The importance of phosphorus availability in spring wheat during early spring cannot be over emphasized in the Northern Prairie Region where the soil does not heat up fast enough to speed up mineralization of P in soil. This is important for no-till farming and in prolonged cool and wet spring conditions after seed emergence.

A study was conducted in 2016 to assess the response of four wheat varieties to 40 lbs of P₂O₅ (as triple super phosphate) on a fine sandy loam soil in the Red River Valley of Minnesota. Soil test P was 8 ppm and soil organic matter was 5.2%. Two main observations from the study were:

1. Yields responded significantly to P applied. Yield difference between the untreated (control) and treated plots were significant for each variety (Fig 1.) Different letters for the same variety mean the yields were significantly different. Yield increased by 6.5 bushels on average per variety. It must be noted that significant yield differences between varieties were primarily due to the respective yield potentials.
   
2. Total P removed in the grains was not significantly different between the control and 40 lbs P (Fig 2). This suggests that when P was needed for growth and development (tillering) early in the season the 40 lbs treatment of P had begun impacting yield until P availability increased from mineralization later in the season when the impact could not be reversed. On average, about 0.4 to 0.5 lbs of P₂O₅ was removed by the grain to produce a bushel.
   

The important message here is that even though P deficiency is not easily noticeable, except in more severe conditions from stunted growth, P deficiency can seriously impact yields. Because profits from P application are tied to fertilizer and grain market prices, consult the NDSU wheat fertilizer recommendation to help in your P application decisions for the upcoming growing season: https://www.ag.ndsu.edu/pubs/plantsci/soilfert/sf712.pdf

Thank you to the Minnesota Wheat Research and Promotion Council for funding this research, Mr. Ken Asp (producer), and Dr. D. W. Franzen for permission to use the web link.

Jasper M Teboh, Ph. D.
Soil Scientist