Quality of Whole Crop and Pressed Forage from Mechanically Dewatered Alfalfa, Red Clover, and Birdsfoot Trefoil
Forage harvesting techniques that reduce losses in yield and quality that normally occur during field wilting of silage and curing of hay are needed. A 2-yr field study was conducted to evaluate mechanical dewatering of first-cutting forage of alfalfa (Medicago sativa L.), red clover (Trifolium pratense L.), and birdsfoot trefoil (Lotus corniculatus L.) harvested at four stages of maturity. Each species, grown on Plano silt loam soil (fine-silty, mixed, mesic Typic Argiudolls), was harvested at weekly intervals beginning on 27 May 1980 and 26 May 1981, and the forage was macerated and pressed at 6.9 × 105 Pa for 2 min. Samples of the whole crop collected immediately after cutting and of the pressed forage were dried at 55°C to constant weight. Birdsfoot trefoil was the highest in N concentration of the three whole crops, and red clover was higher in N than alfalfa in 1 of the 2 yr. Pressed forage of alfalfa averaged 6.0 g kg−1 less N than the whole crop. Pressed forage averaged 106, 151, and 49 g kg−1 more neutral detergent fiber (NDF) than whole crop for alfalfa, red clover, and birdsfoot trefoil, respectively. Birdsfoot trefoil in vitro dry matter disappearance (IVDMD) was affected least by Pressing, and red clover IVDMD was affected most. Results of this 2-yr experiment indicate that mechanical dewatering reduced IVDMD and generally N, and increased NDF concentration. Differences in legume species response to pressing were substantial and would preclude generalization of mechanical dewatering responses across species. However, whole crop dry matter, N, and IVDMD predicted 0.81 or more of the variation in pressed forage IVDMD of the three species, indicating that pressed forage IVDMD predicted from whole crop composition.
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