Fertilizing; Why Wait?
By: Kelsey Morris, Agronomist
I am not sure if there is a better definition for this past spring other than chaos. Once the snow finally cleared and the temperatures started to rise, it was a mad dash to the field to prepare for the coming crop. Unfortunately, mother nature has this control over us. To help conquer springs like the past one, spread out your work load. One thing that can easily get checked off your list in the fall is your phosphorus and potassium applications.
With low commodity prices showing no signs of improving anytime soon, economics weigh heavy in almost every farm management decision. Each input cost takes careful agronomic, environmental and economic consideration. One of the biggest advantages of fall fertilizer application is the lower cost. More times than not, 98% to be exact, fall fertilizer costs are less expensive than in the spring. On top of this, the soil moisture is generally lower in the fall, so the risk of soil compaction is lower than with wet spring soils.
If fall tillage is planned, fall fertilizing should strongly be considered. We have seen positive yield response to phosphorus and potassium applications incorporated into the root zones of next year’s crops. This also ensures your P&K stays put as winter moves in.
As you think about fall fertilizer, it’s important to keep in mind the keys to maximizing economic returns from phosphorus (P) and potassium (K) applications. The foundation for this is a comprehensive soil testing program. This not only helps you understand your P&K numbers but essentially gives you the roadmap to keep them above their critical levels. Through much research, most agricultural universities will tell you phosphorus levels should be at least 16-20 ppm and 160-200 ppm for potassium. These are important to keep in check if you want to keep cranking out the big yields we have seen the past couple years. Evaluating removal plays an important role in the equation; especially keeping big yields in mind. For every bushel of corn harvested, removal is .38 units of phosphate and .27 units of potassium. Every bushel of soybeans is taking .84 units of phosphate and 1.3 units of potassium. For example, if you are harvesting 250 bushel corn your removal is x-95-68. And if you are harvesting 75 bushel beans your removal is x-63-98. It’s imperative to put back on what you are pulling off. Why not take advantage of the cost and time savings by fertilizing
in the fall?
When time and money gets tight, P&K seem to be the first item on the list to go. However, we must remember phosphate and potassium play vital roles in helping us achieve the record yields we strive for each year.
Phosphorus
- Stimulates root development necessary for plant support as well as nutrient uptake.
- Required for photosynthesis
- Promotes storage and transportation of nutrients throughout the plant.
- Helps the crop to mature at the right time. Plants that lack phosphorus take more time to mature and produce poor ears/pods.
- Legumes that fix nitrogen in the soil, cannot carry out this function without phosphorus.
- Plants that have their phosphorus needs met can more effectively resist diseases because healthy and well-developed plants withstand adversity much better than others.
Potassium
- Improves the drought resistance of the plant for those hot summer days we frequently see.
- Potassium helps with root growth and photosynthesis
- Helps the plant maintain its turgor, which reduces water loss, wilting, respiration, and energy losses. This helps to build cellulose and reduces lodging, especially during strong summer storms.
- Aids in the formation of food, enhances translocation of sugars and starch, produces grain rich in starch, and increases the plant’s protein content. All of which help to produce the strong test weights we hope to see every year.
Don’t let P&K be limiting factors to high yield. Take advantage of more economical fall fertilization while crossing off an item on your spring to-do list.
