Relationship of tissue potassium content with yield and fiber quality components of Bt cotton as influenced by potassium application methods

The fast fruiting and early maturing cotton varieties demand higher potassium (K) supply to achieve full yield potential. The supplemental foliar application of K may enhance the efficacy of soil applied basal dose of K. The main objective of this study was to quantify the impact of foliar application of KNO3 alone and in combination with soil applied K on cotton yield and lint quality. The treatments included control (no K application), four foliar sprays of 2% KNO3, 100 kg K2O ha−1 to soil, 200 kg K2O ha−1 to soil, combination of 100 kg K2O ha−1 to soil + four foliar sprays of 2% KNO3, and combination of 200 kg K2O ha−1 to soil + four foliar sprays of 2% KNO3. The results revealed that foliar and basal-applied K in alone and in different combinations significantly improved the plant morphology, seed cotton yield, boll characteristics and K concentrations in various plant parts. The K concentration in vegetative and boll components was improved with the higher K application rate. On overall basis, a yield benefit of 406 and 432.5 kg ha−1 was achieved with foliar spray in combination with 100 and 200 kg K2O ha−1 compared to their respective sole soil application. Non-significant differences for ginning out turn (GOT), staple length, strength, micronaire and uniformity index due to various K application methods indicate that K fertilization does not improve the fiber quality and GOT when soil has adequate K levels. It is concluded that foliar K application should be combined with basal K applications to achieve the highest returns from cotton grown on K-deficient soils.