Spring Yield and Silage Characteristics of Kura Clover, Winter Wheat, and in Mixtures

Kura clover (Trifolium ambiguumM. Bieb.) grown in monoculture is difficult to harvest mechanically because of its decumbent growth habit, and legumes in general have poor ensiling characteristics. Our objectives were to assess forage yield, nutritive value, and silage characteristics of kura clover–winter wheat (Triticum aestivum L.) mixtures to determine usefulness as a silage crop. ‘Cardinal’ winter wheat was sown in monoculture and into an ‘Endura’ kura clover sward in autumn at two locations and in 2 yr, and harvested at wheat boot and milk stages the following spring. Sole kura clover was harvested at the same time as winter wheat and mixtures. In addition, two mixtures of kura clover with winter wheat were created at each harvest by blending desired proportions from crops grown in monoculture. The mixture of kura clover with winter wheat yielded 7.4 Mg dry matter (DM) ha while sole kura clover yielded 3.4 Mg DM ha and sole winter wheat 9.05 Mg DM ha. However, kura clover yield in the binary mixture was similar to sole kura clover. Neutral detergent fiber and acid detergent fiber concentrations were lower in kura clover than winter wheat and intermediate in mixtures. Fermented mixtures had similar pH to sole winter wheat (pH 3.8) and lower than sole kura clover (pH 4.1). The proportion of total N recovered as nonproteinN in silage was 9% lower in kura clover and in mixtures than in winter wheat. Water-soluble carbohydrate (WSC) concentrations of wilted foragewere higher inmixtures than sole kura clover (157 vs. 105 g kg DM), and mixtures had lowerWSC than sole winter wheat (198 g kg DM). Lactate concentration was 13% higher in silage from mixtures than sole kura clover. Spring forage production of kura clover–winter wheat mixtures was greater than sole kura clover, possessed adequate nutritive value for high-producing livestock, and mixture silage characteristics were better than sole kura clover. PRESERVING forage legume nutritive value as hay or silage is a challenge. Silage has the advantage of reducing weather risks and its adverse effects on the nutritional value of forage (Albrecht and Beauchemin, 2003). However, the ensiling of forage legumes often results in rapid and extensive degradation of proteins before and during fermentation (Albrecht and Muck, 1991). Legumes like alfalfa (Medicago sativa L.) and white clover (Trifolium repens L.) have high protein content, high buffering capacity, and low levels of WSC, making them susceptible to extensive proteolysis during fermentation. Some strategies reported to decrease proteolysis in legumes are ensiling at high DM concentration (Muck, 1987), increasing the level of soluble sugar in the plant by harvesting later in the day when plants have higher levels ofWSC (Owens et al., 1999), applying organic acids to decrease pH faster (Davies et al., 1998), or rapid silo filling, good packing, and good sealing to minimize heating and maximize pH decline (Muck, 1987). Reduction of proteolysis in legume ensilage is important because it maintains the nutritional value of proteins, improving the value of the ration for dairy cows (Bos taurus) (Broderick, 1995). Cereals have been studied widely for forage production and preservation as silage. Winter small grains harvested in early June at early heading stage can yield from 7.0 to 8.9 Mg DM ha (Maloney et al., 1999). Silage quality of oat (Avena sativa L.), wheat, and barley (Hordeum vulgare L.), ensiled at milk and dough stages was reported acceptable after fermentation. The pH ranged from 3.8 to 4.1, and WSC were higher in milkstage than dough-stage silages. Moreover, wheat had a lower buffering capacity and higher WSC content than oat and barley (Bergen et al., 1991). Because of the difference in WSC concentration between grasses and legumes, research has been conducted to evaluate blends as a way to drop pH quickly and to reduce proteolysis. Mixing ryegrass (Lolium multiflorum Lam.) (250 g WSC kg DM) with white clover (66 gWSC kg DM) decreased silage pH by 2.21 units and increased lactic acid by 250% compared to sole white clover silage which had pH 5.75 and lactic acid concentration of 54 g kg DM (Davies et al., 1998). In mixtures of red clover (T. pratense L.) and timothy (Phleum pratense L.), WSC concentration increased as the proportion of timothy increased, but because of the large amount of silage preservative (formic and orthophosphoric acids) used, pH was similar among treatments (Syrjala-qvist et al., 1984). These reports establish that mixing grass or cereals with a legume could increase WSC concentration, drop the pH faster, diminish proteolysis, and enhance the nutritive value of the silage. Kura clover is gaining popularity as forage in the northernUSA because of excellent persistence. Its nutritive value is greater than that of alfalfa and red clover (Allinson et al., 1985; Sheaffer and Marten, 1991), making it a potentially useful forage crop for dairy cows. While kura clover forage nutritive value changes little with maturity, its nutritive value must be preserved throughout storage. Ensiling is a feasible method to retain kura clover nutritional value. Recent research suggests kura clover ensiles well with a final pH of 4.08 and little effect of fermentation on forage quality (Seguin and Mustafa, 2003), but like alfalfa, low waterF.E. Contreras-Govea and K.A. Albrecht, Dep. of Agronomy, 1575 Linden Dr., Univ. of Wisconsin-Madison, Madison, WI 53706; R.E. Muck, USDA-ARS, U.S. Dairy Forage Research Center, 1925 Linden Dr., Madison, WI 53706. Funding has been partially provided for this research and publication from the USDA Cooperative State Research, Education and Extension Service (CSREES) Hatch Project WIS04802. Received 26Aug. 2005. *Corresponding author (kaalbrec@