Submitted to: Transactions of the ASAE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 1, 1995
Publication Date: N/A
Interpretive Summary: Large losses of yield and quality occur during the harvest of forage, and these losses can greatly reduce the value of the crop as animal feed. There is a need for models that can predict these losses. Such models could be used to better evaluate and compare forage systems. They may also be used to predict the value of forage produced on a given farm. Such prediction would allow an animal producer to better manage feed reserves and to make best use of available feeds. Models were developed which predict losses based upon physical and chemical characteristics of the crop so that they could be applied across crop species. Although actual losses are very variable, the models developed were able to predict hay and silage harvest losses with reasonable accuracy. The models will be used in a comprehensive dairy forage system model. This integrated model will be used to compare a variety of alfalfa and grass production systems. Analyses of production systems will provide farmers with information on how to manage their farm to produce high quality feeds while reducing potential environmental problems in crop production.
Technical Abstract: Substantial dry matter and nutritive losses occur during forage harvest due to plant and microbial respiration during the field curing process, rain damage, and the shattering or dropping of plant material by machinery. Information gathered through a comprehensive review of the literature was used to develop models which predict dry matter and nutrient losses during harvest for a wide range of forage species and environmental conditions. Losses were predicted from physical and chemical characteristics of the crop to provide models that can be applied across crop species. Respiration loss is a function of crop temperature, moisture content, and drying rate. Rain damage is predicted from the portion of the crop that is leaves, crop moisture content, the type of conditioning used, the concentration of cell contents in the plant material, swath density, and the amount of rain received. Crop factors that influence the amount of machine induced loss include the portion of legume leaves in the crop, moisture content, stage of development and the density of material laying in the swath. Respiration and rain damage deplete readily available nutrients from the crop. The change in nutrient concentration in the remaining crop is predicted by the loss of a given nutrient relative to the loss of total dry matter. Rain or machine induced losses change the leaf-to-stem ratio in the remaining crop. Change in nutrient concentration is then predicted from the ratio of leaf loss to stem loss and the nutrient concentrations of leaf and stem material. Harvest system losses predicted with the models compared reasonably well to measured losses for dry hay and wilted silage systems. The models are intended for use in forage enterprise models used to evaluate or compare forage systems.