1	3
Number of inter culturing	2	2	2	2	2	2
Previous crop	Rice	Rice	Rice	Plant cane	Plant cane	Plant cane
Pest and diseases	NIL	NIL	NIL	NIL	NIL	NIL
Plantstand and seasonal conditions	Normal	Normal	Normal	Normal	Normal	Normal
Rainfall	1675 mm 48 Day	2170 mm 66 Day	2310 mm 63 Day	2170 mm 66 Day	2310 mm 63 Day	1709 mm 66 Day

Table 2.

Initial soil properties of three different sites.

Parameters	2017-18 [F 4(B)]	2018-19[B-5]	2019-20[F-11]
pH (1:2.5)	7.59	8.24	7.47
EC (1:2.5) (dS/m)	0.18	0.93	0.22
OC (%)	0.42	0.57	0.74
Av. N (kg ha− 1)	203	226	223
Av. P2O5 (kg ha− 1)	48.24	60.32	80.00
Av.K2O (kg ha− 1)	301	443	305
Av. S (mg kg− 1)	23	16	21
Boron (mg kg− 1)	0.16	0.34	0.21
Zinc (mg kg− 1)	0.42	0.40	0.48

*Site location was given in parenthesis.

Three budded setts of sugarcane which were procured from agronomy farm, Navsari Agricultural University, Navsari were planted at an inter row spacing of 90 cm. The fertilizer dose for the plant crop was 250:125:125 kg ha⁻¹ of N: P₂O₅: K₂O. The same field was used for the ratoon crop and the recommended doses of NPK (325:62.5:125 kg ha⁻¹ of N: P₂O₅: K₂O) were added. Fertilizers were applied using di-ammonium phosphate (DAP), urea, muriate of potash, borax, and zinc sulfate.

The entire phosphorus (P) and potash (K) doses were applied at the time of planting, whereas N was applied in four equivalent splits. At the time of planting, micronutrients were applied to the soil according to the treatments. Recommended agronomic practices such as earthing up, weedicide spray, hoeing and irrigation practices were regularly followed across all the treatments. Details on planting time, irrigation frequency and intercultural operations are summarized in Table 2. No incidence of pest and diseases was noted throughout the crop growth period.

Soil and plant analysis

Composite soil samples were collected from each plot at a depth of 0–15 cm using a screw auger, both before the initiation of the experiment and after the harvest of the crop. Each composite sample consisted of five subsamples collected diagonally across the plot, excluding border rows. Soil samples were dried, ground, and sieved (<2 mm) before being analyzed for their chemical properties. The following soil parameters were analyzed: pH was measured using 0.01 M CaCl₂ in a 1:2.5 soil-to-solution ratio and electrical conductivity (EC) was determined using 1 M KCl²². Organic carbon content was estimated by the dichromate oxidation method ²³. Available nitrogen (N) was determined using the alkaline permanganate method²⁴. Available phosphorus (P₂O₅) was extracted with 0.5 M NaHCO₃ (Olsen’s extractant) at pH 8.5 and estimated colorimetrically²². Available potassium (K₂O) was extracted using 1 N ammonium acetate (NH₄OAc) at neutral pH and measured with a flame photometer²². Available zinc (Zn) was extracted using 0.005 M DTPA buffered at pH 7.3²⁵, and available boron (B) was extracted with hot water and quantified colorimetrically using the azomethine-H method²⁶.

Using random sample technique, several plant morphological characteristics were noted during the experiment. Numerous observations were made before (growth attributes), during (yield attributes and quality metrics) and after harvest (growth attributes) of the crop. Data on yield metrics such as total plant height (cm), millable cane height (cm), millable cane weight (kg cane⁻¹), cane yield (t ha⁻¹) and green top yield (t ha⁻¹) were recorded at the time of harvest. For the estimation of quality parameters, such as brix value, sucrose content, and commercial cane sugar (CCS) yield, ten stalks from both the plant cane and ratoon crop in each plot were collected on the day of harvest. Brix value which is a measure of soluble solids, was measured using a refractometer (ATAGO, PAL-BX/RI) from the juice of the stalk²⁷. Sucrose percentage in freshly extracted and filtered juice samples was estimated using an ATAGO AP-300 automatic polarimeter, after clarification with basic lead acetate. The sucrose content was determined using the standard Schmitz’s table, following the procedure described by²⁸. Five randomly selected plants were harvested from the net plot area of 4.6 m x 3.6 m (gross plot area: 7.2 m x 6 m) in each treatment plot at peak maturity. The plants were separated into stalk and leaf components.

