Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/8/2012
Publication Date: 4/5/2012
Publication URL: http://hdl.handle.net/10113/54118
Citation: Krueger, E., Ochsner, T., Baker, J.M., Porter, P.M., Reicosky, D.C. 2012. Rye-corn silage double-cropping reduces corn yield but improves environmental impacts. Agronomy Journal. 104(4):888-896. Interpretive Summary: There is much concern about the environmental impact of large dairies. One issue is the potential transport of nitrogen from applied manure into ground water. Another is the lack of surface soil protection resulting from harvest of silage corn. Winter cover crops can potentially address both issues by scavenging excess nitrate and by providing surface cover following silage harvest. We compared surface cover and root zone N concentrations in conventional corn silage plots against plots where winter rye was grown following silage harvest over a 3-year period. In both treatments, dairy manure was injected in the fall after silage removal. Soil nitrate accumulated at a rae of 74 kg ha-1 yr-1 in the conventional plots, but there was no accumulation in the cover cropped plots, indicating that the rye was effective in scavenging N. Average soil solution N and leaching losses were also lower in the cover cropped treatment, though the leaching losses were relatively low in both cases. The winter rye cover crop also resulted in significantly higher ground cover, averaging 30% versus 10% in the conventional treatment. Totla forage production was not different between the two systems. We conclude that a winter rye cover crop addresses the primary environmental concerns associated with conventional dairy silage production systems, but with no increase in total forage production.
Technical Abstract: Recent proliferation of large dairies has prompted concern regarding the environmental impacts of associated corn silage production and high rate manure application. Our objectives were to compare forage production and environmental impacts of corn (Zea mays L.) silage and rye (Secale cereal L.)-corn silage cropping systems fertilized with liquid dairy manure near Morris, MN. From 2007-2009, corn for silage was seeded into silt loam soil as a mono crop in early and mid-May and as a double crop after rye in mid-May and early June. Manure was fall applied annually at average N and P rates of 393 and 109 kg ha-1, respectively. Total forage yield and N removal were similar for all treatments. Soil NO3-N accumulated at an average rate of 74 kg ha-1 yr-1 with mono cropping, but accumulation was not observed with double cropping. Average soil organic C concentration from 0-5 cm increased in the mono (15%) and double crop (22%) systems over three years. Average soil solution NO3-N concentration was high for mono crop (57 mg L-1) and double crop (40 mg L-1) systems but leaching load was only 11 kg ha-1 yr-1 and 6 kg ha-1 yr-1, respectively. Ground cover was often less than 10% with mono cropping until the corn was established but was usually greater than 30% with double cropping. The primary environmental concerns identified for mono crop corn silage production were soil NO3-N buildup and inadequate ground cover. Each concern was addressed with double cropping, however total forage production was not increased.