Yield and potassium uptake of rice as affected by potassium rate in the middle reaches of the Yangtze River, China

Abstract

Abstract Potassium is an essential macroelement for rice ( Oryza sativa L.), but K deficiency in paddy ecosystems has increased widely and limited sustainable rice production in China. Two‐year field trials were conducted with five K levels (0, 60, 120, 180, and 240 kg K 2 O ha –1 , designated as K0, K60, K120, K180, and K240) in Qichun county, Hubei Province, to investigate grain yield, K uptake characteristics, and K use efficiencies of rice. The results showed that application of K increased rice yield by 9.8–29.3%, compared to K0. No significant differences were observed in rice yield among the K120, K180, and K240 treatments. The K uptake in aboveground biomass increased linearly with the K rate, while K harvest index decreased. As K uptake increased, rice yield increased linearly at first and then stabilized, showing the phenomenon of luxury consumption of K. The growth period for fast K uptake in different rice varieties and K levels was 29–67 d after transplanting, and sufficient nutrient supply is needed to ensure the increase of rice yield and growth during this period. Internal use efficiency (IUE), agronomic efficiency (AE), and physiological efficiency (PE) declined as the application rate of K increased. These results indicated that absorption and utilization of K in rice were affected by the K supply rates, and that luxury consumption occurred when K application was excessive. The luxury consumption of K by rice was mainly stored in straw.