Combined application of organic materials and inorganic fertilizers improving rice yield and soil fertility of yellow clayey paddy soil

Agricultural organic materials are very important reusing resources, and they can play important roles in ensuring crop yields and improving soil fertility. In order to find the most optimum mode to bettering soil fertility in yellow clayey paddy soil in south China, we investigated the effects of different organic materials on rice growth and soil fertility when in combined application with inorganic fertilizers by a 3-year field study, which was carried out in Jinhua County, Zhejiang Province. Six treatments were included: no fertilizers(CK), NPK alone(F), NPK plus mushroom residue compost(FR), NPK plus green manure(FG), NPK plus cattle manure(FM) and NPK plus rice straw(FS). All fertilization treatments received the same quantity of inorganic fertilizers(N: 180 kg/hm², P2O5: 90 kg/hm² and K2O: 120 kg/hm²). For organic materials, according to local usage, the application rates were as follows: mushroom residue compost(dry weight: 1500 kg/hm²), green manure (fresh weight: 22500 kg/hm²), cattle manure (fresh weight: 13500 kg/hm²), rice straw (dry weight: 3000 kg/hm²). We determined the rice grain yield, yield components and biomass at different growth stages during 2011-2013, and soil organic matter (SOC), total nitrogen (TN), available phosphorus (P), exchangeable potassium (K), cation exchange capacity (CEC), pH, soil bulk density of 0~20 cm were determined after rice harvest in 2013. In addition, we measured the mechanical-stable and water stable soil aggregates(size classes: >5 mm, 2~5 mm, 1~2 mm, 0.5~1 mm, 0.25~0.5 mm) at the same time. The results showed that: 1) combined application of organic materials significantly increased average rice yield for the 3 years, and FR, FG, FM and FS improved by 9.7%, 9.5%, 12.3% and 9.5% respectively compared to NPK alone; 2) combined application of organic materials improved SOC, TN, available P, exchangeable K and soil bulk density to some extent, especially for the FM treatment, it significantly increased SOC, available P and CEC by 12.5%, 37.7%, and 16.1% respectively compared to NPK alone; 3) FR and FM increased soil mechanical-stable aggregates (>5 mm) by 10.4% and 6.7%, and all treatments with organic materials significantly decreased the percentage of soil aggregate destruction. Overall, combined application of organic materials with inorganic fertilizers increased rice grain yield, improved soil fertility, enhanced stability of soil aggregates, and FM performed the best.