ISSUE 2    May 12, 2005


Although some soybeans are in the ground, there are many additional acres yet to be seeded.

Briefly, here are soybean fertility guidelines-



Myth and legend 1- Soybeans build soil organic matter

Soybeans only build soil organic matter if they are tilled under before harvest as a green manure. Rotation studies have shown that when soybeans are introduced, organic matter levels decrease at a greater rate than previous non-annual legume rotations. Research has suggested that under soybeans, rate of organic matter breakdown is increased, evidently helping soybeans by providing additional soil N so that the soybean carbohydrate contribution to nodules is reduced. The increased rate of organic matter breakdown and N mineralization is part of the source of our soybean previous crop N credit we give crops following soybeans.

Dave Franzen
NDSU Extension Soil Specialist
(701) 231-8884

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