Development of forage maize yield–water functions by applying simultaneous different levels of irrigation and treated municipal wastewater

The aim of this study is to develop forage maize yield–water functions by applying different levels of irrigation and treated municipal wastewater. This research was conducted during May–August (2019 and 2020) in the field of the Marvdasht municipal wastewater treatment plant in a completely randomized block design with 12 treatments, 3 replications and 2 factors: (a) management of traditional deficit irrigation at 4 levels (full irrigation [FI] [100% irrigation requirement]) and deficit irrigation at 40, 60 and 80% levels of water requirement); (b) use of wastewater at 3 levels (wastewater [WW], one‐to‐one mixture of well water and wastewater [50/50], and well water [W]). Statistical models of evaluation were used to develop and evaluate yield–water functions and relative reduction in yield versus relative reduction in water consumption. The results of statistical evaluation of yield–water functions in three growth stages showed the relative advantage of yield–water functions of leaves in the vegetative stage, yield–water functions of stems in the flowering stage and yield–water functions of total dry matter in the grain‐ripening stage compared to other functions. The yield response factor (Ky) for total dry matter in the three stages of vegetative, flowering and ripening were 0.38, 0.52 and 0.63, respectively, and it was found that the most susceptible stage of maize growth to water deficiency was in the stage of grain ripening. Analysis of the interactive effect showed that the highest values of total dry matter yield in the vegetative and flowering stages, and grain yield in the ripening stage were 7260, 9857 and 3158 kg ha‾¹ in the WW‐FI treatment (full irrigation with wastewater), while the lowest levels of yield were 5052, 6069 and 1508 kg ha‾¹in the W‐DI60 treatment (60% deficit irrigation with well water). The results showed that the use of wastewater in traditional deficit irrigation conditions is beneficial for forage maize, so it can be recommended. Résumé Cette étude vise à développer des fonctions de rendement–eau du maïs fourrage en appliquant différents niveaux d'irrigation et d'eaux usées municipales traitées. Cette recherche a été menée de mai à août (2019 et 2020) dans le domaine de la station municipale de traitement des eaux usées de Marvdasht dans un plan en blocs complètement randomisé avec 12 traitements, 3 répétitions et 2 facteurs: (a) la gestion de l'irrigation déficitaire traditionnelle à 4 niveaux (irrigation complète (FI) (100