Coupling effects of reduced nitrogen, phosphorus and potassium on drip-irrigated cotton growth and yield formation in Northern Xinjiang

Abstract

ABSTRACT To elucidate the effects of nitrogen (N), phosphorus (P) and potassium (K) on cotton growth and yield, field studies with four N treatments (506, 402.5, 299 and 195.5 kg ha−1 designated as N1, N2, N3 and N4, respectively) and four managements (M) of P and K application, designated as PK-M1 (total P and K applied at squaring stage (SS)), PK-M2 (25%:75% at SS and bloom-bolling stage (BS)), PK-M3 (50%:50% at each stage), PK-M4 (75%:25% at SS and BS) were conducted in 2018 and 2019. Results are shown in reproduction growth, PK-M3 under N treatments had the highest maximum biomass (K’) and fastest speed of biomass accumulation (Vmax), and N2PK-M3 obtained higher K’ and Vmax than others, followed by N3PK-M3. The average boll number, boll weight and yield in N2 were greater than others, and N3 with a decrease of 3.4–6.1% in average yield over N2. Although the yield in N3PK-M3 reduced by 1.4–1.5% compared to N2PK-M3 (losses about $8–32 per hectare), the fertilizer input decreased about $60–63 per hectare than N2PK-M3. Results suggest that 50% PK application ratio during SS and 50% during BS coapplied with proper reduced N application rate could compensate the yield loss by maintaining a higher level of reproduction biomass accumulation.