An Investigation on Physiological and Photosynthetic Parameters of Forage Maize at Regulated Deficit Irrigation and Partial Root Zone Draying Methods

Water shortage is the most important factor affecting crop production in the world. The deficit irrigation is a way to reduce water consumption in farming. The Partial Root- zone Drying (PRD) irrigation is a new improvement in deficit irrigation in which the half of the root zone is irrigated alternatively in scheduled irrigation events. In the fixed partial root zone drying (FPRD) the irrigation is fixed to one side of the root zone in the growing season. Maize is a drought sensitive crop. In maize, secondary traits related to drought resistance are considered in producing tolerate cultivars.
An experiment was conducted in order to investigate the effects of regulated deficit irrigation, variable partial root zone drying (PRD) and fixed partial root zone drying (FPRD) on the yield, physiological and photosynthetic parameters of forage maize (KSC 704) during the growing seasons of 2014 in Mashhad region. A factorial experiment based on randomized complete block design with four replications was carried out. The treatments included the full irrigation (FI) and the deficit irrigations (regulated deficit irrigation (DI) and the replacements of 80 % (DI80) and 60 % (DI60) of total water requirement, fixed PRD (FPRD) at 100% (FPRD100), 80% (FPRD80) and 60%(FPRD60) of water requirement, and variable PRD at 100% (PRD100), 80% (PRD80) and 60% (PRD60) of water requirement). Drip irrigation tapes were placed between plant rows. In the full irrigation and regulated deficit irrigation treatments, the plants were irrigated from two sides for every irrigation. In the PRD, one of two neighboring tapes was alternatively used for irrigation. In FPRD, a drip tape was used for two plant rows and irrigation was fixed to one side of the root. The irrigation interval was 3 days for all treatments. Dry and fresh forage yield, leaf area index (LAI), stomatal conductance, leaf relative water content (RWC) and chlorophyll content were measured.
All the measured traits were affected by the deficit irrigation. The highest fresh forage yield (72099 kg/ha) was produced by the full irrigation treatment. The statistical comparison showed that there was no significant difference between regulated deficit irrigation and PRD method for the fresh forage yield. But the FPRD treatment reduced the fresh forage yield. There was no significant difference between the fresh forage yield of FI and PRD80 treatments. The dry forage yield was affected by the different irrigation methods, irrigation levels and the interaction effects of the treatments All the measured traits were affected by the deficit irrigation. The highest fresh forage yield (72099 kg/ha) was produced by the full irrigation treatment. The statistical comparison showed that there was no significant difference between regulated deficit irrigation and PRD method for the fresh forage yield. But the FPRD treatment reduced the fresh forage yield. There was no significant difference between the fresh forage yield of FI and PRD80 treatments. The dry forage yield was affected by the different irrigation methods, irrigation levels and the interaction effects of the treatments (p According to the results, it seems that the negative effects of water stress on physiological and photosynthetic parameters in the early growing season is not significant and increases with the aging of the plants. Water stress decreases the absorption of carbon dioxide and the photosynthesis by reduction in the stomatal conductance. As well as, reducing the leaf area decreased photosynthetic area and the production of asymylats in the water stress conditions and ultimately reduced the forage yield significantly. The PRD method increased irrigation water productivity. With respect to this fact that no difference between the dry matter yield, LAI, chlorophyll content and RWC in the FI, PRD100 and PRD80 treatments was observed, it seems that applying Partial Root- zone Drying (PRD) method will result in lower water consumption during forage maize production at Mashhad environmental conditions.