Impact of Lime Placement on Corn Grain Yield Response and Soil Properties.

Claypan soils in Missouri that are managed for corn (Zea mays L.) production often have optimum surface pH for crop growth, but acidic subsoils may inhibit root growth leading to reduced drought tolerance and grain yields. Lime application can increase soil pH, improve soil structure and provide calcium and magnesium to the soil, but these amendments rarely affect the subsoil and its potential chemical and physical restrictions for root growth. The objectives of this study were to determine the effects of surface and deep placement of lime on corn growth and to assess the impacts of these placement methods on subsoil acidity. Field trials were conducted from 2012 to 2014 in Northeast Missouri with treatments of lime applied at 0, 3.4, and 6.3 Mg ha^-1 either on the soil surface or with deep placement. Soil test pH in the top 13 cm of soil was not affected by deep lime placement but at depths of 15 to 25 cm soil pH increased 0.5 points for deep placed lime applied at 3.4 Mg ha^-1. No differences in soil pH were observed 28 to 51 cm. deep in the soil profile 1, 2, or 3 years after application. Differences in grain yields over the three years of the study appeared to be affected by lime application rate, reaction time, climatic conditions and whether lime was applied to the surface or to the subsoil. Residual effects of placement methods and treatments will be assessed for subsequent years to evaluate long term effects on both soil and plant responses.