Back H. Tokeshi1, M. C. Alves1, A. B. Sanches2 and D. Y. Harada2
Luiz de Queiroz, College of Agriculture, University of Sao Paulo, Piracicaba, SP, Brazil1 and
Mokich Okada Foundation, Ipeuna, SP, Brazil2
Full Paper (PDF File: 235KB)
Abstract
Soils treated with Effective Microorganisms (EM) were found to be suppressive to the soil-borne plant pathogenic fungus, Sclerotinia sclerotiorum, EM also improved certain soil physical properties including a decrease in hardpan density, increased soil aggregation, and improved drainage. All of these benefits were obtained in half the time compared with organic biodynamic agriculture or minimum tillage.
The mechanisms responsible for the control of Sclerotinia sclerotiorum were studied by burying sclerotia in a) suppressive soil, b) a + water at a 5 cm depth, c) a + water at a 10 cm depth, and d) a + water at a 15 cm depth. The treated soil was placed in pots equipped with a water reservoir to maintain the soil columns at different heights above the water table and to ensure uniform soil moisture and humidity. Drainage was provided for removal of excess water from irrigation or rainfall. A field study was conducted according to a completely randomized design with 4 treatments and 10 replications. Each pot was placed in a 50 x 50 cm plot at a predetermined depth and 50 sclerotia per pot were sown at a 0.5 cm depth. Parameters assessed were: number of apothecia in 5 growth periods; number of fertile and aborted sclerotia; surface soil moisture; number of apothecia per sclerotium; volume of residual water in pots; number of natural apothecia in the field; and incidence of disease in commercial plantings. The results showed that surface soil moisture is one of the main factors which controls apothecia production. The number of apothecia in natural soil was lower than for the other treatments at the 1% level of probability, and sporulation did not coincide with the plant's maximum susceptibility period at the 5% level of probability.
The following control mechanisms were noted: a) evasion; b) reduction in the number of apothecia; c) abortion of germinated sclerotia; d) reduction in the number of soil sclerotia; and e) competition for nutrients at the plant surface. Leveling of the soil in the experimental area affected the results and caused the loss of some plots. Consequently, the data were analyzed as a 2 x 2 factorial, transformed into log (x + 0.5), and utilized a uni- and multi-variate, non-parametric analysis with 8 replications. Results for the natural soil differed statistically at the 10% level of probability and at the 5% level of probability for the other treatments.