Influence of boron and zinc application on quality and nutrient uptake of Indian mustard (Brassica Juncea)

Introduction

India is the fourth-largest producer of oilseed crops globally, after the USA, China, and Brazil. Oilseeds play a crucial role in the production of edible oils, while whole oilseeds are valuable sources of energy, protein, and fibre; the oil cakes derived from them are extensively used as feed for livestock. Among oilseed crops, Indian mustard (Brassica juncea L.) occupies a prominent position in India, contributing substantially to the nation's edible oil supply and supporting the rural economy. India ranks among the leading countries in rapeseed-mustard cultivation, with an area of 86.29 lakh hectares, production of 126.06 lakh tonnes, and an average productivity of 1,461 kg ha⁻¹ during the 2024-25 crop year (July-June) (Anonymous a). At the state level, Rajasthan is the largest producer of rapeseedmustard, recording a production of 5.76 million tonnes, followed by Uttar Pradesh (1.96 million tonnes) and Madhya Pradesh (1.92 million tonnes) (Economic Survey 2024-25). Despite its economic importance, mustard productivity in India is often limited by soil nutrient constraints, particularly deficiencies of micronutrients such as zinc (Zn) and boron (B). Zinc is vital for enzymatic activity, protein synthesis, and auxin metabolism, while boron plays a key role in cell wall formation, pollen tube growth, and reproductive development. Deficiency of these nutrients results in stunted growth, chlorosis, poor seed set, and reduced yield and quality. Boron deficiency, in particular, causes sterility manifested as fewer pods and seeds per pod, leading to low seed yield, whereas boron application has been reported to improve oil and protein content in mustard seed (Choudhary and Bhagal, 2017) [2] . Research has shown that supplementation of Zn and B, either alone or in combination with recommended doses of NPK fertilizers, can significantly enhance growth attributes, seed yield, oil content, and nutrient uptake in Indian mustard. (Pandey et al., 2018) [9] . The combined application of these micronutrients has often outperformed sole applications in terms of productivity and seed quality, highlighting the importance of balanced fertilization for improving both yield and economic returns in mustard production systems.

Materials and Methods

A field trial was conducted in the college farm of N.M College of Agriculture, Navsari Agricultural University, Navsari during the rabi season of 2019-20. The study area falls under the heavy rainfall zone of South Gujarat, characterized by deep black clayey soils with medium to poor drainage, good water holding capacity with an initial soil reaction of 7.68 and normal electrical conductivity of 0.38 with low available N (238.6 kg ha -1 ), medium available P (50.8 kg ha -1 ) and high available K (356.2 kg ha -1 ). The trial was laid out in a Randomized Block Design (RBD) with factorial concept in three replications constituting the following treatment combinations of T1 (RDF), T2 (1 Kg B/ha), T3 (2 Kg B/ha), T4 (4 Kg Zn/ha), T5 (8 Kg Zn/ha), T6 (1 Kg B + 4 Kg Zn/ha), T7 (2 Kg B + 4 Kg Zn/ha), T8 (1 Kg B + 8 Kg Zn/ha) and T9 (2 Kg B + 8 Kg Zn/ha). A fine tilth suitable for sowing was achieved through field preparation using a tractor-drawn plough, followed by harrowing and planking. Basal application of organic manures, viz., FYM and bio-compost, along with inorganic fertilizers such as urea, single super phosphate, zinc sulphate, and borax, was carried out as per the respective treatment requirements. Indian mustard (Brassica juncea L.) variety GDM-4 was sown on 19 November 2019 using a seed rate of 3.5-4.0 kg ha⁻¹ at a depth of 3-4 cm, maintaining a spacing of 45 × 15 cm. An optimum plant population was ensured through thinning and gap filling at 10 days after sowing (DAS). Weed management was undertaken through two hand weedings, and irrigation was provided as per the crop requirement to ensure normal crop growth. Biometric observations recorded during the experimentation included plant population, plant height, number of branches per plant, days to 50% flowering, number of siliquae/plant, number of seed/siliquae, Siliquae length, Seed and stover yield (kg/ha), Harvest index and test weight (g). Besides these quality parameters, such as protein content and oil content, and biochemical parameters like N, P, K, B, and Zn content and uptake by mustard, soil N, P, and K levels were calculated before and after harvest. The crop was harvested during the first week of March 2020. After adequate drying, the total biological yield was recorded, and plot-wise threshing was carried out manually by beating with sticks, followed by winnowing and cleaning of the grains. The cost of cultivation was computed for each treatment by accounting for all field operations from preparatory tillage to threshing, based on prevailing local market rates. Gross returns (₹ ha⁻¹) were calculated from seed and straw yields using the respective market prices, while net returns were estimated by subtracting the total cost of cultivation from the gross returns. The benefit-cost (B: C) ratio was calculated as the ratio of gross returns to the total cost of cultivation. Data pertaining to growth, yield, and yieldattributing characters were subjected to analysis of variance (ANOVA) appropriate for a randomized block design, following the procedure described by Fisher (1950) [11] . Treatment means were compared using the critical difference (CD) at the 5% level of significance wherever the F-test indicated significant differences among treatments.

The protein content in Indian mustard improved significantly with boron and zinc fertilization. The highest protein content was obtained in the T9 (25.91%) treatment which remained statistically at par with treatments T8, T7 and T6 over control. The application of 2 Kg B + 8 Kg Zn/ha increased the protein content of Indian mustard by 32.12% over control.

