legumes, supply N (Scott et al., 1987). Many studies in the North Central USA on legume interseeding in Cropping systems that improve soil conservation are needed for established corn stands report grain yield losses that mixed grain and forage enterprises in the upper Midwest. Our objective was to determine whether established kura clover (Trifolium are attributed to moisture stress (Kurtz et al., 1952; ambiguum M. Bieb.) stands could serve as a living mulch for no-till Pendleton et al., 1957), N deficiency (Scott et al., 1987 corn (Zea mays L.) production, followed by a return to clover without Triplett, 1962), and reduced corn populations associated replanting. Treatments included corn sown into established kura clowith wider row spacing (Schaller and Larson, 1955; ver that was: (1) killed and sidedressed with N, (2) killed, (3) band- Stringfield and Thatcher, 1951). Living mulch systems killed, leaving 15 cm of untreated kura clover between rows, (4) have also been evaluated where existing forage is mansuppressed and sidedressed with N, and (5) suppressed and (6) unaged with herbicides to allow corn production. Corn treated kura clover without corn. Corn whole-plant yield in 1996 yields in such systems were equal to or greater than ranged from 14.0 to 15.7 Mg ha Ϫ1 and was greatest in Treatments 2 those in conventional corn production, but these systems and 4 and least in Treatment 5. Corn whole-plant yield in 1997 ranged were evaluated in the northeastern states, where seafrom 9.5 to16.9 Mg ha Ϫ1 and was greatest in Treatments 1 and 2 and least in Treatment 5. Grain yields in 1996 were not different among sonal precipitation is higher than in the Midwest (Entreatments, while in 1997 yields ranged from 7.2 to 11.1 Mg ha Ϫ1 and ache and Ilnicki, 1990; Mayer and Hartwig, 1986). Simiwere greatest in Treatments 1 and 2 and least in Treatment 5. Clover lar results in the North Central states have not been yield in 1997 following 1996 corn production was greatest in the achieved consistently, primarily because of the continuntreated control, but there was no clover yield difference in 1998 ued problem of competition for water, and to a lesser following either 1996 or 1997 corn production. Kura clover can be extent, light and nutrients (Eberlein et al., 1992; Echtenmanaged as a living mulch in corn with little or no corn whole-plant kamp and Moomaw, 1989).or grain yield reduction and clover will recover to full production Kura clover is a long-lived, perennial, rhizomatous within 12 mo without replanting.

soil type. George et al. (1973) found that, under favorable conditions in 1965 in Indiana, the apparent N re-Nitrogen rate, grass species, and soil type may affect the efficiency covery (ANR) after split applications of N to timothy of N fertilizer use by cool-season perennial grasses of the North-Central USA. Knowing how these factors affect apparent N recovery (Phleum pratense L.), smooth bromegrass, and or-(ANR) and N use efficiency (NUE) could help producers reduce N chardgrass in a four-harvest system was as high as 0.48, losses into water resources and improve economic returns. Estimated 0.72, and 0.67 kg N (kg N applied) Ϫ1 , respectively. These ANR and NUE were determined for monoculture Kentucky bluegrass ANR values uniformly decreased as annual N rates ex-(Poa pratensis L.), smooth bromegrass (Bromus inermis Leyss.), and ceeded 126 kg ha Ϫ1 for timothy and 168 kg ha Ϫ1 for orchardgrass (Dactylis glomerata L.) in three separate experiments smooth bromegrass and orchardgrass. During 1964, conducted from 1994 to 1996 on Plano silt loam (Typic Argiudoll) when dry conditions were present, the cumulative anand Rozetta silt loam (Typic Hapludalf) near Arlington and Lancaster nual ANR for any of these species did not exceed 0.49 WI, respectively. Swards were managed in a three-harvest system and and was as low as 0.14 for timothy for N rates of 1008 given N fertilizer split-applied at annual rates of 0, 56, 112, 168, 224, kg ha Ϫ1 . In Maryland, Wagner (1954) reported an ANR and 336 kg N ha Ϫ1 . As expected, total forage dry matter (DM) yield increased for all species with increased N rate. Mean ANR at either of 0.85 for orchardgrass when N was applied at either location ranged from 0.28 to 0.47 kg N (kg N applied) Ϫ1 for Kentucky 90 or 179 kg ha Ϫ1 , but this fell to 0.69 when N was bluegrass, 0.17 to 0.44 for smooth bromegrass, and 0.32 to 0.50 for applied at 269 kg ha Ϫ1 . Work in Pennsylvania has shown orchardgrass. Similarly, mean NUE ranged from 12 to 18 kg forage that the cumulative annual ANR of orchardgrass ranged DM (kg N) Ϫ1 for Kentucky bluegrass, 9 to 16 for smooth bromegrass, from 0.26 to 0.30, depending on soil type and associated and from 11 to 28 for orchardgrass. Relatively stable ANR values temperature regime in a two-harvest system where N during drought, greater annual DM yields, and a more seasonally was split-applied (Stout and Jung, 1992). The researchuniform growth habit suggest that orchardgrass may be the most ers noted that the ANR was approximately 0.42 in the prodigious N user among the species studied and would provide the spring growth period and fell to 0.15 in the fall period least risk for N losses to the environment.