Fresh plant samples collected were cleaned, weighed, oven dried at 65 °C and ground for estimating nutrient contents. The concentration of N, P and K in plant was analyzed using standard procedure. Wet digestion with concentrated H₂SO₄ using the Kjeldahl apparatus was adopted for the determination of total N²⁹. Wet digestion of samples with a 4:1 mixture of HNO₃ and HClO₄, followed by the adoption of the Vanado-molybdate method & flame emission photometry, and was used for the determination of phosphorus (P) and potassium (K), respectively²². Zinc content in plant samples was estimated following wet digestion of dried and finely ground material using a diacid mixture (HNO₃: HClO₄ in a 3:1 ratio), as per the method described by Lindsay²⁵, using an ADS1000 FSX atomic absorption spectrophotometer (Motras Scientific, India). Boron content in plant samples was determined using the azomethine-H colorimetric method, as described by³⁰, with readings taken at 420 nm using a 1600 V spectrophotometer (Motras Scientific, India). Total uptake of nutrients by sugarcane plant was calculated by multiplying the nutrient concentration (%) with cane yield (q ha⁻¹).

Statistical analysis

The data collected from the experiment were subjected to pooled analysis of variance (ANOVA) using a factorial randomized block design to assess the main effects and interactions of Zn and B doses³¹. Prior to analysis, the assumptions of ANOVA were verified, including normality of residuals using the Shapiro-Wilk test (p > 0.05 indicates normal distribution) while homoscedasticity was evaluated with Levene’s test (p > 0.05 suggests equal variances). Since the treatments were based on quantitative doses, regression analysis was also performed to evaluate dose-response relationships on various parameters under study using the following model (Supplementary table S2).

1

• Y_ijk: sugarcane yield for the i^th level of Boron, j^th level of Zinc, k^th replication.

• µ = overall mean.

• B_i = effect of the i^th Boron level.

• Z_j =effect of the j^th Zinc level.

• (BZ)_ij= interaction effect.

• ϵ _ijk = random error term assumed N (0, ).

Treatment means were compared using the Critical Difference (CD) at 5% probability level, and standard error of the mean (SEm) was reported for each parameter.

Results and discussion

Given the consistent lack of significant interaction between zinc and boron levels in both plant cane and ratoon crops, their individual effects could be distinctly evaluated and are therefore presented separately (Supplementary table S3 and S4). The results represent a comprehensive pooled analysis of data collected over three years for both crop cycles.

Effect of B fertilization on growth, yield, quality and nutrient composition of sugarcane

The pooled analysis of the data from three years revealed that individual effect of B and Zn were significant on growth and yield attributes of sugarcane (Table 3). In both cane and ratoon crops, no appreciable variations in the overall plant height were imparted by boron treatments. The tallest plants, however, were observed with the application of B @ 2 kg ha⁻¹ (364 cm) in the plant cane, and its residual effect (320 cm) in the ratoon crop. The results of growth and yield attributes viz. millable cane height and millable cane weight in pooled analysis were affected significantly by different levels of boron except for millable cane height of ratoon cane. There were notable variations in the millable cane height of plant cane, with application of B @ 3 kg ha⁻¹ having the maximum height (211 cm). In both cane and ratoon crops, the amount of boron applied had a considerable impact on the millable cane weight where B@ 2 kg ha⁻¹ produced the maximum weight at 1.20 kg cane⁻¹ for the ratoon crop, and B at 3 kg ha⁻¹ produced the highest weight at 1.39 kg cane⁻¹ for the plant cane. These effects may be credited to physiological role of the nutrient in promoting cell division and elongation, regulating hormone activity, and facilitating carbohydrate partitioning, all of which contribute to enhanced vegetative growth and overall sugarcane productivity^32,33. Surprisingly, in contrast to our results³⁴, found that boron had no apparent effect on the weight of cane, with performance analogous to that of the control and other micronutrients.

Table 3.

Effect of B and Zn on growth and yield attributes of sugarcane.

