|Rethinking Forage Legumes|
By Don Ball
At present many livestock producers are talking about forage legumes. This is a new development because in recent decades most livestock producers have not invested much time, energy or money in growing legumes. However, it is not unprecedented because there was a time (before World War II) when they were widely grown in Alabama and in many other states.
Many livestock producers presently appear to be on the brink of changing their attitudes toward forage legumes. Obviously, decisions regarding the forage species grown on a farm greatly affect livestock production and profit. Therefore, the "pros" and "cons" of growing forage grasses versus growing legumes or, as is more commonly the case, grass/legume mixtures is worthy of a closer look.
Advantages of Forage Grasses
Forage grasses offer a number of important advantages. In general, they are easier to establish than legumes, they tend to be more dependable and, when comparing perennial grasses with legumes, usually are more persistent. Except for rare occurrences with a succulent annual-like ryegrass, livestock bloat is not a problem with grasses.
Grasses respond to liming and fertilization, but many are fairly tolerant of soil acidity and/or low levels of various nutrients. The forage yields of many grasses are good, especially if regular applications of nitrogen are made which is relatively easy for producers to do. Most grasses require less overall management than legumes and leaf shatter is not a concern if grasses are cut for hay.
Advantages of Forage Legumes
Proponents of legumes point to their generally superior forage quality, which can result in significantly higher average daily gains and often better livestock reproduction. Legumes also tend to improve soil tilth and increase soil organic matter. In addition, the taproot-type root system of some legumes penetrates the soil deeply and leaves root channels that aid growth of subsequent plants. In some cases, growing legumes with grasses will increase forage dry matter yield and/or extend the grazing season.
Last, but not least (and this is a big reason for the current surge in interest), legumes have the unique ability to fix nitrogen in association with Rhizobium bacteria that are in close proximity to their roots. This is of great importance, because nitrogen is the nutrient required in the large amounts for forage production and is also the most expensive nutrient. While nitrogen fertilizer is a major cost input in grass forage production, legumes provide their own supply and even supply nitrogen to plants growing with or after them.
What’s The Answer?
In many management situations, there is actually no "right" or "wrong" approach. It is a matter of attitude, personal preference and a person’s perceptions regarding which approach will make the most of the resources available.
As an analogy, one football coach may decide to use a particular offensive scheme while a rival uses another. Furthermore, depending on the skills of his players and other factors, a given coach may use different approaches at different times.
Given their wide adaptation, productivity and dependability, it makes sense most forage programs in Alabama should be based around perennial grasses. However, while forage legumes are not suitable for every field or even every farm, they offer major advantages that should not be ignored. After all, they actually have the potential to improve animal performance while lowering expenses! By turning management up a notch to include legumes in a forage program, the profitability of many livestock operations could be substantially increased.
Don Ball is an Extension Forage Crop Agronomist with Auburn University.