Global Journal of Science Frontier Research, D: Agriculture and Veterinary, Volume 23 Issue 1

Soil moisture values were estimated gravimetrically in two dimensions x and y then converted to soil matric potential. The parallel soil electrical conductivity values were estimated in saturated soil paste and in 1:2.5 suspension, ECe and EC, respectively (Jackson, 1973) using EC meter, at 25 o C then converted to soil osmotic potential. The soil total potential was calculated using the additive function taking into account the SI unites and prefixes which figurate the states of soil water each day in the wetting and drying cycles. The soil stress index was calculated from equation (1). The plant stress index was calculated from equation (2). The soil hydraulic capacitance was calculated from equation (3). The strain of straw sap was calculated from the change of straw sap water potential between two days divided by the straw sap of the first one. The FORTRAN programing language was used to model the relation between the soil hydraulic capacitance and plant response functions which start to do on, (0/1), compensation according to. SSIMOD (Hegazy, 2022a). The model assumes that the soil-moisture profile is as a series of capacitors (each of which represents water storage in a given layer), which are linked via the variable (potential-dependent) resistance of unsaturated Darcian flow. When current flows from the atmosphere downward (analogous to infiltration), it charges up the capacitors, causing soil wetting up. That storage is subsequently discharged by continued downward drainage beyond the bottom of the root zone or by upward flow in response to atmospheric evaporation of moisture from the soil surface. Each layer in the root zone is also discharged by roots present within it, and the extracted water thus flows toward and through the stem to the canopy and then to the atmosphere in the process of transpiration, now and then, each wetting-drying cycle (Hillel, 2002). The latter evapotranspiration is weather controlled by the water's upward forces in plant and soil, the surface tension and capillarity (Fig. 4). As the salinity treatments are natural, the salinity levels 10.3 and 9.7 mS/cm are combined because both of them are approximately clayey texture and convergent to a similar salinity level. SSI= 1 n m 1 ∗ n m (m=1/n) (1) Where SSI: soil stress index. , n, m: hydraulic parameter could be predicted by HYDRUS 1D.- 4.17 (Simunek et al., 2013). Ψ, Ψ*: total soil potential at a given temporal or spatial condition and at optimum condition for wheat growth in the field under investigation, respectively. Ψ* could be predicted by HYDRUS 1D.-4.17 (Simunek et al., 2013) ( ) + = ( ) + −( ) ( ) + ( ( ) = = ) + ( ) = = Where SSI: soil stress index. Kc: crop coefficient. PSI: ratio between actual and potential transpiration. i: soil depth (cm). j: time (days). © 2023 Global Journals 1 Year 2023 32 Global Journal of Science Frontier Research Volume XXIII Issue ersion I VI ( ) a) The AMUN_SHC D The Modified Richard’s Equation for Assessing the Impact of Drought and Salinity in Arid and Semi-Arid Zones. Part Two: A Soil Hydraulic Capacitance