Treatments	Total plant height (cm)		Millable cane height (cm)		Millable cane weight (kg cane− 1)		Cane yield (t ha− 1)		Green top yield (t ha− 1)
	Cane	Ratoon	Cane	Ratoon	Cane	Ratoon	Cane	Ratoon	Cane	Ratoon
Boron
B @ 0 kg ha⁻¹	355a	311a	196b	185a	1.23c	1.09 b	83.19c	68.40a	16.93c	11.75a
B @ 1 kg ha⁻¹	359a	316a	200b	187a	1.27bc	1.13 ab	86.02bc	70.90a	17.38bc	11.98a
B @ 2 kg ha⁻¹	364a	320a	203ab	191a	1.34ab	1.20 a	89.01ab	71.84a	18.19ab	12.21a
B @ 3 kg ha⁻¹	360a	319a	211a	192a	1.39a	1.18 a	91.53a	73.54a	18.84a	12.18a
S.Em. ±	4.75	4.13	3.25	2.72	0.03	0.02	1.179	1.351	0.316	0.178
Zinc
Zn @0 kg ha⁻¹	351 b	306 b	193 c	182 b	1.19 c	1.07 c	81.14 d	66.91 b	16.67 c	11.49 c
Zn @5 kg ha⁻¹	356 b	314 b	198 bc	188 ab	1.28 b	1.14 bc	85.17 c	71.01 a	17.49 bc	11.87 bc
Zn @7.5 kg ha⁻¹	360 ab	317 ab	207 ab	190 a	1.32 b	1.17 ab	89.25 b	72.31 a	18.26 ab	12.08 b
Zn @10 kg ha⁻¹	371 a	329 a	212 a	195 a	1.43 a	1.23 a	94.17 a	74.44 a	18.92 a	12.67 a
S.Em. ±	4.85	4.15	3.34	2.71	0.03	0.025	1.162	1.354	0.306	0.177
Interaction	0.81 (NS)	0.416 (NS)	0.567 (NS)	0.972 (NS)	0.204 (NS)	0.607 (NS)	0.949 (NS)	0.849 (NS)	0.685 (NS)	0.645 (NS)
CV%	8.03	8.04	9.91	8.84	13.80	13.01	8.14	11.69	10.46	9.01
Adj. R2	0.576	0.778	0.721	0.690	0.678	0.625	0.823	0.266	0.567	0.682

Pooled data over three years (2017–2020 for plant cane and 2018–2021 for ratoon cane) are presented. Means followed by the same letter within a column are not significantly different at p ≤ 0.05 according to Duncan’s Multiple Range Test (DMRT).

Boron application significantly enhanced plant cane yield, with B at 3 kg ha⁻¹ and 2 kg ha⁻¹ resulting in approximately 10 and 7% increases over the control, respectively; though, the difference between the two treatments was not statistically significant. Green top yield in plant cane also responded positively, showing an increase of nearly 11% with B at 3 kg ha⁻¹. Boron’s positive impact on sugarcane yield and growth is supported by various studies. The vital role of boron in promoting plant growth and reproduction was emphasized by²⁰. Application of boron improves the growth traits in crops by transporting photo assimilates from leaves to roots^35,36. All of these studies supports the idea that increased sugarcane productivity is positively correlated with boron treatment. However, in contrast with our findings, many previous studies reported little to no effect of boron application on sugarcane yield and productivity, particularly when doses exceed 2 kg ha^−121,37. A previous study [²⁰] reported that B application and its residual effect at rates of 1 and 2 kg ha⁻¹ led to reduced sugarcane yields, likely due to boric acid toxicity. However, the required dose of this nutrient largely depends on factors such as soil conditions, cultivar response, environmental conditions or the form of B applied, which can influence the necessity for either higher or lower boron supplementation. The residual effect of B application showed no significant impact on cane yield, despite a slight numerical increase of approximately 7.5% at the highest dose. Similarly, the ratoon crop exhibited only marginal (~ 4%) improvement with B at 2 kg ha⁻¹, with no significant variation observed among treatments. These findings are consistent with those of³⁸, who reported toxicity at the highest B dose (8.8 kg ha⁻¹) and along with no residual effect in the first ratoon. Similarly^21,39, also reported no residual impact of B application on stalk or aboveground biomass yields in subsequent ratoon crops. Although B application in our study significantly enhanced cane and green top yields in the plant cane, its residual effect was not evident in the ratoon crop, aligning with the observations reported in these earlier studies.

