Guiding cover crop establishment to scavenge residual soil nitrate nitrogen using site-specific approaches

Abstract

There is evidence that well managed winter cereal cover crops can scavenge a goodly amount of post summer cereal harvest residual nitrogen (N), reducing nitrate-N losses to leaching or runoff. The objective of this study was to compare nitrate-N phytoremediation areas derived from five sources of information: site specific, non-site specific, or a combination. The non-site specific source was a single “composite” soil nitrate sample. The site specific sources were: a) a dense soil nitrate-N grid sampling; and b) a N removal map calculated from yield and grain N concentration, both determined at the same grid density as soil nitrate-N. The source combinations were: a) a yield map and a single grain N concentration value taken from published information; and b) a yield map and a single field “composite” grain N concentration value. The results indicated that the published grain N value was inferior to measured grain N values, and that the maize (Zea mays L.) yield map best serves as a stratification tool, delineating similar crop performance areas. Random soil sampling within those areas further optimizes residual nitrate-N recovery management. Site specific technologies can guide establishment of N scavenging cover crops to simultaneously improve resource use efficiency and water quality.