Richard H. Leep

Establishment Systems for Glyphosate-Resistant Alfalfa

Glyphosate-resistant alfalfa offers new weed control options for alfalfa establishment. Field studies were conducted in 2004 and 2005 to determine the effect of establishment method and weed control method on forage production and alfalfa stand establishment. Seeding methods included clear seeding and companion seeding with oats. Herbicide treatments included glyphosate, imazamox, imazamox + clethodim, and no herbicide. Temporary stunting from the glyphosate treatments was observed (< 7%); however, injury did not reduce forage yield or stand density in 2004. No glyphosate injury was observed in 2005. Weed control with glyphosate was more consistent than with imazamox or imazamox + clethodim. In 2004, total seasonal forage yield, which consisted of alfalfa, weeds, and oats (in some treatments), was the highest where no herbicide was applied in the oat companion crop and was reduced where herbicides were applied in both establishment systems. In 2005, seeding method or weed control method did not affect total seasonal forage production. Alfalfa established with the clear-seeded method and treated with glyphosate yielded the highest alfalfa dry matter in both years. Imazamox injury reduced first-harvest alfalfa yield in the clear-seeded system in both years. When no herbicide was applied, alfalfa yield was higher in the clear-seeded system. The oat companion crop suppressed alfalfa yield significantly in both years. Alfalfa established with an oat companion crop had a lower weed biomass than the clear-seeded system where no herbicide was applied in both years. Nomenclature: Clethodim, glyphosate, imazamox, alfalfa, Medicago sativa L., oat, Avena sativa L. ‘Ida’

Forage Quality of Glyphosate-Resistant Alfalfa as Influenced by Establishment Systems

Abstract Field studies were conducted in 2004 and 2005 in Michigan to determine the effect of seeding establishment method and weed control on forage quality of glyphosate-resistant alfalfa in the establishment year. Seeding methods included alfalfa only (clear-seeding) and alfalfa with a companion crop of oat (companion-seeding). Herbicide treatments included an untreated control and glyphosate treatment for both establishment systems, and either imazamox in the clear-seeding system or imazamox + clethodim in the companion-seeding system. The greatest differences among treatments in forage quality were observed at the first harvest in both establishment years. Results suggest high quality, productive alfalfa stands can be established utilizing glyphosate-resistant alfalfa in a clear seeding system. Nomenclature: Clethodim; glyphosate; imazamox; alfalfa, Medicago sativa L.; oat, Avena sativa L. ‘Ida’

Effect of Seeding Rate and Weed Control on Glyphosate-Resistant Alfalfa Establishment

Abstract The introduction of glyphosate-resistant (GR) alfalfa offers a new weed management system for alfalfa establishment; however, alfalfa seeding rates are based on conventional cultivars. Determining optimum seeding rates allows forage producers to maximize yield, quality, and profitability with GR alfalfa. Field experiments were established in 2005 and 2006 to determine the effect of seeding rate and weed control on GR alfalfa yield, forage quality, and persistence up to 3 yr after establishment. Seeding rates of 4.5, 9.0, and 18 kg ha−1 were evaluated. Weed control methods during the seeding year included no herbicide, glyphosate applied once before the first harvest, and glyphosate applied once before the first harvest and then 7 to 10 d following subsequent harvests. Alfalfa yield was greater at higher seeding rates and when weeds were removed with glyphosate. Season forage yields were the greatest with the 18 kg ha−1 seeding rate and where no herbicide was applied. Weed biomass often was lower at the higher seeding rates and was 91 to 98% lower in the glyphosate treatments compared to the nontreated. Forage quality was not affected by seeding rate but varied by herbicide treatment depending on establishment year. Plant density increased with seeding rate and treatment effects persisted for three growing seasons. Herbicide treatment did not affect stand density as greatly as seeding rate and did not influence stand longevity. Nomenclature: Alfalfa, Medicago sativa L

