Forage Legume Pastures in
Eastern Oklahoma:
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This study illustrated that forage legumes, good grazing management, and appropriate pasture fertilization can lead to profitable pasture production in eastern Oklahoma on less than ideal sites. The desirability of multiple legumes in each paddock to hedge against the failure of any single species was demonstrated. The "best" forage legume species or grass species and combinations was not addressed in this study. That choice probably depends primarily on the individual producers practices and preferences. This study brought out the need for improved guidelines as to how and when to evaluate legume stands and allowable grass residue. The necessity to monitor forage species in each paddock at critical periods during the year is underscored. Additional studies are needed to develop methods that producers will use to evaluate pastures. Characterizing pasture periodically will allow for improved management recommendations to minimize failures and predict when corrective measures may be needed to compensate for a "bad" clover year. A weakness of using only a grass-legume system in eastern Oklahoma is the prolonged hay-feeding period, approximately 150 days, if stockpiled forage is not available. Excess standing forage cannot be accumulated for fall and winter grazing without being detrimental to the reestablishment of clovers (Woods et al., 1991). Once in place, the system provides its own weed control. The combination of 1) proper soil fertilization, 2) aggressive forages, and 3) proper stocking encourages highly nutritious forage and discourages weed encroachment. Mowing for weed control and herbicide applications are employed only as spot treatments where hay was fed or other high traffic areas. Taken together, all activities primarily for weed control cost about $1 per acre per year in labor, equipment operation, and consumables. Grass-legume pastures may be best implemented on a farm scale as one part of a total system. For example, some pastures should be managed to have very little grass residue in the fall, while allowing forage to accumulate in others for use as dry standing forage in the fall and early winter. Such an approach would serve as an additional hedge against "poor clover years" and help reduce winter feeding costs. To compliment this type of system, other pastures should be managed as grass-with-nitrogen areas to optimize stockpiling as a means to reducing winter hay-feeding. Beginning in 1996 this additional component was added. INTRODUCTION Research in eastern Oklahoma has shown that grass-legume pastures can provide sufficient dry matter of adequate nutritive value to sustain a year-round stocking rate of 1 cow per 2 acres (Rommann, 1975). In one trial 1.88 acre per cow was required on bermudagrass overseeded with hairy vetch. In another study, 4575 lb of forage per acre was produced by bermudagrass and white (ladino) clover mixed pastures (Elder and Murphy, 1961). One of the traditional problems with clover pastures
reported by producers in eastern Oklahoma has been "boom and bust" forage
production, and producers commonly refer to "good" or "bad" clover
years. By using several different forage legumes and well-adapted, resilient grasses,
cycles of overproduction and underproduction can be overcome for calf-calf herds. Other factors limiting producer success with legumes include: 1) Lack of adequate soil fertility and low soil pH. Soils in eastern Oklahoma are typically low in phosphorus and potassium and have pH levels lower than desirable for legumes (Westerman and Tucker, 1982). 2) Lack of understanding and failure to use rotational stocking. Producers tend to use continuous stocking and over graze, resulting in low forage production, weed encroachment, and the need for extra hay as well as protein and energy supplements. 3) Excessive grass residue when cool-season legumes are germinating and beginning to grow. Traditionally, producers accumulate forage in late summer and fall for use as dry standing forage in early winter as a means to delay feeding hay. Accumulated grass residue creates excessive shading that is detrimental to legume seedling establishment and development. This study was conducted from 1987 to 1997 to demonstrate and describe a forage management system that could consistently rely on forage legumes and maintain an annual stocking rate of 1 cow per 2 acres without supplemental feeding or nitrogen fertilizer. Most previous trials were limited to small plots and clipping studies; thus, the intent of this study was to validate research with farm-scale demonstrations. Materials and Methods The study site is on the Eastern Oklahoma Research Station, near Haskell, where the average annual rainfall is approximately 41 inches. The study area included 131 acres (north pastures) that had been managed as four pastures from 1978 to 1988. Three of the pastures were divided into two paddocks each for grazing purposes, for a total of seven paddocks. Legumes plantings utilize a single-disc-opener grain drill with no seed bed tillage. Weeds have been insignificant during the 10 years of the study. Spot treatments require less than a day per year for mowing and herbicide applications. The following pages include Pasture Descriptions, Cattle Herd, Stocking Management, and Soils, all of which are integral parts of this successful system. Pasture Descriptions Two paddocks (1A and 1B), totaling 40 acres, had a base of 'Hardie' bermudagrass. They were overseeded with 'Regal' ladino white clover in September 1989. Ladino clover spread and persisted well. Tall fescue encroached into the paddocks and occupies about 10% of the area. In an attempt to produce forage of high quality somewhat earlier in these paddocks, crimson clover was planted in strips in one paddock and annual ryegrass was planted in strips in the other in 1993. The planted strips alternated with strips of equal width (14 feet) not planted with additional forages. These annual forages did not add appreciably to the early-season yield or total yield, and relatively few plants have been observed in subsequent years from natural re-establishment. Three varieties of annual lespedeza were sown in strips in spring 1997. This was accomplished by dividing the drill box into three compartments, one for each variety. Paddock No. 3 (23 acres) that had a base of endophyte-free tall fescue ('Kentucky 31') was overseeded with 'Mt. Barker' subterranean clover in September 1989. The subterranean clover re-established naturally every fall except 1992. Bermudagrass encroached into about 10% of the area. Crabgrass