One of the common themes of fertility presentations for direct seeding systems in producer meetings has been don't seed place too much fertilizer. Demonstration plots in the north east region depicting some of the mistakes made as producers shift into direct seeding invariably showed last season the detrimental effects of seed placing all required fertilizer even in high moisture springs.
When presenters talk about seed placing fertilizer they usually refer to the fact sheet Guidelines For Safe Rates of Seed Placed Fertilizer. They almost invariably say "off the record" that these are only guidelines and they probably error if anything on the safe side. When you get producers actually talking about their own experiences very few talk about seeing significant damage from seed placing too much fertilizer. If they do it is frequently on sandy or lighter land. The data from six of the direct seeding Do's & Don'ts plots in the NE region during last growing season certainly showed that seed placing higher rates of required fertilizer in tight bands reduced stand establishment even in a high rainfall spring like most areas experienced last year.
Plots of wheat and flax seeded next to the Naicam Canola Production Site last year received a good 2 inches of rainfall in the week of seeding. A good portion of this was received after seeding which should have effectively diluted the toxicity of the fertilizer away from the seed. Plant counts graphed in Figures 1 & 2 show seed placed (SP) trials with greatly reduced plant counts as compared to side banded (SB). Flax particularly shows stand thinning with 80 lbs actual N. It is interesting to note that the spread percentage with the side bander is probably about 11%. This is medium textured land. With good soil moisture the recommended guideline maximum is .
At the Tisdale site wheat and canola were seeded into quite warm moist growing conditions. The only difficulty with the site was that there was very little residue on the particular location where the plots were seeded. This is clay and heavy clay land and it can dry out quite quickly after seeding. For this reason the shallow seeded canola was a little too shallow and the deeper seeded trial had almost double the plant counts numbers. Figure 3 shows that canola with SP (seed placed) fertilizer had canola plant counts about ½ that of the SB (side band) seeded at the same depth.
Figures 5 & 6 from the Conservation Learning Center also depict similar reductions in plant counts with the fertilizer seed placed as compared to side band. Interestingly field peas which only received 40 lbs actual P and 10 lbs actual N still had a stand establishment reduction of almost 30%!
In closing, these observations clearly demonstrate that we cannot place all the fertilizer usually called for in the NE region with the seed!
