Effects of polyethylene colors and thickness on the efficiency of soil solarization under the environment of the UAE

The effects of soil mulching with different polyethylene colors and thicknesses on seed viability of Portulaca oleracea (common purslane) were evaluated through the estimation of final germination percentage and germination rate. Common purslane is often used as an indicator species such that its control with solarization will often result in control of most weed species. This experiment was carried out from June 10 to July 25, 2003 in a farm near Al-Ain, UAE. Fresh seeds of P. oleracea were buried in the soil at 2.5 cm and 15 cm depths for 15, 30 and 45 days. The used soil polyethylene colors and thickness were: 120μm opaque black, 50μm transparent (thin), 75μm transparent (medium) and 150μm transparent (thick). The exhumed seeds were germinated in an incubator adjusted to 15/25°C. The results showed that the most effective plastic (polyethylene) sheets in deteriorating seed germination were the thin and medium thickness of the transparent sheets. The deterioration in seed viability increased with the increase in solarization duration and this was more pronounced in thin transparent plastic than in thick transparent and black plastics. The deteriorative effect of solarization on germination speed was less than that on final germination. The germination was significantly slower at 2.5 cm depth after 45 days solarization under all plastic types and at 2.5 and 15 cm after 30 and 45 days solarization under the transparent thin plastic. This further supports the efficiency of thin transparent in deteriorating the seeds of the two depths after shorter period of time. The results strongly recommend the use of thin or medium thickness of transparent sheets instead of black sheets, which are regularly used in the UAE.