Impact of Environmental and Harvest Management Variables on Alfalfa Forage Drying and Quality
- J. M. Iwan,
- J. F. Shanahan and
- D. H. Smith
The objective of this study was to determine the impact of environment and harvest management variables on drying duration and quality of alfalfa (Medicago sativa L.) forage grown under semiarid conditions of the western USA. Untreated and conditioning agent (CA)-treated forage was harvested with a commercial mower-conditioner on four dates in 1989 to provide variation in drying duration. Drying duration was determined by periodically monitoring moisture concentration of the forage after harvest until the forage was baled at 180 g water kg−1 herbage. Samples from the bales of each harvest were taken to determine forage quality. Solar radiation, air temperature, air vapor pressure deficit (VPD), soil moisture, and windrow density were monitored during drying. To determine the effect of enviornmental and harvest management variables on drying, temperature- and VPD-based models were used to predict forage moisture concentration at the end of several drying intervals. The VPD model included the variables of VPD, solar radiation, soil moisture, windrow density, and application of CA. The temperature model included of all the previous variables, except air temperature was substituted for VPD. The CA reduced drying duration by a maximum of 50% across the four harvests, with the greatest effect occuring under high solar radiation, temperature, and VPD. Crude protein was improved only slightly by the CA, with a maximum increase of 5.9% for the third harvest. Observed and predicted moisture concentration for several drying intervals closely agreed for both models (r2 = 0.80 for VPD, and 0.78 for temperature). These results suggest that manipulation of all variables included in the models should hasten alfalfa forage drying.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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