Evaluation of Weed Control Practices during Spring and Summer Alfalfa Establishment

Abstract

Weed management during alfalfa (Medicago sativa L.) establishment is a major concern for producers in the northeast USA. The objectives of this research were to determine the yield, quality, and economic consequences of controlling weeds during the establishment of spring‐ and summer‐seeded alfalfa. Alfalfa was band‐seeded during spring (April and May) and late summer (August and September) into a conventionally tilled seedbed of Hagerstown silt loam (fine‐loamy, mixed, mesic Typic Hapludalfs) at Landisville, PA, in 1991 and Murrill silt loam (fine‐loamy, mixed, mesic Typic Hapludult) at Rock Springs, PA, in 1991 and 1992. Weed control treatments for the spring seedings included: (i) no herbicide or nurse crop (no weed control); (ii) oat (Avena sativa L.) nurse crop; (iii) benefin preplant incorporated; and (iv) sethoxydim and 2,4‐DB postemergence. Weed control treatments for late‐summer seedings were the same as those in the spring except that the nurse crop was replaced with a paraquat application to dormant alfalfa. Seeding alfalfa later, compared with earlier, in the spring tended to increase weed and decrease alfalfa dry matter (DM) yield but did not affect total DM yield or forage quality during the seeding year. For spring‐seeded alfalfa, weed control treatment effects on alfalfa and weed DM yield during the seeding‐year were sporadic, however, net economic return per acre was generally greatest when no weed control was used. Neither time of spring seeding nor weed control treatments produced consistent differences in yield, quality, or net economic return per acre after the seeding year. Delaying alfalfa seeding in the summer reduced first harvest alfalfa yield (704 lb/acre less) and season total alfalfa yield (1121 lb/acre less) compared with early seedings. Generally, weed control treatments in summer‐seeded alfalfa did not improve alfalfa or total DM yield, forage quality, or net economic return per acre compared with no weed control. We conclude that when alfalfa is either spring or summer seeded, the weed control practices used in this study were not economically beneficial and may actually reduce net return per acre because of associated additional costs compared with seeding alfalfa with no companion crop or herbicide. Research Question Concerns over the perceived deleterious effects of weeds on alfalfa survival and forage quality cause many producers to employ a prophylactic weed control practice during alfalfa establishment. These practices not only add to the cost of forage production, but also can involve the use of chemicals, which are increasingly under environmental scrutiny. This study examines the effect of different weed control practices during alfalfa establishment on forage yield and quality and net economic return per acre. Literature Summary Weed management during alfalfa establishment is important for improving forage yield and quality on the approximately 250 000 acres planted to alfalfa each year in the northeast USA. Numerous practices, including nurse crops, herbicides, and time...

The effect of companion crops and herbicides on economic returns of alfalfa-bromegrass establishment

“…In this study, the use of herbicides resulted in either lower or similar net returns to treatments without herbicide control. This result is consistent with the findings of Hall et al (1995). The impact of herbicides on net returns primarily occurred in the establishment year, and herbicide cost was a major factor.…”

“…Mixtures of legumes and grasses reduce the herbicide options available for weed control (Alberta Agriculture, Food and Rural Development 1996). Hall et al (1995) reported the use of herbicides for control of weeds during forage establishment provided no economic benefit, either from higher yields or improved forage quality. Brothers et al (1994) found no difference among tillage systems for forage establishment.…”

Weed Management During Forage Legume Establishment

“…The use of cereal grain companion crops also eliminates the use of pre‐emergent herbicides and greatly limits post‐emergent herbicides available to control weeds. Hall et al (31) reported pre‐ and post‐emergent herbicides provided better weed control and higher forage yields than using a companion crop; therefore herbicides are generally replacing companion crops for weed suppression (25).…”

Light competition for invasive species control: A model of cover crop–weed competition and implications for Phalaris arundinacea control in sedge meadow wetlands

“…In agriculture, for example, initial reductions in annual crop production due to competition from weeds and cover crops are generally unacceptable. Delays in crop production may be acceptable in perennial cropping systems, especially if the cover crop has economic value (Hall et al, 1995). The usefulness of an effective cover crop will depend on both the amount of time that is required for desired species to recover from cover crop competition and on the ability of land managers to accept delays in the establishment and growth of desired species.…”