Comparison of deficit irrigation management strategies on root, plant growth and biomass productivity of silage maize

Knowledge about biomass partitioning of maize grown in arid and semi-arid climates is scarce and yet essential to select a robust and effective deficit irrigation management (DIM) strategy for these regions. The objectives of this study were to: i) investigate the effects of different levels of water application under two DIM strategies on the root and aboveground characteristics, the response factor to water stress (K-y) and irrigation water use efficiency (IWUE) of silage maize at different growth stages, and ii) determine the best DIM strategy that would maximize biomass productivity. Field pot experiments were conducted in Isfahan, Iran, during 2009 and 2010. The two DIM strategies were fixed irrigation interval-variable irrigation depth (M-1), and variable irrigation interval-fixed irrigation depth (M-2). Each DIM strategy was tested at four water-deficit levels, including: severe, moderate, mild, and a full-irrigation. In M-1, irrigation intervals were consistent for all irrigation treatments but Were varied over the growing season. Treatment effects were measured at the 10-leaf, 16-leaf, tasseling, milk, and silage harvest crop growth stages. There was significant effect of irrigation and growth stage on total aboveground biomass (TB), leaf area (LA), root biomass (RB), and root:shoot ratio (RSR) for both DIM strategies during the two years. For M-2, there was significant difference in TB, LA, RB, and RSR between all irrigation levels at all growth stages. TB production was on the average around 25% higher for M-1 compared to M-2, even though total applied irrigation water was only 6% higher for M-1. Comparing the two DIMs showed that RSR and K-y were both higher for M-2, indicating that the crop was more sensitive to this strategy. In conclusion, M-1 was selected as the best management practice since it had more favorable effects on improving the IWUE and also on the development of maize roots during the growing season. (C) 2016 Elsevier B.V. All rights reserved.