عنوان مقاله [English]
Background and objectives: Increase of water holding capacity induced by polymers has been developed in arid and semi-arid regions. The effect of polymers on increasing water holding capacity and the effect of selected polymers on some growth characteristics of corn plant under drought stress was carried out in both experimental and greenhouse condition, respectively.
Materials and methods: The present research included two complementary parts performed in laboratory and greenhouse. First, the effect of 11 polymer treatments (polymer type and concentration) including Karacoat 1and 3 %, Acrylic 1 and 3 %, Polyvinyl acetate 1 and 3 %, Superab 0.5 and 1 %, Stockosorb 0.5 and 1 % and control without polymer on moisture changes of two soils (loamy sand and sand) during 11 times (0, 12 h, 1, 2, 4, 6, 8, 10, 12, 16, 20 day) were studied in laboratory and 4 best polymer treatments were selected for greenhouse cultivation. In greenhouse, the effect of polymer treatments (Karacoat 1and 3 %, Stockosorb 0.5 and 1 % and control without polymer) under drought stress (30, 50 and 80 % field capacity) on some growth characteristics of corn plant (leaf number, height, wet and dry weight of stem and wet and dry weight of root) were studied separately in loamy sand and sandy soils.
Results: Results showed that increase of moisture in both treated soils was higher than control and from this point of view, water soluble polymer-Karacoat 3 % (18.5 % compared to loamy sand control and 35.9 % compared to sandy control) and Stockosorb 1 % hydrogel (95.8 % compared to loamy sand control and 3.4 times compared to sandy control) were more powerful. Mean moisture after 20 days for water soluble polymers and Superab hydrogel was higher in loamy sand than sandy soil. But, Stockosorb 1 % hydrogel was more effective in sandy soil (16.1 % increase compared to loamy sand soil). With increasing polymer concentration, the moisture content of polymer treated soil samples increased. To increasing water holding capacity Stockosorb 1% hydrogel in loamy sand (0-12 day) and sandy (0-16 day) soils was more successful than other polymer treatments. Both water holding capacity during the time and final moisture content in sandy soil treated with polymers were more than loamy sand soil. Leaf number, stem height, wet and dry weight of stem and dry weight of root in corn plant were reduced under drought stress. In contrast, height, wet and dry weight of corn stem were better in stockosorb hydrogel 1 % treatment. Wet weight of corn stem in loamy sand soil under drought stress was significantly affected (P < 0.01) by stockosorb hydrogel. Stockosorb 1% hydrogel increased wet weight of stem 59.29, 82.41 percent and 3.82 time in low, medium and severe stress compared to control, respectively.
Conclusion: According to the results karacoat 3 % and stockosorb 1 % are recommended for increasing moisture and water holding capacity of coarse texture soils. Moreover, polymer materials with properties such as useful longevity, high efficiency at low concentrations, and local application in the root zone of trees could provide ideal condition for plant which growth in soils with low water holding capacity. In addition, they are ideal for drought condition that is common in arid and semi-arid regions where rain is low and evaporation is high.