The effect of boron treatments on sugarcane quality metrics such as brix (%), juice sucrose percentage, and CCS yield in both plant cane and ratoon crops is presented in Table 4. Both cane and ratoon crops’ brix percentage (soluble solids content of the sugarcane) was considerably impacted by B treatments. With 23.05% for the plant cane and 22.43% for the ratoon crop, B applied at 3 kg ha⁻¹ had the highest brix values. Higher boron levels appear to promote sugar accumulation, as indicated by the gradual rise in brix percentage. The sucrose content in juice of plant cane varied significantly, with application of B at 3 kg ha⁻¹ having the highest figure (19.97%), but was at par with treatment supplied B at 2 kg ha⁻¹ (19.56%). Boron improves sugarcane production and quality by strengthening cell wall structure ( B is known to be involved in pectin cross-linking and maintaining membrane integrity) facilitating sucrose transport, and sugar metabolism. Concerning the ratoon crop, the residual effect of boron fertilization did not lead to any significant increase in sucrose yield, though B at 3 kg ha⁻¹ continued to have a numerical advantage of 19.63%. Boron application significantly impacted CCS yield in both crops with plant cane production of 12.45 t ha⁻¹ and a ratoon crop yield of 9.95 t ha⁻¹, at the level of 3 kg ha⁻¹ maximum. The significant rise in CCS yield with application of B emphasizes how the nutrient improves sugar yield and sugarcane quality. All three quality parameters studied showed higher value in plant cane compared to ratoon crop at all levels of boron application⁴⁰. reported that applying B at a rate of 1.5 kg ha⁻¹, along with the recommended dose of NPK fertilizers, resulted in optimum cane yield and sugar recovery. B is primarily associated with sugar transport and sucrose metabolism, contributing to increased sucrose accumulation in sugarcane.³⁵. In a two-year study conducted on sandy loam soils, the application of boron at a rate of 10 kg ha⁻¹, followed by a 2% FeSO₄ spray, resulted in an increased sucrose percentage in cane juice at harvest³³. A study by¹⁹ reported that a 0.1% foliar spray application of boron resulted in a higher brix percentage of 21.9%. Positive effects of boron fertilizers on sugarcane crop and its quality have been reported by other researchers also^20,32. These studies highlight the importance of maintaining an optimal boron level for maximizing both yield and sucrose content in sugarcane.

Table 4.

Effect of Boron and zinc on quality parameters of sugarcane and Ratoon cane.

Treatments	Brix (%)		Sucrose (%) in juice		CCS yield (t ha− 1)
	Cane	Ratoon	Cane	Ratoon	Cane	Ratoon
Boron
B @ 0 kg ha⁻¹	22.19 c	21.79 b	19.12 b	18.95a	10.86 c	8.88 b
B @ 1 kg ha⁻¹	22.51 bc	22.09 ab	19.34 b	19.30a	11.33 bc	9.40 ab
B @ 2 kg ha⁻¹	22.79 ab	22.38 a	19.56 ab	19.30a	11.80 ab	9.46 ab
B @ 3 kg ha⁻¹	23.05 a	22.43 a	19.97 a	19.63a	12.45 a	9.95 a
S.Em. ±	0.159	0.16	0.203	0.20	0.24	0.226
Zinc
Zn @0 kg ha⁻¹	22.13 c	21.99 a	19.17a	19.07a	10.63 c	8.73 c
Zn @5 kg ha⁻¹	22.44 bc	22.08 a	19.30a	19.15a	11.19 c	9.32 bc
Zn @7.5 kg ha⁻¹	22.75 ab	22.19 a	19.62a	19.32a	11.91 b	9.57 ab
Zn @10 kg ha⁻¹	23.22 a	22.43 a	19.89a	19.64a	12.70 a	10.09 a
S.Em. ±	0.160	0.16	0.203	0.20	0.23	0.226
Interaction	0.450 (NS)	0.713 (NS)	0.822 (NS)	0.909 (NS)	0.995 (NS)	0.823 (NS)
CV%	4.30	4.30	6.32	6.33	12.40	14.77
Adj. R2	0.368	0.143	0.155	0.137	0.589	0.194

Pooled data over three years (2017-2020 for plant cane and 2018-2021 for ratoon cane) are presented. Means followed by the same letter within a column are not significantly different at p ≤ 0.05 according to Duncan’s Multiple Range Test (DMRT).

