Effect of Fall Cover Crops Under Different Tillage Systems on Soil Moisture, Soybean Growth and Grain Yields.

Cover crops and conservation tillage are gaining popularity to improve soil health and long-term sustainability of crop yields. Most of the previous work on cover crops was in conventional tillage (CT) and not much information is available on how different cover crops perform under different tillage systems and how they affect soil moisture dynamics and main crop grain yields. In the current study, effect of fall cover crops wheat (WW) and hairy vetch (HV) along with fallow (F) under CT and three-year-old no-till (NT) systems established in a very fine sandy loam soil were evaluated on soil moisture dynamics, and soybean nutrient uptake, growth and grain yields. Soil moisture (VWC) was monitored using TDR soil moisture sensors as well as periodical gravimetric soil sampling. Fall cover crops under NT system increased VWC in the top 30 cm by about 4 to 10 %, while no impact was observed between 30 to 45 cm depth. Under CT system, HV had no impact while WW had increased the VWC. Infiltration rate was higher in NT system compared to CT system. Fall cover of HV increased soybeans N and S concentration compared to fallow under both CT and NT systems. Fall cover of wheat has no impact on N and S concentration in CT, while it has negative effect in the NT. In NT, most of the soybeans tissue nutrient concentrations were lower compared to CT except P, K and Mg. Average tissue N-content under CT was 5.3 %, while it was 4.6% in NT, which was about 12% lower. However, NT had 4.3 and 2.2 % higher P and K concentrations in NT compared to CT. Soybean growth, based on plant height, was higher under CT by up to 33%, consistent with tissue N concentrations. Despite high tissue N and better growth, soybean grain yield under CT was not significantly higher than NT. Increase in N content by vetch had no significant effect on increasing grain yield.