Zonal tillage boosts crop yields, but has little effect on above-ground litter decomposition
Management of cover crops and soil structure directly affects the temporal and spatial turnover of nutrients and their contributions to future cash crop productivity. Additionally, intensive management practices like in-season tillage can alter soil food web composition such that below-ground processes (e.g. decomposition) are either stimulated or constrained. We conducted a litterbag study to determine the effects of in-season soil disturbance and litter quality on the rate of cover crop litter decomposition. The study was conducted in summer 2012 at the Russell Larson Agricultural Research Center in Rock Springs, PA. We placed bags filled with litter of hairy vetch (low C:N) or cereal rye (high C:N) along transects running perpendicular to the direction of soil disturbance (i.e. mid-ridge, row, interrow) in a corn-soybean cropping system managed under two disturbance regimes: uniform disturbance (chisel plow) or zonal disturbance (ridge-tillage). Litter bags were collected three times during the growing season to determine mass remaining. We also measured decomposition processes indirectly by assessing the growth response of a corn phytometer.
Hairy vetch decomposed significantly faster than cereal rye regardless of disturbance regime. Rates of hairy vetch litter decomposition were also spatially variable, and were lowest for litter placed directly in the crop row. Overtime, however, these spatial relationships diminished. Corn yields in the zonal disturbance treatment were significantly higher than yields in the uniform treatment. Similarly, leaf nitrogen content and plant heights were higher after in-season tillage in the zonal treatment compared to the uniform disturbance treatment suggesting that the zonal disturbance stimulated nutrient turnover. The effects of zonal disturbance on the corn phytometer may have been mediated, in part, by increased resource inputs to the soil food web community that stimulated nutrient turnover following disturbance to the crop root system.