| Jiangxi province is the typical double rice region in the south of China, playing an important role in rice production in our country. Fertilization is an important way to increase and security crop yield. However, long term inorganic fertilizer can easily lead to soil degradation, fertility decrement and non-point pollution, etc. The enhancement of organic fertilizer such as green manure, barnyard manure and straw can not only improve soil structure and organic content, guarantee crop high and stable yield, but also reduce inorganic fertilizer input and environment pollution risk. Therefore, it is necessary to comparably analyze the productivity and stress resistance of double rice cropping system under long term green manure application, and thus evaluate scientific fertilization method. And it is of important theoretical significance and practical value for paddy productivity increment and food security guarantee in our country.Based on long-term fertilizer experiment (28 years,1981-2008) and 4 years nutrient exhausting experiment in Jingxian, Jiangxi province, we analyzed the differences in productivity and its trend, harvest index, fertilizer use efficiency among 6 green manure application treatments. The treatments included control, normal green manure (GM), high green manure (2GM), green manure combined with barnyard manure (G-F), green manure combined with straw manure (G-F-S), and chemical fertilizer (NPK). Associated with the study on the trends of paddy productivity, the coefficient of variation (CV) and the sustainability yield index (SYI) under different long-term green manure application treatments, we elucidated the integrated effects of different long-term green manure application on the productivity and stress resistance of double rice cropping system in Jiangxi province. The main results were as follows:1. The productivities of double rice cropping system under different long-term green manure application were significantly higher than control. The yearly averaged rice yield under G-F and G-F-S treatment was 64.8% and 68.5% higher than CK treatment, the increasing effects under G-F and G-F-S treatments were significant higher than the GM. 2GM and NPK treatments. The effect of long-term green manure application treatments were in different with that of NPK treatment. The N and P use efficiency was significantly higher in NPK treatment than in G-F and G-F-S treatments but lower than in GM and 2GM treatments. The annualaboveground biomass and grain yield were stable in NPK treatment with the yield decreasing with years (-4.9 kg hm-2 y-1). However, the yields in green manure application treatments were increased. The yield sustainability was lower in NPK treatment than green manure application treatments. The 4 year exhaustion experiment showed that, under the same conditions with no fertilization application, the yield decline rates were as follows:GM< NPK< 2GM< G-F-S< G-F. Besides, the results also showed that the tolerance ability of double rice cropping system under long-term NPK application was only lower than the GM treatment and higher than other green manure treatments.2. With the increased manure application, the effects were not always better. The yield-increasing effects between 2GM treatment and GM treatment were insignificant and so did the stability and sustainability. However, the yield-increasing trend was higher in GM treatment than 2GM treatment, and the tolerance ability of paddy ecosystem was significant higher under long term GM treatment than 2GM treatment. Therefore, the green manure application combined with chemical fertilizer was better to applied with appropriate amount. The yield-increasing effects were significant higher in G-F and G-F-S treatments than GM treatment. And the yield and biomass sustainabilities were higher under G-F and G-F-S treatments than GM treatment. Only under G-F or G-F-S treatment, the yield-increasing trends were not enhanced, the CV of yield and biomass was similar with that under green manure application, but the tolerance ability of paddy ecosystem was lower than GM treatment.3. Moreover, the combining application of appropriate manure with chemical fertilizer also maintained stable and sustainable yield, increased N,Pand K use efficiency, enhanced productivity and stress resistance. There is no significant difference between the grain yield under GM,2GM and NPK treatment, but the green manure application could annually decrease the inputs of chemical N, P and K fertilizers by 90.0 kg hm-2,9.9 kg hm-2 and 72.0 kg hm-2, respectively. Although compared with the treatment of GM, the increasing effect of G-F and G-F-S treatment is better, GM treatment sharply decreased fertilization input. This will save resources and production cost, decrease environmental pollution risk and thus achieve good effects on ecological environment improvement, and energy saving and emission reduction. The results further proved adopting application of chemical fertilizer combined with appropriate green manure is an important way for income increasing and cost saving as well as energy saving and emission reduction with double season rice in Jiangxi province. |
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