Improved Nutritive Value of Kura Clover– and Birdsfoot Trefoil–Grass Mixtures Compared with Grass Monocultures

erates frequent defoliation in monoculture (Peterson et al., 1994) or in binary mixture with grass (Kim, 1996) Improved dry matter (DM) production of cool-season grass monoand is suitable for hay or pasture production in this cultures may result from either N fertilization or the addition of legumes such as kura clover (Trifolium ambiguum M. Bieb.) or birdsregion (Sheaffer and Marten, 1991; Sheaffer et al., 1992). foot trefoil (Lotus corniculatus L.). Such improvements could affect Kura clover has been identified as a grass-compatible forage nutritive value and potential milk production from dairy cattle legume with excellent persistence in mechanically har(Bos taurus). Laboratory estimates of forage nutritive value as well vested production systems (Kim, 1996; Zemenchik et al., as potential milk production per unit mass and area were compared 2001). However, there is limited information available for six levels of N fertilizer on Kentucky bluegrass (KBG; Poa praregarding laboratory estimates of forage quality or potensis L.), smooth bromegrass (SBG; Bromus inermis Leyss.), and tential milk production changes that may result by addorchardgrass (OG; Dactylis glomerata L.) in monoculture or with ing kura clover to cool-season grass swards. Peterson et either kura clover or birdsfoot trefoil in binary mixture with each al. (1994) reported that kura clover leaf proportion of grass. Experiments managed in a three-harvest system were conducted total harvested forage DM was positively correlated to from 1994 through 1996 near Arlington and Lancaster, WI. Either legume reduced neutral detergent fiber and acid detergent fiber and crude protein (CP) and inversely correlated to concenincreased crude protein when added to grass. These effects increased trations of acid detergent fiber (ADF) and neutral deterwith greater mixture legume DM proportions. Compared with grass gent fiber (NDF). Kim (1996) related harvest frequency monocultures averaged across years and locations and for any N rate, and height to legume composition of kura clover–grass mixtures had greater potential milk production per megagram of DM mixtures and kura clover monoculture but did not inand followed KBG SBG OG. Similarly, potential milk production clude a grass monoculture as one of the control treatper hectare for kura clover–grass mixtures exceeded that of monoculments. Zemenchik et al. (2001) estimated that kura clotures by at least 49% for KBG and 12% for SBG while birdsfoot trefoil– ver grown in binary mixtures with Kentucky bluegrass grass mixtures were greater by at least 28% for KBG and 20% for SBG. (KBG) resulted in total-season DM yields equivalent to Orchardgrass required maximum N rates to match milk production per 251 kg N ha 1 split-applied to that grass in monoculture. hectare of the mixtures. Adding either kura clover or birdsfoot trefoil will improve potential milk production of these grasses while reducing Similarly, estimated N replacement value of kura clover reliance on fertilizer N in the North-Central USA. with orchardgrass (OG) was 93 kg N ha 1 and for smooth bromegrass (SBG), ranged from 74 to 325 kg N ha 1, depending on the year. Birdsfoot trefoil is more widely used by forage proA balanced rations for lactating dairy cattle, manducers and has been more extensively studied than kura aged grasslands of the North-Central USA are clover. It is known to be bloat safe because it contains often too low yielding, deficient in protein and minerals, a relatively low concentration of tannins (Lees et al., and excessively high in fiber. Producers may rely on 1984) and has thick cell walls compared with other forfertilizer N in this environment to improve forage dry ages (Lees et al., 1981). Moreover, it is a prolific seed matter (DM) production and persistence of desirable producer that can persist in pastures by self seeding if grass species. However, for decades, the region’s prothe grazing or harvesting interval exceeds 60 d in midducers have used forage legumes as an alternative to summer (Sheaffer et al., 1984). Birdsfoot trefoil mainfertilizer N to improve sward DM production and nutritains its nutritive value longer than many other legumes tive value. Populations of alfalfa (Medicago sativa L.), as it matures (Buxton et al., 1985) and can be stockpiled birdsfoot trefoil, red clover (Trifolium pratense L.), and in pastures for subsequent utilization by grazing animals white clover (Trifolium repens L.) intended to improve (Marten and Jordan, 1979). sward DM yield and dietary quality rarely persist more Birdsfoot trefoil and kura clover performance in forthan a few years under frequent defoliation in this region age production systems for lactating dairy cattle should because of disease, drought, mismanagement, competibe evaluated after considering changes in both forage tion, and winterkill. Kura clover is a long-lived, perennial, rhizomatous DM yield and forage nutritive value because both of these legume (Bryant, 1974; Taylor and Smith, 1998) that tolparameters influence milk yield per unit land area (Mertens, 1973; Reid et al., 1988; Van Soest, 1994a). OptiR.A. Zemenchik, CNH Soil Manage. Div., Route 150E, Box 65, Goodmum milk production from forages of different quality field, IL 61742; K.A. Albrecht, Dep. of Agron., Univ. of Wisconsin, occurs at the point of maximum feed intake (Mertens, 1575 Linden Dr., Madison, WI 53706; and R.D. Shaver, Dep. of Dairy 1985). Intake of low-fiber, high-energy forage is reguSci., 266 Animal Sciences, 1675 Observatory Dr., Univ. of Wisconsin, Madison, WI 53706. Contrib. of the Wisconsin Agric. Exp. Stn. Research was partially funded by Hatch Project no. 5168 and 3270. Abbreviations: ADF, acid detergent fiber; CP, crude protein; DM, Received 27 Apr. 2001. *Corresponding author (kaalbrec@facstaff. dry matter; KBG, Kentucky bluegrass; NDF, neutral detergent fiber; wisc.edu). OG, orchardgrass; SBG, smooth bromegrass; TDN, total digestible nutrients. Published in Agron. J. 94:1131–1138 (2002).