TY - JOUR
T1 - Managing the trade off between nitrogen supply and retention with cover crop mixtures
AU - White, Charles M.
AU - DuPont, S. Tianna
AU - Hautau, Mena
AU - Hartman, Dave
AU - Finney, Denise M.
AU - Bradley, Brosi
AU - LaChance, James C.
AU - Kaye, Jason P.
N1 - Publisher Copyright:
© 2016 Elsevier B.V.
PY - 2017/1/16
Y1 - 2017/1/16
N2 - The ability of cover crop mixtures to provide both nitrogen (N) retention and N supply services has been extensively studied in research station experiments, especially with grass-legume bicultures. Mixtures are often as effective as grass monocultures at N retention, but the N supply service can be compromised when non-legumes dilute the presence of legumes in a cover crop stand. To study the tradeoffs between N retention and supply when using cover crop mixtures, we measured N retention and supply in distributed on-farm experiments, developed multiple linear regression models to predict N retention and supply based on cover crop functional characteristics and environmental variables, and synthesized the regression models into a graphical analysis tool. The experiments took place on three organic farms and a research station in Pennsylvania, USA and tested 3-species and 4-species cover crop mixtures in comparison to commonly used grass and legume monocultures. Cover crop treatments were planted between a small grain crop harvested in mid-summer and a maize (Zea mays L.) crop planted the following spring. Potential nitrate (NO3−) leaching below 30 cm, an indicator of the N retention service, declined as the presence of non-legume species in a cover crop increased (r2 = 0.72). Potential NO3− leaching increased as the August soil NO3−-N concentration increased and as the fall biomass N content of winter-killed species or canola (Brassica napus L. ‘Wichita’) increased. Relative maize yield, an indicator of the N supply service, decreased as fall and spring cover crop biomass carbon-to-nitrogen (C:N) ratios increased and increased as total spring biomass N content and soil carbon (C) concentration increased (r2 = 0.56). Synthesizing the regression models in a graphical analysis tool revealed a tradeoff between N supply and retention services for cover crop mixtures, where increasing the fractional non-legume seeding rate to reduce potential NO3− leaching also reduced relative maize yield. The tradeoff could be minimized by managing environmental conditions and cover crop composition so that potential NO3− leaching remains low even when the fractional non-legume seeding rate is low. The regression models suggest this could be achieved by maintaining low soil NO3−-N concentrations prior to cover crop planting in August, not including winter-killed legumes in the mixture, and using non-legume species that are the most efficient at N retention. Thus, with thoughtful management of cover crops and soils, farmers may be able to realize the potential of cover crop mixtures to provide high levels of both N retention and supply services.
AB - The ability of cover crop mixtures to provide both nitrogen (N) retention and N supply services has been extensively studied in research station experiments, especially with grass-legume bicultures. Mixtures are often as effective as grass monocultures at N retention, but the N supply service can be compromised when non-legumes dilute the presence of legumes in a cover crop stand. To study the tradeoffs between N retention and supply when using cover crop mixtures, we measured N retention and supply in distributed on-farm experiments, developed multiple linear regression models to predict N retention and supply based on cover crop functional characteristics and environmental variables, and synthesized the regression models into a graphical analysis tool. The experiments took place on three organic farms and a research station in Pennsylvania, USA and tested 3-species and 4-species cover crop mixtures in comparison to commonly used grass and legume monocultures. Cover crop treatments were planted between a small grain crop harvested in mid-summer and a maize (Zea mays L.) crop planted the following spring. Potential nitrate (NO3−) leaching below 30 cm, an indicator of the N retention service, declined as the presence of non-legume species in a cover crop increased (r2 = 0.72). Potential NO3− leaching increased as the August soil NO3−-N concentration increased and as the fall biomass N content of winter-killed species or canola (Brassica napus L. ‘Wichita’) increased. Relative maize yield, an indicator of the N supply service, decreased as fall and spring cover crop biomass carbon-to-nitrogen (C:N) ratios increased and increased as total spring biomass N content and soil carbon (C) concentration increased (r2 = 0.56). Synthesizing the regression models in a graphical analysis tool revealed a tradeoff between N supply and retention services for cover crop mixtures, where increasing the fractional non-legume seeding rate to reduce potential NO3− leaching also reduced relative maize yield. The tradeoff could be minimized by managing environmental conditions and cover crop composition so that potential NO3− leaching remains low even when the fractional non-legume seeding rate is low. The regression models suggest this could be achieved by maintaining low soil NO3−-N concentrations prior to cover crop planting in August, not including winter-killed legumes in the mixture, and using non-legume species that are the most efficient at N retention. Thus, with thoughtful management of cover crops and soils, farmers may be able to realize the potential of cover crop mixtures to provide high levels of both N retention and supply services.
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U2 - 10.1016/j.agee.2016.12.016
DO - 10.1016/j.agee.2016.12.016
M3 - Article
AN - SCOPUS:85006954139
SN - 0167-8809
VL - 237
SP - 121
EP - 133
JO - Agriculture, Ecosystems and Environment
JF - Agriculture, Ecosystems and Environment
ER -