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A macro scale survey was performed to investigate the content of soil available nitrogen (N) and its spatial distribution in the main vegetable production areas of the Pearl River Delta.Preliminary enrichment-deficient index of available N was then developed,which was a base for increasing fertilizer application efficiency and vegetable yield as well as for constructing soil testing and fertilizing formula.In general,most of the vegetable growth areas in Pearl River Delta were N-deficient or medium-N-deficient.There was 30%-62% increase in yield of Chinese cabbage on the N-deficient soil after application of N; when soil available N content was less than 145 mg/kg,the yield increased with application of N fertilizer at a rate of 60-70 kg/hm2.
A macro scale survey was performed to investigate the content of soil available nitrogen (N) and its spatial distribution in the main vegetable production areas of the Pearl River Delta. Preliminary concentration-deficient index of available N was then developed, which was a base for increasing fertilizer application efficiency and vegetable yield as well as for constructing soil testing and fertilizing formula. In general, most of the vegetable growth areas in Pearl River Delta were N-deficient or medium-N-deficient. there was 30% -62% increase in yield of Chinese cabbage on the N-deficient soil after application of N; when soil available N content was less than 145 mg / kg, the yield increased with application of N fertilizer at a rate of 60-70 kg / hm2.