Bio-chemical properties of sandy calcareous soil treated with rice straw-based hydrogels

Completely randomized drip irrigated field experiments, with three replications for each treatment, were conducted at El-Saff-Giza Governorate, Egypt to evaluate the beneficial effects of applying the rice straw (RS)-based hydrogels as soil conditioners for sandy calcareous soil. In this respect three successive growing seasons (summer season 2010 using tomatoes vs. custle rock, winter season 2010–2011 using wheat vs. Seds 1 intercropped with onion vs. Giza 20, and summer season 2011 using caw pea vs. Bafb as indicator crops) were carried out. Two rice straw-based hydrogels (with two rates; 2 and 4 g kg−1 soil) were examined. After the third growing season some biochemical properties of the soil were determined.The results obtained show that, application of the investigated hydrogels positively affects bio-chemical properties of the soil. These effects are assembled in the following: (a) slightly decreasing soil pH, (b) increasing cation exchange capacity (CEC) of the soil indicating improvement in activating chemical reactions in the soil, (c) increasing organic matter (OM), organic carbon, total nitrogen percent in the soil. Because the increase in organic nitrogen surpassed that in organic carbon, a narrower CN ratio of treated soils was obtained. This indicated the mineralization of nitrogen compounds and hence the possibility to save and provide available forms of N to growing plants, (d) increasing available N, P and K in treated soil, and (e) improving biological activity of the soil expressed as total count of bacteria and counts of Azotobacter sp., phosphate dissolving bacteria (PDB), fungi and actinomycetes/g soil as well as the activity of both dehydrogenase and phosphatase.