Fertilizer Issues And Strategies Of Sustainable Agriculture Development In Nanjing

Faced with the pressure of population and food production, the consumption of chemical fertilizer increased year after year in China It is one of the outstanding issues in sustainable agriculture development with higher efficiency of fertilizer use and less environmental stress, while it is the base of increasing efficiency of fertilizer use to clarity the current status of crop fertilizer use. In this research, we evaluated the present situation of crop fertilizer application by generally analyzing of Nanjing agriculture development and surveying the crop fertilizer use through sampling farmers combined with fertilizer field experiments results, crop nutrient principles and keeping sustainable agriculture development. The main results are as follows:1. Over application of chemical fertilizerThe application of chemical fertilizer in Nanjing reached 759kg/ha in 1995, which was higher than that of the middle level in Jiangsu province and also higher than that of developed countries such as Britain and the Netherlands. At the beginning of 21st century, because of rapid increasing of the total amount, the application level was 653kg/ha and 34.8 kilograms per person in 2001; the corresponding number in 2002 was 703kg and 32.7kg respectively. The benefit of chemical fertilizer was decreased with excessive application. From the 1980's to the beginning of 21st century, the contribution of agricultural gross value from chemical fertilizer has been reduced by at least 25%, the one from grain reduced by at least more than 60%. Furthermore, the quality of some products has been reduced because of unreasonable applying of fertilizer. Among them, the decrease of vegetable quality was the most serious. The strategy is to control the application amount, especially paying attention to the chemical fertilizer use of model production field. At present, controlling nitrogen application is the main measure.2. Unreasonable NPK ratioThe ratio of N:P2O5:K2O in Nanjing is about 1:0.32:0.56-0.61. The use of P has approached or reached the state of equilibrium. However, the ratio of K has been enhanced in some degree, but still below 0.4, seriously lower than the lowest demanding level of 0.55. Theproposed countermeasure is to control N, keep P and increase K, which is the practical strategy in Nanjing for the future.3. Unbalanced fertilizer use among cropsIn the 1980's, the emphasis of fertilizer application is on conventional crops such as rice, wheat and rape, while the fertilizer amount applied in vegetable land is very low. With the further adjustments in agricultural structure, the area and amount of fertilizer application in vegetable land increased rapidly. By 2002, the fertilizer amount used in vegetable unit area was 60% higher than the other crops, accounting for half of the total fertilizer use of main four crops, and the amount is twice the rice. Viewed from the balance between application amount and output, the surplus in vegetable land is also prominent. The countermeasure is to emphasize the study on applying technology of vegetable fertilizer and properly control the amount.4. Organic Fertilizer inefficiently usedFrom the 1990's, whether the crop yields or the feeding numbers of livestock and poultry was increased greatly, compared with that in the 1980's. Therefore, the amount of organic fertilizer should be increased normally. But in fact, the application amount was only about 2.5 to 3.5 million ton in the 1990's, which accounted for 60-70% of the amount applied in the 1980's. Among the organic fertilizer, the use of farmyard manure was sufficient, but less use of manure from cities. Recently the cultivated areas of wheat have been decreased largely, whereas fallow land was not used adequately for green manure, so the area is still small. Crop litter is a vast resource of organic fertilizer, but this kind of manure merely occupies 23~32% of the total crop litter. About 40% of crop litter has being burnt for life energy and unfortunately, such incidences often happen in fields. The countermeasure is to make good use of or...