Uptake and Leaching Potential of Potassium and Sulfur When Split Applied for Corn On Irrigated Soil.

Corn (Zea mays L.) planted on coarse textured soils, such as sand, often face nutrient loss problems due to rapid internal drainage and a low capacity to hold cations such as potassium (K). The objectives of this study were to determine whether crops responded better to split applications of K or sulfur (S) and to assess the potential for movement on irrigated soils. Two trials, one focused on K and one on S, were established at 4 locations over 2 years. Trials were established using a split plot design. Main plots consisted of fertilizer applied at or before planting and were split into sub plots which similar rates were applied over all pre- or at planting treatments. Fertilizer K rate was 0, 74, 149, and 223 kg K ha-1 and S was applied at 0, 14, 28, and 42 kg S ha-1. Soil solution K or S was monitored using lysimeters at a depth of 60 cm. Nutrient uptake was assessed by sampling the whole above ground plant at V5 to V8 and sampling ear leaves at approximately the R2 growth stage. Early plant K or S uptake was increased by pre-plant fertilization, but there was no difference between rates. By the R2 growth stage there was no difference in ear leaf S concentration. For K sites tissue K concentration was affected by pre-plant and side-dress K application. The effect of side-dress K was similar across pre-plant K rates. However, tissue concentrations were well within normal ranges for crops even when soil K tested low. Analysis of water samples showed no increase in K concentration at 60 cm over the growing season. For S, there were large increases in soil solution S when soils were very sandy. Overall, it appears that there is no clear benefits from split applications of K or S for corn. In terms of leaching potential, S moved more rapidly as expected through the soil profile while there was no evidence that K moved out the top 15 cm.