Suzhou district is one of the highly productive agricultural regions of intensive farming and high fertilizer imput.In the recent years,the rate of application of nitrogen fertilizets for each rice crop season in this region has attained an average above 150 kg.of N pet hectare which is believed to be the amount required by rice plants in order to get 7500 kg.of grain per hectare.It was showed by ¹⁵N-tracing experiments with the similar fertilizer application rates that the loss of fertilizer-N during tie growing season accounted for 30% to 70% of the fertilizer-N applied in this region,and some studies revealed that deep-dresing,granulation and appropriate timing of the application for nitrogen fertilizers seemed to be effective for increasing the efficiency of fertilizer-N in the rice field.