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Alfalfa Stubble Height

As a preliminary step in evaluating alfalfa-grass stubble height effects, we developed regression equations to estimate the impact of stubble height on preharvest NDF concentration of alfalfa [GIS-23]. In New York, where the stubble height of alfalfa varies due to terrain, accuracy of predictive equations may be reduced. We developed and evaluated alfalfa NDF equations that incorporate intended stubble height. Stands of first-cut alfalfa were sampled in producers’ fields in New York in 2007, and cut into 2-inch segments. Predictive NDF equations were developed to evaluate the effect of changing stubble height on yield and quality. These equations can be used by New York producers to obtain a more accurate estimate of preharvest NDF concentration. Alfalfa increases about 0.70 percentage units NDF/day, while grass increases about 0.85 to 1.0 percentage units/day.

Conclusions:

  • For every inch of stubble height left in the field, alfalfa NDF will decrease about one percentage unit.
  • Increasing the mowing height by 2 inches would move the optimum harvest date forward about 2.5 days.
  • In a 50:50 alfalfa-grass stand, leaving one additional inch of stubble would result in forage quality similar to harvesting one day earlier, with substantial yield loss.