Loss of production to weed infestations is a major concern of both farmers and livestock graziers. This concern has created a multi-billion dollar worldwide market for chemical and mechanical weed control products. From the amount of money and scientific effort being directed toward the problem, it would seem that great progress should be made and that real control would be within reach. Instead we find that the problem is becoming worse in all areas and under most management programs.
This trend will continue until we stop looking at weed plants as the problem and realize that dense concentrations of the plants we term weeds are the results of basic fallacies in our management of the land. Weed infestations are a symptom of rather than the cause of our problem. From a graziers' standpoint, scattered plants of most "weed" species are not harmful but actually play a beneficial role in the soil-plant-animal complexes that are our pastures. It is only when weed concentrations become dense enough to retard the growth of forage species and thus affect animal production that we have a weed problem. Poisonous plants would seem to refute this statement but without going into great detail, poisonous plants become much less of a problem in healthy well managed pastures. The same is true of the bur producing plants that plague wool and hair growers.
The key is understanding that weeds become a problem and animal production is lost not because weeds are present but because conditions are such that weeds are better adapted to the situation then are the forage plants. Our management practices determine the conditions in our pastures and the conditions determine what plants will be present. There is a tremendous amount of variety within the plant kingdom with different plants being adapted to different sets of conditions. All areas have many species of plants present and some plants will be adapted to any set of growing conditions found within an area. Nature hates bare ground and will find some plants that can thrive in nearly any situation. A change in long term growing conditions will bring about a new population of plants better suited to the new conditions. This is the process scientists speak of as biological succession. If growing conditions are improved, succession will advance and if conditions deteriorate, succession will regress.
The plants most valuable for grazing are mostly high successional plants that share similar characteristics. They are wide leafed, deep rooted, long lived plants that are able to efficiently convert large amounts of sunlight, water and mineral nutrients into plant energy. These traits make them preferred as forage plants but also make them vulnerable to abusive grazing which reduces their ability to gather the necessary amounts of sunlight, water and minerals. Anything that degrades long term growing conditions tends to favor lower successional plants, reduce the number of species present and push succession backwards. Reducing the soil's ability to capture and hold moisture, slowing the rate at which minerals cycle through the soil-plant-animal complex and lowering the amount of energy available to the complex are the main ways that succession is forced backwards. A problem with any of these three ecological processes [water cycle, mineral cycle or energy flow] will cause weed proliferation. Most of the plants we term weeds are low successional plants that act as natures scabs to try to heal a sick environment. They are able to establish and survive under conditions too harsh for the higher order plants. By living (taking up nutrients, converting solar energy to biological energy, increasing organic matter in the soil, etc.) these plants improve long term growing conditions and thus prepare the way for higher seral plants.
Established stands of "improved" grasses such as Bermuda, fescue and bahia can improve the water cycle and to some extent the mineral cycle by trapping rainfall, building soil organic matter, slowing soil erosion and reducing soil compaction. We have serious weed problems in these type pastures because we have reduced diversity in the soil-plant-animal complex by managing for a monoculture. The fewer the number of species present, the shorter the time period over which energy flow and mineral cycling can occur at high rates. Every plant species and even every variety within a species has different needs and different abilities with which to satisfy these needs. We all recognize warm and cool season plants and plants that need a wet environment as opposed to those that grow in drier areas. The range of needs and abilities of plants, however, covers many other factors such as degree of shade, soil pH, ability to extract minerals from the soil, ability to tolerate the deficiency or excess of various soil minerals, depth of rooting, length of maturity cycle and how they respond to different degrees and frequencies of defoliation. A list of these needs and abilities is almost endless and our understanding of the complex relationships within a diverse plant community is very limited. We do know that the more species there are present in a community, the more efficiently all available resources will be utilized and the higher and more sustained will be both energy flow and mineral cycling. Anytime weeds become a problem in pastures, nature is telling us that we have unfilled ecological niches in our plant community. These niches will be filled by some plant. Whether they are filled with "weeds" or desirable forage plants depends upon our knowledge and skill as pasture managers.
In native grass areas the answer to weed problems is straightforward. If grazing management is such that long-term growing conditions are improved, succession will advance and the valuable forage plants will predominate. This won't happen over night but it will happen if we can keep from helping by spraying weeds, root plowing, disking or using other of the "range improvement" techniques that have little long term effect except to retard succession and cost money. This is not to say that there will be no weeds in the pasture sward. The plants that we consider weeds will still be present but not in high concentration and probably will now contribute to the health and vigor of the pasture rather than detracting from it. There will still be the “year effect” outbreaks of weeds that follow a period of drought, fire or other serious disturbance of the local environment. These outbreaks will become less severe and less frequent as the health of an area of grassland increases. This increased stability is a function of complexity and one of the major benefits of good grazing management.
