Effects of amendments and hydrogel application on water retention, water release pattern, growth and yield performance of soybean-wheat cropping system

In a field experiment, water retention and release pattern of a sandy loam (Typic Haplustept) soil was studied along with growth and yield performance during 2009–10 in soybean-wheat cropping system. Main treatment included three amendment types namely FYM, tank soil applied @ 5 t ha⁻¹ and no amendments and sub-treatments included three rates of super hydrogel i.e. 5, 2.5 and 0 kg ha⁻¹, applied at 5-7cm depth along with seed in rows using a manual seed drill. Soil water content at various suction and soil water content changes during drying cycle after watering were monitored. Results revealed that changes in soil water content per unit change in suction became negligible after 100 kPa, therefore soil water content at 100 kPa suction was labeled as critical soil water content (CSWC). Soil water characteristic showed that at all suctions, water retained in gel treatments was always higher. In soybean, when pan evaporation ranged between 4–7 mm day,⁻¹ CSWC in FYM with gel treated plots reached in 14 days, whereas, in other treatments CSWC arrived early. In wheat, during early growth when pan evaporation ranged between 1–1.8 mm day⁻¹, CSWC arrived in 28 days in FYM with gel @ 5 kg ha⁻¹ treatment. Application of hydrogel @ 2.5 kg ha⁻¹ significantly increased the dry biomass, root growth, grain yield and water use efficiency over no hydrogel, while further increased in hydrogel application @ 5 kg ha⁻¹ growth parameters and water use efficiency increased marginally. Results further indicated that a mixture of both FYM and hydrogel was more efficient for improving hydraulic properties of the soil and crop growth parameters than applying each of them alone.