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Forage legumes provide valuable N and Save Money
by LuAnn Rolling, District Conservationist

Forage legumes like alfalfa and red clover together with manure were once the only way to provide additional nitrogen (N) to non-legume crops. The ability to synthetically produce nitrogen fertilizers greatly decreased agricultural reliance on traditional nitrogen sources beginning in the early 20th century. Dr. Christine Jones, one of the world’s preeminent microbiologists from Australia, wrote an article titled Nitrogen: the double-edged sword, in which she says that prior to the Industrial Revolution, around 97% of the nitrogen supporting life on earth was fixed biologically. Over the last century, intensification of farming, coupled with a lack of understanding of soil microbial communities, has resulted in reduced biological activity and an increased application of industrially produced forms of nitrogen to agricultural land.

Legumes still can provide valuable N to today’s cropping systems. Legumes also contribute a non-nitrogen rotation effect due to the addition of soil organic matter and improvement in soil health. According to a study by the University of Minnesota Extension, corn grown following alfalfa stands that are 2+ years old (and contained at least 50% alfalfa) require no nitrogen fertilizer on many soils. Red clover N credits are less than for alfalfa.

By extrapolating from nitrogen recommendations comparing 1 and 2+ year old alfalfa stands, it appears that a fall incorporated 1 year old stand of alfalfa can contribute from about 30-60 lb/N per acre to a subsequent corn crop on medium or fine textured soils.

There is a new variety of clover that is showing exceptional nitrogen fixation capacity. In a trial conducted at the Ewing Demonstration Center (EDC) in Illinois, decomposing FIXatioN Balansa clover added 269 pounds of nitrogen per acre over a period of six and a half months compared to the control variety, Dixie Crimson clover, which only added 14 pounds of nitrogen per acre. In return, FIXatioN Balansa clover improved the soil nitrogen contribution and soil ammonium ppm by 40 percent and 80 percent versus Dixie Crimson clover in just four weeks after corn emergence (WAE).

While you’re adding to your seed costs, legumes quickly pay for themselves in the amount of nitrogen added to the soil which is immediately available to succeeding crops. The cash savings on nitrogen fertilizer reduction is just part of the equation when it comes to figuring ROI of legumes. For starters, plant-based nitrogen is more stable than manufactured nitrogen and is also not detrimental to your soil’s pH. Extensive taproot systems also do wonders for soil structure, breaking up compaction and burrowing into deep nutrient resources that can be utilized by following crops.

As you start doing your homework for how legumes can be incorporated into your row crop or forage program, remember that clover is not clover, just like corn isn’t corn – varieties matter. Improved plant breeding has given producers access to high performing plant genetics and the ability to select for consistency of performance to avoid yield and cover ratio variation.