Tillage and seeding rate effects on wheat cultivars: II. Yield components

Tillage is declining in dryland wheat production systems. Our objectives were to determine if tillage X cultivar, seeding rate X cultivar, and tillage X seeding rate X cultivar interactions occurred for the yield components of hard red spring wheat (Triticum aestivum L. emend. Thell.) in a wheat-fallow monoculture. The cultivars AC Minto, Amidon, Bergen, Grandin, and Norm were seeded at 123,247, and 371 kernels m(-2) in conventional-till (CONT), reduced-till (RT), and no-till (NT) systems in a randomized complete block in a split-split plot arrangement during 1995-1998. Tillage X cultivar and tillage X seeding rate X cultivar interactions did not occur for any yield component (P > 0.05). A seeding rate X cultivar interaction occurred for both plant stand and tiller production, but the interaction resulted from a change in the magnitude of response and not in the ranking of cultivars to seeding rate adjustments for either yield component. Plant stand and the number of tillers per plant were unaffected by tillage systems, but the number of spike-bearing tillers increased from 411 m(-2) under CONT to 457 m(-2) under NT. Tillage systems did not affect the number of kernels per spike or kernel weight. More spike-bearing tillers per square meter occurred as the seeding rate increased, but there were fewer tillers per plant and a negative quadratic response in the number of kernels per spike. Results of this study indicate that the ranking of contrasting hard red spring wheat cultivars for yield components is unchanged by reductions in tillage in a wheat-fallow monoculture.