Soybean Cultivar Performance as Influenced by Tillage System and Seed Treatment

Abstract

Tillage systems can influence soybean [Glycine max (L.) Merr.] yields, other agronomic characteristics, and disease potential. This study was conducted to evaluate soybean yield and plant growth as influenced by no-till, reduced-till (chisel plow), and conventional-till (moldboard plow) conditions, cultivars, and fungicide seed treatments. Six cultivars with a relative maturity range of 88 to 115 d were treated with Apron (metalaxyl) [N-(2,6-dimethylphenyl)-N-(methoxyacetyl) alanine methyl ester] or Vitavax 200 [carboxin (5,6-Dihydro-2-methylN-phenyl-1,4-oxathiin-3-carboxamide)-thiram (tetramethylthiuram disulfide), 17%-17%] and solid-seeded into corn (Zea mays L.) residue at Arlington and Janesville, WI. Studies were conducted during 2 yr at each location on a Piano silt loam (fine-silty, mixed mesic, Typic Argiudoll). Cultivars differed in all measured variables and average yields ranged from 56.9 bu/acre for ‘Ozzie’ to 70.6 bu/acre for ‘DSR-171’. Averaged across both locations and years, conventional-till soybeans yielded 8.0 bu/acre more than in no-till and 5.2 bu/acre more than in reduced-till. Averaged across environments, plant density at V2 was 10 000 to 39 000 plants/acre less in no-till than conventional-till, but all cultivars had a stand density above 127 000 plants/acre. Lodging was 1.0, 0.6, and 0.6 (scale of 1 to 5) higher in no-till than conventional-till for ‘Asgrow 2187’, DSR-171, and ‘Century 84’, respectively. Cultivar responses differed with tillage system for seed weight, stand density, and lodging. Crop yield rankings of different cultivars were not affected by tillage system, however. Vitavax 200 seed treatment reduced stand density by 8000 plants/acre at V2. Apron seed treatment in no-till increased yields 2.1 and 1.7 bu/acre over control and Vitavax 200 treatments, respectively. Seed treatment × cultivar interactions were significant for yield. Apron seed treatment was beneficial under no-till and with certain cultivars, but not in the higher yielding reduced and conventional tillage systems. From these studies it appears that use of conservation tillage in solid-seeding situations would need to be justified on the basis of soil erosion control or reduced tillage costs. Seed treatment and cultivar selection did not always overcome yield reductions associated with conservation tillage.