Study on high efficiency nutrient use and regulation of soil nutrient dynamics for high yield rice

Rice crop plays a crucial role in food production of China. Hunan is the largest rice production province in China with an annual production of 29.1 M t. To study high efficiency nutrient use and regulate soil nutrient dynamics for increasing rice yields, Hunan Institute of Soil and Fertilizer collected in 2011 a total of 24 samples from eight main double-rice production counties.

Results showed that the amounts of bacterium, fungi, and actinomycetes and the contents of soil microbial biomass carbon (SMBC) and soil microbial biomass N (SMBN) in both high and medium productive paddy soils did not differ significantly. Similarly, the observed trends in activities of urease, phosphatase, invertase, dehydrogenase in both high and medium productive paddy soils showed no significant difference. Double rice planting areas in Hunan, with a history of applying P fertilizer for the last 50 years at least leading to high soil P levels, resulted in no significant differences in phosphatase activity in high, medium, and low productive paddy soils. Correlation analysis showed that soil bacterium and actinomycetes had the best correlation with soil organic carbon (SOC), total N (TN), total K, and available N (AN). Soil urease and invertase activities had the best correlation with SOC, SMBC, SMBN, TN, AN. Most of the microbiological and biochemical indicators did not differ significantly between high and medium productive paddy soils, but differed significantly from the low productive paddy soil. Therefore, low productive paddy soil should get more attention in terms of balanced application of organic manures and inorganic fertilizers. High productive paddy soil in double-rice cropping regions of Hunan showed 48±12 g/kg of organic matter content, 2.7±0.7 g/kg of TN, 40±14 mg/kg of available P, and 106±23 mg/kg of available K. Textures of high productive paddy soils were generally loamy and sandy clay loam with weak K retention capacity. Therefore, since the available of K content was not high in highly productive paddy soils, these soils would benefit from an application of K fertilizer. Hunan-16