Maximal amount of
chemical fertilizer used and its increase space as well as its effect on crops yield were studiedthrough statistic analysis of
total amount of chemical fertilizer used, total yield of crops and total cultivated area in different areas ofChina in 1990-2000. The results showed that, the maximal of amount of chemical fertilizer applied in China was 225-375 kgha-1. Thecounties with 300-375 kgha-1 of fertilizer applied and 306.8 kgha-1 in
average distributed in higher
fertilization region, and the countieswith 225-300 kgha-1 chemical fertilizer consumption and 262.4 kgha-1 in average distributed in
medium fertilization region, and thecounties with 150-225 kgha-1 fertilizer used and 217.2 kgha-1 in average distributed in lower fertilization region. The ranges of yieldsof crops in higher, medium and lower fertilization regions were 6000-7500, 4 500-6 000 and 3 000-4 500 kgha-1with a 6183.9,5497.9 and 5351.3 kgha-1 in average, respectively. At present productivity level, fertilization increase space in China was 167.4107,467.1107 and 292.2 107 kg in higher, medium and lower fertilization region respectively with average fertilizer consumption at 35.6,64.0 and 82.6 kgha-1. Total fertilization space in China was 926.7107 kg with 59.6 kgha-1. That means there are still 22.3% spaces forfertilization increase based on present fertilization level. Two provinces were selected from higher, medium and lower fertilizationregion respectively to study the relation between the use efficiency of chemical fertilizer and application rate per unit area . The resultsindicated that the application rate of use amount of chemical fertilizer per unit area increase with the relative decrease of use efficiencyof chemical fertilizer at the same time, and the trend of change was different in different regions.
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