Seed Row Tolerance of 16-20-0-13 and 12-40-0-6.5S-1Zn in Western Canada

The majority of P-based fertilizers are either applied directly in the seed furrow (seed row), or side-banded close to the seed row for the growing of small grain cereals and canola in the Western Prairie provinces of Canada. Farmers using ammonium phosphate-sulfate (16-20-0-13S) fertilizer have reported that they can safely apply greater amounts of phosphate in the form of 16-20-0-13S in the seed row compared to monoammonium phosphate (11-52-0). To determine if this is accurate, a research study assessing the effect of low and elevated rates of 16-20-0-13S placed in the seed rows of both spring wheat and canola was arranged with a private research association (Hamman Research Inc., Lethbridge, Alberta). The experimental design was a randomized complete block experiment with 13 treatments, replicated four times. The P application rates ranged from a low rate of 20 lb P₂O₅/A up to 40 lb/A, in 5 lb increments. There were additional treatments using 11-52-0 and Rock 40 (12-40-0-6.5S-1Zn) at selected P rates, the same as some of the 16-20-0-13S treatments, for comparison.

In 2015, the crop was planted in early May and no significant precipitation was received until early June. For assessing potential adverse effects of seed row-applied fertilizer for spring wheat, this lack of rainfall was useful to observe the effects of seed row fertilizer under dry soil moisture conditions. However, at this site the higher application rates of 16-20-0-13S (30, 35, and 40 lb P₂O₅/A) did not decrease seedling emergence for spring wheat, compared to decreased emergence observed at lower rates of application with some other forms of P fertilizer. The grain yields of spring wheat were very similar for both low rates and high rates of seed row-applied fertilizer. For the canola, a smaller-seeded crop that is more sensitive to seed row-applied fertilizer, higher application rates of 16-20-0-13S (35 and 40 lb P₂O₅/A) decreased emergence of canola seedlings by up to 33%, compared to a 20 lb/A rate of 11-52-0 fertilizer. However, since canola is a so-called "plastic crop", it is able to compensate in growth, by increasing stem branching to fill crop canopy and produced as much yield as with 20 lb P₂O₅/A of 11-52-0 fertilizer.

One additional year of research will be used to determine whether or not 16-20-0-13S reduces emergence and yield of spring wheat and canola compared with 11-52-0.