|Poffenbarger, Hanna - Iowa State University|
|Weil, Ray - University Of Maryland|
|Spargo, John - Pennsylvania State University|
Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/3/2015
Publication Date: 10/27/2015
Citation: Poffenbarger, H.J., Mirsky, S.B., Weil, R.R., Kramer, M.H., Spargo, J.T., Cavigelli, M.A. 2015. Legume proportions, poultry litter, and tillage effects on cover crop decomposition. Agronomy Journal. 107:2083-2096.
Interpretive Summary: Cover crops are nonmarket crops that are used as multi-functional tools to provide agro-ecosystem services. The extent to which a service is provided will vary by cover crop species and how they are managed (till vs. no-till). Combining species into a cover crop mixture is a useful approach to maximize multiple services. Our research focused on combining grass and legume cover crops to optimize weed and fertility management. Legumes are useful in providing nitrogen to the subsequent cash crop while grasses provide good weed control as a mulch, slow nitrogen release rates for better synchrony with crop uptake, and scavenge soil nitrogen. To best make recommendations to farmers on how to use cover crop mixtures, we must understand how soil and crop management practices (fertilizer and tillage), influence the cover crop once terminated. Therefore, we conducted an experiment at two locations for two years to assess how cover crop sown proportions, tillage, and poultry litter application and method of application (broadcast vs. subsurface banded), influence cover crop decomposition. We observed from 40% to 80% biomass decomposition and 0 to 90% nitrogen loss based on proportion of initial biomass and nitrogen content. Decomposition rates increased with increasing legume proportion of total biomass, except when poultry litter was broadcasted over the cover crop mulch. Incorporation of cover crops through tillage significantly increased the overall rates of decomposition for all cover crop mixture proportions. However, when poultry litter was incorporated in the soil through a subsurface banding machine, cover crop decomposition on the soil surface was unaffected. Our work will be used to develop process-based models for estimating cover crop decomposition across broad regions. Furthermore, farmers can use our results to help shape their cover crop management decisions as it relates to biomass and nitrogen availability.
Technical Abstract: Hairy vetch (Vicia villosa Roth.)–cereal rye (Secale cereale L.) cover crop mixtures can provide N scavenging and N provisioning benefits in grain cropping systems. The objectives of this research were to determine, under field conditions, the effects of species proportions, tillage, and pelletized poultry litter (PPL) application (0 vs. 67 kg plant-available N ha-1), and placement (broadcast vs. subsurface banded) on the extent and rate of cover crop residue mass and N losses during a subsequent growing season. Measuring cover crop residues placed in mesh litter bags, we found that increasing hairy vetch proportion led to greater proportional mass and N losses (cumulative mass loss ranged from 40% to 80% and N loss ranged from 0 to 90% of initial), as well as higher rates of mass loss in all tillage and PPL treatments. Nitrogen release rate was higher for residues containing hairy vetch than for pure cereal rye, except in the broadcast PPL treatment where there was no species proportion effect. Incorporation of residues and PPL with tillage increased the rates of mass and N losses for cover crops containing hairy vetch. Although tillage and broadcast PPL application affected cover crop decomposition patterns, subsurface banded PPL application did not. Results show that cover crop mixtures pose less risk for early-season N losses than hairy vetch monocultures due to lower cumulative N release, also that subsurface banded PPL can provide supplemental N to corn without affecting surface mulch decomposition.