Equal K Amounts to N Achieved Optimal Biomass and Better Fiber Quality of Late Sown Cotton in Yangtze River Valley

Abstract

Potassium (K) fertilizer plays a crucial role in the formation of the biological and economic yield of cotton (Gossypium hirsutum L.). Here we investigated the effects of the amount of K on biomass accumulation and cotton fiber quality with lowered N amounts (210 kg ha⁻¹) under late sowing, high density and fertilization once at 2 weeks after squaring. A 2-year field experiment was performed with three K fertilizer amounts (168 kg ha⁻¹ (K₁), 210 kg ha⁻¹ (K₂), and 252 kg ha⁻¹ (K₃)) using a randomized complete block design in 2016 and 2017. The results showed correspondingly, K₃ accumulated cotton plant biomass of 7913.0 kg ha⁻¹, next to K₂ (7384.9 kg ha⁻¹) but followed by K₁ (6985.1 kg ha⁻¹) averaged across two growing seasons. Higher K amounts (K₂, K₃) increased biomass primarily due to a higher accumulation rate (32.68%–74.02% higher than K₁) during the fast accumulation period (FAP). Cotton fiber length, micronaire, and fiber strength in K₂ were as well as K₃ and significantly better than K₁. These results suggest that K fertilizer of 210 kg ha⁻¹ should be optimal to obtain a promising benefit both in cotton biomass and fiber quality and profit for the new cotton planting model in the Yangtze River Valley, China and similar climate regions.