Debates Continue About Benefit Of Extra Nitrogen On Soybeans

Legume crops such as soybeans and field peas can fix their own nitrogen from the atmosphere via a relationship with certain soil bacteria. Farmers including an inoculum of the bacteria with the seed at planting promote this natural relationship. However, the amount of nitrogen the bacteria provide can depend on many factors including residual nitrogen in the soil, weather, and soil conditions.

There is debate on whether bacteria can provide enough nitrogen to soybeans for maximum yield potential or not. A lot of energy is required to generate nodules (root structures for bacteria to provide nitrogen) on soybeans and when nitrogen is available from application or residual in the soil, crop growth may be greater pushing yield potential. In addition there is debate on the optimum application timing of nitrogen on soybeans. At planting could increase early growth and later in season may help push yield.

With discussion around applying potassium and micronutrients later in the growing season it makes sense to be considering nitrogen requirements too. I think that farmers should try a couple of areas in their fields and see if differences were made. Throw down some nitrogen at planting, put some down in season in another strip and as always leave an untreated check to compare the treatments. It comes down to market prices though. In the past prices have been good and pushing yield potentials with nitrogen could pencil out but with low prices or poor growing conditions they probably won’t.


3 thoughts on “Debates Continue About Benefit Of Extra Nitrogen On Soybeans

  1. owenroberts

    Soybean prices are high enough to warrant extra nitrogen, aren’t they? There must be some formula to know when the extra nitrogen makes a significant difference. I always thought one of the big environmental advantages of soybeans was their low (if any) nitrogen requirement.

  2. buddc Post author

    In the past couple of years soybean prices have been good but they may not always be since we are competing with large producers such as Brazil, China and the USA who in good years are increasing their acreage as well. There seems to be more of a trend to try other fertilizers such as potassium and micronutrients later on in the growing season rather then nitrogen right now and yes with high market prices these methods can pay off. From what I have read in the the Ontario Farmer is that researchers are not sure exactly when the extra nitrogen can make a significant difference. It seems that only when the crop is doing really well can its need for nitrogen exceed the crops ability to fix enough nitrogen itself and this is when extra nitrogen may pay. It is defiantly a large environmental benefit about soybeans, edible beans (white, adzuki, etc.), field peas, alfalfa and other legume (can fix nitrogen) crops.


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