Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 9/17/2003
Publication Date: 10/14/2003
Citation: Shanahan, J.F., Francis, D.D., Schepers, J.S. 2003. Nutrient management implications of relay cropping on the environment. In Proceedings of the North Central Extension-Industry Soil Fertility Conference. 19:165-168. Interpretive Summary: Residual nitrogen (nitrate-N) remaining in the root zone after seed corn production is frequently greater than under commercial corn production. This nitrate is subject to leaching into the shallow ground water of the Platte River Valley in South-Central Nebraska, as noted by elevated nitrate-N concentrations under seed cornfields compared to other fields. Relay cropping has the potential to reduce nitrate leaching, increase carbon sequestration, and increase profitability for seed corn producers. It does so by providing a crop to capture residual soil nitrate and solar energy during the seven months when summer annual crops normally are not growing. The concept of relay cropping is not new to the area, but the practice is seldom used because of climatic limitations (timeliness and amount of precipitation and short growing season). Yet, the idea has significant economic merit and the environmental implications are very positive if producers can find ways to overcome the challenges. Relay cropping is essentially a special version of double cropping, where the second crop is planted into the first crop before harvest, rather than waiting until after harvest. In this way, the second crop can take advantage of a longer growing season. The objective of this study was to introduce the relay-cropping concept into a seed corn/soybean rotation under center-pivot irrigation in Nebraska to use the winter wheat crop as a scavenger of residual N and hopefully protect the groundwater for nitrate leaching.
Technical Abstract: Residual nitrogen (nitrate-N) remaining in the root zone after seed corn production is frequently greater than under commercial corn production. This nitrate is subject to leaching into the shallow ground water of the Platte River Valley in South-Central Nebraska, as noted by elevated nitrate-N concentrations under seed cornfields compared to other fields. Hard-red winter wheat was planted into seed corn residue in early October of 2001 as a cover crop to scavenge residual-N from the root zone and thereby reduce the potential for nitrate leaching. Soybean was inter-seeded in the wheat in early June and wheat was harvested in early July. Soybean plants emerged from the wheat stubble and matured in late September. Nitrogen uptake by wheat amounted to 130 lb/acre (90 lb N/acre from 68 bu/acre yield). The subsequent soybean crop that yielded 55 bu/acre functioned as a second scavenger crop. A second attempt at relay cropping was initiated in October of 2002 after harvest of center-pivot irrigated seed corn. Residual-N in the root zone prior to planting wheat ranged from 31 to 111 lb N/acre and between 9 and 42 lb N/acre after harvest.