In tame grass areas the problem is a little more complex. Most of our tame grasses such as Bermuda, fescue, Bahia and lovegrass are basically low successional plants. They were selected and bred because they have the ability to survive and produce under conditions that drive succession backwards. Ability to survive abusive grazing was the most important selection criteria but the ability to utilize large amounts of nitrogen fertilizer [quick growth cycle and opportunistic feeding] was also a large factor. The fact that these plants are low successional, means that the conditions that favor them also favor the low successional plants we call weeds. We can drive succession forward on these pastures by lengthening the recovery period between grazings and thus favor the wider leafed, deeper rooted, slower growth cycle high successional grasses. In time they would replace the tame grasses but the short term cost to the grazier for this practice would be high due to reduced animal performance. The longer rest periods would mean that the tame grasses are constantly being grazed in an overly mature, high fiber condition. Another approach would be to manage these pastures in such a way as to increase the diversity of species present and thus decrease the opportunity for weed proliferation and increase the length of the quality-grazing season. Not all low successional plants are low quality. All annuals are low successional but some [rye grass, crab grass, annual clovers] have excellent quality. There are also many high quality lower successional perennial plants [dallis grass, Johnson grass, red and white clover] that fit the growth cycles of the tame grasses fairly well. These can survive and produce under recovery periods short enough to keep from losing all quality from the tame grass portion of the mixture. Every forage species added to a pasture plant population means that much less opportunity for low quality plants to proliferate as weeds.
The age of forage is, as a general rule, a more important quality factor of forage then is the species of the forage. If the age of forage presented to the grazing animal can be controlled, livestock will eat and thrive on the immature forms of many weed species. Since these species are less tolerant to defoliation then the forage species, grazing reduces the competitive advantage of the weeds while providing quality forage to the animal and increasing the rate of mineral cycling. Grazing can be our most effective means of weed control. Animals should not be forced to eat weeds but rather made to want to eat them by presenting this material to the animals at its proper stage of growth. Long-term weed control through grazing comes mainly from improvement of the soil and from promotion of the health, diversity and vigor of the forage species, which places weeds at a disadvantage. Properly managing these lower successional pastures requires more thought, planning and observation than we are accustomed to giving our pastures but the monetary costs are less than we are used to and the benefits are worth the effort.
Many of the plants we term weeds are valuable forage plants for cattle at some stage of their growth and many others are valuable to other species of grazing animals. Given free choice cattle, horses, elk, bison and other mass graziers will select their diet in the order- grasses, forbs, browse; sheep, deer and some antelope prefer forbs, browse, grasses and goats will choose browse, forbs, grasses. Some of our “weed problems” can be solved in a positive manner simply by adding other species to our stocking mix. A good example is the proliferation of eastern red cedar in native grass ranges. The incursion is being caused by a number of factors, mainly poor grazing management and range sward simplification with herbicides, and the standard remedy of increased use of fire tends to create the very conditions that promote the spread of cedar and other woody plants. A much more logical approach would be to add species that relish plants such as cedar, blackberry and sericea lespedeza thus turning the “problem” into an asset. The danger in this approach is that some people look on sheep and goats strictly as a means of solving a “brush problem” or “weed problem” and abuse both the animals and the land in attempts to “goat out that brush”. Managing for what you do not want (brush, weeds, coyotes, etc.) is seldom a winning strategy while managing for what you do want (healthy pastures, profit) is always beneficial. It is critical to understand that the well being of sheep and goats depends upon their ability to select a very high quality diet. They must have a variety of plants from which to choose and must have access to young growing material in the plants utilized. All plants have toxins, which serve to limit the amount of grazing pressure on that species. If animals have only a few species from which to choose, their feed intake and their performance will suffer. Stocking more sheep or goats than their preferred food sources can sustain is a guaranteed way to have poorly performing animals and can easily bring about the parasite and disease “wreck” that cowboys are fond of quoting as a reason for not owning sheep and goats. If the stocking rates of sheep and goats and the grazing management practices are tailored to the available suitable forage, the performance of the animals will be good and the overall health and productivity of the land will increase. It is worth mentioning that animals prefer those plants that they grazed with their mothers; animals that are moved to new areas will take some time to determine what plants to graze during various time periods.
Pastureland and its' grazing can be managed so that long-term growing conditions are improved, diversity of species is increased and stability of the system is improved. If this is done, many of our "problems" will become much less important. We don't have weed problems, animal performance problems or even profitability problems. These things are symptoms of our failure to recognize and understand the many and complex relationships that are present within the soil-plant-animal complex and how our actions effect these relationships. We need to realize that there are no quick and simple solutions when dealing with the natural world. Only when we seriously attempt to analyze the total effect of our management decisions, will we began to make real progress. For most of us this will require a major shift in our ways of thinking. For many years agricultural research and education has been geared to the quick fix solution and the concept that the answer to the problems of technology is more technology. Technology can make our lives easier and more productive but only if we learn to evaluate a practice in terms of its' total long-term effect. Real and sustainable progress will come when we decide to quit being crisis managers and instead determine what we want our land to be like and then plan to bring this condition about.
Walt Davis © 1989
262 SR 70E
Calera, OK 74730
580-434-4021
wwdranch@brightok.net