My findings and results on 7 years of experience with this system are as follows. Done lots of research this winter on this topic as well. I've been told a seedling only lives off its own nutrients within the seed and the direct nutrients around the seed until the 2-3 leaf stage . A plant is growing a root structure but not really mining for nutrients through its roots until the 2-3 leaf stage. So that's why phos very close to a seed is very important for good pop-up and good root growth. Since phos is not mobile in the soil, is 1.5 inches away from the seed to far?
I have done both Phos with and phos away from seed, phos with is better from my findings. But i'm starting to find that only 25-30 lbs with the seed may not be enough, because of salt effect i'm causious of adding to much more with the seed. In the past couple of years I think that i'm possibly starting to see a less vigorous start. I guess i'm wondering if i'm not putting back enough phos to replenish the levels that the yeild's have been removing. Do I need to add More to keep future yeild's growing, i think so but that now becomes a delivery problem and how many products do we want to handle at seeding?
I use liquid Nit, liquid sulfur in fert knife. Dry phos, dry potash with seed in seed row. I run this way for several reasons, cost of dry potash, and sectional liquid control of nitrogen beinging two of the biggest reason's. I think i need to now add liquid Phos to the fert band to increase the Phos number's as this will be the easiest way to get more phos down. Hoping others contribute more thoughts on this thread. I think there is much more to be added on this topic.