Glyphosate-Resistant Alfalfa Response to Harvest Frequency and Weed Management

Abstract Glyphosate-resistant (GR) alfalfa offers growers new options for weed control in alfalfa. One potential benefit of using GR alfalfa is increased longevity of an alfalfa stand under frequent harvests. It was hypothesized that GR alfalfa would have a greater longevity because of removal of weed interference with minimal crop injury. To study GR alfalfa yield, weed invasion, alfalfa stand persistence, and relative forage quality (RFQ), a field experiment with three weed control methods (no herbicide, glyphosate, and hexazinone) under two harvest frequencies (high and moderate) was established in August 2003 at the Michigan State University Agronomy Farm in East Lansing, MI. Forage yield of established alfalfa was not adversely affected by herbicide treatments. There were no differences in weed biomass between alfalfa treated with glyphosate and that treated with hexazinone, except in 2007. Average GR alfalfa stand density decreased approximately 90% (from 236 to 27 plant m−2), and yield decreased approximately 30% (from 11.04 to 7.87 Mg ha−1) during the 7-yr period (2004 to 2010) of the experiment. Stand density of GR alfalfa showed natural thinning during the 7-yr period regardless of harvest intensity or herbicide treatment. In most production years (4 out of 5 yr), relative forage quality of GR alfalfa was higher under a high-intensity harvesting system (4 to 5 harvests yr−1) than it was with a moderate intensity harvesting system (3 to 4 harvests yr−1). Relative forage quality was not affected by weed removal with herbicides in most years. Weed removal and harvest intensity in established GR alfalfa had no effect on stand persistence. Nomenclature: Glyphosate; hexazinone; alfalfa, Medicago sativa L.

Improving pasture and hay ground with manure slurry-enriched seeding

Red Clover (Trifolium pretense) and orchard grass (Dactylis glomerata) were sown in an established smooth bromegrass sod (Bromus inermis) in a Capac fine sandy loam soil (fine-loamy, mixed, active, mesic Aquic Glossudalfs) on the campus of Michigan State University in East Lansing, Michigan. The red clover and orchardgrass with no-till drilled, frost seeded and slurry seeded with swine slurry. The manure slurry seeding process involved mixing red clover or orchardgrass seed in the slurry tank and passing the seed-laden slurry through drop tubes to the fractured and loosened soil behind each set of aeration tines. No-till drilling and slurry seeding resulted in more uniform stands of red clover and orchard grass than frost seeding. Inter-seeding orchard grass in an existing brome grass stand increased the botanical diversity but did not increase dry matter yield. Compared to the no aeration, no manure control, the no-till, slurry and frost seeded red clover plots increased yields by 105%, 87% and 43%, respectively.

Manure Slurry-Enriched Seeding of Cover Crops in Diverse Cropping Systems

Manure slurry-enriched seeding of cover crops is a new process that combines low-disturbance aeration tillage, land application of liquid manure and seeding of cover crops in one efficient operation. In this new process, low-disturbance aeration tillage creates an absorptive surface in untilled ground that mitigates overland flow and soil erosion by fracturing the soil, increasing surface roughness, improving infiltration, and conserving crop residues. In the same pass, cover crop seed mixed with the manure in the spreader tank is banded over the aeration slots through drop tubes behind each set of aeration tines. The nutrient-rich, seed-laden slurry quickly infiltrates the soil matrix. The developing cover crop captures nutrients and forms a vegetative barrier to overland flow. Results of field trials from 2004-2006 showed the slurry seeding process to be an efficient and effective cover crop establishment method for diverse cropping systems. Oil seed radish and oriental mustard were established in sugar beet rotations; cereal rye and wheat were established in corn silage stubble; and forage rape, forage turnips, oats and sorghum-sudan grass were established in small grain stubble for late season grazing. Biomass yields of manure slurry-enriched crops were equal to or greater than conventionally drilled crops. Compared to conventionally drilled stands, slurry-seeded stands (plants m-2) were generally less, but biomass yields (kg ha-1) were similar because individual plant biomass was up to 6 times greater with slurry seeding. There were no cases when the conventionally seeded crops yielded significantly more than the slurry-seeded crops.