Articles
CONTROL OF RHIZOCTONIA SOLANI BY SOIL SOLARIZATION
A piece of loamy clay land in Giza was divided into 3.2 m2 plots and prepared, as usual, for lupin cultivation.
During the first season (1980/1981) 50 % of the plots were artificially infested with the pathogen Rhizoctonia solani All plots were then sown with lupin for the bioassay.
The pathogen was found to cause death to 33 and 82 % of lupin sown in naturally (nat) and artificially (art) infested soil, respectively.
The yield obtained in art was 45 % of that of nat soil.
The land was left fallow till solarization when 50 % of the plots of both nat and art were mulched with transparent colourless polyethylene sheets during the summer of 1981 for 6 weeks.
Upon measuring the soil temperature at different depths, an increase in soil temperature was recorded in mulched soil especially at 16 o’clock.
The differences averaged 7°C. The temperature in mulched soil at the depths of 5,15 and 25 cm was found to surpass air temperature in the shade by 12,8 and 4°C respectively.
Every care was then taken to avoid both contamination and disturbance of the soil.
The bioassay of the treatments showed an overall decrease by 22 % in damping-off and an increase of 92 % in the yield of lupin plants grown in mulched soil.
The land was left fallow during the summer of 1982 till early November when it was sown again with lupin.
The bioassay revealed a trend similar to that obtained in the previous year, but the magnitude was quite different.
While the percent of damped-off plants dropped on the average by 36 %, the yield recorded an increase equal to 7.5 folds over that of the previous season.
The records of the middle rows indicate, to some extent, that recolonization of the soil over a period of 20 months by R. solani could be overruled.
The data also revealed that the yield increase could be attributed to the reduction in damping-off and diseased plants, and possibly to additional benificial effects occurring in the mulched soil.
Solarization was found to induce enhanced growth of lupin plants as well as the production of more and bigger seeds.