Moisture Conservation Potential with Conservation Tillage Treatments in the Thick Loess Area of Western Iowa1

Abstract

AbstractMoisture is usually in short supply for production of corn (Zea mays L.) on thick loess derived soils in western Iowa. Practices that conserve moisture should increase crop yields but quantitative data is very scarse. The objectives were to develop a yield response curve for moisture applicable in western Iowa and evaluate the potential effect of conservation tillage systems on corn yields. Computerized modeling techniques were used to develop the yield response curve and to evaluate conservation practices.Moisture stress indices, which were highly correlated with measured corn yields, were used to evaluate the effectiveness of modeled tillage treatments in terms of corn yield. The model budgeted daily soil moisture use based on initial soil moisture measurements, actual weather data, and simulated hydrologic processes. The appropriate hydrologic processes were modified to approximate the tillage system under study. The hydrologic processes assumed most altered by conservation tillage management were surface runoff and surface evaporation in the spring fallow period.The modeled tillage practices were evaluated at three assumed spring soil moisture levels in combination with actual long term weather records. When spring soil moisture levels were at 100% of the plant‐available water capacity (PAWC), tillage practices had little effect on estimated corn yields. At the medium and low spring soil moisture levels, modeled conservation tillage was effective in increasing yield estimates over those obtained with conventional tillage.