Yield stability analysis reveals sources of large-scale nitrogen loss from the US Midwest

Bruno Basso,Guanyuan Shuai,G Philip Robertson,Jinshui Zhang

doi:10.1038/s41598-019-42271-1

Bruno Basso, Guanyuan Shuai + Show 2 more

Open Access

https://doi.org/10.1038/s41598-019-42271-1

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Abstract

Loss of reactive nitrogen (N) from agricultural fields in the U.S. Midwest is a principal cause of the persistent hypoxic zone in the Gulf of Mexico. We used eight years of high resolution satellite imagery, field boundaries, crop data layers, and yield stability classes to estimate the proportion of N fertilizer removed in harvest (NUE) versus left as surplus N in 8 million corn (Zea mays) fields at subfield resolutions of 30 × 30 m (0.09 ha) across 30 million ha of 10 Midwest states. On average, 26% of subfields in the region could be classified as stable low yield, 28% as unstable (low yield some years, high others), and 46% as stable high yield. NUE varied from 48% in stable low yield areas to 88% in stable high yield areas. We estimate regional average N losses of 1.12 (0.64–1.67) Tg N y−1 from stable and unstable low yield areas, corresponding to USD 485 (267–702) million dollars of fertilizer value, 79 (45–113) TJ of energy, and greenhouse gas emissions of 6.8 (3.4–10.1) MMT CO2 equivalents. Matching N fertilizer rates to crop yield stability classes could reduce regional reactive N losses substantially with no impact on crop yields, thereby enhancing the sustainability of corn-based cropping systems.

Highlights

Reactive nitrogen loss to the environment is one of the most widespread and recalcitrant environmental problems in major crop-producing regions of the world today
Stable high yield areas constitute 38–52% of total corn and soybean cropland across these states, with the highest proportions in Wisconsin, Iowa, Minnesota, and the Dakotas (Table 1)—all located in the northwest portion of the region
Stable high yield subfield areas made up 46% of corn-soybean cropland in the 10 Midwest states analyzed here and appear to utilize fertilizer N much more efficiently than low yield areas, which appeared incapable of supporting crop growth at a level sufficient to utilize the majority of the N applied

Summary

Introduction

Reactive nitrogen loss to the environment is one of the most widespread and recalcitrant environmental problems in major crop-producing regions of the world today. For more than a decade gains in N fertilizer use efficiency (and associated gains in environmental protection) were hoped to be achieved through precision N management, but that promise has yet to be realized In large part this is because current use of variable rate technologies is low even in technologically advanced countries like the U.S due to the complexity of converting geospatial information on soil and plant status into appropriate crop management information, and as well to low economic returns based on current application www.nature.com/scientificreports/. In 2012 yield mapping was used on about half of U.S corn and soybean farms but variable rate application technology, whether for seeds, pesticides, lime, or fertilizers, on only 16–26% in aggregate[25]

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