Balance and control of soil nutrent in agro-ecosystem in the desert oases

Through a research on the surplus and deficent of soil nutrient balance during the period of 1980～1996, the results show that N changed in a range of -26.9～+27.2%, P₂O₅ was in a big surplus 188.1%, and K₂O was deficient, chemical fertilizer has occupied 74.9% of the total spread nutrient and the proportion of organic nutrient is reduced in the new oases. A concept of the good nutrient cycle index(M_N) is put forward in the paper, and the currentM_N is only 0.128 in the new oases in Xinjiang. It is expounded that the M_N will be able to reach 0.581 and the recycling coefficient of organic nitrogen(H) will be able to near 1 when fertilizer spreading system by artificial controlled is implemented. In order to fertilize the soil fertility, the model of nutrient balance demands that the surplus of N should be over 40% so as to achieve a good nutrient cycle in the oases agro-ecosystem.