Oil Content (%) Significantly higher oil content was recorded under treatment T9 (44.08%), which was statistically at par with treatments T8, T7, and T6. In contrast, the lowest oil content was observed under control (T1). The increase in oil content under T9 was 13.19% over the control. The enhanced oil content may be attributed to improved metabolic activity associated with the biosynthesis of carbohydrates, organic acids, amino acids, and other biochemical constituents (Sethupathi, 2019) [10] . Zinc plays a crucial role in the activation and synthesis of several enzymes, thereby facilitating oil biosynthesis in mustard seeds. Furthermore, the individual and interactive effects of boron and zinc on oil content were significant (Kumar et al., 2014) [6] . The present findings are in close agreement with earlier reports by Hallur (2011) [5] and Nadaf and Chandranath (2019) [7] . Nutrient Content and Uptake by Indian mustard: The highest nitrogen content in seed was recorded under treatment T9 and was statistically at par with treatments T8, T7, T6, and T5, whereas the lowest value was observed under the control (T1). Seed P₂O₅ and K₂O contents were not significantly influenced by the treatments; however, maximum P₂O₅ (0.59%) and K₂O (0.79%) contents were noted under T9, while minimum values occurred under T1. Nitrogen uptake by seed was significantly highest under T9 (40.29 kg ha⁻¹) and remained at par with T8, T7, and T6. Similarly, P₂O₅ uptake was highest under T9 (14.82 kg ha⁻¹) but was statistically comparable with T8, T7, T6, and T5. The highest K₂O uptake by seed was recorded under T9 (19.88 kg ha⁻¹), remaining at par with T8, T7, and T6. Significantly lower uptake of N, P₂O₅, and K₂O was recorded under the control (T1). Enhanced nutrient uptake under boron and zinc fertilization may be attributed to improved seed setting, seed quality, and nitrogen absorption (Nandi et al., 2020) [8] . The superior nutrient uptake recorded under treatment T9 could further be ascribed to enhanced vegetative growth and better root development, leading to increased absorption of N, P, and K from the soil and improved metabolic activity within the plant (Nandi et al., 2020) [8] .

Zn and B content and uptake by Indian mustard

Significantly highest Zn content in seed was recorded with treatment T9 (18.73 ppm) which remained statistically at par with T8, T5, T7, T6 and T4. The highest B content was recorded with treatment T9 (15.12 ppm) and remained statistically at par with treatments T7, T3, T8, T6 and T2. The lowest Zn and B content in seed was registered under control (T1). Considerably highest Zn uptake by seed was recorded with treatment T9 (47.39 mg/ha) which remained at par with treatments T8, T7, T5 and T6 and B uptake by seed was significantly highest under treatment T9 (38.19 mg/ha), which remained statistically at par with treatments T7, T8 and T6. The lowest uptake by seed was observed under treatment T1 for both the nutrients Zn and B. The suggested fertilization of Zn and B nutrients will increase the concentration of both nutrients in the plant tissue (Debnath et al., 2015) [3] . Debnath et al. (2015) [3] reported that the combined application of Zn and B tended to enhance B uptake by mustard grown in the alluvial soils of Kanpur, Uttar Pradesh. Increased B uptake was observed at all levels of B application with increasing Zn supply, indicating that adequate Zn availability facilitates B accumulation in mustard grain, seed, and stalk. Furthermore, higher B supply under elevated Zn application rates resulted in improved Zn uptake, suggesting a synergistic interaction between B and Zn. This implies that B application can enhance Zn uptake when Zn is supplied at adequate levels (Kumar et al., 2014) [6] .

References

1. Anonymous. High-yielding seeds, increased acreage to boost mustard production: experts. Business Standard. 2025 Jul 9. Available from: https://www.businessstandard.com
2. Choudhary S, Bhagal NS. Effect of boron on yield, quality and its uptake in Indian mustard (Brassica juncea L.) genotypes. Annals of Plant and Soil Research. 2017;19(4):394-397.
3. Debnath P, Pattanaaik SK, Sah D, Pandey AK, Sen D, Chandra G, et al. Response of boron and zinc fertilization to productivity of rice in piedmont soil of Arunachal Pradesh. International Journal of Agriculture, Environment and Biotechnology. 2015;8(4):911-913.
4. Government of India. Economic Survey 2024-25 statistical appendix. 2025. Available from: https://www.indiabudget.gov.in/economicsurvey/doc/st at/tab1.18.pdf
5. Hallur C. Studies on zinc, iron and boron nutrition on yield, quality and nutrient uptake by cabbage (Brassica oleracea var. capitata L.) in northern transition zone of Karnataka [thesis]. 2011. Available from: http://krishikosh.egranth.ac.in/handle/1/5810004110
6. Kumar V, Singh SK, Suman SN. Zinc-boron interaction effects on yield, nutrient uptake and quality of mustard (Brassica juncea L.) in Ustifluvents. RAU Journal of Research. 2014;24(1-2):59-63.
7. Nadaf S, Chandranath HT. Effect of zinc and boron on nutrient uptake, yield and quality of mustard under rainfed condition. International Journal of Current Microbiology and Applied Sciences. 2019;8(6):24902495.
8. Nandi R, Reja H, Chatterjee N, Bag AG, Hazra GC. Effect of Zn and B on the growth and nutrient uptake in groundnut. Current Journal of Applied Science and Technology. 2020;39(1):1-10.
9. Pandey M, Singh S, Singh UN. Direct effect of boron and zinc on productivity, quality and nutrient uptake by Indian mustard (Brassica juncea) and their residual effect on succeeding pearl millet (Pennisetum glaucum) in mustard-pearl millet crop sequence. Indian Journal of Agricultural Sciences. 2018;88(10):1613-1617.
10. Sethupathi S. Effect of zinc and boron on yield and quality of onion (Allium cepa L.) in Alfisols of Tamirabarni tract. Madras Agricultural Journal. 2019;106(2-4):293-296.
11. Fisher RA. The significance of deviations from expectation in a Poisson series. Biometrics. 1950 Mar 1;6(1):17-24.