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Nutrient balance index on cultivated land and grain yield of China |
Note: GBI refers to the ratio of pure input nutrient volume to pure nutrient volume absorbed by crops, which GBI=1 indicates a general nutrient balance being achieved, while GBI>1 indicates a surplus nutrient input situation and GBI<1 shows an inadequate one.
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Source: Institute of Agricultural natural Resources and Zoning, Academy of Agricultural Sciences of China,1995， China cultivated land, China Agricultural Sci-tech Publishing House，p100. |
