نوع مقاله : مقاله پژوهشی
نویسنده
گروه علوم و مهندسی آب، دانشکده کشاورزی و منابع طبیعی، دانشگاه بین المللی امام خمینی(ره)، قزوین، ایران.
چکیده
کلیدواژهها
موضوعات
عنوان مقاله [English]
نویسنده [English]
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.
کلیدواژهها [English]
EXTENDED ABSTRACT
Due to the reduction of soil water potential in salinity stress conditions, the amount of water uptake and transpiration of crop decreases. By using the water uptake reduction functions (Such as models of Mass and Hoffman (1977), Van Genuchten and Hoffman (1984), Dirksen and Augustijn (1988) and Homaee et al (2002b)), the amount of crop water uptake is simulated under salinity stress conditions. In past researches, the water uptake reduction functions were evaluated by the constant coefficients in the crop growth period. But the aim of this research is to investigate the effect of maize growth stages sensitivity on the application of water uptake reduction functions.
This research was conducted on maize S.C 704, in Qazvin region in 2021. The experiment was performed as factorial and in a completely randomized design. The effect of soil salinity and crop growth stage sensitivity were investigated on the amount of crop water uptake. The soil salinity treatments (main factor) were defined at 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 and the growth stages (sub-factor) were consisted of initial (P1), development (P2), mid (P3) and late (P4) steps. 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. The calibration of models (functions) was done by real data in treatments of S1, S3, S5 and S7 and the evaluation of models was done in treatments of S2, S4, S6 and S8. The calibration of models was done once for the whole growth period (by constant coefficients) and again by considering the crop growth stages sensitivity (by variable coefficients).
Due to the salinity stress, the soil water potential, water uptake and transpiration of crop was decreased. At different soil salinity levels (from S1 to S8 treatment), the slope of water uptake reduction at P1 to P4 growth stages and whole growth period, was estimated to be 6.81%, 7.4%, 9.13%, 4.25% and 7.9%, respectively. Therefore, the highest to lowest crop sensitivity to salinity stress was observed in P3, P2, P1 and P4 growth stages, respectively. The crop water uptake efficiency was decreased by salinity stress, and its effect was different in crop growth stages. By knowing the crop sensitivity in growth stages, the amount of water use is determined according to the actual water requirement of crop. The results showed that in a specific model, the function coefficients were different in the growth stages. Therefore, the functions calibration for whole growth period (with a constant coefficient) was less accurate for determining the water uptake during the growth period. Among the different models (with variable coefficients), the priority of choosing the optimal model was given to models of Mass-Hoffman, Van Genuchten, Van Genuchten -Hoffman and Dirksen- Augustijn, respectively.
By using the separate coefficients for each growth stage, a more accurate prediction of water uptake reduction under salinity stress is performed. Evaluation statistics of CRM, EF, R2, RMSE and ME with the values of -0.0005, 0.993, 0.995, 0.016 and 0.031 showed that the Mass-Hoffman function (with variable coefficients) was the optimal model for simulation the water uptake reduction. As a result, by calibration of functions in the crop growth stages, the actual amount of water uptake is simulated.
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