Protocol Status
Section Title
Corn Starter Phosphorus
Trial Information
The purpose of this project is to quantify the impact of starter phosphorous in corn when planted into soils with high soil phosphorous levels.
- Corn fields with high soil phosphorous ratings will we located and sampled to confirm.
- The grower will plant a corn hybrid with and without starter phosphorus.
- The grower will plant the strips of corn with and without additional starter phosphorus.
- Strips should be full length of the field (minimum 1000 ft.) and width to allow for a full “pure” pass with the combine header.
- The grower will keep the rest of the fertility the same on the strips and will manage their crop as per their normal best management practices.
- 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.
Results
In 2025, two sites (CRNSP03 and CRNSP07) remained unharvested at the time of publication, which leaves 16 site years of data to build a conclusion from. Three in 16, or 19 per cent, of site years showed yield results of statistical significance. These three sites consistently exhibited a yield bump in the same treatment across four replicates. However, 2024-CRNSP02 had a yield improvement in the additional phosphorus treatment and the reverse was demonstrated in both 2025-CRNSP04 and 09. There was more precipitation in spring 2024 than in 2025, so that could be a factor in the yield increase with the added phosphorus treatment and soil-P mobility, especially in a lower soil-P scenario. There are many factors that cannot provide an exact explanation to each circumstance. More data is needed to come to a conclusion.