Studies on fertility characteristics of different productive paddy soils in double-rice copping regions of Hunan province

Fertility characteristics of different productive paddy soils were studied to provide scientific basis for the management and sustainable utilization of paddy soils. Fraction of organic matter (total organic matter and humus composition) and nutrient contents (total and available nutrients) and their relationships with rice yield were investigated by soil sampling and recorded rice yield from double-rice cropping areas of eight important rice production counties in Hunan province. The results show that the contents of organic matter (47.7411.59 g/kg), total N (2.700.72 g/kg) and available P (39.814.21 mg/kg) of the high productive paddy soils are at their very rich levels, respectively, the contents of organic matter, total N and available P in the middle productive paddy soils are at their rich levels, and the contents are not significant differences between the high productive paddy soils and the middle productive paddy soils. The contents of the low productive paddy soils are significantly lower than those of the high and middle productive paddy soils. Available K contents are at the middle level (105.8322.73 mg/kg) in high productive paddy soils, and are at deficient and very deficient levels for the middle and low productive paddy soils, respectively. The contents of organic matter, total N and available P are at the very rich levels in high productive paddy soils because of the long-term rice cultivation and fertilization, and both organic matter and P pool are at very rich and surplus states. Textures of the high productive paddy soils are generally loamy soils and sandy clay loam soils with a weak K retention capacities, and the available K contents are not rich in high productive paddy soils, it should be pay attention to rational application of potassium fertilizer, organic matter and rice straw returning to soil for maintaining the balance and increase of soil K pool. For most of the middle productive paddy soils, due to relative rich with contents of organic matter, total N and available P, could achieve rice yield target of high productive paddy soils only under good field management practices. Soil physical properties and nutrients of the low productive paddy soils are all poor, it should be pay attention to rational combing application of organic manure and inorganic fertilizer for improving the soil physical quality and soil fertility.