In-furrow Starter Fertilizers for Winter Wheat
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.
When it comes to over-wintering of winter wheat, there are several advantages to using starter fertilizer this fall. Starters that contain both nitrogen and phosphorus can aid in good root development and the production of more fall tillers. However, many growers question which source of nitrogen and phosphorus is safest when applied in-furrow or if pre-mixing fertilizer with seed is an option.
A recent publication from Kansas State University suggests that growers follow some simple guidelines for in-furrow fertilizer applications based on row spacing and soil texture. In general, higher rates of nitrogen (non-urea fertilizer) and potassium containing fertilizers can be made in-furrow when soil textures are medium to fine, as compared to coarser textured soils.
Since monoammonium phosphate (MAP) and diammonium phosphate (DAP) do not contain nitrogen as urea, both are acceptable to be pre-mixed with the wheat seed and applied at the same time. However, is there a limit on the amount of time before yield may be affected due to mixing fertilizer and seed for too long before application? This study shows that pre-mixing DAP and wheat seed for up to 12 days before application had little to no negative effect on yield. However, farmers should be aware of potential ammonium toxicity issues if their pH is alkaline.
Effect of wheat yield from mixing phosphorus fertilizer (at 60 pounds P2O5 rate) with the 70 pounds of seed per acre and drilled (adapted from Chris Weber, K-State Research and Extension).