How can I promote native forages in my pasture and control Texas croton?
R.E.TexasAnswer: Texas croton (Croton texensis) is sometimes called “goatweed.” Croton is a native warm-season annual forb that becomes very coarse, almost woody, when mature. It frequents disturbed sites on sandy to sandy-loam soils, whose seeds are valuable for birds. Seed spread by birds may account for infestations of this forb into range sites in good condition.Native pastures are resilient, consisting of numerous deep- and shallow-rooted plant species that occupy all the available niches above and below the soil surface. Maintaining a dense, productive pasture includes fostering plant diversity and managing defoliation through mowing or grazing to benefit native plants while discouraging weeds.MowingThe frequency of mowing for the control of annual weeds like croton depends on rainfall. A single summer mowing is usually beneficial after flowering but before the seeds set. However, additional clippings will be required if later summer rain results in significant lush weed regrowth. Mowing after flowering in this manner will reduce weed seed production and decrease the amount of weed seeds in the soil for the following year. Native grasses do better when mowed while dormant. However this is difficult to achieve when controlling croton on Texas rangeland, because the croton is blooming when the grass is still vegetative. In addition, some grass species might be bolting (stem elongation for seedhead production) at this time. If the grass is still green, mow as high as you can to remove weed tops after flowering but to try to keep the growth point of the grass intact. Prior to bolting the grass growing point is low, whereas after bolting the grass growing point is elevated with the developing seedhead. Tall bunch grasses can regrow from above-ground growing points when they are mowed or grazed prior to seed stem elongation. Cutting native grasses like little bluestem or switchgrass when a seed stem is present forces the plant to regrow from root reserves, which is a slower process than if cut prior to stem elongation. During this time, annual weeds have an opening to exploit and can get ahead of native grasses. This is why management to maintain grass in its vegetative stage (prior to seed stem elongation) is critical. Grass is much more competitive when it is actively growing.In a stand of perennial native grasses, not every plant will produce seed each year. In addition, seeds of many kinds, including perennial grasses, lie dormant in the soil. Mowing for one or two seasons will most likely not have a long term negative effect on native plant longevity. More destructive forces like non-native invaders, overgrazing, and erosion are a bigger concern for native plant loss. GrazingControl of seed production is only one strategy in annual weed management. Another management technique to employ is prescribed grazing. Prescribed grazing can be thought of as a process of developing a grazing system that seeks to integrate the economic and ecological realities that ranchers are faced with on native range. The controlled harvest of vegetation with grazing or browsing animals, managed with the intent to achieve a specified objective, is referred to as prescribed grazing. Management objectives addressed by prescribed grazing include:? Improve or maintain the health and vigor of selected plant(s) and to maintain a stable and desired plant community;? Provide or maintain food, cover, and shelter for animals of concern;? Improve or maintain animal health and productivity;? Maintain or improve water quality and quantity;? Reduce accelerated soil erosion and maintain or improve soil condition for susceptibility of the resource.A very crucial aspect of a prescribed grazing regime is the development of a workable and ecologically appropriate grazing management plan. Designing an effective grazing plan isn’t as daunting as it seems. Mostly it is applying observation to management, observing some more, and then adjusting as needed. There are five areas to consider in developing a grazing plan. They are (1) Inventory, (2) Define Goals, (3) Determine Grazing Units, (4) Develop a Schedule, and (5) Development of a Monitoring and Evaluation Plan.InventoryThis is for gathering baseline information to allow you to make appropriate decisions about land and pasture use. Find out what plants are in each pasture, and evaluate the pastures based upon a condition score. Utilize features such as key species, percent canopy cover, amount of bare ground, presence of noxious weeds, annual forage production in pounds per acre, amount of residue, etc. Define Goals Make a list of what you want to accomplish. This will be a list of your expectations and will guide you in making plans and decisions. Do you want to improve the economic value of the ranch? Maintain wildlife habitat? Improve water quality and quantity? Reduce noxious weeds? Also consider available acreage and the amount of time you have to put into this project.Determine Grazing UnitsDivide the pastures into units that you can rotate animals through. This will allow you to rest pastures and allow for regrowth following grazing. It will also allow you to rotate grazing on a seasonal basis as well. Determine how much forage is available in each grazing unit and map it out. Note key species, percent cover, water availability, facilities, and