INTRODUCTION
Average annual rainfall in Oklahoma varies from almost 60 in. in the southeast to about 15 in. in the panhandle. Likewise, soils vary from shallow to deep including sands to clays. These factors, along with drastic differences in soil fertility and pH, dictate that forages vary greatly because no single group of forages could sustain the 5-6 million cattle in the state. Figure 1 shows that native grasses dominate with nearly 12 million acres, but tall fescue (Festuca arundinacea Schreb.), bermudagrass(Cynodon dactylon (L.) Pers.), and small grains for forage are produced on more than 1, 3.4, and 5 million acres, respectively.
Forage legumes are produced on more than 1.5 million acres. Statewide, the most important forage legumes include alfalfa (Medicago sativa L.), annual lespedeza [Kummerowia stipulacea (Maxim. Makino)], white clover (Trifolium repens L.), and arrowleaf clover (T. vesiculosum Savi) (Fig. 2). Alfalfa represents more than 66% of the legume acreage in the western half of the state; however, most legumes acres in the eastern part of the state are occupied by white clover, and annual clovers, and lespedezas (Fig. 3). The purpose of this paper is to summarize highlights of Oklahoma forage legume research and extension activities.
ALFALFA
Both alfalfa research and extension activities are designed to develop improved strategies for sustainable production. Many Oklahoma alfalfa producers aim for the cash hay market with dairies as the primary market; however, alfalfa is a mainstay for the beef cattle industry. Alfalfa for horses is a speciality market attracting certain producers.
Most research activities focus to some extent on effective pest control. Richard Berberet initiated alfalfa weevil (Hypera postica Gyllenhal) control activities in the early 1970’s. His work includes identifying chemical control options and harvest management considerations for controlling the alfalfa weevil. Late fall and winter alfalfa grazing has proven to be important in decreasing alfalfa weevil egg numbers and delaying the date of reaching economic thresholds. Currently this line of research focuses on the potential of spring grazing and early haying to avoiding chemical alfalfa weevil control.
John Caddel joined the alfalfa research team in the late 1970’s, introducing an expanded variety testing program and selection for insect and disease resistance. Breeding activities resulted in the release of ‘OK 49’ and new germplasms for the southern plains in the early 1990’s. In addition to breeding for crown and root rot resistance, much progress has been made toward identifying selection procedures for spotted alfalfa aphid (Therioaphis maculata Buckton) and blue alfalfa aphid (Acyrthosiphon kondoi Shinji) resistance.
Jim Stritzke also joined the alfalfa research team in the late 1970’s, concentrating on economical weed management and integrating weed control into harvest management activities for an array of different alfalfa varieties. His dimensions allow the team to examine cause and effect relationships among a diverse array of factors.
Most recently, Bill Raun has initiated studies that allow the team to examine how soil fertility interacts with other alfalfa management decisions. Much of this work involves interactions between sources and application methods of phosphorus and their effects on weed population development and forage yield. It may also impact soil test calibrations and fertilizer recommendations.
A partial list of conclusions from these lines of research that impact alfalfa production in the southern plains include:
Harvesting and grazing alfalfa throughout fall and early winter can reduce the impact of alfalfa weevils without negatively affecting forage yield or stand persistence. This is based on many different studies and differs from common recommendations for much of the U.S.
Fall grazing can reduce cool-season weed populations and lessen the importance of herbicide applications.
The timing of alfalfa harvest at first cut can take place from early-bud to mid-bloom stages without negative effects on stand persistence or season-long forage yields.
Alfalfa varieties with resistance to important diseases and insects persist longer with all types of harvest timing and pest control.
‘Alfagraze’ and other varieties, selected for tolerance to continuous stocking, persist longer than traditional hay-type varieties when stocked continuously during the growing season. High-yielding hay-type varieties have greater yield potential and should be used when rotational stocking is employed or when alfalfa is only occasionally grazed.
Cool-season weed control affects alfalfa weevil damage, and alfalfa weevil control affects weed infestations in first-harvest forage. Appropriate chemical weed control and alfalfa weevil control are required in conjunction with improved multiple-pest resistant varieties and fall harvesting for high yields of weed-free forage at first harvest.
Early results indicate that present soil test calibrations may result in lower phosphorus recommendations than required for high forage yields, and application of up to 50 lb/acre of nitrogen from 18-46-0 (as a phosphorus source) does not enhance weed interference in alfalfa.
