Savvy forage producers know that adding legumes to grass pastures and hayfields can go a long way toward decreasing the need for nitrogen fertilizer. While there are a variety of benefits to planting clovers, many producers are surprised to learn that making nitrogen isn’t one of them.
So how exactly do legumes decrease the need for nitrogen fertilizer then? The first thing to keep in mind is that nitrogen is everywhere, including in the air we breathe. In fact, 78 percent of the air is actually nitrogen. Legumes have a symbiotic relationship with a type of bacteria that forms on the nodules of legumes. As a result, the bacteria in the nodules take nitrogen from the air and it is converted into a form that legumes use to make protein. This process is known as nitrogen fixation.
The legume is then able to use the nitrogen to grow, despite the fact that the surrounding clover plants don’t have access to that nitrogen. However, there is an indirect process in place. When legumes produces new leaves, roots and root hairs are replaced. When these parts break down in the soil, nitrogen is released into the soil. This makes the nitrogen accessible to grass that uses it in uptake and growth. In other words, nitrogen is transferred through a recycling process that takes place when legumes die.
This process is important because many producers shy away from herbicides in order to prevent the death of clovers. The reality is that the death of clover plants actually provides the nitrogen grass needs, allowing for the incorporation of herbicides without damaging the process of transferring nitrogen.
In light of these facts, you might want to spray in December or January to kill weeds. Even if this kills clovers, grass will still be available in the spring because of the nitrogen transfer. Depending on the type of herbicide used, clover can be replanted in a month or so and little or any damage will occur in hayfields or pastures.
Toward the end of February, a combination of white clover and red clover should be planted. The seed can be mixed and broadcast over hayfields or pastures. The soil to seed contact is aided by freezing and thawing.
Depending on the type of herbicide used, you may have to wait a month before planting clovers. If you used a herbicide with chemicals that have residual activity, you will have to wait until the following fall or winter.
Clovers are an important part of quality forage management. One of the most important reasons why that is true is its ability to put nitrogen into the soil.
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