Phosphorus management is and must be a long term proposition. Phosphorus behaves very differently than nitrogen in the soil, as it binds tightly to soil particles and releases slowly over time. This is good and bad — it’s not subject to the same loss risk that N is, but it also means that sometimes the nutrient isn’t always available when crops need it. Phosphorus is also needed very early in the season, usually, but there are limits to how much seed-placed fertilizer is safe, especially when it comes to a P-sensitive crop like soybeans.
To complicate matters, soybeans are a big user of phosphorus and a big user late in the season, a combination of facts that means farmers have to manage phosphorus availability for soybeans differently than most other crops. In this episode of the Soybean School West, John Heard, soil nutrient specialist with Manitoba Agriculture, Food and Rural Development, explains the dangers of high seed-placed phosphorus rates, the pros and cons of soybeans’ big phos demand and what you have to do this year (and next) to feed this hungry crop.