The sensitivity effect of maize growth stages on application of water uptake reduction functions, under salinity stress conditions

Simulation of water uptake amount during crop growth period, leads to optimal management of water consumption. This research was conducted on maize S.C 704 in lysimetric space (in Qazvin), in 2021. The research aim was simulation of salinity stress effect on crop water uptake amount. The experiment was performed as factorial and in a completely randomized design. The effect of soil salinity with levels of; 0.5(S1), 1.7(S2), 2.5(S3), 3.5(S4), 4.5(S5), 5.5(S6), 6.5(S7) and 7.5(S8) dS.m-1, were investigated in growth stages of initial(P1), development(P2), mid(P3) and late(P4). For simulating the amount of water uptake reduction in salinity stress conditions, the functions of Van Genuchten, Van Genuchten-Hoffman, Dirksen-Augustijn and Mass-Hoffman were used. Models calibration was done by real data in S1, S3, S5 and S7 treatments and models evaluation was done in S2, S4, S6 and S8 treatments. The models calibration was done once for whole growth period (by constant coefficients) and again by considering the crop growth stages sensitivity (by variable coefficients). The slope of water uptake reduction at P1 to P4 stages and whole growth period, was estimated to be 6.81%, 7.4%, 9.13%, 4.25% and 7.9%, respectively. The highest to lowest crop sensitivity to salinity stress was observed in P3, P2, P1 and P4 stages, respectively. The functions calibration for whole growth period, was less accurate for determining the water uptake amount. Evaluation statistics (CRM: -0.0005, EF: 0.993, R2:0.995, RMSE: 0.016 and ME:0.031) showed that the Mass-Hoffman function was optimal model for simulation the water uptake reduction. By considering the effect of crop growth stages sensitivity, were done a more accurate estimation of water uptake and actual crop water requirement amounts.