Effect of Deficit Irrigation and Partial Root Zone Drying (Fixed and Variable) on Root Growth Characteristics of Forage Maize

Irrigation management is one of the most important factors affecting the development and expansion of the plant root. The aim of this study was to investigate the effect of different deficit irrigation treatments on the root characteristics of fodder maize (KSC 704) in surface drip irrigation system. This research was conducted in agricultural research center of Khorasan Razavi during the 2014 growing season. A factorial experiment based on randomized complete blocks design with nine treatments and four replications was carried out. Treatments included full irrigation (FI), deficit irrigation (DI) and replacements of 80 and 60% of total water requirement, partial root zone drying (PRD) at 100, 80 and 60% of water requirement and fixed partial root zone drying (FPRD) at 100, 80 and 60% of water requirement. Water requirement was determined based on compensation of soil moisture deficit using an electromagnetic moisture meter. Water was measured by volume meters and distributed in the field. The first stress was applied at the 6-leaf stage of maize. Two weeks after applying the first deficit irrigation treatment in the 10-leaf stage of the plants, the first root sampling performed. Dry weight and volume, lateral and deep penetration of roots were measured at each sampling. The results showed that in all treatments the average amount of all measured traits decreased with decreasing water consumption. There was no significant difference among root dry weight of FI, PRD100 and PRD80 treatments. Root volume was affected by water stress but application of PRD80 method prevented the negative effects of water stress on root volume. Therefore, PRD method is more efficient compared to DI and FPRD methods when applied water stress, and water and nutrients will be absorbed at a higher level by root.