Early results of measurements in producers’ fields indicate that inadequate fertilizing and liming practices may be the most important limitation to alfalfa production in the state. Depending on the method of selecting fields, between 75 and 90% of alfalfa fields in the state are below pH 6.4 and have inadequate amounts of phosphorus or potassium. Lower than adequate pH and fertility results in yield reductions estimated at 20 to 40%. This translates to a loss of about 375,000 tons of hay per year or about $25 million in lost revenue.
Herbicides for warm-season weeds can result in weed-free hay, but increased value of weed-free hay rarely covers the cost of chemicals.
Most alfalfa extension activities in Oklahoma focus on integrated pest management, harvesting procedures, and marketing hay. IPM extension activities have been coordinated by Gerrit Cuperus since the early 1980’s.
Jim Stritzke has been working with the Alfalfa Integrated Management (AIM) team since its inception in the 1980’s. His primary roles include weed control and harvest management, and he also plays the role of general agronomist
Clem Ward has interacted with the alfalfa extension team to assist with analyzing economic impacts of recommended components of alfalfa management practices. He also took the lead in developing HAYMARKET, a listing of visually and chemically tested alfalfa hay.
Ray Huhnke brings an engineer’s approach to examining stand establishment procedures and haylage bale wrapping methods. He has also taken the lead in developing AGMACH$, a software package designed to assist in understanding machinery costs as they affect profitability of alfalfa production and harvesting.
John Caddel joined the extension part of the AIM team in 1991 as an extension forage agronomist with emphasis on variety testing, forage quality, and general agronomy. Phil Mulder recently joined the on-campus team as an extension entomologist after serving as an area specialist for 10 years, working with a wide range of crops including alfalfa.
The AIM team works closely with county agricultural agents and with area agents throughout the state. Area agents specialize in agronomy, entomology, economics, livestock, or plant pathology and are part of the AIM team along with several county agents. Another component of the AIM team is the Oklahoma Alfalfa Hay and Seed Association, a group of producers and industry representatives from seed, chemical, and machinery businesses.
The AIM team has developed a series of publications on alfalfa production and pest management. The series includes alfalfa variety recommendations, forage sampling and quality interpretations, stand establishment, marketing strategies, hay storage, pest identification and control measures, expert systems, etc. In 1995 the AIM group published a highly integrated circular on alfalfa harvest management, with cost-benefit analysis, based on frequently asked questions by producers. In 1996 the thrust will be “Alfalfa Stand Establishment with Cost-Benefit Analysis”, also based on frequently asked questions.
Members of the AIM group also contribute to the NEWS, the monthly newsletter of the Oklahoma Alfalfa Hay and Seed Association. Each member contributes timely topics and production tips that go directly to county agents and Association members. The Association also provides a forum for producers to actively interact with research and extension specialists.
OTHER FORAGE LEGUMES
The acreage of forage legumes other than alfalfa is much larger than the acreage of alfalfa (Fig. 3) and probably affects more cattlemen and hay producers. Research and extension efforts devoted to these species is small compared to alfalfa because they are not viewed as “cash crops”. They are marketed almost exclusively as cattle. During this era of increasing nitrogen fertilizer costs and depressed cattle markets, many cattlemen are looking to forage legumes to make their forage production more economical. John Caddel, Jim Stritzke, and Larry Redmon devote a small portion of their time to research and extension activities on pasture legumes. Robert Woods, Jim Enis, and Roger Gribble, area extension agronomists, also devote significant time to other forage legumes.
The main concerted effort to illustrate the importance of forage legumes in grazing has been taking place at the Eastern Research Station, where a 60 cow-calf herd has been maintained for 7 years without nitrogen fertilizer and without feed supplements. Hay from outside the 130-acre pasture system was used during only one winter, and herbicides have been shown to be nonessential for the system. This system is large enough to demonstrate its profitability to area cattlemen who watch the system closely.
Six of the seven pastures have a base of bermudagrass, and one is based on tall fescue. White clover was sown on two of the paddocks in the beginning of the study. Subterranean clover (T. subterraneum L.) was sown in the tall fescue pasture and has successfully reseeded all but one year. A mixture of red clover (T. pratense L.) and arrowleaf clover was oversown on the other four pastures and was resown in September of years 2 through 5.
Pastures are rotationally stocked, moving from pastures as forage is used (not on a set time interval). When more forage is produced than is needed for the herd, it is harvested as hay for winter feeding of the same herd.
Initially soil pH ranged from 4.5 to 5.5, and all pastures were limed prior to establishment. Legumes have flourished and soil pH levels continue to increase. Each pasture was fertilized with phosphorus and potassium during years 1 through 5, based on soil tests. During the last 2 years, only two pastures required additional fertilizer.
