Effect of Lime and Annual Application of Phosphorus and Potassium On Soybean Yield and Soil Fertility Indices of An Acid Mississippi Silty Upland Soil.

Soybean (Glycine max) is one of the major row-crops in Louisiana and its production value contributes about $400 million annually to the state’s agriculture economy. Employing effective soil fertility management practices is one of the key components of a successful and productive soybean industry. This study was conducted from 2004 through 2007 on an irrigated, acidic Gigger silt loam in north Louisiana to evaluate soybean yield response and soil chemical properties as affected by lime and annual application of phosphorus (P) and potassium (K). The treatments were laid out on a split-plot design using lime rate (0 and 2 tons ha^-1) as main plot and thirteen combinations of P and K rates of 0, 34, 67, 101 and 134 kg ha^-1 as subplots with four replications. Application of lime and K significantly increased soybean grain yield (P<0.05) in 2005, 2006, and 2007. On K fertilized plots, lime application raised soybean yield by 213 and 125 kg ha^-1 for 2005 and 2006, respectively. On the other hand, P fertilization did not result in significant yield increases. In general, there were significant differences observed on soil pH, Al, and Mehlich-3 extractable Ca, K Mg and Fe attributed to liming. Liming also altered soil Cu and Zn but only in 2005 and 2006, respectively. This study also documented an unusual declining trend of Mehlich-3 extractable P and K with time even with annual fertilization of P and K. With the diverse nature of soils in Louisiana under soybean production, calibration research for lime and essential macronutrients should be a continuous program to deliver a robust nutrient management program to soybean producers.