Response of rice-rice ecosystem productivity and yield stabilityto long-term fertilization

The productivity and yield stability of rice-rice ecosystem in Huazhong with different fertilizers were investigated using experimental data from the Chinese Ecosystem Research Network at Taoyuan Station of Agro-ecology Research, Chinese Academy of Sciences. The field trials included no fertilizer (CK), chemical fertilizer (NPK), rice straw with low N, K and high P (optimal fertilization, OF) and rice straw with some amount of NPK (general fertilization, GF). The results showed that fertilization was the basic mode of maintaining or increasing productivity of rice in paddy ecosystem. Productivity and stability were different in paddy ecosystems with different fertilizers. The total rice biomass was significantly higher in fertilizer treatments than in no fertilizer treatments; 0.33~1.23 times higher for the period of 2005 to 2010. The order of stability from high to low was OF > GF > NPK > CK. OF treatment improved total biomass stability in the study area. Yield under fertilizer treatments was 0.35~1.02 times higher than under no fertilizer treatment for the period of 2005 to 2010. It was 0.35 times higher in GF than CK in 2005, 0.82 times higher in NPK than CK in 2007 and 1.02 times higher in OF than CK in 2010. The stability of rice yield was high in OF treatment and significantly low in CK treatment. Yearly variation coefficient under CK, NPK, OF and GF treatments was 22.4%, 15.8%, 10.3% and 15.7%, respectively. Productivity of underground biomass was significantly higher in fertilizer treatments than in no fertilizer treatment. Also ecological stability was significantly higher under GF treatment than the other treatments. In conclusion, rice productivity and production stability were highest under OF treatment and lowest under CK treatment. While fertilizers influenced rice yield stability and total or over-ground rice biomass, they little affected the stability of below-ground biomass productivity.