Relationship of Alfalfa Cultivar Yields to Specific Leaf Weight, Plant Density, and Chemical Composition1

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AbstractThe objective of this study was to determine the relationship of dry matter yield to various plant parameters in 11 alfalfa (Medicago sativa L.) cultivars that represented a wide range of winterhardiness. The parameters measured were specific leaf weight (SLW), plant density, and concentrations of protein‐N, P, K, Ca, and Mg in the forage. Suggestions and reports have been made in the literature that plant parameters such as specific leaf weight and K concentration in the forage are positively correlated with yield of alfalfa. Previous research reports have not contained correlations of all our parameters with dry matter yield from broadcast‐seeded field plots. The cultivars were broadcast‐seeded in 2.1 ✕ 7.6 in plots on a Humic Hapludult soil and harvested five times at approximately 1/10 bloom during the next year.Dry matter yield of cultivars was positively correlated with plant density but not correlated with SLW or with concentration in the forage of any of the following elements: protein‐N, P, K, Ca, Mg. When averaged over all cultivars, the SLW generally was higher on the sampling dates preceded by higher mean air temperatures. When averaged over all harvests, the range in concentration of each element was not large. Apparently correlations previously reported between SLW of alfalfa and net photosynthetic rate on a unit leaf area basis did not extend to yield on a unit land area basis in broadcast‐seeded field plots. Individual elemental concentration of protein‐N, P, K, Ca, or Mg, when sampled at 1/10 bloom harvest, was not a good parameter for evaluating the immediate dry matter production of the alfalfa cultivars.