Characteristics of K Nutrient Input/Output and Its Balance for Wheat Season in China

In this study, the input and output parameters of potassium (K) for wheat season were collected from 2000 to 2011 to evaluate the nutrient cycling and balance in North Central China, the Middle and Lower Reaches of the Yangtze River and Northwest China. The results showed that the K fertilizer application rates for each region were 74.7, 102.9 and 50.6 kg K/ha, the K brought from previous crop were 99.5, 19.8 and 23.4 kg K/ha, and brought from seeding were 1.0, 0.8 and 0.7 kg K/ha, respectively. The K input from atmospheric deposition and irrigation were all considered zero. The K uptake by harvest in above-ground plant in North Central China, the Middle and Lower Reaches of the Yangtze River and Northwest China were 131.8, 159.9 and 119.8 kg K/ha. As a result, The K balance in North Central China showed surplus by 43.6 kg/ha, while in the Middle and Lower Reaches of the Yangtze River and Northwest China, the K balance were both deficiency by 36.4 and 45.1 kg/ha, even though it did not affect the crop yield. While it is suggested that we need to adjust the K fertilizer application in a long term, in order to maintain the sustainable soil fertility.