EFFECTS OF SOIL SOLARIZATION ON ARABLE WEEDS UNDER MEDITERRANEAN CONDITIONS - CONTROL, LACK OF RESPONSE OR STIMULATION

Field experiments on soil solarization were conducted in a Mediterrane an climate at ICARDA in northern Syria from 1985 to 1988. Fifty-seven species from 25 families were included in this study. Of these, 46 wer e reduced in numbers as a result of the treatment; five species were i ncreased, six were unaffected. After 20, 30, 40 and 50 days of solariz ation, weed dry weight was reduced by 84, 87, 86 and 94%, respectively , in a lentil crop and by 61, 76, 81 and 85% in a faba bean crop. Most annual weeds, especially Sinapis arvensis, were controlled up to 100% . Low to zero control or even stimulation occurred with weed species h aving bulbs (Muscari racemosum, Bellevalia sp., Ornithogalum narbonens e), heat-tolerant seed (Coronilla scorpioides, Scorpiurus muricatus), a deep-lying root system or other perennial organs (e.g. Gladiolus ale ppicus, Aristolochia maurorum, Leontice leontopetalum, Geranium tubero sum). A higher number of Muscari racemosum plants m-2 was encountered after solarization, indicating stimulation by the treatment. The numbe rs and dry weight of this weed after 20 days of solarization were incr eased by 85 and 87% in faba bean and lentil, respectively. Dry weight of spring and summer weeds after 50 days of solarization decreased by 89.2 and 90.3%, respectively. The maximum temperature reached at 5 cm soil depth under the plastic was 57-degrees-C.