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Chesley, Ontario | From an environmental perspective, the hoopla is definitely overblown. From an agronomic point of view, there are still reasons to be careful about applying N to soybeans (aside from the cost of N fertilizer).
If there are high levels of nitrate-N in the soil during the early growth of the soybean plant, this will inhibit the activity of the rhizobia. Either nodules won't form, or they will form but not be effective. If there is enough N in the soil to carry the plant through to maturity, this is not a problem, but if the plant runs out of N during flowering the nodules won't be there to make up the difference. Ammonium-N doesn't seem to have the same effect, so it would be OK to apply manure just before planting, but not to plant soys into a field that had manure in the fall or early spring since much of the N would have converted to nitrate.
The other considerations with growing soys in manured ground are weed pressure, and the possibility of pushing too much vegetative growth on the beans. This can lead to increased lodging and/or white mould, and actually reduce yields. That being said, some of the highest soy yields I have seen have come off fields receiving liquid hog manure!
Edited by Ontario Keith 10/11/2006 17:42
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Soybean tillage
