Research on the Farm (ROTF)

Background & Info

Research from Johnston et al. (2006) determined that 25% of fields are rated low to very low in soil P and cannot supply adequate phosphorus for a corn crop. Starter P is typically applied generously as a result of this data.

This project looks at the yield benefit vs. yield draw of starter P applied on high-P testing soils

Trial fields received starter phosphorus amounts ranging from 20-45 lb/ac of P2O5, as per their respective spring soil analyses

Corn has high phosphorus requirements for plant development, beginning at germination. It is a favourable practice to seed-place a portion of the phosphorus blend, resulting in vigorous seedling growth and development. The remainder of the blend can be placed in a band near the seed row, though some grain corn farmers have adopted a split application process in-crop.

Starter phosphorus increases early-season biomass and plant height when measured at V4 and V7, respectively (Rogalsky, 2016). In the same research, silking date was 2–7 days earlier in starter-P treatments than untreated checks.

Result

Only one site showed a significant decrease in yield when no phosphorous was applied.

Starter phosphorus applications in fields with high residual-P did not provide an economical boost in grain corn yield in four out of eight sites. In fact, one of those four sites had virtually the same yield in both treatments.

In the three sites that did have a yield improvement with starter-P applications, this increase was not statistically significant and provided no economical benefit to the additional phosphorus provided to the crop.

The only site that did see a statistically significant decline in yield when no phosphorous was applied had the lowest soil phosphorous test overall. In this case, they saw a 7.29 bu/ac increase when applying soil phosphorous. Based on current cost of production estimates from Manitoba Agriculture this site saw an increase in net profit of $16.46/ac when phosphorous was applied