Quantifying nitrogen leaching response to fertilizer additions in China's cropland

Abstract

a b s t r a c tAgricultural soils account for more than 50% of nitrogen leaching (L N ) to groundwater in China. When excess levels of nitrogen accumulate in groundwater, it poses a risk of adverse health effects. Despite this recognition, estimation of L N from cropland soils in a broad spatial scale is still quite uncertain in China. The uncertainty of L N primarily stems from the shape of nitrogen leaching response to fertilizer additions (N rate ) and the role of environmental conditions. On the basis of 453 site-years at 51 sites across China, we explored the nonlinearity and variability of the response of L N to N rate and developed an empirical statistical model to determine how environmental factors regulate the rate of N leaching (LR). The result shows that L N -N rate relationship is convex for most crop types, and varies by local hydro-climates and soil organic carbon. Variability of air temperature explains a half (~52%) of the spatial variation of LR. The results of model calibration and validation indicate that incorporating this empirical knowledge into a predictive model could accurately capture the variation in leaching and produce a reasonable upscaling from site to country. The fertilizer-induced L N in 2008 for China's cropland were 0.88 ± 0.23 TgN (1s), significantly lower than the linear or uniform model, as assumed by Food and Agriculture Organization and MITERRA-EUROPE models. These results also imply that future policy to reduce N leaching from cropland needs to consider environmental variability rather than solely attempt to reduce N rate .

The Variability of Nitrogen Forms in Soils Due to Traditional and Precision Agriculture: Case Studies in Poland

“…Several authors reported that the most significant factors that determine N content in soils are, i.e., bulk density, soil clay content, organic matter, pH, climate, vegetation, terrain topography, and human activity [3,4]. The amount of N released into the soil-water environment is also significantly influenced by factors like the dose and type of N fertilizers, time and frequency of their application, efficiency of the use of N by plants, depth of the plant root system, and soil permeability [5][6][7][8]. According to Mosier et al [9], in Europe, where N fertilizers are used the most frequently, leaching and denitrification are the main processes responsible for N losses to the environment.…”

The Structure and Diversity of Nitrogen Functional Groups from Different Cropping Systems in Yellow River Delta

“…However, only 27-40% of applied N is taken up by crops [4]. The retained N is lost in soil through nitrate leaching, runoff and N oxides emission [5], resulting in nitrate contamination and green house pollution [6][7][8]. Therefore, improving N use efficiency has become a significant concern for agricultural sustainable development in the YRD.…”

Detection and attribution of nitrogen runoff trend in China's croplands

“…In addition, in situ measurements of N runoff are scarce in Northwest China (e.g., Xinjiang province), leading to large uncertainty in RTN estimates in this regions. Previous studies 432 indicated that the dominant pathways of N losses would be ammonia volatilization to the atmosphere and N leaching to aquifers (Gao et al, 2016;Van Damme et al, 2017), 434 rather than surface N runoff. More importantly, this region accounts for only 8.6% of N fertilizer application and 11% of the sowing area in China and has a low N runoff rate observed in the NPCP (0.…”

“…Previous studies indicated that RTN tends to increase with water input (Gao et al, 2016;Hou et al, 2016), because high precipitation and irrigation events in turn resulted in large runoff pulses (Sorooshian et al, 2014). As we illustrated, the decline in water input mainly occurred due to the decrease in irrigation inputs, rather than a marked change in precipitation patterns, except in Taiwan, Hainan and parts of northwestern China (Fig.…”