Munoz, J. D., J. Steibel, S. Snapp, and A. N. Kravchenko. 2014. Cover crop effect on corn growth and yield as influenced by topography. Agriculture, Ecosystem and Environment 189:229-239.
The use of cover crops is reported to enhance ecosystem services, however their adoption by farmers has remained limited. A challenge to farmer uptake is high spatial and temporal variability in cover crop growth and performance. Since topography plays an important role in spatial processes that ultimately affect plant performance, it could be used to quantify cover crop spatial variability and cover crop contribution to a subsequent cash crop. We assessed the effects of topography and cover crop (red clover)biomass on corn yields. Hierarchical path analysis was used to identify direct and indirect relationships among topography, red clover biomass, and corn yield, while taking into account the effects of agricultural management practices, multiple years, and multiple experimental fields. We observed that topography contribute significantly to explaining the variability in both red clover biomass and corn yields. Higher red clover biomass was produced in flat areas, whereas higher corn yield was produced in areas with high curvature. Red clover biomass positively influenced corn yield, however, the magnitude of that effect varied both temporally and spatially. The effect of red clover on corn yields was significant only in the years with lowest precipitation; and its magnitude was more pronounced at summit and slope topographical positions. Therefore, a good cover crop stand will be most beneficial to subsequent corn crop at summit and slope positions. Accounting for variability in fields and years using a hierarchical model significantly improved analysis of the interactive relationships between topography, red clover, and corn; therefore we encouraged its use in agroecological research.
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