EFFECT OF HYDROGELS AND ORGANIC COMPOSTS ON SOIL HYDROPHYSICAL PROPERTIES AND ON PRODUCTION OF TOMATO

A two successive years field experiments with trickle irrigated tomatoes (Lycopersicon esculentum ‘448’) as the indicator plant, were conducted on a sandy soil at El-katta, Giza governorate, to study the conditioning effect of hydrogels when mixed with or grafted on organic composts, on production and use efficiency of water and fertilizers by growing plants. Examined treatments were: a) untreated soil, b) soil treated with 0.5 kg and 1 kg of organic compost (OM)/plant pit, c) soil treated with 2 and 4 g of polyacrylamide K polyacrylate gel (G)/plant pit, d) soil treated with mixtures of 0.5 kg OM + 1 g G, 0.5 kg OM + 2 g G, 1 kg OM + 1 g G and 1 kg OM + 2 g G /plant pit, and e) soil treated with 12.5 and 25 g of polyacrylamide K polyacrylate grafted on organic compost (grafted G)/plant pit. Applied conditioners positively affected hydrophysical properties of sandy soil. Tomato yields per unit of irrigation water or added fertilizers proved the importance of using either OM or G, or both, for increasing the agricultural potential of sandy soils under the severe conditions of our deserts, i.e., the limited water resources and the inadequate water retention and low fertility of such soils. Grafting G on OM proved to be an effective soil conditioner in sandy soil as it improves productivity and both water and fertilizers use efficiency by growing plants. The conditioning effect of studied treatments per plant pit decreased as follows: 25 g grafted G ≈ 1 kg OM +2 g G > 0.5 kg OM + 2 g G ≥ 4 g G > 1 kg OM + 1 g G ≥ 12.5 g grafted G > 0.5 kg OM + 1 g G ≈ 2 g G > 1 kg OM > 0.5 kg OM.