Alfalfa Establishment with and without Spring-Applied Herbicides

No-till establishment of alfalfa (Medicago saliva L.) has increased significantly over the past decade, yet few studies have documented the effect of herbicide use at establishment on no-till establishment-year yield and forage quality. Studies conducted in Michigan in 1989 and 1990 compared alfalfa establishment by conventional and no-tillage methods. Four establishment herbicide treatments (no herbicide, paraquat, paraquat + 2,4-DB, paraquat + EPTC + 2,4-DB) were compared within each tillage system. Treatments were evaluated by determining alfalfa plant population, forage yield, species composition, forage quality, and net economic return. Spring alfalfa populations varied between establishment method, but no differences were observed in the fall of the seeding year. Establishment method did not affect forage yield or quality. In conventional establishment, treatments with no herbicide had greater forage yield but lower percentage of alfalfa than did treatments with herbicide. No differences in forage or alfalfa yield were observed in the third harvest of the seeding year or in the year following establishment for either establishment method. Treatments with no herbicide in both conventional and no-tillage seedings had lower forage quality than treatments with herbicide only in the first harvest of the seeding year. In both years and with both establishment methods, no significant differences were found in net economic return among herbicide treatments. Research QuestionNo-till establishment of alfalfa has increased significantly over the past decade. This study determined the effect that alfalfa establishment system (conventional vs. no-tillage) and establishment herbicides had on alfalfa plant population, forage yield, forage quality, and net economic return. Literature SummarySeveral studies have documented the success of no-tillage alfalfa establishment. Herbicide use is a common practice in conventional alfalfa establishment. This practice decreases total forage dry matter yield while increasing pure alfalfa yield, thus increasing forage quality. This herbicide effect has been observed primarily in the initial harvests of the establishment year. Herbicide use in no-tillage alfalfa establishment should have the same effect on forage dry matter yield and forage quality, but this has not been evaluated in alfalfa research published to date. Study DescriptionField experiments were established in the spring of 1989 and 1990 at the Kellogg Biological Station, Hickory Corners, MI. Alfalfa variety: ‘Big Ten’, 15 lb of pure live seed per acre Soil: Oshtemo sandy loam Previous crop and management: Corn silage removed the previous fall Fertility: Fertilizer applied according to Michigan State University soil test recommendations Treatments for conventional establishment: Alfalfa—no herbicide Alfalfa—2,4-DB (1.0 lb a.i./acre) postemergence Alfalfa—EPTC (3.0 lb a.i./acre) prior to planting plus 2,4-DB (1.0 lb a.i./acre) postemergence Treatments for no-tillage establishment: Alfalfa—no herbicide Alfalfa—Paraquat (0.5 lb a.i./acre plus nonionic surfactant at 0.25% v/v) prior to planting Alfalfa—Paraquat (0.5 lb a.i./acre plus nonionic surfactant at 0.25% v/v) prior to planting and 2,4-DB (1.0 lb a.i./acre) postemergence Applied QuestionWhat effect did establishment method have on alfalfa plant population, forage yield, and forage quality? In 1989, plant populations 45 d after planting were greater in conventional than in no-till establishment. By the fall, plant population did not differ between establishment methods in either year. Seasonal forage dry matter yield and forage quality were not affected by establishment method. What effect did establishment herbicide have on alfalfa plant population, forage yield, and forage quality? Alfalfa plant population was not affected by herbicide treatment in either conventional or no-tillage establishment. With conventional alfalfa establishment in 1989, the no-herbicide treatment had greater forage dry matter yield than did the herbicide treatments in the first harvest (Fig. 1). Herbicide use increased the proportion of forage that was alfalfa. By the third harvest of the establishment year, forage dry matter yield and alfalfa yield did not differ among herbicide treatments. The 1990 conventional seeding followed this trend as well. Fig. 1Forage dry matter and alfalfa yield for three harvests in 1989 of alfalfa established by conventional methods in the spring of 1989 at Kellogg Biological Station. (Bars with the same letter are not different at P = 0.05. Capital letters denote differences in forage dry matter yield; small letters denote differences in alfalfa yield.) The no-tillage seedings followed trends similar to conventional establishment in both years. The no-herbicide treatment had greater forage dry matter yield in the first harvest, but by the end of the establishment year, forage dry matter yield did not differ among herbicide treatments (Fig. 2). The increase in forage dry matter yield that was due to weeds in the no-herbicide treatments lowered forage quality in the first harvest of the establishment year. Forage quality did not differ among herbicide treatments after the first harvest. Fig. 2Forage dry matter and alfalfa yield for three harvests in 1989 of alfalfa established by no-tillage methods in the spring of 1989 at Kellogg Biological Station. (Bars with the same letter are not different at P = 0.05. Capital letters denote differences in forage dry matter yield; small letters denote differences in alfalfa yield.) In both years and with both tillage systems, no significant differences were found in net economic return among herbicide treatments. RecommendationsEstablishing alfalfa using no-tillage methods can produce stands that are equivalent in production to conventional establishment. Alfalfa can be economically established without herbicide in sites with light or moderate annual weed pressure if the producer has use for forage in the initial harvest that is of lower quality.