2008 Joint Annual Meeting (5-9 Oct. 2008): Effect of Phosphorus and Potassium Rate and Placement on Corn Development in Conservation Tillage.

In conservation tillage systems, like no-till (NT) and strip-till (ST), phosphorus (P) and potassium (K) typically become vertically and/or horizontally stratified in the soil.� This stratification has the potential to make P and K less available and to limit corn yield.� The objective of this study is to determine the influence of tillage and P and K placement and rate on soil P and K content, soil water status, root and shoot development, and grain yield of corn.� The experiment was arranged in a split-split-block design with three replications in a corn-soybean rotation. Tillage/placement� NT broadcast (NT-BC), NT deep placement at 15 cm (NT-DP), and ST deep placement (ST-DP)� as the main plot, P rate (0, 23, 46, and 68 kg P₂O₅ hectare^-1 year^-1) as the subplot, and K rate (0, 41, 82, and 164 kg K₂O hectare^-1 year^-1) as the sub-subplot. Soil and plant samples were collected through the season. Soils P and K concentrations decreased with increasing soil depth.� Corn grain yield was not influenced by tillage-placement method or K rate.� The 68 kg P₂O₅ hectare^-1 produced �690 kg ha^-1 increase in grain yields over the control (no P added), with the greatest response in NT-BC.� Soil water was not influenced by treatment, but at the end of the season, the in row positions had more soil water compared to the between rows position.� Dry matter accumulation at R3 development stage was increased by 1,214 kg ha^-1 with the highest K rate compared to no K application and by 2985 kg ha^-1 in NT-BC compared to NT-DP.� Root analysis indicates no influence of treatment on root distribution in the soil profile.� There was a two-fold decrease in root length density for each successive depth increment from the 0-5, 5-10, 10-20, and 20-40 cm depths.