Methods of Rose Clover Establishment into Barmudagrass Sod

Rose clover (Trifolium hirtum All.), a cool-season annual, has been grown on rangelands of California since the late 1940s. ‘Overton R18’ is the first rose clover cultivar selected for the southeastern USA. Planting method and seeding rate information for rose clover in pasture systems prevalent to this area of year-round rainfall are not available. The objective of this study was to evaluate planting methods and seeding rates for successful overseeding of rose clover into a ‘Coastal’ bermudagrass [Cynodon dactylon (L.) Pers.] sod. Planting methods evaluated were: (i) undisturbed sod, drill seed, (ii) undisturbed sod, broadcast seed, (iii) drill seed, apply grass desiccant postemergence, and (iv) disk sod 1 to 2 in. deep, broadcast seed, and harrow to cover seed. Seeding rates within each planting method were 4, 8,12,16, 20, and 24 lb/acre. Seedling density was determined approximately 6 wk after planting and dry matter production by two harvests per growing season. Drilling rose clover in an undisturbed or desiccated sod or broadcasting on a shallow disked sod resulted in the best seedling densities and yield. Influence of seeding rate on seedling density and yield was linear (P < 0.01). A seeding rate of 12 lb/acre was an acceptable compromise between seed cost and forage production. If rose clover is managed for reseeding and first year forage production is not critical, then seeding rates of 6 to 8 bl/acre are satisfactory. Research Question’Overton R18’ is the first rose clover cultivar developed for adaptation to the southeastern USA. Information on establishing rose clover in a warm-season perennial grass, the conventional pasture system in the lower South, is not available. The objective of this study was to evaluate various planting methods and seeding rates for overseeding Overton R18 rose clover into ‘Coastal’ bermudagrass. Literature SummaryWarm-season perennial grasses are overseeded with cool-season annual clovers in the southeastern USA to improve forage quality, extend the grazing season, add N to the pasture system, and provide spring weed control. Rose clover has the desirable attributes of adaptability to marginal soils and a high hardseed percentage, which enhances natural reseeding. Older clutivars have been selected for California or Australia rangelands under a Mediterranea climate of dry summers and moist, mild winters. Year-round rainfall in the southeastern USA encourages the use of cool- and warm-season forage mixtures. Competition for light, moisture, and nutrients in autumn occurs between the warm-season perennial grass and emerging cool-season annual. Study DescriptionThe study was planted in October of 1991 and 1992 on a Coastal bermudagrass sod in northeast Texas. Planting methods were (i) undisturbed sod, drill seed, (ii) undisturbed sod, broadcast seed, (iii) drill seed, desiccate grass sod with sethoxydim at 0.12 lb/acre 2 wk after clover emergence, and (iv) disk sod lightly (1 to 2 in. deep), broadcast seed and drag with a flex harrow to cover seed. Seeding rates within each planting method were 4, 8, 12, 16, 20, and 24 lb/acre. Seedling density was determined 6 wk after planting and forage production was determined in the spring following planting. Applied QuestionWhat planting methods and seeding rates can be used for successful establishment of rose clover in a warm-season perennial grass sod? Shallow planting (0 to 0.25 in.) is necessary for good rose clover establishment. Drilling seed into a 1 in. tall grass sod or broadcasting seed on a lightly disked (1 to 2 in. deep) sod and harrowing to cover the seed produced the best seedling density and yield (Table 1, Fig. 1). Broadcasting the seed on a short, undisturbed sod resulted in lower seedling density and yield. If a seed drill isnot available to the producer, however, broadcasting the seed on an undisturbed sod will provide results simlar to the better planting methods if the seeding rate is increased about 4 lb/acre. RecommendationOverton R18 rose clover should be planted at 12 to 16 lb/acre when overseeding Coastal bermudagrass in autumn. The cost of seed at this time ($3/lb) is relatively high because Overton R18 is a new cultivar and seed supply is limited. Seeding rates of 6 to 8 lb/acre would be adequate if maximum forage production in the establishment year is not a critical factor. Overton R18 produces approximately 70% hard seed at harvest. This high production of hard seed limits summer germination and prolongs seed viability beyond 4 yr. Seed production can be maximized by grazing lightly until the bud stage in early May and then removing livestock. Removing excess grass growth the following autumn will enhance establishment of a volunteer stand. Table 1Influence of planting method on rose clover seedling density and dry matter OM) production. Seedling densityDM productionPlanting method1991–19921992–19931991–19921992–1993-------- plants/sq ft ------------ lb/acre -----Undisturbed, drilled 9.0a* 26.1ab*1618b4208a Drilled, desiccate9.0a27.9a1437bc4094abLight disk, broadcast11.7a25.2b2168a4012abUndisturbed, broadcast9.9a18.9c1170c3390b*Means within a column followed by the same letter are not significantly different at P = 0.05 according to Walter-Duncan Multiple Range Test. Fig. 1Influence of rose clover seeding rate (averaged across planting methods) on seedling density and annual dry matter (DM) production.