other aspects important to you. Remember that livestock should always be within at least two hours walking distance from water. This will help you to determine grazing unit size (for large parcels). Develop a ScheduleThis will be a graphic illustration of your plans for grazing each unit during the grazing season. Develop the schedule based on your total Animal Units (AUs) and available Animal Unit Months (AUMs) in each unit. If you have a 100 acre pasture with 2 AUMs per acre, you have 200 animal unit months of forage available. At 50 percent allowable use, cut it in half to 100 AUMs. This means you have enough forage available to feed 100 animal units for one month. Or, said another way, 50 animal units for two months, 33 for three months, and so on. For more detailed information on calculating AUM’s see the Montana Grazingland Animal Unit Month (AUM) Estimator located at: www.mt.nrcs.usda.gov/technical/ecs/range/technotes/rangetechnoteMT32.htmlImportant concepts here are duration of grazing and time for regrowth. Some range ecologists and managers believe that grazing intensity is also important, and it is. A plant needs to have green leaves left after grazing for photosynthesis and subsequent regrowth. However, others feel that grazing severity isn’t as important as regrowth time. Whichever you choose, it is important to remember to allow plenty of time for adequate regrowth before the animal gets to bite a plant a second time. Take a look at the native plants on an upland range site if you have the opportunity. Some, like little bluestem, are large-statured and can handle several bites from an animal in one grazing event. Some, like black grama, are smaller, and one bite is all it takes to reduce the plant to stubble. Cattle, especially, tend to graze severely, so don’t get too caught up in how much they take off. Strive for 50 percent use, and allow for regrowth. For some sites on dry ranges, this will mean one grazing event per year. For areas with more moisture, you might be able to return every 15 to 30 days for another grazing event. MonitoringThis is the most neglected part of range management, and the most important. A good monitoring system will allow you to check how your management decisions are working on the ground. It will allow you to determine, for instance, if a particular grazing plan is having the desired effect over time. A monitoring plan will often involve a few important evaluation criteria, such as plant species composition, percent cover, and frequency of species. By comparing these measurements over time, you can start to see trends, and by comparing them to your grazing system, you can alter and adjust where you need to in order to arrive at your goals. To obtain more detailed information on rangeland monitoring contact Lee Rinehart at ATTRA at 800-346-9140.OvergrazingIt is important to remember that overgrazing is not really a function of how many animals are on a pasture, but how long they remain there. In grazing management, time is the most important factor to consider in establishing a grazing system for sustained forage production. Continuous grazing allows livestock to selectively graze the most palatable plants over and over. The problem with this isn’t necessarily in the selective grazing activity, but in the fact that the grazed plant does not get the time to regrow before it is grazed again. New growth is more palatable and contains more nutrients than older growth, so animals will come back for a second and third bite as long as they are in the pasture, resulting in the most palatable forages being killed out. A grazing system should allow the animal to be in the pasture long enough to take only that first bite. Frequent movement from pasture to pasture is a way to ensure that all plants have ample time to re-grow after grazing. In addition, for pastures with adequate water during the growing season, a very high stock density encourages animals to graze the pasture more uniformly than if the pasture was lightly stocked. In this situation the ?weedy? species are being grazed at the same intensity as the ?good? species.Managing for DroughtDrought is a natural ecosystem process. The concept of an ?average? or ?normal? precipitation or temperature is a fabrication that humans use to try to understand complex systems and attempt to predict behaviors and outcomes. Whether in a humid zone or an arid environment, a producer will experience relative wet and dry years. Dealing with the dry years is a real challenge to livestock operations that rely on water to grow the plants and recharge the aquifers and streams that feed the animals. Having a drought plan is a very important component of a well-thought out farm or ranch management plan. A drought-management option that deserves serious consideration is for a producer to maintain cow numbers at 75 percent of carrying capacity for ?normal? years, and utilize the extra forage in wet years for high value animals such as stockers. In dry years the pastures will be better able to accommodate current cow numbers. Another option is to slow down rotations during dry years, thereby allowing more paddock or pasture rest time. This option can be effective especially when the herd is split between different pastures to minimize the impact on drought stressed plants. ReferencesHatch, S. and J. Pluhar. 1993. Texas Range Plants. College Station: Texas A&M University Press.