Do’s and Don’ts of Forage Legume Establishment and Use
by Walt Davis

Do not use any herbicides or nitrogen fertilizers on the areas where legumes are to be grown. Nitrogen fertilizer is toxic to the rhizobia bacteria with which legumes must form an association to fix nitrogen from the air. Also, grasses are more efficient than legumes in utilizing nitrogen so abundant soil nitrogen allows grasses to out compete and choke out legumes. Some herbicides can kill germinating small seeded legumes for several years after being applied and all herbicides reduce biodiversity and thus work against the long term best interests of graziers.
Soil test to be sure that sufficient calcium is present but do not add large amounts (+ 2000#) of lime at one time in an effort to raise pH as large amounts degrade both the chemistry and the biology of the soil. If phosphorus is needed, phosphorus applied, as animal or green crop manure is less likely to be tied up by chemical reaction in the soil then is phosphorus from acidified rock phosphate fertilizer. Natural rock phosphates become available to higher plants slowly through the actions of soil microbes and are less likely to become tied up in unavailable compounds. Good long-term mineral nutrition comes about when the soil becomes highly biologically active. Soils with good organic content and high biological activity will be both more productive and more stable than soils with higher amounts of mineral nutrients but low soil life.
Inoculate each type of legume seed with the proper rhizobia bacteria before planting; seed dealers can get the proper strains of bacteria and the amount needed will be on the package. Moisten the seed with a sticker agent (milk, dilute molasses, methyl cellulose solution, etc.) that will serve to stick the bacteria medium to the seed and also provide a source of food for the bacteria when it becomes active. Stir the seed well after adding the sticker and again after adding the bacteria so that each seed is coated with the bacteria medium. Stir in a little (one cup per 50# of seed, more won’t hurt) of colloidal soft rock phosphate (the correct material is as fine as talcum powder) to provide a little phosphate in close contact to the germinating seed; do not use acidified phosphate (18-46-0, 0-46-0) as this will kill the bacteria. If too much sticker is used and the seed clumps, the excess can be taken up with more colloidal phosphate or some finely ground limestone. Keep the inoculated seed cool and in the shade as the bacteria will be killed by direct sunlight and excessive heat. If seed is not planted within forty-eight hours of being inoculated, it should be re-inoculated before planting. Different kinds of legume seed can be mixed for planting provided each is inoculated with its’ proper bacteria before mixing.
Do not plant too deeply; a rule of thumb is no deeper than twice the diameter of the seed. For most small seeded legumes, the ideal situation would be to have the seed setting on firm mineral soil covered only by one half inch of fine organic matter. It is hard to regulate seed depth in loose or cloddy seedbeds and these seedbeds have poor moisture retention, strive for firm fine seedbeds. In cases where shallow placement of the seed is difficult, mixing the legume seed with ryegrass and placing the mixture in a drill row can allow the grass to help the legume seed that is planted too deeply to emerge. In most cases, no-till or very low- tillage gives the best results. Seeding cool season legumes in the fall after growth of the warm season grasses slows usually gives the best results where winters are not severe. Good results have been achieved by broadcasting legume seed onto frozen ground or even snow in the early spring and allowing the freeze-thaw-freeze sequence plant the seed.
Shade is a major concern in both establishing and maintaining legumes in mixtures with grasses. The existing grass should be grazed or mowed to a stubble height of no more than two inches for sod grasses or five inches for bunch grasses before legumes are seeded. If the existing grasses are growing vigorously, it may be advantageous to slow their growth rate by grazing or mowing to a short height and then coming back to defoliate again when two or three inches of re-growth has occurred. Be careful, this is a powerful tool that should not be over used or used when plants are in stress. Tall growing legumes such as alfalfa, sweet clover and red clover or vine formers such as vetch and Singletary peas will do better in tall growing grasses than will shorter growing legumes. If forage is stockpiled in the fall for winter grazing, to keep legumes in the mixture, the same areas should not be stockpiled every year and re-seeding may be needed on the areas stockpiled.
Bloat is much less a problem on legume pastures that are grazed under time control. Bloat is most severe when animals have access to pure stands of very immature legume. If the legume is presented to the animals only after it has matured enough to have good energy to protein ratios (usually early bloom) very high percentage legume pasture can be grazed without metabolic problems. Animals do best when they are consistently grazing forage that has a narrow range of physiological age whether or not that forage contains legumes. When grazing high legume content forage, graze periods should be kept short (no more than three days with less being better) so that the stage of maturity of the forage can be controlled. There are some animals that cannot tolerate a legume diet and they should be removed. Hungry animals should not be turned to legume pasture and fewer problems and better gains will be seen when grass makes up at least forty percent of the pasture sward. There are non-bloating legumes such as arrowleaf clover and Berseem clover and including these plants in the pasture mix helps reduce the incidence of bloat. Bloat can also be caused, even on non-legume pasture by chemical imbalance in the soil with too high nitrogen or potassium levels being the most common culprits.

Do’s and Don’ts of Forage Legume Establishment and Use by Walt Davis

Do’s and Don’ts of Forage Legume Establishment and Use
by Walt Davis