|
| I have heard such a question asked to soil fertility specialists and some will disappear off into tangents, referencing soil type, rotations, specific soil testing method, sampling depth etc etc, and I agree that there may not be a universal answer.
Based upon your location, a quick answer is illustrated below. It cites work from the University of Kentucky and illustrates how much P205 (there is 46lb of P2O5 in 100 lb of DAP for example) is required to build soil test P (in lb/ac, PPM x 2 = lb/ac).
It illustrates the snowball effect. Once you let the soil test P drop to very low values, it takes a lot of P2O5 to start the process of building it back up (and that's outside of the crop removal requirements).
Once soil test P values start to increase, less is required. etc etc.
If its rented ground or if the soil test levels are low, banded nutrient placement is a sound option. While this will require equipment modifications, I think its best done at planting time.
I am not sure such a chart exists for K. But I have heard (depending on the soil type), 2 to 6 pounds of K2O are required to increase the soil test by 1 pound K per acre. (again PPM x 2 = lb/ac)
Phil N
http://www.needhamag.com/
Edited by Phil N 11/22/2009 17:21
 (Soil Test P LR.jpg)
Attachments
----------------
 Soil Test P LR.jpg (93KB - 89 downloads)
| |
|
Build up of fertilizer requirement
