Dry Matter and Nitrogen Partitioning in Mechanically Dewatered Alfalfa, Red Clover, and Birdsfoot Trefoil1

Abstract

AbstractImproved forage harvesting techniques are needed to reduce the losses incurred during field drying silage or hay, especially in areas where rainfall is high. A 2‐yr field study was conducted to evaluate mechanical dewatering of first cutting forage of alfalfa (Medicago sativaL.), red clover (Trifolium pratenseL.) and birdsfoot trefoil (Lotus corniculatusL.) harvested at four maturity stages. Separate plots of each species grown on Plano silt loam soil (Typic Argiudolls) were harvested at weekly intervals beginning on 27 May 1980 and 26 May 1981 and the forage was macerated and pressed at 6.9 ✕ l05Pa for 2 min. A protein concentrate was obtained by heating the whole juice to 80°C using steam. Pressed forage dry matter (DM) concentration increased as whole crop DM increased. Alfalfa was the highest of the whole crops in DM concentration and thus produced the highest DM pressed forage, suggesting that modification in processing conditions might be necessary to produce pressed forages consistently > 300 g DM/kg of total mass. Stepwise multiple regression indicated that a model including whole‐crop DM and neutral detergent fiber (NDF) accounted for significant portions of variation in pressed forage DM concentration in every case. Pressing removed an average of 45% of the initial fresh weight and 20% of the DM from alfalfa, about the same amounts from red clover, and somewhat less from birdsfoot trefoil. Higher whole crop DM concentrations reduced extraction of both total fresh weight and solids. The protein concentrate contained 8.5, 7.0, and 4.9% of whole crop DM for alfalfa, red clover, and birdsfoot trefoil, respectively. The alfalfa protein concentrate and deproteinized juice fractions contained a greater percentage of the whole crop N than the same fractions from red clover and birdsfoot trefoil. Red clover was generally intermediate in N percentage contained in the protein concentrate and deproteinized juice. Results of this 2‐yr experiment indicate that significant species and maturity differences exist in crop response to mechanical dewatering, which are related to differences in the concentrations of DM and NDF in the whole crop.