In semiarid tropical locations, polyhalite (K2Ca2Mg(SO4)4H2O) and muriate potash (KCl) were tested for their ability to increase cane growth, yield, and recovery at potash (K)- and calcium (Ca)-deficient sites.
The treatments involved control plots with no potash fertilizer (T1); T2 and T3 applied potassium through (muriate potash) MOP only at 80 and 120 kg K2O ha−1, whereas T4 and T5 applied potassium with half of MOP and polyhalite at 80 and 120 kg K2O ha−1, respectively.
At 35 days after harvest (DAH), T2 (10.82%), T3 (24.1%), T4 (34.9%), and T5 (34.9%) had a greater ratoon resprouting rate than did the control treatment, where it was just 37.0 out of 100 harvested canes. At 308 DAH, T2 (−5.9%), T3 (−5.7%), and T5 (−6.6%) presented greater leaf chlorophyll contents than did T1. The K-fertilized plots yielded 64.31 t ha−1 in T2 and 65.97 t ha−1 in T5, whereas the control plot yielded 61.5 t ha−1. Compared with the control plots, the T5 plots experienced fewer stalk borer (−28.6%), top borer (−23.3%), and early shoot borer (−23.3%) attacks. T2, T4, and T5 presented higher percentages of commercial cane sugar (CCS) (6.82, 8.83, and 8.74%, respectively) than did the control plots. T1 and T3 had similar CCSs (10.99 and 11.33%, respectively). The CCS weight per area ranged from 7.98 to 8.47 t ha−1 near maturity. T4 (8.59 t ha−1) and T5 (8.60 t ha−1) had significantly greater values than did T1–T3. Compared with the control, the applied potassium fertilizer increased the economic output by 8,711, 11,687, 13,485, and 13,857 INR ha−1 in the T2, T3, T4, and T5 plots, respectively. The higher cost of polyhalite than MOP has reduced its economic advantages. Thus, the T4 plots outperformed the other treatments in terms of growth, yield, and quality indices, but their higher values (120 kg K2O ha−1) were statistically equivalent.
Finally, the study concluded that MOP and polyhalite at a 50% ratio of 80 kg K2O ha−1 may help improve sugarcane growth, yield, and quality in semiarid tropical locations.