Forage yield was sampled during 1994 and 1995 each time cattle moved into a new pasture or it was hayed. Forage yields was approximately 5.5 tons of dry matter per acre annually (available forage was about 68 lbs/day/cow-calf pair). Protein concentration of sampled forage was in the range of 11 to 17%.
The most important weakness of the present system is hay feeding for 150 days per year. A tall fescue pasture without legumes for spring grazing and stockpiling for winter will be added during 1996 to alleviate much of the hay feeding. In the present grass-legume pastures, it is important to graze or hay most of the standing forage and remove thatch in September to improve the environment for seedling establishment, resulting in limited stockpiled forage. Our objective is to reduce feeding hay to only those days with ice or snow while maintaining 2 acres per cow-calf pair.
Other legumes have been tried in this system with only limited success. Annual lespedeza was originally sown with subterranean clover in the tall fescue pasture. Lespedeza is present but produces relatively little forage for the late summer and early fall. In the same pasture birdsfoot trefoil (Lotus corniculatus L.), red clover, and both grazing and hay-type alfalfas have been sown, resulting in only slight increased forage production. Crimson clover (T. incarantum L.) has been oversown into an existing white clover-bermudagrass pasture with little success at producing legume forage earlier in the spring. It is not clear why these legumes do not become established components as the other legume species have.
Annual ryegrass (Lolium multiflorum Lam.) has also been oversown into an bermudagrass-white clover pasture, in an attempt to increase early spring production. This resulted in little additional forage.
One of the traditional problems with clover pastures in eastern Oklahoma has been “boom and bust” forage production. By using several different forage legumes and two well-adapted, resilient grass bases, we have successfully overcome cycles of overproduction and underproduction for a cow-calf herd.
Some of the forage legumes not included in studies deserve mention. Hairy vetch (Vicia villosa Roth) has a great production potential and is utilized by producers in mixtures with small grains for pasture and hay. Vetch seems to suffer the problem of having a single relatively short growth period with little production during the rest of the year.
Few producers effectively utilize sweetclovers in pastures or hay making operations. Sweetclovers (Melilotus alba Medik. and M. officinalis Lam.) grow profusely in nongrazed areas where calcareous soils predominate, but improper grazing management appears to eliminate sweetclovers from pastures.
The main forage legume present in late summer in many areas of eastern Oklahoma is annual lespedeza. Its late season growth lets it take advantage of summer rains, but it does not seem to flourish where grasses are well-established and productive.
Alfalfa, as a pasture species for summer grazing, seems to hold promise for the near future throughout Oklahoma but producer doubts are strong. We are initiating a search for other forage legumes to be used for western pastures. Rose clover (T. hirtum All.) seems to hold much potential as an annual for the west where other clovers have been tried with little success, but it has not yet passed the test of time. Limited research on sainfoin (Onobrychis viciifolia Scop.) has shown that it is harder to manage than alfalfa, needs to be reseeded more frequently and does not fix as much nitrogen as alfalfa.
SELECTED REFERENCES
Anderson, M.P., C. Bensch, J.F. Stritzke, and J.L. Caddel. 1995. Uptake, translocation and metabolism in alfalfa (Medicago sativa) selected for enhanced tolerance to terbacil. Weed Sci. 43:365-369.
Woods, R.L., and J.L. Caddel. 1994. Managing clover pastures in eastern Oklahoma. Amer Forage & Grassl. Council Proc. 3:167-171.
Dowdy, A.K., R.C. Berberet, J.F. Stritzke, J.L. Caddel, and R.W. McNew. 1993. Interaction of alfalfa weevil (Coleoptera: Curculionidae), weeds, and fall harvest options as determinants of alfalfa productivity. J. Econ. Entomol. 86:1241-1249.
Caddel, J.L., R.C. Berberet, K.T. Shelton, and A.A. Zarrabi. 1992. Registration of OK 49 alfalfa. Crop Sci. 32:280.
Dowdy, A.K., R.C. Berberet, J.F. Stritzke, J.L. Caddel, and R.W. McNew. 1992. Late fall harvest, winter grazing and weed control for reduction of alfalfa weevil (Coleoptera: Curculionidae) populations. J. Econ. Entomol. 85(5):1946-1953.
Latheef, M.A., R.C. Berberet, J.F. Stritzke, J.L. Caddel, and R.W. McNew. 1992. Productivity and persistence of declining alfalfa stands as influenced by the alfalfa weevil, weeds, and early first harvest in Oklahoma. Can. Entomol. 124:135-144.
