Comparative influence of tillage systems and nutrient timing on the soil environment and crop response in Iowa soils

Licht, Mark
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Tillage systems can affect soil productivity, crop N availability and use efficiency, and seedbed conditions (soil temperature, moisture, and penetration resistance). The challenges associated with some tillage systems, namely conventional tillage and no-tillage, have prompted this study to (i) evaluate the effects of strip-tillage on corn (Zea mays L.) productivity as compared to conventional tillage and no-tillage (ii) identify the effect of strip-tillage and N timing on the N availability and use efficiency (iii) determine the impact of strip-tillage on soil moisture, temperature, and penetration resistance. The study was conducted at two sites in 2001 and 2002. One site was near Ames, Iowa where the soils were Nicollet (Aquic Hapludolls) and Webster (Typic Haplaquolls). The second site was near Nashua, Iowa where the soils were Kenyon (Typic Hapludolls) and Floyd (Aquic Hapludolls). The impacts of tillage treatments on crop response were determined by measuring corn emergence, dry matter, plant N uptake, and grain yield. Residual soil NO₃-N, NO₃-N movement, and water use efficiency, along with soil temperature and soil penetration resistance, were estimated for different tillage systems. Results of this study suggest strip-tillage offers no significant advantages in improving corn production over no-tillage or conventional tillage. In this study, strip-tillage had a slight advantage early in the growing season in improving corn emergence due to improvement of soil temperature over no-tillage by 1.4-1.9à °C, but this advantage did not significantly increase yields. There was no significant difference in soil moisture content between all tillage systems at any depth, but generally strip-tillage showed greater water content than conventional tillage and a similar water content to no-tillage at the lower soil depths. Strip-tillage had no significant advantages in improving plant N uptake, water use efficiency, or reducing N leaching over no-tillage regardless of the timing of tillage implementation and N fertilizer application. Soil penetration resistance of strip-tillage was often comparable with no-tillage, but greater than conventional tillage at the 0-20 cm depth. Penetration resistance and soil moisture for all treatments were inversely related throughout the soil profile, where the differences were most pronounced at the 30 and 60 cm depths.