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Title: Can placement of seed row away from relic stubble reduce Rhizoctonia root rot in direct-seeded wheat?

item Huggins, David
item Paulitz, Timothy

Submitted to: Soil & Tillage Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/28/2008
Publication Date: 9/1/2008
Citation: Davis, R.A., Huggins, D.R., Cook, R.J., Paulitz, T.C. 2008. Can placement of seed row away from relic stubble reduce Rhizoctonia root rot in direct-seeded wheat? Soil & Tillage Research. 101 (2008) 37–43. doi:10.1016/j.still.2008.05.014

Interpretive Summary: With direct-seeding or no-till production of cereal, seeds are planted directly into the previous year’s crop residue without plowing. However, soilborne diseases can become a problem in no-till systems. A possible cultural management strategy for soilborne cereal diseases is to avoid planting in the previous year’s row, using a precision planter with a highly accurate GPS system. We tested the hypothesis that planting away from the stubble row would reduce Rhizoctonia root rot, a major root pathogen in the Pacific Northwest. Based on 2 years of field trials and one greenhouse trial, we concluded that row placement did not consistently reduce root disease, although there was measurable disease pressure, based on pathogen-free control treatments. Rhizoctonia and other soilborne pathogens may be distributed throughout the upper soil profile, unlike with crown diseases such as Fusarium or take-all, which produce inoculum on the lower stems.

Technical Abstract: Rhizoctonia root rot of wheat can become a problem in direct-seed, no-till systems, especially during the transition from conventional tillage. There are no effective chemical controls or resistant varieties, leaving only cultural methods to manage this disease. In a direct-seed system, residue and inoculum of soilborne pathogens are not moved by cultivation, therefore the inoculum may be concentrated in the seeding row of the previous year. Using GPS tracking systems with sub-meter accuracy, the seeding row could be placed away from the row of the previous year. We tested the hypothesis that seeding away from the relic row may reduce the disease. In two field experiments, plants were sampled at three distances from the seed row, as well as from fumigated plots. Intact soil cores were also removed from the field, planted with seeds at various distances from the previous row, and grown in the greenhouse under controlled conditions. Pasteurized cores served as controls. Disease pressure was higher in the field in the second year, but there was no consistent effect of seed row placement on disease or plant parameters. However, soil fumigation and pasteurization had significant effects, indicating the presence of disease pressure. Unlike Gaeumannomyces graminis var. tritici, the causal agent of take-all, inoculum of Rhizoctonia is not produced in the crowns and lower stems of the plant, but the pathogen survives in living and dead roots of the previous year crop, volunteers, and grassy weeds. Thus high inoculum levels may be present in between the relic rows, as well as within the rows, so precision placement.