|KORUCU, TAYFUN - Kahramanmaras Sutcu University|
Submitted to: Soil & Tillage Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/4/2018
Publication Date: 8/1/2018
Citation: Korucu, T., Shipitalo, M.J., Kaspar, T.C. 2018. Rye cover crop increases earthworm populations and reduces losses of broadcast, fall-applied, fertilizers in surface runoff. Soil & Tillage Research. 180:99-106. https://doi.org/10.1016/j.still.2018.03.004.
Interpretive Summary: Applications of phosphorus and potassium-containing fertilizers are often required to produce corn and soybean crops. If some of this fertilizer is transported to streams and lakes in surface runoff it can cause water quality problems. This can be a particular concern when corn leaves and stalks are harvested for animal feed or as feedstock for the production of biofuels because of an increased potential for runoff. This concern is further exacerbated with no-till crop production when the fertilizer is surface-applied in the fall and not incorporated into the soil. In this study we investigated whether this concern could be mitigated by planting a cereal rye cover crop after corn and soybean harvest. We used a simulator to apply a heavy rainfall, one likely to occur only once every 10 years, to plots that had a rye cover crop planted each of the last 14 years and identically managed plots without a cover crop one hour after they were fertilized. It took significantly longer for the plots with the living rye to produce runoff and runoff volume was reduced by 65%. There were even greater reductions (83-91%) in nutrient losses. Our results suggested that long-term planting of a rye cover crop improved soil structure and increased earthworm populations, which increased infiltration and reduced runoff and nutrient losses. This research is of value to farm managers and regulators as it indicates that the potential impact of fall fertilizer applications on water quality can be substantially reduced by planting cover crops after harvest.
Technical Abstract: Corn (Zea mays L.) silage and soybean [Glycine max (L.) Merr.] rotations in the US Upper Midwest leave minimal amounts of surface residues, which can contribute to soil degradation and a reduction in water quality. Planting cover crops after harvest can reduce these concerns, but their effectiveness in reducing nutrient losses in surface runoff shortly after fall planting and fertilization has not been thoroughly investigated. Therefore, we applied 65 mm of simulated rainfall in 60 min to five replicate, 1.5 by 3.0 m, plots in a no-till, corn silage-soybean rotation that were planted with a rye (Secale cereale L.) cover crop each of the last 14 years and to five plots with no cover crop. The simulations were conducted in October 2014 about a month after corn silage harvest and rye planting and ~ 1hr after broadcast application of monoammonium phosphate and potassium chloride fertilizers. It took significantly longer (5.7 min, P < 0.05) for plots with a living rye cover to produce surface runoff and total runoff volume was 65% less than that from plots without a cover crop, which resulted in a similar significant reduction in sediment (68%) loss. Even greater significant reductions were noted for the fertilizer-applied nutrients (NH4-N - 86%; total P - 83%; total dissolved P - 84%; K - 91%) due to significant reductions in their average concentrations. Earthworm populations and biomass, measured using electrical extraction after rainfall simulation were 1.2 and 1.4 times greater in cover crop plots than in no cover plots and 3.2 and 2.5 times greater when measured the following spring. Our results suggested that a living cover crop and their long-term usage can contribute to improvements in soil structure and increased earthworm populations that can reduce sediment and nutrient losses in surface runoff due to a severe storm shortly after post-harvest broadcast application of fertilizer.