Effects of long-term green manure application on rice yield and soil nutrients in paddy soils

A long-term field experiment on rice yield and soil fertility under different fertilization systems were carried out to study the effects of manure application on rice yield and soil nutrients in paddy soils. In this paper, the 26-year experimental results were analyzed. The results show that the long-term applications of green manure combined with chemical fertilizers are in favor of stable and high yields of rice, reduce amounts of fertilizer applications, and raise agronomic efficiencies (beyond 60%) of chemical fertilizer NPK nutrients. The average rice yield of the OM3 treatment is the highest in 26 years, which is about 64.47% and 6.86% higher than those of the treatments of CK and chemical fertilizer NPK application. The agronomic efficiency of the manure application is 16.33kg.kg-1, which is 118.9% higher than that of the treatment of applying chemical fertilizer NPK. The contents of soil organic matter, total N and total P are increased under the green-chemical fertilizer applications, the accumulated amounts are related with the fertilizer application and manure types, and the OM3 treatment is the optimal treatment. The amounts of soil potassium are all in deficiency, the total and available potassium contents are lower than those at the beginning of the experiment, and the OM4 treatment is the optimal treatment, in which the total and available K are 4.28% and 13.94% higher than those of the CK treatment. By analyzing the correlation between rice yield and organic matter, total N, total P and total K in soils, the highest correlation coefficient(r=0.808**) is the soil total K, therefore the K deficiency is the main fertility factor for high yield of rice in paddy soils derived from red soils.