Bergman, D.K., J.W. Dillwith, A.A. Zarrabi, J.L. Caddel, and R.C. Berberet. 1991. Epicuticular lipids of alfalfa relative to its susceptibility to spotted alfalfa aphid (Homoptera: Aphididae). Environ. Entomol. 20:781-785.
Derkaoui, M. , J.L. Caddel, and W.W. Stroup. 1990. Biomass partitioning and root development in annual Medicago spp. Agricoltura Mediterranea 120:407-416.
Reid, J.L., R.C. Berberet, and J.L. Caddel. 1989. Effects of alfalfa dormancy on egg and larval population levels of the alfalfa weevil (Coleoptera: Curculionidae). J. Econ. Entomol. 82:264-269.
Jimenez, H.O., J.L. Caddel, R.C. Berberet, and R.W. McNew. 1989. Indices of plant damage and heritability of tolerance to the spotted alfalfa aphid in alfalfa. Crop Sci. 29:1337-1340.
Latheef, M.A., J.L. Caddel, R.C. Berberet, and J.F. Stritzke. 1988. Alfalfa forage yield, stand persistence, and weed colonization as influenced by variable first harvest in Oklahoma. J. Prod. Agric. 1:155-159.
Sholar, J.R., J.F. Stritzke, J.L. Caddel, and R.C. Berberet. 1988. Response of four alfalfa cultivars to fall harvesting in the Southern Plains. J. Prod. Agric. 1:266-270.
EXTENSION PUBLICATIONS
FORAGE LEGUMES:
Redmon, L., J. Caddel, and J. Enis. 1995. Forage Legumes for Oklahoma. OSU Extension Facts 2585.
Caddel, J. and L. Redmon. 1995. White Clover. O.S.U. Agron. Prod. Tech. Forage Crops 95-29.
Caddel, J. and L. Redmon. 1995. Arrowleaf Clover. O.S.U. Agron. Prod. Tech. Forage Crops 95-13.
Caddel, J. and L. Redmon. 1995. Red Clover. O.S.U. Agron. Prod. Tech. Forage Crops 95-17.
INSECTS:
Mulder, P. & R. Berberet. Alfalfa Aphids in Oklahoma. OSU Extension Facts 7184.
Mulder, P. & R. Berberet. Alfalfa Forage Insect Control. OSU Extension Facts 7150.
Mulder, P., R. Berberet, & S. Coppock. Alfalfa Weevil and Its Management. OSU Extension Facts 2097.
Mulder, P., R. Shawley, & J. Caddel. Blister Beetles and Alfalfa. OSU Extension Facts 2072.
HARVEST MANAGEMENT, VARIETIES & STAND ESTABLISHMENT:
Caddel, J. & J. Prater. Alfalfa Varieties for Oklahoma — 1995. OSU Current Report CR-2106.
Caddel, J., J. Stritzke, R. Huhnke, & G. Johnson. Alfalfa Stand Establishment. OSU Extension Facts 2089.
Caddel, J., J. Stritzke, P. Mulder, R. Huhnke, R. Berberet, and C. Ward. 1995. Forage Harvest Management — Discussion with cost benefit analysis. Oklahoma Coop. Extension Circular E-943.
FORAGE QUALITY:
Caddel, J. & E. Allen. Forage Quality Interpretations. OSU Extension Facts 2117.
Caddel, J. & E. Allen Hay Judging. . OSU Extension Facts 2588.
SOIL FERTILITY:
Allen, E. & G. Johnson. OSU Soil Test Interpretations. OSU Extension Facts 2225.
Johnson, G. & E. Allen. How to Get a Good Soil Sample. OSU Extension Facts 2207.
Johnson, G. & E. Allen. Causes and Effects of Soil Acidity. OSU Extension Facts 2239.
MACHINERY & STORAGE:
Huhnke, R. & W. Bowers. AGMACH$ – Agricultural Field Machinery Cost Estimation Software. OSU Oklahoma Cooperative Extension Service.
Huhnke, R. Round Bale Hay Storage. OSU Extension Facts 1716.
UTILIZATION & MARKETING:
Ward, C. & C. Richardson. Utilization and Value of Alfalfa in Dairy Rations. OSU Extension Facts 4013.
Ward, C. Alfalfa Marketing Plan. . OSU Extension Facts 539.
WEEDS: Stritzke, J. Weed Control in Alfalfa. OSU Extension Facts 2761.
