Objective

To assess yield impact of phosphorus on four spring wheat varieties grown in North Dakota.

Method

• Varieties grown (2018): Albany, Bolles, Linkert, Prosper
• Triple super phosphate fertilizer was broadcast and incorporated one day before seeding, at the equivalent rate of 0, 12, 24 lbs P₂O₅/ac.
• Another treatment was applied with the seed at 7.2 lbs P₂O₅/ac.
• Soil test for P was low (4 ppm). The NDSU phosphorus recommendation for spring wheat is that, application with the seeds should be reduced to one third of the broadcast rate.

Results

• Yields were significantly different between varieties in this order: Albany (54.2 bu) = Prosper (53.7 bu) > Bolles (48.7 bu) > Linkert (44.1 bu).
• There was no clear evidence to suggest that phosphorus had significantly more impact on yield of one variety than another.

• Application of 7.2 lbs P with the seed significantly improved grain yield by 6.4 bushels compared to the control (0 lbs P), and by 4.2 bushels compared to 12 lbs P applied by broadcasting.
• Yield improved by 4.9 bushels with 24 lbs P broadcast and incorporated, compared to the control.
• Meanwhile, yield differences were not significant between the control and 12 lbs rate, and between 12 and 24 lbs P rates.

• Crop vigor was assessed 42 days after planting, by measuring light reflectance (NDVI) from the crop canopy of each plot using the GreenSeeker sensor.
• The most vigorous treatments were at P = 7.2 lbs seed applied, and 24 lbs broadcast and incorporated.

Conclusion

• In-furrow application of starter phosphorus at one third the recommended broadcast rate produced the highest yields. This is consistent with the in-furrow recommended rate of phosphorus as a percentage of the broadcast rate for yield optimization in the current growing season.
• Consideration for rates to apply must include, in addition to soil test, cost of application and grain price. For more on phosphorus recommendation for spring wheat visit this page by Dr. Dave Franzen https://www.ag.ndsu.edu/publications/crops/fertilizing-hard-red-spring-wheat-and-durum-1/sf712.pdf

Jasper M. Teboh, Ph. D.
Jasper.Teboh@ndsu.edu
Soil Scientist