Profitability of Overseeding Alfalfa with Wheat or Ryegrass
to Extend Stand Life
R.C. Berberet, D.C. Cummings, J.F. Stritzke and A.D. Bisges
Oklahoma State University, Stillwater, OK 74078
The goal of this research is to evaluate overseeding with cool-season grasses in combination with early-spring grazing for improved profitability of declining alfalfa stands. The rationale for this approach is that the overseeded grasses will greatly increase biomass produced, which in a mixture with the remaining alfalfa will provide high quality forage for livestock. In addition, the overseeded grasses compete with cool-season weeds such as shepherdspurse, Capsella bursa pastoris L.; henbit, Lamium amplexicaule L.; and downy brome, Bromus tectorum L.; and result in less weed interference. Grazing is an efficient way to utilize winter/early spring growth of alfalfa and the overseeded grasses. Hale et al. (1998) reported that early-spring grazing can be conducted without reducing stand/vigor of alfalfa, and that grazing also provides effective control of alfalfa weevil larvae, Hypera postica (Gyllenhal); and blue alfalfa aphid, Acyrthosiphon kondoi Shinji; and saves the cost of insecticide application(s).
Experiments were conducted from fall, 1998 to fall, 1999, in Grady County (‘Garst 630'; 6 yr stand) and Garvin County (‘Cimarron VR’; 7 yr stand). At each location, treatments were replicated 4 times in a RCB design as follows: 1)no pesticides, w/o overseeding or grazing; 2)herbicides (terbacil, imazethapyr, and norflurazon) + insecticide (cyfluthrin) as needed, w/o overseeding or grazing; 3) no pesticides, early-spring grazing (1999), w/o overseeding; 4) no pesticides, grazing and overseeded with ‘Marshall’ ryegrass (fall 1998); 5) no pesticides, grazing and overseeded with ‘Tonkawa’ wheat. Population densities of alfalfa weevil larvae and aphids were estimated from 25-stem samples taken from each plot during March and April. Alfalfa stand density (stems/0.1 m2) was estimated from counts in each plot before each harvest. Aside from grazing as listed above, all forage was harvested by clipping @30-35 day intervals. The percentage of total forage comprised by alfalfa, overseeded grass, and weeds was visually estimated at each harvest. Profitability of treatments was determined from gross income, calculated at $81/Mg for high-quality alfalfa (<10% grass/weeds) with discounts up to $27/Mg (>40% weeds) and $14/Mg (>40% overseeded grass). Net income was determined by subtracting fixed costs (fertilizer, land, etc.) and variable costs (pesticides, overseeding, harvesting) from gross income.
Overseeding significantly reduced cool-season weed interference at both locations. Due in part to dry weather, warm-season weeds were also suppressed in overseeded plots at Garvin County. Although populations of alfalfa weevil larvae were higher in overseeded treatments, grazing reduced numbers equivalent to insecticide application. Alfalfa was competitive with the overseeded grasses, with exception of ryegrass at Garvin County. Overseeding significantly increased production of forage taken at grazing and first cut. At Grady County, where the initial alfalfa stand density was >20 stems/0.1 m2, overseeding was less profitable than other treatments. At Garvin County (ca.12 stems/0.1 m2), overseeded treatments were most profitable, particularly in comparison to the treatment with pesticides.
Reference
Hale, T.C., R.C. Berberet and J.F. Stritzke. 1998. Early-spring grazing of alfalfa for efficient forage utilization and pest management. Proc. N. Am.
Alfalfa Improvement Conf. Vol. 36.