Cover Crops for Silage in Soybean Systems.

Iowa often has extreme weather events in the spring, a time when few fields in the state have a living cover, leading to nutrient leaching and soil erosion.  These intense rain events also lead to excess soil moisture and runoff.  While cover crops help address these issues and more, there has been adoption of cover crops on only 1-2% of farmed acres in Iowa.  A commonly cited concern is that cover crops are not cost effective in the short term.   To offset costs, some farmers use their cover crops as forage, but the impacts of adopting this practice have not been well studied in Iowa.  To address this, an experiment was designed to determine whether cover crop harvest for forage had an influence on soybean grain yields and overall economics in Iowa.  A replicated plot study was conducted near Ames, Iowa during the 2012-2013 and 2013-2014 growing seasons to investigate the effects of cover crop entry, termination date and residue removal on subsequent soybean grain yield.  Cover crop entries included Secale cereale ‘Spooner’, Brassica napus ‘Sitro’, Camelina sativa ‘Bison’, B. rapa ‘Purple Top’, and a no-cover crop control.  The first year of the study found no statistically significant effect on yield while the second year showed a significant effect of cover crop type and termination date.  Cover crop entry also had a significant effect on weed density, accumulated cover biomass, carbon and nitrogen, spring soil nitrate concentration, relative feed value of the cover crop forage and overall economics.