Nutritional content and uptake (mg kg⁻¹) of cane and green trash in sugarcane crops was affected by varying levels of B and Zn. The individual effect of different levels of B was found non-significant on primary nutrient contents of sugarcane in both plant cane (Fig. 1A) and ratoon cane (Fig. 1B) except for N content in plant cane. Though non-significant, B application at the rate of 3 kg ha⁻¹ recorded higher nutrient concentrations in the crop and its ratoon (Fig. 2A). This may be attributed to interactions of boron with other nutrients, as evidenced by its ability to enhance nitrate reductase activity, stimulate ATPase activity⁴¹ and induce β-K⁺ channels in roots⁴², all of which reflect B–nutrient interactions. Similarly, B application up to 3 kg ha⁻¹, along with its residual effect, had no significant influence on zinc status (Fig. 1C and D). Overall, neither direct boron application nor its carryover effect substantially affected Zn accumulation. In contrast to its negligible effect on macro nutrients and Zn, different levels of boron and its residual impact significantly influenced boron accumulation in both cane and trash components. In plant cane, B content increased by 13.3% in cane and by 15.3% in trash at 3 kg ha⁻¹ compared to the control. This trend sustained in the ratoon crop, where its residual effect raised cane and trash B content by 6.7% and 10% , respectively. These differences were statistically significant across both crop cycles, underscoring the direct and residual roles of boron in enhancing its own uptake and accumulation within the plant system. This minimal response may be explained by the fact that B primarily influences structural and reproductive activities rather than directly improving macronutrient absorption. Additionally, its relationship with NPK uptake may not be apparent unless B levels are low or high, especially in soils that already contain adequate B.

Fig. 1.

Effect of boron fertilization on N, P₂O₅, and K₂O content in (A) plant cane and (B) ratoon cane; Zn and B content in (C) plant cane and (D) ratoon cane in cane and green trash. Bars represent means ± SE for Zn @ 0, 1, 2, and 3 kg ha^− 1. Different letters indicate significant differences (p < 0.05).

Fig. 2.

Effect of zinc fertilization on N, P₂O₅, and K₂O content in (A) plant cane and (B) ratoon cane; Zn and B content in (C) plant cane and (D) ratoon cane in cane and green trash. Bars represent means ± SE for Zn @ 0, 5, 7.5, and 10 kg ha^− 1. Different letters indicate significant differences (p < 0.05).

Table 5.

Effect of boron and zinc on nutrient uptake of sugarcane and ratoon cane.

Treatments	N uptake (kg ha− 1)		P2O5 uptake (kg ha− 1)		K2O uptake (kg ha− 1)		B uptake (g ha− 1)		Zn uptake (g ha− 1)
	Cane	Ratoon	Cane	Ratoon	Cane	Ratoon	Cane	Ratoon	Cane	Ratoon
Boron
B @ 0 kg ha⁻¹	149c	136 c	65.59a	60.47 c	207c	168 b	558d	418 c	609b	509a
B @ 1 kg ha⁻¹	159b	144 b	71.04a	64.30 bc	218bc	179 ab	605c	455 b	657a	525a
B @ 2 kg ha⁻¹	172a	147 ab	71.38a	66.21 ab	231ab	186 a	655b	470 ab	685a	525a
B @ 3 kg ha⁻¹	179a	152 a	70.75a	68.64 a	241a	191 a	699a	481 a	686a	526a
S.Em. ±	3.32	2.42	1.920	1.431	4.55	4.43	10.09	8.94	14.69	10.92
Zinc
Zn @0 kg ha⁻¹	148d	133 c	65.25c	63.23a	203d	162 c	579c	429 b	520d	458 c
Zn @5 kg ha⁻¹	160c	143 b	67.90bc	65.35a	217c	177 b	607c	458 a	620c	509 b
Zn @7.5 kg ha⁻¹	170b	149 ab	71.65ab	64.75a	231b	187 ab	650b	464 a	698b	539 b
Zn @10 kg ha⁻¹	181a	154 a	73.94a	66.29a	246a	198 a	680a	473 a	799a	579 a
S.Em. ±	3.32	2.45	1.945	1.418	4.53	4.42	10.15	9.08	15.27	10.93
Interaction	0.884 (NS)	0.748 (NS)	0.353 (NS)	0.622 (NS)	0.372 (NS)	0.961 (NS)	0.981 (NS)	0.418 (NS)	0.785 (NS)	0.440 (NS)
CV%	12.07	10.10	16.81	13.49	12.38	14.92	9.83	11.91	13.59	12.81
Adj. R2	0.648	0.380	0.373	0.410	0.650	0.589	0.842	0.701	0.830	0.619

