Yield and Quality of Ratoon Sugarcane Are Improved by Applying Potassium under Irrigation to Potassium Deficient Soils

Abstract

The current study was carried out at the experimental farm of Rana Sugars Ltd., Buttar Seviyan, Amritsar, Punjab, India, to identify methods to improve the yield and quality of ratoon sugarcane in potassium-deficient soils. The treatments comprised two levels of irrigation, resulting in plants which either received sufficient water (I1) or were water-stressed (I2), and four rates of potassium (K) application: 0 (K1), 40 (K2), 80 (K3) and 120 (K4) kg K2O ha−1. The results showed that the irrigation levels did not influence crop parameters significantly, although all parameters presented higher values for I1-treated plots. Compared to the K1 (i.e., 0 kg ha−1 K fertiliser applied) treatment, the K2, K3 and K4 treatments yielded 11.16, 37.9 and 40.7%, respectively, higher millable canes and 1.25, 5.62 and 13.13% more nodes per plant, respectively. At 280 days after harvest of the first (plant) crop, the I1 treatment provided ratoons which were up to 15.58% higher than those obtained with the I2 treatment, with cane girths up to 7.69% wider and yields up to 7.29% higher than those observed with the I2 treatment. While the number of nodes per plant did not differ significantly between treatments, there were significant differences in other parameters. Quality parameters (with the exception of extraction percentage) were significantly enhanced by the K3 treatment. The benefit-to-cost ratio (B/C) was higher for the I1 treatment than for the I2, due to a reduced productivity associated with the I2 treatment. At both irrigation levels, the K3 treatment resulted in the highest quality parameters. K1-, K2- and K4-treated plots presented more instances of insect infestations than plots receiving the K3 treatment. Relative to the K3 plots, infestation by the early shoot borer (Chilo infuscatellus) was 18.2, 6.0 and 12.2% higher, respectively, in plots that underwent the K1, K2 and K4 treatments, while infestation by the top borer (Scirpophaga excerptalis) was 21.2, 9.21 and 14.0% higher, and that by the stalk borer (Chilo auricilius) was 10.7, 0 and 8.10% higher. Not all infestation differences between treatments were significant. Our research demonstrates that growing sugarcane in potassium-deficient soils with applications of 80 kg K2O ha−1 under irrigation should be recommended to increase yield and quality while minimising insect infestation and to implement sustainable ratoon sugarcane production.