Submitted to: Plant Disease
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/2/2007
Publication Date: 9/20/2006
Citation: Schroeder, K.L., Paulitz, T.C. 2006. Root diseases of wheat and barley during the transition from conventional tillage to direct seeding. Plant Disease. 90-1247-1253 Interpretive Summary: The dynamics of diseases in the conversion from conventional tillage to direct seeding were studied in replicated field plots. During the first two years of the transition, there were no major differences in yield and diseases between the two tillage treatments. However, in the 3rd and 4th year, yields were significantly reduced in the direct-seeded plots, and R. solani was in higher populations levels, compared to the conventionally tilled plots. 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.
Technical Abstract: Two separate field studies were established to examine the impact of these pathogens during the conversion to direct seeding. In both studies, comparisons of direct seeding to conventional tillage were made in the early years of the transition as well as 12 to 21 years into the transition. A pair of replicated field plots was established near Garfield, WA. One plot was managed by direct seeding for 12 years prior to initiating the study and the second location had a long history of tillage. At each location, portions of the plots were maintained with tillage and other portions with direct seeding. Spring wheat and barley were also planted at each location. Reduced numbers of tillers and crown roots were observed in direct seeded plots when compared with tillage, regardless of the duration of direct seeding. Upon assessing root diseases, the incidence of Rhizoctonia root rot was found not to differ in the first and second year of the transition to direct seeding. However, in the third and fourth years, a substantial increase in Rhizoctonia root rot was observed in direct seeded plots along with a corresponding reduction in yield. Hyphal activity of R. solani, as measured using the toothpick baiting assay, was found at elevated levels in the direct seeded plots in the third and fourth years of the transition. However, there was no difference in hyphal activity of R. oryzae between management systems, indicating that this pathogen is unaffected by direct seeding. In this same study, following 12 years of direct seeding, the incidence of Rhizoctonia root rot and yield did not differ between tilled and direct seeded plots. In addition, the incidence of take-all and populations of Pythium spp. did not differ with management practice or duration of direct seeding.