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United States Department of Agriculture

Agricultural Research Service

Research Project: DEVELOPING ANALYTICAL AND MANAGEMENT STRATEGIES TO IMPROVE CROP UTILIZATION OF .... AND REDUCE LOSSES TO THE ENVIRONMENT

Location: Crop Systems & Global Change

Title: Capturing residual soil nitrogen with winter cereal cover crops

Authors
item Snyder, C -
item Meisinger, John

Submitted to: International Plant Nutrition Institute (IPNI) Agronomy Information Bulletin
Publication Type: Popular Publication
Publication Acceptance Date: September 27, 2012
Publication Date: September 28, 2012
Citation: Snyder, C.S., Meisinger, J.J. 2012. Capturing residual soil nitrogen with winter cereal cover crops. International Plant Nutrition Institute (IPNI) Agronomy Information Bulletin. p. 1-6.

Interpretive Summary: The wide-spread summer drought in 2012 has reduced crop growth, lowered yields, and increased the likelihood of having high residual nitrate-nitrogen in the soil. This residual nitrogen can potentially increase nitrate losses to ground and/or surface waters, as well as increase nitrogen carry-over for the 2013 corn crop. There are two main approaches for managing high levels of residual nitrogen: planting a fall-winter cover crop to convert nitrate into plant protein, or spring monitoring of soil nitrate and adjusting corn fertilizer nitrogen rates accordingly. An adapted early-sown winter cereal or radish cover crop can rapidly take up residual nitrogen, converting mobile nitrate into immobile plant protein, which is then processed by soil microbes into slowly available soil organic matter. The sequestering of residual nitrogen into organic nitrogen can improve soil quality and simplify fertilizer management for the next cash crop. The second approach, of monitoring the spring soil nitrate, results from the fact that the fate of fall nitrate is very difficult to predict because of our inability to forecast winter precipitation and temperatures, the large spatial variability of residual nitrate across a landscape, and the large range of natural soil drainage and tile drainage conditions. Spring monitoring of soil nitrate is common in the western part of the Corn Belt, but may also be beneficial on drought sites farther east next year. The above two approaches for managing residual nitrogen will assist Certified Crop Advisors, University Extension specialists, USDA Soil Conservationists or other skilled agronomic professionals in advising farmers on making winter cover crop decisions, and on making spring soil sampling decisions. The over-arching goal of both of these residual nitrogen management approaches is to improve the nitrogen use efficiency in the next cash crop by either conserving nitrogen with a winter cover crop or by accounting for potential carry-over of residual nitrate into the next cropping season.

Technical Abstract: The wide-spread drought during the 2012 summer has resulted in reduced crop growth, poor yields, and an anticipated increase in residual nitrate (NO3) nitrogen (N) in the soil profile. This residual N can potentially increase NO3-N losses to ground and/or surface waters, as well as increase carry-over N for the 2013 corn crop. There are two primary methods for managing high levels of residual N: planting a fall-winter cover crop to convert nitrate N into plant protein, or spring monitoring of soil NO3-N and adjusting corn fertilizer N rates accordingly. An adapted early-sown winter cereal or brassica cover crop can rapidly take up residual soil NO3-N, converting mobile NO3-N into immobile plant protein, which is ultimately converted to slowly available organic N within the soil N cycle. The sequestering of residual soil NO3-N into slowly available organic N can improve soil quality and simplify fertilizer N management for the next cash crop. The second approach, of monitoring the spring soil NO3, results from the fact that the fate of fall NO3-N is very difficult to estimate because of our inability to forecast winter precipitation and temperatures, the large spatial variability of residual N across a landscape, and the large range of natural soil drainage and tile drainage conditions. Spring monitoring of soil NO3-N is commonly practiced in the western part of the Corn Belt, but may also be beneficial on drought sites farther east next year. The above two approaches for managing residual N will assist Certified Crop Advisors, University Extension Specialists, USDA Soil Conservationists or other skilled agronomic professionals in advising farmers on making winter cover crop decisions and on making spring soil sampling decisions. The over-arching goal of both of these residual N management approaches is to improve the N use efficiency in the next cash crop by either conserving N with a winter cover crop or by accounting for potential carry-over of residual NO3-N into the next cropping season.

Last Modified: 9/20/2014
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