稻田生态系统氮素吸收功能及其经济价值

稻田生态系统中水稻植株吸收土壤中氮素并转化为秸秆中的氮素以及籽粒中的蛋白质和氨基酸的过程是稻田氮素转化的主要过程。在2003年上海市郊五四农场田间试验数据的基础上，研究了稻田生态系统氮素吸收功能及其形成过程，然后运用替代价格法估算了稻田氮素吸收经济价值，同时还对不同地区、施氮水平和作物的氮素吸收物理量和价值量进行了对比。结果表明，稻田植株地上部分氮素累积吸收量在拔节期至抽穗期之间增长最快，抽穗期至成熟期增加减缓，而在收获前有所下降。稻田植株氮素吸收经济价值随生育期不断提高，到成熟期显著增加。施加氮肥对水稻氮素吸收物理量及其价值量都具有促进作用。就不同作物而言，水稻氮素吸收转化量及其经济价值高于小麦和油菜。几乎所有作物籽粒氮素吸收量及其经济价值都高于秸秆。

Process of nitrogen uptake by rice paddy ecosystem and its economic value

Rice plants in paddy ecosystems take up nitrogen from the soil, store it in straw or transform it into protein and amino acid in seed. This is one of the most important processes of nitrogen cycling in rice field ecosystems. Based on the data from field experiment in Wusi Farm of Shanghai in 2003, we examined the process of nitro- gen uptake by rice plants, estimated its economic value with the method of replacement price and compared the quantities of the nitrogen uptake and their economic values among different regions, fertilizer dose and crops. The results indicated that the nitrogen uptake by rice plants accumulated rapidly between tillering and heading stage and decreased a short time before harvest stage. The economic values of nitrogen uptake increased with growth stages. Fertilization promoted the accumulation of nitrogen uptakes and their economic values. The nitrogen uptakes by rice plants and their economic values were higher than those by wheat and rape. The quantities of the nitrogen transformed into seed and their economic values were more than that into straw.