Wheat Response to Time and Placement of Phosphorus Fertilizer
Cristie Preston, Ph.D.
Agriculture has always been an integral part of Dr. Cristie Preston’s life. She grew up in southwest Virginia and had interest in crop and animal agriculture since an early age. Once she began college, she initially chose to study animal science but switched to soil science. Dr. Preston attributes her decision partly to an influential professor who told her, “You can’t understand animals until you understand what they eat.” She received a Bachelor of Science degree in animal science and a Master of Science degree in crop and soil environmental science from Virginia Tech. Dr. Preston holds a Ph.D. in agronomy, focusing on soil fertility from Kansas State University. While completing her advanced degrees, Dr. Preston conducted more than six years of field and lab research. Dr. Preston has experience in laboratory research measuring volatility loss from urea-based fertilizers. Her field research has focused on phosphorus availability and the interactions with tillage and placement. She also has extensive experience in working with large data sets and analysis. Her main priority is helping growers to identify yield-limiting factors and fix those issues as cost efficiently as possible.
Phosphorus management in winter wheat production can be impacted by the previous crop in the rotation. As an example, wheat grown in Arkansas might follow either rice or soybean. Phosphorus availability in wheat grown following rice could be limited by saturated soil conditions that alter phosphorus forms making it less available for upland crops. Additionally, since wheat is a cool-season crop, cooler soil temperatures can slow phosphorus diffusion increasing the need for supplementation.
In this article, researchers at the University of Arkansas have conducted trials to determine if phosphorus placement and timing would have any effect on wheat grown following rice. Phosphorus banded with the seed or supplied after a topdress after seeding did result in greater biomass early on, but there were no differences in yield between banding and any broadcast application made before early spring (late March/early April).
Traditionally, farmers have waited until spring to make phosphorus applications after assuring a proper stand. That approach may still make sense, but these results also show that phosphorus banded at planting supports early growth.