Legume Planting for Forage and Soil Regeneration
CJ Brinlee, Soil Conservationist Student Trainee; Randy Moore, Wildlife Biologist, USDA-NRCS

 Long before the invention of nitrogen fertilizer during World War I- and still used throughout the world today to replenish soil- crops of legumes were used in crop rotation.  Legumes are a uniquely adapted plant that has a symbiotic relationship with microorganisms called rhizobia that have the invaluable ability to transform atmospheric nitrogen back into a form readily available to plants in the soil.  Therefore, legumes such as clovers and alfalfa have always been planted to restore the integrity of the soil and boost production.  Today, with the rising price of fertilizer, the value of legumes can be once again realized.

Performance of the legume crop depends on the species chosen for planting.  In Texas the forage legume species planted are as diverse as the soil types and climate across the state.  For successful legume production it is imperative to know your soil type and which species are adapted to that soil.  Due to the normally hot and dry climate of Texas, cool season legumes tend to fair the best.  They are generally planted in mixes with rye grass or small grains in September or October.  The most productive, but also the most expensive method for planting is prepared seedbed, which allows grazing to begin around December.  The light disking method enables the forage to be available about six weeks later, and is more economical but not as productive.  The least productive method is to overseed your pasture with no tillage.  It provides a shorter, less productive grazing season due to a later planting date in October or November.  A soil sample should be analyzed before the seedbed is prepared to determine liming and nutrient requirements.

In order to assure nitrogen fixation, seed should be inoculated with strains of Rhizobium bacteria before planted.  Inoculants should be purchased when purchasing seed, the most effective inoculants are those that have a greater number of rhizobia per gram of inoculant and are mixed with a sticker such as HiStick or Pelinoc-Pelgel that will hold the inoculant to the seed.  If necessary water, buttermilk, or coke can be applied to the seed as a sticker, though diet drinks aren’t as effective because of the lower sugar content.  Inoculated seed should be drilled into the soil if possible to protect the bacteria from the sun and higher temperatures. 

When establishing a new stand of legumes they should be protected from weed infestation.  The only preplant herbicides that can be used on clovers are Balan and Eptam which must be incorporated into the soil and can only be used in prepared seedbed situations.  Neither of these herbicides can be used on a clover-grass mixture.  Post emergent herbicides include 2, 4-DB and Kerb.  Before using an herbicide make sure that it is cleared to be used on legumes and grasses (if present).

In addition to their ability to return 60-80 pounds per acre of nitrogen to the soil, legumes also improve soil condition by increasing soil tilth, enhancing the micro-organism environment, adding organic matter, and reducing weed competition.  Moreover, they provide better forage for livestock since they are easier to digest and higher in protein, calcium, magnesium, and phosphorous. Improved forage quality can extend forage production allowing grazing to begin 30-60 days earlier, reduces the days of feeding hay therefore lowering the cost of animal production while increasing animal performance.

Nitrogen fixation takes place in legumes due to microbial organisms called rhizobia that infect the roots of legumes and form a tumor-like node in which they inhabit and transform nitrogen trapped in the soil air into ammonium.  The rhizobia provide the legume with nitrogen in the form of ammonium while the plant provides the bacteria with carbohydrates.  The effectiveness of a legume to fix nitrogen depends upon the strain of rhizobia which infects it, the level of soil nitrogen since the legume would rather get its nitrogen from the soil than the air, amount of legume plant growth, how the legume is managed, and length of the growing season.  A forage legume crop can provide anywhere from no nitrogen to two hundred pounds per acre depending on these factors.  Usually, however, you can estimate the amount of nitrogen gained at 50-100 lbs/acre for annuals, and around 200 lbs/acre for alfalfa.   Common legumes in our area are crimson clover, ball clover, hairy vetch, singletary pea, and white clover. For more information on planting legumes please contact the USDA-NRCS office located at 200 E First Street, at 903-583-9513 x3.   You may also contact us by email at:  randy.moore@tx.usda.gov or the Fannin SWCD’s web site: http://fanninswcd.com.