Root Diseases of Wheat and Barley During the Transition from Conventional Tillage to Direct Seeding

K. L Schroeder; T. C Paulitz

doi:10.1094/PD-90-1247

The use of direct seeding (no-till) in place of tillage can reduce soil erosion and improve water infiltration. However, despite these improvements in soil quality, growers in the Pacific Northwest are reluctant to adopt direct seeding, partially because of fears of increased root diseases caused by Gaeumannomyces graminis var. tritici, Rhizoctonia spp., and Pythium spp. To examine the effect of the transition from conventional tillage to direct seeding, field plots were established at two locations. One site had been managed with direct seeding for 12 years, and the second had been conventionally tilled. Over 4 years, a portion of each plot was tilled or direct seeded, and planted to wheat or barley. Plants in the tilled plots had consistently more crown roots than plants in direct-seeded plots. Rhizoctonia root rot and yield did not differ between tillage types during the first 2 years of the study. However, in the third and fourth years of the transition to direct seeding, a higher incidence of Rhizoctonia root rot, increased hyphal activity of R. solani, and reduced yields were observed in direct-seeded plots. Populations of R. oryzae and Pythium spp., and incidence of take-all were the same for both management practices. Root diseases of cereals can limit yields in dryland production areas of the Pacific Northwest. Wind and water erosion of the soil can also be problematic, especially in areas of eastern Washington with steep hillsides. More growers are adopting direct-seeding or no-till practices, where the crop is seeded directly into the last year's stubble. This practice reduces erosion, improves soil quality and organic matter, and reduces fossil fuel inputs. However, many growers report more root disease when tillage is reduced or stopped, during the transition from conventional tillage to direct seeding. This research investigates the dynamics of root diseases in the conversion from conventional tillage to direct seeding, using replicated field plots over a 4-year period. Another study site examined the changes in a long-term direct-seeded plot where conventional tillage was resumed. During the first 2 years of the transition from conventional tillage to direct seeding, there were no major differences in yield and diseases between the two tillage treatments. However, in the third and fourth years, yields were significantly reduced in the direct-seeded plots, and Rhizoctonia solani was in higher population densities compared with the conventionally tilled plots. However, R. oryzae, Pythium spp., and Gaeumannomyces graminis var. tritici were not affected by tillage. In the plots that had been direct seeded for the past 12 years, bringing back the plow and using conventional tillage did not give any yield advantage or disease reduction. Further work is needed to understand the mechanisms behind the shift in disease dynamics.

Root Diseases of Wheat and Barley During the Transition from Conventional Tillage to Direct Seeding

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