Should I Be Applying Phosphorus This Fall?

Combines should be starting to roll through the fields. As your data is coming through the yield monitor, you are probably thinking about the products you planted this year and what next year’s fertility plan should be to help maximize yield potential. 

Fall is a prime time to be soil testing, which should be the basis for nutrient applications. This allows time to change fertility needs based on yield goals and crop rotations.  

So, should I apply phosphorus (P) this fall? Mother Nature can be our worst enemy in this business. As farming operations get larger, more acres are being covered, which can lead to a later harvest window. Springtime weather can be too wet for field operations; therefore, many farmers apply most of their dry fertilizer needs (including P) in the fall. This allows for the P to work its way below the soil surface in conservation tillage programs or be tilled in.

The availability of P for plant uptake is greatest within a few days to two weeks after application and drops slowly with time.¹ Because of cooler soil temperatures and usually drier soils in the fall and winter, P can remain in the soil profile for four to six months and be available for early spring plant growth. Applying P in the fall gives farmers more time to think about other spring activities including planting, which seems to get started earlier every year.  

In conclusion, maintaining P (as well as other plant nutrients) at critical levels rather than waiting for crops to show a deficiency during the growing season can help maximize yield potential and profit. Fall fertility applications for the following crop is critical for your bottom line and helps get you ahead of wet spring-time soil conditions. With crop prices at all-time highs, make sure you are getting the most from your farming operation.

¹Pagliari, P. 2017. Fall vs. spring: When to apply phosphorus. Minnesota Crop News. University of Minnesota Extension. https://blog-crop-news.extension.umn.edu/2017/11/paulo-pagliari-nutrient-management.html#:~:text=Phosphorus%20will%20be%20most%20available,six%20months%20before%20plant%20uptake.