Effect of Soil Solarization on Orobanche Soil Seed Bank and Tomato Yield in Central Rift Valley of Ethiopia

An experiment was conducted to evaluate the effect of soil solarization on Orobanche control in tomato fields of the Central Rift Valley of Ethiopia namely Melkassa, Ziway and Merti in summer 2002 and 2003. Naturally infested fields with Orobanche ramosa and Orobanche cernua were chosen to conduct this experiment. Clear and black polyethylene sheets were used to cover the soil and evaluated for their efficiency to transfer solar heat to the soil Orobanche control. Soil temperature was raised from 32 to 48°C, 33 to 46°C and 37 to 49°C by covering with clear polythene sheet. Whereas, a rise in temperature from 32 to 42°C, 30 to 42°C and 32 to 41°C by covering the soil with black polyethylene sheets was recorded at Melkassa, Ziway and Merti, respectively. The effect of soil solarization between clear and black polyethylene sheets were compared in reducing Orobanche soil seed bank. The result showed that a control of Orobanche was 97, 92 and 91% for white sheet cover whereas 89, 88 and 86% control for black sheet cover at respective locations. Thus, clear polyethylene sheets was slightly more effective than black. Yield of tomato increased by covering with clear polyethylene sheets compared to uncovered soils. The Ratio of uncovered to covered with white sheet was 650/854, 232/447 and 411-660 whereas, the ratio of uncovered to covered for black polyethylene sheets was 533/810, 580/930 and 490/600 kg ha 1 at Melkassa, Ziway and Merti, respectively.