Pooled data over three years (2017–2020 for plant cane and 2018–2021 for ratoon cane) are presented. Means followed by the same letter within a column are not significantly different at p ≤ 0.05 according to Duncan’s Multiple Range Test (DMRT).

Nutrient uptake responded positively to boron application, with a marked increase observed under higher doses (Table 5). Among the treatments, boron applied at 3 kg ha⁻¹ resulted in the highest uptake of N and K₂O in both plant cane and ratoon crops. Although the effect of boron fertilization on phosphorus (P₂O₅) uptake in plant cane was not statistically significant; however, its residual effect was evident, with the highest uptake (68.64 kg ha⁻¹) recorded at the highest dose. This trend was consistent for micronutrient accumulation as well, with B at 3 kg ha⁻¹ leading to the highest uptake of boron (699 g ha⁻¹ in cane and 481 g ha⁻¹ in ratoon) and zinc (686 g ha⁻¹ in cane and 526 g ha⁻¹ in ratoon). Compared with the different levels of B supplementation, control treatment (0 kg ha⁻¹ B) showed the lowest nutrient uptake ability in both the plant and ratoon crops highlighting the positive influence of B on nutrient accumulation. Similar results were reported by²¹, who observed consistently higher B uptake at an application rate of 2 kg ha⁻¹, though they noted phytotoxicity symptoms at higher doses (4 kg ha⁻¹). However, no phytotoxic effects were witnessed in our study, where the maximum B dose was restricted to 3 kg ha⁻¹. The enhanced nutrient uptake in response to B fertilization can be attributed to boron’s critical role in modulating enzymatic reactions that govern nutrient absorption and transport. This is further supported by²⁰, who emphasized boron’s contribution to improved nutrient assimilation through its stimulation of root growth and function. Furthermore¹⁸, highlighted the role of boron in maximizing plant nutrient use efficiency. Its role in auxin synthesis and enzymatic activity could be the reason for the increase in nutrient uptake. According to the available data, boron is essential for improving nutrient concentration and uptake, which in turn promotes better sugarcane growth and harvest.

Effect of zinc fertilization

The application of zinc at 10 kg ha⁻¹ markedly enhanced growth and yield attributes in plant cane resulting in greater total plant height (371 cm), millable cane height (212 cm), and millable cane weight (1.43 kg) (Table 3). A similar trend was evident in the ratoon crop, where the residual effect of zinc application continued to enhance growth parameters, though the magnitude of improvement was relatively lower compared to the plant cane. These findings are in close agreement with⁴³, who observed that zinc application at 12.5 kg ha⁻¹ significantly increased plant height and number of millable canes, highlighting zinc’s strong influence on crop performance. The increased cane height could be attributed to more vegetative development due to the availability of balanced Zn nutrition²¹ and its critical role in the enhancement of plant growth³³, revealed that the application of micronutrients, particularly Zn, significantly enhances sugarcane weight, thereby contributing to increased cane yield. The improvement in stripped cane height⁴⁴ succeeding the application of micronutrients, particularly those containing Zn, might be attributed to involvement of the nutrient in the biosynthesis of tryptophan, a critical precursor in protein metabolism processes.