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 birds-region 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 Ͼ SBG Ͼ 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 trefoilver 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 Ϫ1 split-applied to that grass in monoculture.

production. However, populations of alfalfa (Medicago sativa L.), birdsfoot trefoil, red clover (Trifolium pra-Kura clover (Trifolium ambiguum M. Bieb.) is a perennial legume tense L.), and white clover (Trifolium repens L.) inthat, when grown in mixture with grass, may improve forage yield tended to improve sward yield and dietary quality rarely while providing biologically fixed N. Kura clover's value as an alternative to N fertilization of cool-season grasses for improved yield is persist more than a few years in this region under freunknown. Fertilizer N replacement values (FNRVs) of kura clover quent, intense defoliation because of disease, drought, and birdsfoot trefoil (Lotus corniculatus L.), in terms of total season mismanagement, competition, and winterkill. A more forage yield, were compared when grown in binary mixtures with persistent legume is needed that would be compatible Kentucky bluegrass (Poa pratensis L.), smooth bromegrass (Bromus with introduced grasses and provide biologically fixed inermis Leyss.), or orchardgrass (Dactylis glomerata L.). Separate N that could increase sward yield while maintaining high experiments for each grass were conducted from 1994 through 1996 forage quality. near Arlington and Lancaster, WI. Treatments in each experiment The FNRV is the amount of N fertilizer required for included six levels of N fertilizer on grass monocultures and two nona grass monoculture to yield as much dry matter (DM) as N-fertilized binary mixtures of grass with either legume. The FNRV the same grass grown in mixture with a legume. Legume for either kura clover or birdsfoot trefoil correlated positively with total season legume yield. When averaged across locations, kura clo-FNRV in grass-legume mixtures has been estimated ver-smooth bromegrass mixtures had annual FNRVs that ranged from using various replacement series methods (Barnett and 74 to 325 kg N ha Ϫ1 while those of birdsfoot trefoil-smooth bromegrass Posler, 1983; Carter and Scholl, 1962). Carter and Scholl mixtures ranged from 147 to 295 kg N ha Ϫ1 . When averaged across (1962) found little difference between the herbage yield years and locations, FNRVs for kura clover and birdsfoot trefoil were of smooth bromegrass or orchardgrass monocultures 251 and 269 kg N ha Ϫ1 in orchardgrass, respectively. Grass yields in receiving 269 kg N ha Ϫ1 annually and the total yield of mixtures were similar to grass monocultures receiving no fertilizer N. non-N-fertilized mixtures of either grass with alfalfa. Because kura clover outyielded birdsfoot trefoil in all 1996 mixtures, Krueger and Scholl (1970) measured the annual yields we expect the FNRV of kura clover to exceed that of birdsfoot trefoil of binary mixtures of alfalfa with orchardgrass, reed in the long term.canarygrass (Phalaris arundinacea L.), and smooth bromegrass and compared them to yields of the same grasses receiving 0 to 224 kg N ha Ϫ1 annually. The yields R.A. Zemenchik, DMI Tillage Business Unit, CNH Global, Rt. 150 ply of biologically fixed N could improve the profitabil-...

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