Last week I wrote about phosphorus (P) fertility philosophies or approaches. This week I am writing about Nebraska research that compared those phosphorus fertilizer approaches. This research was published in the 2018 Soil Science Society of America Journal by UNL faculty Wortmann, Shapiro, Shaver, and Mainz. One of the objectives of their research was to determine if another fertilizer P management approach was superior to the currently recommended UNL sufficiency approach for continuous corn production.
The research was conducted from 2011 to 2016 in Dixon, Saunders, and Lincoln counties in Nebraska. Dixon County near Concord was a rainfed site on Nora silty clay loam soil with an initial soil test P of 10 ppm. Saunders County near Mead was a pivot-irrigated site on Yutan silty clay loam soil with an initial soil test P of 6 ppm. Lincoln County near North Platte was a pivot-irrigated site on Cozad silt loam soil with an initial soil test P of 14 ppm. The experimental design was continuous corn with two different tillage systems, tillage with annual tandem disk and no-till at each site. Within each tillage system, there were five P treatments or approaches:
- no applied P,
- P applied according to UNL recommendation for continuous corn,
- P applied to replace P removal in the previous grain harvest,
- build/maintain soil test P at 25 ppm,
- and build/maintain soil test P at 35 ppm.
Each P treatment or approach was replicated four times within each tillage system and the same plots were maintained for the 6-year study at all three sites.
Continuous corn yields from the five different P treatments were not significantly different between tillage systems. The average corn yields across years, locations, and tillage system by P treatment were:
- 154 bu/ac (no P),
- 163 bu/ac (UNL P rec),
- 169 bu/ac (replace P removal),
- 166 bu/ac (maintain 25 ppm soil test P),
- 170 bu/ac (maintain 35 ppm soil test P).
The corn yield was statistically the same for replace P removal, maintain 25 ppm soil test P, and maintain 35 ppm soil test P approaches. Meaning that the 1 to 3 bushel per differences are not likely due to the three different P approaches. However, the UNL recommendation yielded 3.3% less than replacing P removal in the previous grain harvest and the maintaining the soil test P at 35 ppm.
The amount of P fertilizer rate applied over the 6 years was quite different between the approaches. For example at the Saunders County site, cumulative total P205 applied was approximately:
- 250 lbs/ac for UNL P recommendation,
- 260 lbs/ac for replacing P in grain harvest,
- 355 lbs/ac for build/maintain at 25 ppm,
- and 611 lbs/ac for build/maintain at 35 ppm.
Assuming $0.45 per pound P205 cost, replacing P removed in grain harvest cost $117 per acre while the build/maintain soil test P at 35 ppm cost $275 acre. Overall, the best management approach for continuous corn production in this 6-year study in Nebraska was replacing P removed in grain harvest each year. We will dive into more details in part 2 next week.
Contact me with questions or suggest topics for me to write about in regards to phosphorus management at or 402-821-1722. Know your crop, know your tech, know your bottom line at croptechcafe.org.
