Submitted to: Indiana Certified Crop Advisors Conference
Publication Type: Proceedings
Publication Acceptance Date: 12/15/2010
Publication Date: 12/15/2010
Citation: Kovar, J.L. 2010. How does fertilizer/manure placement affect P and K availability in the root zone? In: Vyn, T. (ed.). Indiana Certified Crop Advisors Conference Proc., December 14-15, 2010, Indianapolis, IN. CDROM.
Interpretive Summary: From both an agronomic and an environmental perspective, nutrient-use efficiency (NUE) is a key variable in today’s crop production systems. To improve NUE, fertilizer materials must increase the amount of plant-available nutrients in the soil, and the plant root system must be able to take advantage of this increase. Proper placement of fertilizer nutrients in soil is just as important as choosing the correct amount to apply. During the past several years, our research has focused on the relative profile distribution of available phosphorus (P) and potassium (K) applied in surface and sub-surface bands. Studies have included both commercial liquid and granular fertilizers, as well as swine manure, applied in fall or spring. In general, results have shown that that at least some of the P and K applied on or near the soil surface at the time of planting moves into the soil profile. Increased levels of available P and K in the root zone will not only benefit the crop throughout the growing season, but also minimize potential losses by runoff and erosion. The results of this research will benefit both commercial growers and the fertilizer industry by providing nutrient management alternatives that maximize crop utilization and minimize potential nutrient losses. Results will also contribute useful information to swine producers, local environmental groups, and Cooperative Extension and NRCS personnel interested in reducing the negative effects of agricultural production on water quality.
Technical Abstract: Proper placement of fertilizer nutrients in soil is just as important as choosing the correct amount to apply. Optimum placement of added nutrients improves utilization by the crop root system, which sets the stage for maximum yields. Due to the complexity of the plant-soil system, the most effective placement will vary with the type of nutrient(s) applied, the crop being grown, and the environment in which the crop is grown. During six years of field trials, we found that at least some of the phosphorus (P) and potassium (K) in liquid fertilizers applied on the soil surface two inches to the side of the corn row at the time of planting moved two to four inches into the soil. These higher levels of plant-available P and K in the root zone could benefit the corn plant throughout the remainder of the growing season. In a separate field study comparing liquid swine manure application with knife injection and a low-disturbance injection system, manure application increased available soil P in the four to six inch soil layer following knife injection, while the highest P levels were detected in the two to four inch layer following low-disturbance injection. Our results suggest that low-disturbance injection of swine manure can minimize losses of P to surface runoff, while providing optimum P availability to a subsequent agronomic crop. The purpose of this presentation is to provide a brief overview of factors affecting soil supply of P and K, and to discuss the relationship of these soil processes with P and K placement.