filled almost all areas not occupied by other forages in summer. Annual lespedeza was sown in spring 1990 to provide additional high-quality summer forage and has been present in the pasture but contributed relatively little forage. It was resown in spring 1996 and produced abundant forage in summer 1996. In an additional attempt to improve seasonal distribution of forage production, in 1993, replicated 14-foot strips of other annual and perennial forage legumes were planted. These included birdsfoot trefoil, red clover, alfalfa (both hay- and grazing-type varieties), and rose clover. Both alfalfa varieties contribute to late-summer yield; however, birdsfoot trefoil plants are sparsely scattered. Rose clover's natural re-establishment is, so far, less than anticipated. Hard seed, characteristic of this legume, may allow it to begin contributing to mid-summer production in the future. Two paddocks (2A and 2B), occupying 38 acres, consisted of common bermudagrass, 'Plains' old world bluestem, and several warm- and cool-season annual grasses. These were overseeded each September (1989 through 1993) with 4 lb per acre of both arrowleaf clover and red clover. Rye was sown in fall 1996 in 2B to add to the cool-season forage supply. Two paddocks (4A and 4B), with a total of 30 acres, had a base of 'Hardie' bermudagrass and common bermudagrass. They were overseeded each September (1989 through 1993) with 4 lb per acre of both of arrowleaf and red clover. Three varieties of annual lespedeza were sown in strips in spring 1997 in 4B, as described for 1A and 1B. The last four paddocks described above were subjected to a special test within the overall pasture system. In fall 1994 and 1995 the two clovers were resown in strips. The planted strips alternated with strips of equal width (14 feet) not planted to additional forages. This was done to determine if adequate seed was available for re-establishment without risking a decreased production for the system as a whole. Red and arrowleaf clovers were observed over the entire area indicating a large quantity of seed for natural reseeding and no need for annual replanting. In 1996 no clover was planted. Cattle Herd The 60-cow herd, consisting of English/Continental crosses, typical of many herds in eastern Oklahoma, is divided into 24 fall-calving cows and 36 spring-calving cows. Average weight of the cows was 1226 lb when the study initiated and 1222 lb when calves were weaned in 1993. Charolias bulls were used for the first several years as a terminal cross. Thereafter, other Continental breed bulls were used. Stocking Management A flexible rotational stocking system has been maintained during each growing season since 1989. Cattle are moved from paddock to paddock on an "as needed" basis as contrasted to a number-of-days system. Cattle graze in a paddock until the forage canopy is down to a height of 2 to 4 inches and moved to another paddock with abundant forage. Cattle graze as one herd during the forage growing season and are divided into spring and fall-calving herds for winter. Grazing in some paddocks is deferred during times of rapid growth, and excess spring and early-summer forage is harvested as hay. Timing and duration of stocking paddocks and hay harvests are based on forage availability. Excess residue in late summer and early fall is removed by grazing, if possible, or by mowing, if necessary. Hay harvests are scheduled to fit with other farming activities. All hay is tested for crude protein and fed according to nutrient requirements for the two groups (Barnes et al., 1986). Lactating cows receive hay with >10% crude protein while dry cows are fed hay with 8-10% crude protein. Within the flexible rotational stocking system it has been possible to introduce stock-piled forage. When forages are more abundant than needed for grazing and haying in late summer and early fall, pastures are left unharvested. Then after active forage growth stopped in the fall (usually late November), the stock-piled paddocks are utilized. The two paddocks, consisting of 40 acres with white clover and bermudagrass had adequate stocked-piled forage for the entire herd for about 30 day in December 1993. The same two paddocks as well as the fescue-based pasture was used in a similar way in 1996 to reduce the number of hay-feeding days and maintain a good diet for all animals. Stockpiled forage in these pastures delayed hay feeding more than 50 days.
The site was selected because it typified some of the least productive pastures in the area. Much of the area had been cultivated for many years, and soils were low in pH, phosphorus, and potassium. Many areas within the pastures had been severely eroded. Fourteen different soils are represented in the 131-acre site. The three major soil series are, Chouteau silt and Dennis silt loam, and Parsons silt loam (Gray and Nance, 1978). Soil samples are collected from each paddock in April, and fertilizer is applied, according to OSU soil test interpretations (Allen and Johnson, 1993) in July. Average soil test values for pH, potassium, and phosphorus are shown in Figure 1. The only nitrogen applied is a consequence of using 18-46-0, the only locally available source of phosphorus. Actual nitrogen applied per acre in 1993, for example, was 40 lb on 19 acres, 23 lb on 20 acres, 12 lb on 19 acres, and 9 lb on 53 acres. Since 1993, soil tests for most pastures have indicated little or no additional P or K fertilizer was required. Three of the seven pastures were fertilized in 1994 and 1995, and no fertilizer was applied in 1996. Lime (1 ton ECCE per acre) was applied to all pastures in 1989. In 1993, strips of limed (1 ton ECCE per acre) and non-limed areas were established in pasture 3 to determine the benefit of additional lime. All other pastures were limed with 1 ton ECCE per acre in spring 1997. RESULTS AND DISCUSSION The objectives of the demonstration were achieved -- A flexible, yet sustainable, forage system was demonstrated.
Stocking and forage quality --
Summary of forage legume used --
Soil fertility and liming -
Economic analysis -- An economic analysis of this demonstration, indicated that the grass-legume forage system, without N fertilizer, has a return (above costs) of more than 25% higher than if N fertilizer is applied to grasses without legumes. Economics is discussed in the next section. Weather's impact -- The following example indicates how weather conditions can have a long-lasting impact on a forage production system. Observations during several growing seasons are required before a system can be declared sustainable.
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