Morphological Stage of Development as a Predictor of Alfalfa Herbage Quality1
- Bernard A. Kalu and
- Gary W. Fick2
Variations in the nutritive value of herbage are related to the environmental and physiological history of the crop. Previous work indicated that a precise and quantitative method for specifying morphological stage of development in alfalfa (Medicago sativa L.) is a good basis for predicting alfalfa herbage quality. The purpose of this study was to test the consistency of the stage rating system as a predictor of crude protein (CP), in vitro true digestibility (IVTD), neutral detergent fiber (NDF), acid detergent fiber (ADF), and lignin in alfalfa herbage. The field study was conducted over 3 years and with three stand ages and two soil types (Typic Fragiochrept and Aqueptic Fragiudalf). Sequential harvesting was used to establish plots varying in herbage age and stage at common points in time. The 10-stage classification system that was used included three vegetative, two bud, two flowering, and three seed-pod stages. The system was tested by relating individual stages to herbage quality. There was a consistent pattern of quality change among stages, but absolute values differed for each year and age. The mean stage of an herbage sample (MSW) was calculated as the average of the stages of the individual shoots present weighted for the dry weight contributed by each stage. In all cases, MSW consistently provided highly significant linear or quadratic relationships for predicting herbage quality: CP (R2 = 0.883), IVTD (r2 = 0.957), NDF (R2 = 0.946), ADF (r2 = 0.899), lignin (r2 = 0.841). These relationships verified the practical applicability of the MSW procedure for predicting alfalfa herbage quality.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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