Potassium disproportion affects leaf C/N ratio, amino acids Pool and yield of cotton under reducing-nitrogen supply

A new competitive and cost-effective planting model specified with late-sowing, high-density and reduced-nitrogen (N) rate with once-fertilization is a potential alternate to the conventional high-cost cotton cropping system. In this model, as the N rate is reduced, a question remains as to what the optimal K application rate should be due to its significant role in cotton physiology and yield formation. So, three K rates: K-1 = 168 K2O kg ha(-1), K-2 = 210 K2O kg ha(-1), and K-3 = 252 K2O kg ha(-1) under reduced N rate (210 N kg ha(-1)) with four replications were used to quantify the effect on leaf C/N ratio, amino acid pools, and yield of cotton during 2016 and 2017. The results exhibited that higher K rates (K-2 and K-3) considerably lowered leaf C/N ratio and amino acid pools while enhancing the lint yield and seed cotton yield in both growing seasons. Enhanced leaf K level resulted in reduced amino acid pools and low leaf C/N ratio. The increase in boll weight with increased leaf K and decreased leaf C/N ratio improved the yield. Results further directed that a higher K rate rationally balanced the C/N ratio and amino acid pools to a low range in cotton leaf. However, from economic view point, K rate equal to N is appropriate to get satisfactory yield in late-sown cotton with high-density.