Effect of hydrogel amendment on growth and survival of plants in two types of soils -

Abstract

In this research a laboratory study was conducted to test the effect of SAP potassium polyacrilic acid (STOCKOSORB® 660) on water holding capacity of clay (C) and sandy clay (SC) soils. A field experiment was conducted at The Agricultural Reseach and Educational Center of the American University of Beirut in the Bekaa, where Carob trees (Ceratonia siliqua), South European flowering ash (Fraxinus ornus) and Juda’s tree (Cercis siliquastrum) seedlings were planted in the field after mixing the soil with hydrogel rates of 0, 0.5, 1, 2, and 4 g hydrogel-kg of soil. Survival of trees in the different treatments was monitored. A greenhouse pot experiment on corn (Zea mays) was also run to study the effect of hydrogel on plant growth in SC and C soils. In the pot experiment, the rates of hydrogel were 0, 1, 2, 3 and 4 g hydrogel-kg of soil. Hydrogel was applied using two methods: banding (in one layer mixed with 20-20-20 fertilizers) and mixing where the hydrogel and fertilizers were thoroughly mixed with the soil. The growth was measured 7 weeks after planting. A second pot experiment was run on pine (Pinus pinea) trees to study the effect of hydrogel on the length of the survival period without any further irrigation. The rates of SAP used were 0, 2, 3 and 4 g hydrogel-kg of soil. Banding and mixing methods and clay and sandy clay were also used in this experiment. Results of the laboratory study showed that hydrogel increased water holding capacity of the sandy clay soil but had minor effects in the clay soil. The negligible effects of SAP in clay soils were verified by the field experiment where the use of hydrogels did not significantly benefit tree survival. The corn pot experiment indicated that banding hydrogel was more efficient than mixing it with the soil, especially in sandy clay soil. These results were confirmed by the second pot experiment where banding hydrogels significantly helped prolong the life span of pine seedlings. Therefore, it could be concluded that the use of hydrogel signific