The application of ZnSO₄ has been shown to significantly enhance cane yield and green top yield in sugarcane cultivation. The dosage of Zn at 10 kg ha⁻¹ produced significantly higher cane and green top yields in both plant (94.17 t ha⁻¹ and 18.92 t ha⁻¹, respectively) and ratoon crops (74.44 t ha⁻¹ and 12.67 t ha⁻¹, respectively). A consistent and progressive increase in both cane and green top yields was evident with increasing Zn levels from 0 to 10 kg ha⁻¹. Higher number of millable canes and greatest cane yield (98.1 t ha⁻¹) were recorded with application of 50 kg ZnSO₄ ha⁻¹ in combination with N and P fertilization by⁴⁵¹⁹. also reported a remarkable cane yield of 111.9 tons per hectare, accompanied by the highest millable cane production, achieved through the application of zinc at a rate of 15 kg ha⁻¹ to the soil. He further reported no significant interaction between B and Zn, which corroborates and reinforces the validity of our findings. In agreement with our findings that Zn fertilisation led to higher cane and green top yields²¹, reported enhanced aboveground biomass (green matter) and stalk yield after Zn treatment during the plant cane cycle. In both studies, the yield obtained from the residual effect of Zn in the ratoon crop was significantly lower than that of the plant cane, although the difference was statistically insignificant. The fundamental function of zinc in plant processes such as photosynthesis, protein synthesis⁴⁶, plant metabolism, enzyme activity and chlorophyll production could be the likely cause of the increased growth attributes (millable cane height, cane weight, cane yield, and green top yield) noticed when it is applied. Zn deficiency reduces hormone production, which results in shortened internodes and restricted leaf growth⁴⁷. Adequate Zn nutrition, on the other hand, promotes overall sugarcane growth by supporting increase in internode elongation, cane diameter, and cane weight^43,48. As these internodes are the primary sites for sucrose accumulation, the optimal application of micronutrients, especially Zn, is essential for enhancing yield-contributing traits such as cane height, girth, and weight, thereby promoting vigorous growth and overall development of sugarcane^49,50. Additional evidence supporting the beneficial effect of zinc fertilization on the growth potential and quality traits of sugarcane is provided by²⁰, who reported that a Zn application rate of 3.9 kg ha⁻¹ resulted in higher ratoon crop yield, highlighting its sustained influence on crop performance. Positive effects of zinc (Zn) application on sugarcane growth and yield have also been reported by^48,50–56. Conversely, several studies from the literature have indicated minimal or no response of sugarcane to Zn fertilization, even under conditions of low soil Zn levels, findings that differ from our results, which established an evident progress in crop growth and yield with Zn application^57,58.

Data depicted that the application of Zn significantly improved the brix percentage in the plant cane and the CCS yield in both cane and ratoon crops (Table 4). Overall, in Zn dose at 10 kg ha⁻¹, 19 and 15% higher CCS yield was noted in plant and ratoon crop, respectively, than unamended control. Higher stalk and sugar yields in sugarcane were reported by⁵⁹ in a study investigating the residual effects of micronutrient application (B, Zn, Cu, Mn, Fe, and Mo), with or without the use of filter cake. Application of Zn at the rate of 15 kg ha⁻¹ resulted in higher brix percentage of 23.1%¹⁹. Although a similar increasing trend was observed in brix percentage of the ratoon crop and sucrose percentage of both plant and ratoon crops with higher Zn doses, the differences were statistically non-significant. Remarkably, the control treatment (without Zn application) consistently recorded the lowest values across all parameters. Higher brix percentage in canes supplied with zinc may be attributed to its role in photosynthesis and carbohydrate metabolism. Multiple investigations have indicated an elevation in sucrose content across different levels of Zn, likely attributable to augmented sucrose synthase activity^6061,62. reported higher sucrose percentage in cane juice with the application of Zn in combination with N, P, K fertilization. However, these findings contrast with our results. In agreement with our observations⁶³, reported a non-significant effect of Zn fertilization on sucrose percentage in cane juice. However, unlike their findings, we observed a noticeable influence of Zn application on overall sugar yield. Similarly higher sugar yield was reported by³⁴ with the application of micronutrients, especially Zn over control. Results supporting the effect of Zn on sugarcane quality parameters have been recorded previously^52,64.

