Nitrogen was an essential element for plant growth and the application of nitrogen fertilizers was one of the main contributors to the increased agricultural production in the world. However, many environment problems were also induced by the excessive use of nitrogen fertilizer. In China, ground- and surface-water contamination caused by field nitrogen accumulation and leaching has become more and more serious in most major grain production regions. Recently, with the development of intensive agriculture with high resource input, many environmental pollution problems caused by excessive use of nitrogen fertilizer such as groundwater contamination have appeared and more and more serious in oasis, northwest China. The issue that nitrogen accumulation and leaching in oasis agro-ecosystems has been received much attention in recent years. The solution of this problem could decrease waste of resources and improve ecological condition of oasis, and it was also important to sustainable agriculture and oasis stability. In this review, we introduce the advances about nitrate accumulation and leaching that have been carried out in oasis agro-ecosystems. First of all, some research methods about nitrogen accumulation and leaching in agro-ecosystems of oasis were present, and quantity feature and influencing factors in some regions and oases were also summarized. In field ecosystem of oasis, both nitrogen uptake by crops and soil drainage volume determine the amount of nitrogen accumulation and leaching. Fertilization and irrigation management including the adoption of application rates and time, kind of fertilizer, and fertilization and irrigation techniques et,al were the principal factors to effect soil nitrogen accumulation and leaching in the field of oasis. Also, cropping system including chosen of variety and rotation, cultivation and tillage system, plastic film and straw mulching in local region have important effect on nitrogen accumulation and transportation in soil. Some simulations and models were also been developed and applied to estimate regional status of nitrogen accumulation and leaching in oasis agro ecosystems.
There were some suggestion to reducing nitrogen accumulation and leaching in agro-ecosystems of oasis. Firstly, enhancing the nitrogen fertilizer use efficiency through improved filed management was preferential consideration to control exceed nitrogen accumulation and leaching from filed. Secondly, it is also important to develop and improve the soil and plant nutrient monitor techniques, which can offer fertilization criterion for local agricultural practice. Finally, with respect of regional estimation in nitrogen, improving precision and accuracy of nitrogen accumulation and leaching simulation is crucial, but such study are still deficiency. In the future, the world must produce more food to feed the growing population than ever before, and more intensive agriculture management and nitrogen input will lead to more environmental pollution problems, and many problems are still required to taken into account. It was point out that investigation of groundwater nitrate contamination and regional estimation of field nitrogen accumulation and leaching statue are primary work in agro-ecosystems of oasis. Researches concerning the nitrogen accumulation and leaching under the current agricultural management practices and cultivation patterns in the oasis agro-ecosystem should be strengthened, and the human element should be emphasized.