Effects of poly vinyl alcohol/starch as Soil Conditioners on the physical properties of loamy sand and loam soils following different wetting and drying cycles

摘要

This study assesses in loamy sand and loam soils, treated with levels of poly vinyl alcohol/starch 0 , 0.15 , 0,25, 0.35 % on samples, 24 pots wetting and drying (1-4) cycles. After different cycles have been used, the results pointed out a significant increasing in soils moisture. The amount of available water increased 20–25.6%and 21.1–34.6% by weight treated soils?in loamy sand and loam respectively, while soil moisture was increased relative 6.3–11.1% to the control treatments after cycles . Soil available water increased slightly while wetting and drying cycles. The application polymer increased the moisture retention at field capacity and wilting point linearly in loamy sand and loamy soils value of (R2 = 0.949*) and (R2 = 0.907*),(R2 = 0.059) and (R2 = 0. 787*) respectively. Seed germination of Sun flower(Helianthus annuus L.) was not affected In loamy soil, seed germination was higher than In loamy sand soil , and seedling increased with increase in level of polymer compared with control. The amendment with starch decreased the rate of soil moisture losses that caused a delay in wetting in both soils . The amendment was effective in improving soil moisture availability and thus increased seed germination. Keywords: This study, polyvinyl alcohol , wetting sandy, Loamy sand soils.