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

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.