Influence of soil solarisation on soil ,icroflora plant growth and incidence of diseases

Abstract

The influence of solarization on soil microflora, plant growth and incidence of disease was studied during 1985-87 at Madavoor on collar rot of cowpea caused by Rhizoctonia solani Kuhn. The effectiveness of solarization was tested in open and partially shaded conditions in coconut garden using 0.05mm transparent polythene sheets as the mulch. The atmospheric temperature during the period of solarization ranged from 28.50C to 34.20C. The increase in soil temperature, as a result of solarization was more in open field than in partial shade. The soil temperature variation in open nonsolarized treatments was 100C while it was 12.50C in solarized plots. Corresponding figures for partially shaded conditions were 5.50C and 70C respectively. Maximum soil temperature recorded at 15cm depth in open solarized soil was 42.50C. Based on the experimental data two statistical models (1) for predicting soil temperature under polythene mulch and (2) for predicting collar rot of cowpea were developed during the study. Soil solarization significantly reduced collar rot of cowpea. Least incidence of the disease (3.6%) was noticed in open nonirrigated solarized treatments while maximum incidence (24%) was recorded in shade irrigated control. The interaction effect of shade, solarization and irrigation was not significant. Solarization reduced the total fungal population in open conditions while the population of bacteria was not significantly changed. In the case of actinomycetes population, a slight increase was noticed in solarized plots. The nematode population was significantly reduced by solarization in open field. Eventhough solarization substantially reduced weed population in open, it was less effective under partially shaded conditions. Growth parameters like height and number of leaves per plant were not significantly influenced by solarization. But it improved the stand of the crop and yield. An yield increase ranging from 7.62 to 21.69 per cent was obtained in solarized plots over the control. Availability of nitrogen, phosphorus and organic carbon was improved by solarization while there was no change in the level of potassium, calcium, PH and electrical conductivity.