Short-Term Irrigation Level Effects on Residual Nitrate in Soil Profile and N Balance from Long-Term Manure and Fertilizer Applications in the Arid Areas of Northwest China

Effect of Long-Term Nitrogen Addition on Wheat Yield, Nitrogen Use Efficiency, and Residual Soil Nitrate in a Semiarid Area of the Loess Plateau of China

“…For treatments where N fertilization was stopped, after 157.5 and 210 kg N ha −1 was applied in the first two study years (N4s and N5s, respectively), soil NO 3 -N, N accumulation in wheat grain, straw, and aboveground biomass in the third year was also significantly greater than that of the non-N-fertilized treatment, but not in the 17th year (2019). The results showed that the residual effects of fertilizer N increased with the increase of the previous N fertilizer application rate [67], and decreased over time due to the combination of crop N uptake and N loss pathways [73].…”

“…This may be due to the continuous and large-scale application of N fertilizer for a long time, which caused the residual N in the soil to move deeper into the soil [61]. Although the accumulation of NO 3 -N in the soil profile is a slow process due to the absorption and utilization of crops [67], the accumulated NO 3 -N in the soil profile will gradually move downward and leaching to available below the root zone [68] because of the concentrated rainfall in the semi-arid region of the Loess Plateau [43]. Therefore, the accumulation and loss of NO 3 -N in soil could be reduced or avoided by applying N fertilizer in an amount less than or equal to that necessary for the optimal crop yield [69,70].…”

“…These results not only confirmed the previous research conclusions, but also proved that the use depth of soil NO 3 -N by crops might reach to 200 cm. Therefore, it is necessary to find ways to effectively use the accumulated NO 3 -N in the soil, while saving the application cost of N fertilizer on future crops, and reduce the leaching of NO 3 -N deep in the soil profile [67].…”

A Study on the Groundwater Contamination by the Agriculture Fertilizer Inputs and its Spatial Distribution Pattern in the Zhangye Basin, Northwest China

“…agriculture-based economy. The recent rapid economic growth of China has resulted increasing demand of agricultural products, which motivates a rapid expansion of agricultural activities in Heihe River basin (Wang et.al, 2009). The groundwater in the Heihe River basin entirely depends on the river water, which is supplied by the southern Qilian Mountains.…”

“…The significant decline of groundwater level (Wang et.al, 2009) and increasing concentration of nitrogen level in groundwater (Chang and Wang, 2009) are two main environmental concerns in this context. The water quantity issue has gained a significant attention of scholars (Wang et.al, 2009;Chen et.al, 2005;Wang and Chen, 2000) and meanwhile the water quality issues are also addressed in different perspectives including its hydrochemical characteristics, nitrogen infiltration through agricultural activities, ground water recharge process and water quality etc (Wen et.al, 2007;Yang et.al, 2011;Chang and Wang, 2009;Qin, 2011). Zhangye city, which is located in Gansu Province, Northwest of China, is mainly dependent on an ____________________________ The groundwater pollution should be a critical concern not just because the point source pollution, but also its distribution by non-point source pollution.…”