Use of composted sheep manure to increase soil suppressiveness towards Rhizoctonia root rot of wheat

Tzenko Vatchev, Ivo Yanashkov, Svetla Maneva

Abstract: The present study demonstrates the possibility to increase disease suppressiveness of Eutric Fluvisols towards Rhizoctonia root rot of wheat caused by Rhizoctonia solani AG 4 using well composted sheep manure. Experiments were conducted with dry-sterilized (140°С for 6 h) and unsterilized, natural soil in which the organic amendment was preliminary incorporated at a rate of 0, 20, 60, or 100 ml L-1 and then incubated for 90 days. The experimental units used for testing of soils for disease suppressiveness consisted of rectangular plastic planter trays (26 х 6 х 8 cm) with saucers and drain holes allowing manual watering from the bottom of the tray, 7 cm height of the soil column, two-row planting of wheat, c. Laska 5 (2 rows x 12 plants, 2 x 3 cm spacing between plants and rows). As a focal source of inoculum, 20 autoclaved (121°С for 30 min) barley grains overgrown with the pathogen were introduced into the soil at the beginning of the rows after emerging of plants. The incorporation of 60 or 100 ml L-1 sheep manure into soils (corresponding to fertilization doses of 15 and 25 m3, respectively per ha of cultivated land with 25 cm deep soil plough layer) gave a significant (P≤0.001) reduction in spread of Rhizoctonia root rot from the point of inoculum source within the twin rows of wheat stands along with increased number of disease-free plants until the 35th day after inoculation. Levels of disease control achieved with these amounts of the amendment, calculated as area under the disease response curves, were 37.5% and 46.8%, and 31.0% and 55.4%, as compared to untreated controls with sterilized and unsterilized soil, respectively. In the light of the study, it was concluded that well composted sheep manure can be successfully applied for control of Rhizoctonia root rot of wheat, either individually or as an essential component of an integrated disease control strategy.

Keywords: cereal crops; Rhizoctonia solani AG 4; root rot of wheat; soil suppressiveness; sustainable disease control method

Date published: 2017-10-03