Long-term fate of nitrate fertilizer in agricultural soils is not necessarily related to nitrate leaching from agricultural soils

Nitrogen and the future of agriculture: 20 years on

“…We also note that while substantial improvement in NFE is necessary, it is not sufficient to meet water quality standards in major crop producing regions like the US Corn Belt. Cover crops, conservation tillage, and modified cropping systems may also be required (Castellano and David 2014), as well as retirement of the most sensitive land from crop production. For example, strategic conversion of \ 3% of cropland in the Upper Mississippi, Ohio, and Missouri River watersheds is estimated to achieve a 45% reduction in nitrate losses and reduce extent of the hypoxia zone within regulatory targets (McLellan et al 2015).…”

Legacy Nutrient Dynamics at the Watershed Scale: Principles, Modeling, and Implications

“…In terms of legacy soil N resources, the soil legacy reactive N in the root zone is likely to be available for crop uptake, and thus appropriate soil nutrient testing could inform appropriate N fertilizer application rates (Castellano and David, 2014). On the other hand, crop residue decomposition and legacy SON mineralization also can provide a large quantity of available N during the crop growing season, suggesting further potential to reduce N fertilizer application rates (Halvorson et al, 2005).…”

Regional Variability of Agriculturally-Derived Nitrate-Nitrogen in Shallow Groundwater in China, 2004–2014

“…High application rates of N fertilizer have a significant potential for nitrate leaching [3,23]. Research suggests that 8-12% of the applied fertilizer, applied at 120 kg N·ha −1 ·y −1 , leaked toward the hydrosphere [24]. In China, 15-30% of the labeled fertilizer N, applied at 160 kg N·ha −1 ·y −1 , remained in the soil after harvest [25].…”