Yield Response to Phophorus

A network of experiments across Missouri has shown that there is little or no yield response to P fertilizer when previous fertilizer management has maintained soil test levels at the target levels recommended by the University of Missouri.

A network of experiments measuring soybean, corn, and wheat response to phosphorus was conducted all across Missouri between 2000 and 2002. These were conducted in cooperation with the University of Missouri variety trials, mainly on farmer fields. Cooperating farmers had maintained soil test P at levels consistent with University of Missouri recommendations. Most experimental fields had soil test levels between 30 and 60 lb Bray1 P/acre; the University’s target level is 45 lb/acre.

Average yield response to P in these experiments was very nearly zero (see table). This is expected and intended in the University of Missouri’s recommendation system. At the target soil test level, the soil should be able to supply the crop’s entire phosphorus need. Fertilization is then to replenish the soil supply as it is used up. Timing of P fertilization is not critical if soil test values have been maintained at or near the target level.

Crop

Average yield response to P

Number of Experiments

Soybean

0.3

40

Corn

0.2

21

Wheat

-1.0

8

See the complete reports:
Soybean
Corn
Wheat