There was no significant effect of Zn fertilization or its residual impact on the N, P, and K content of either the plant cane (Fig. 2A) or ratoon crop (Fig. 2B). Though non-significant, increase in N and K₂O content has been noticed in both cane and green trash, with N content in cane rising from 0.35 (Zn@0 kg ha⁻¹) to 0.37% (Zn@10 kg ha⁻¹) and potassium content increasing from 0.55 to 0.58% over the same treatments. Unlike the gradual increase in N and K₂O content with the progressive application of Zn, no consistent trend was observed in P₂O₅ content across the zinc levels. However, the ratoon cane consistently exhibited higher P₂O₅ accumulation than the plant cane at all nutrient doses, highlighting the residual effect of zinc fertilization. The decrease in P content with increasing Zn levels suggests the existence of an antagonistic relationship between Zn and P, which may be attributed to the influence of Zn on root physiology, phosphorus mobilization, or its availability in the soil⁶⁵. Analysis of Zn content in cane and green trash exposed a clear linear upsurge in accumulation with increasing zinc application levels (0 to 10 kg ha⁻¹), signifying a marked effect in the plant cane (Fig. 2C) and a remarkable residual impact in the ratoon crop (Fig. 2D). The importance of an adequate zinc source for nutrient uptake and plant growth is emphasized by²¹, who also found that applying a higher dose of Zn (6 kg ha⁻¹) to the soil directed to superior micronutrient buildup over time compared to lower Zn levels. The trend indicates how fertilization with zinc improves its accumulation in sugarcane. Due to its vital role in several enzymes that drive numerous metabolic events in all crops, zinc fertilization and its residual effect may be the cause of the improved nutritional content in both cane and its ratoon. Interestingly²⁰, reported no increase in Zn content in leaves with Zn fertilization, which might be attributed to a dilution effect caused by greater sugarcane growth in response to higher Zn doses. The boron concentration in plant cane and ratoon crop did not significantly change across zinc treatments, suggesting that zinc has little effect on boron uptake. With only minor fluctuations among Zn levels, the amount of boron in green trash also stayed fairly constant and non-significant. Zn@10 kg ha⁻¹ recorded the highest N, P₂O₅, K₂O, B and Zn uptake in plant cane (181 kg ha⁻¹, 73.94 kg ha⁻¹, 246 kg ha⁻¹, 680 g ha⁻¹, 799 g ha⁻¹ respectively) and ratoon crop (154 kg ha⁻¹, 66.29 kg ha⁻¹, 198 kg ha⁻¹, 473 g ha⁻¹and 579 g ha⁻¹respectively) (Table 5), compared to the lowest value of control. Soil application of Zn at the rate of 15 kg ha⁻¹ resulted in increased uptake of nutrients in sugarcane and thus higher N (2.4%), K₂O (0.7%), B (31.7 ug g⁻¹) and Zn (68.5 ug g⁻¹) content in crop¹⁹. Similar studies have been conducted by^51,53,55 reporting the positive effects of Zn on sugarcane nutrition. The supplementation of Zn and other micronutrients within an optimal range positively impacts the nutrient uptake of sugarcane^34,46,64, however, excessive supplementation beyond this range does not provide additional benefits and may sometimes cause adverse toxic effects⁶⁶.

Conclusions

This study was undertaken to evaluate the individual and residual effects of graded levels of boron (B) and zinc (Zn) on the growth, yield, quality, and nutrient dynamics of sugarcane (CoN 5071) and its succeeding ratoon crop under the black soil conditions of South Gujarat. The experimental soils were marginal to deficient in Zn and B, which likely contributed to the significant crop responses observed. No significant interaction between Zn and B was found, but their individual application significantly enhanced growth attributes, cane and green top yields, and Commercial Cane Sugar (CCS) yield in plant cane. Zinc at 10 kg ha⁻¹ and boron at 3 kg ha⁻¹ proved most effective. Although the residual effects in the ratoon crop were less pronounced, Zn continued to show a statistically significant influence on yield and nutrient uptake. Nutrient composition and uptake were also positively affected, particularly for N, K, and the applied micronutrient. Boron’s role in sugar metabolism and Zn’s contribution to enzymatic and photosynthetic activity were reflected in improved quality and productivity traits. These results affirm that targeted application of Zn and B in marginally deficient soils can significantly boost sugarcane productivity and nutrient use efficiency.

Hence, for soils marginal to deficient in Zn and B, site-specific application of boron at 3 kg ha⁻¹ and zinc at 10 kg ha⁻¹ is recommended to optimize sugarcane performance and partially sustain ratoon productivity under similar agroecological conditions.

Supplementary Information

Below is the link to the electronic supplementary material.

Author contributions

All authors contributed equally to the research design, development, and the writing of the manuscript. All authors have read and agreed to the published version of the manuscript.

Funding

The research was funded by the Department of Soil Science, N. M. College of Agriculture, Navsari Agricultural University, Navsari 396450.

Data availability

The data supporting this study are available from the corresponding author upon reasonable request.

Declarations

Conflict of interest

The authors declare no conflicts of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.