Residue Height Influences Stand Dynamics of Alfalfa Grown on a Shallow Soil
- David P. Belesky * and
- James M. Fedders*
Multiuse alfalfa (Medicago sativa L.) cultivars have been developed to meet the need for high-quality and productive forages. A continuum of residual tissue quantities can occur in a stand because of management factors or livestock selectivity, depending on the production system. We conducted a field study to determine the influence of residual herbage height on the productivity and persistence of alfalfa under natural rainfall on a shallow, acidic soil (Lily series; fine-loamy, siliceous, mesic Typic Hapludults) typical of those found throughout the Appalachian Plateau. Three replicates of ‘Alfagraze’, ‘Apollo’, and ‘Cimarron’ alfalfa in each block of a randomized complete block design were clipped to residue heights of <2, 5, or 10 cm. Averaged over the experiment, Apollo yield was greatest, at 8.7 Mg ha−1; Alfagraze (8.0) and Cimarron (7.9) yields were about 10% less than Apollo. Clipping to 10 cm produced yields that were as much as 38% less than with shorter heights. Crown density decreased from about 400 to about 80 crowns in m−2 during the experiment. Clipping to <2 cm caused the greatest variation in crown density among cultivars, with Alfagraze having the most and Cimarron the fewest crowns. With a 10-cm residue, weed competition increased and plant size and shoot number were depressed, especially in Alfagraze. Plants with large crowns produced more stems, which compensated for the gradual decline in plant population. The loss of larger-crowned plants during 1994 to 1995 was reflected in fewer shoots and reduced yield, and created a situation where increased productivity per plant could no longer compensate for plant losses. Reestablishment recommendations based on shoot numbers should be determined after the first clip in the growing season, and not in spring (when shoot numbers are changing rapidly). Our findings suggest that acceptable alfalfa yields can be obtained on a shallow acidic soil with surface liming, fertilizer input, and close clipping. The range of residue heights likely to occur in a stand of alfalfa influence productivity and persistence. Allowing a 10-cm residue to remain would probably accelerate plant loss and yield reduction from the stand.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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