The role of superabsorbent Superab A200 in alleviating drought stress and its influence on nitrogen dynamics and soil alkaline phosphatase and urease activities

The growth and activity of microorganisms in arid soils have always been constrained withpersistent drought stresses. The aim of this study was to assess the role of superabsorbent Superab A200 in reducing drought stresses and its effect on N dynamics and enzyme activities of sandy and clay soils under laboratory conditions. A 2×4 factorial experiment consisting of two levels of soil moisture (30 and 70 % of the field capacity), and four levels of the superabsorbent (0, 0.1, 0.3 and 0.5 %, w/w) arranged in a completely randomized design with three replicates were carried out using two soil textures (sandy and clay). The application of the superabsorbent had a significant, positive effect on most measured properties. But the effect was largely depended upon the quantity of superabsorbent, soil texture and moisture level in the soil. Nitrogen mineralization, ammonification and nitrification rates, microbial biomass N, alkaline phosphatase and urease activities were significantly greater in the clay soils with 70% of the field capacity moisture than in the sandy soil with the same amount of moisture. This is likely due to the high level of C contents. Moisture and texture effects on most soil biological properties were significant. Results indicated that the cumulative ammonification and nitrification increased with increasing superabsorbent level where much of the increases occurred at lower levels than higher levels. The increase in nitrate and ammonium production with 0.1 % superabsorbent was greater than that with other superabsorbent levels.