The aim of this work is to derive an equation to monitor the soil moisture suction (matric potential) using neutron scattering method in situ and effect of sodium and chlorine ions on neutron count ratio. The equation predicts the soil matric suction values to wilting point (15000 mbar). The derivative equation is: h,_mbar = h _b [{(a C.R + b) - q_r}^{-1/ m} (f -q_r )^{1/ m} –1]^{1/ n} Where:        h, is the soil matric suction, mbar (taken positive),            h _b, is the bubbling pressure (air entry suction, mbar),         a, is the regression coefficient of neutron calibration curve for the  Soil depth            under study,        b, is the intercept for y axis( soil moisture content),        C.R, is the neutron count ratio,        q_r, is the residual soil moisture content, cm3 cm-3,and        m,n , are the constants depend on fitting of soil moisture retention curve.                 This study was conducted in desert research center experimental station at Ras Sudr, south of Sinai at different soil depths. This investigated data show that the relationship between soil suction (h) and neutron count ratio (C.R) is inversely function, it can be predicted with matric suction above tensiometric range(0-850 mbar) up to wilting point (15000 mbar). The derivative equation is considered as a faster method to carryout the irrigation scheduling that detected the soil moisture suction in situ. As well as ions of sodium and chlorine have the biggest effect on neutron moderation at high soil matric suction, and summation of Na⁺ and CL^- at each soil layer had correlated with C.R at different soil suction below field capacity on the following relation:   (C.R = A + B/ S (Na⁺ and CL^-)