Earlier in the week, a phone call of one of our hay producers was very interesting to me. As he shared with me his pasture situation after the rain, we started talking about the clover in his meadow. According to the rancher, his meadow had a large number of clovers in it. With the rain, he was having trouble getting his cattle to eat it. We talked about the need of “pushing” the clover with cattle and the benefits of high nutritional forage for his cows.
According to the university of Georgia –Extension, in addition to improving animal performance, a frequently mentioned benefit of including clover in pastures is nitrogen fixation. The earth’s atmosphere is made up of about 80 percent nitrogen; this nitrogen is not, however, in a form plants can utilize. Nitrogen is “fixed” in clovers through a symbiotic relationship with rhizobium bacteria that infect roots. The plant provides energy for the bacteria, and bacteria provide the “machinery” necessary to convert atmospheric nitrogen to a form available to plants.
Nitrogen fixation is one of many economically important features of clover, particularly when clover represents a substantial proportion of available forage. A vigorous stand of white clover will fix 100-150 pounds of nitrogen per year depending on soil and growing conditions. At fertilizer nitrogen prices of $0.30 per pound, this translates to $30-$45 per acre. The economic value of nitrogen fixation alone should more than pay for seed and establishment expenses. Direct benefits of nitrogen fixation are realized almost exclusively by clover plants. Studies have shown that mixed grass and clover stands can produce forage yields equivalent to those of nitrogen fertilized grass stands. In the clover-containing system, overall grass yields decrease, but clover yields offset these decreases.
In addition to clover plants supplying forage without nitrogen fertilization, overall forage quality available to animals is higher in pastures containing clover. Most people envision a “pipeline” that transports nitrogen directly from clover to grass. Unfortunately almost no nitrogen is contributed to grasses this way. Essentially all nitrogen supplied to grasses from clover is indirect. Because of this indirect route, nitrogen from clover root nodules is not immediately available to companion grasses. Root nodules must decompose and nitrogen must be converted into a form available to plants. This conversion or “mineralization” releases nitrogen slowly, much like a time release fertilizer. This slow, steady nitrogen supply from a healthy stand of white clover can keep perennial grasses green and productive through the growing season. Fixed nitrogen from clovers is also supplied to grasses via grazing animals. Most of the nitrogen in consumed high quality clover plants is not digested or deposited in the animal and returns to the pasture as dung or urine. After our discussion, he shared with me his experiences with fertilization and his abundance of forage now.
In a way, I was glad to hear that his cattle were doing good and an excess of forage a good problem to have. For more information on this or any other agricultural topic please call me at 903-885-3443 or email me at m-villari[email protected].
Dr. Mario Villarino, CEA- Hopkins