The objective of this work was to investigate the influence of using each of rice straw (RS), agricultural gypsum requirements (AGR) and combination of them on improving soil physical and chemical properties. A sample of saline sodic, sandy clay loam soil, from the surface layer (0-30 cm) was taken from village 4 El-Tina plan, northern Sinai governorate – Egypt.
A greenhouse experiment was conducted, during winter of 2018/2019, three rates of RS was used: 0.5, 1 and 1.5%, also 6.8, 8.2, and 10.2 ton.fed-1of AGR after calculating the AGR to reduce the ESP for the control sample to 50, 60, 75%, respectively. In addition to combine of 0.5 % RS + each of 6.8, 8.2 and 10.2 ton.fed-1 AGR, each treatment was mixed with soil 30 cm depth in pots. The soil was incubated for one month before cultivation, with Spinach (Spinacia Oleracea, L), in 1st December, 2018 as a guide crop. The amount of irrigation water was determined by weighting each pot to keep the moisture content at the field capacity of each treatment plus 15% as a leaching requirement of applied water.
The obtained results indicated that, the adding (RS) or / and (AGR) led to increase the soil's ability to retain soil moisture content, porosity, water holding pore and H.C. Meanwhile, decreases soil bulk density, penetration resistance (PR), EC, ESP and pH in compared to control. The superior effect on improvement of these parameters was resulted in combine RS+AGR. Also effect of the treatments on these properties in 0-10 cm soil depth > 10-20 > 20-30 cm soil depth. The results revealed that the values of field capacity (FC), available water (AW), H.C, quickly drainable pores (QDP) and water holding pore (WHP) increased significantly by increasing the rate of RS and GR. Moreover, combine RS + each of 6.8, 8.2 and 10.2 ton.fed-1 AGR was increased highly significant effect on, FC , AW, H.C, QDP and WHP as compared to treated by RS, AGR alone or control. Also, it was decreased significantly on PR, bulk density and fine capillary pore. ESP valuesdecrease by leaching control was not considerable andthe soil remained sodic with highly ESP values. However, the final ESPobtained after leaching with amendments gave the highest decrease percent in ESP values by using combine 0.5% RS + each of 6.8, 8.2 and 10.2 ton. fed-1 AGR. Also, the fresh yield of Spinach was higher in soils receiving with increasing rates of AG amendment as compared to RS. The highest shoot spinach yield was, obtained by treatment by combine of 0.5% RS + each of 6.8, 8.2 and 10.2 ton. fed-1 AGR.