Solarization of forest nursery soil for elimination of root pathogens and weeds.
Effect of soil solarization was studied during the month of May-June 2002 by spreading polyethylene sheets over wet soil of forest nursery bed (1 m × 10 m). Temperature variations were recorded daily for a period of one month at 3 depths, 5, 10 and 20 cm. During solarization, maximum soil temperature has gone up to 60°C as compared to 50.5°C in control at 5 cm soil depth. Maximum difference in temperature between solarized and control soil was recorded as high as 12°C at 5 cm depth, 10°C at 10 cm and 8°C at 20 cm soil depth. After one month of solarization, the microbial population drastically decreased. Population of Aspergillus, Penicillium, Fusarium, Rhizopus and nematodes were completely eliminated from upper 10 cm soil depth, while population of AM fungi, Trichoderma and bacteria was significantly reduced. The experiment was repeated during the next year for counting microbial population. Population of weeds like Cynodon dactylon, Cassia tora, Leucaena leucocephala, Ipomoea purpurea [Pharbitis purpurea] and two unidentified weeds, whose population in the control beds was 229 m-2, were completely eradicated after solarization. Therefore, solarization of nursery beds or transported soil (potting mix) is recommended before sowing or for filling root trainers, polybags, etc.