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A THESIS Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Master of Science, Major: Mechanized Systems Management, Under the Supervision of Professors Suat Irmak and William Kranz. Lincoln, Nebraska: November, 2013

Copyright (c) 2013 Ali T. Mohammed

Note: A full text of this thesis is now available to the public for download at .


Water scarcity in many regions of the world, including Nebraska, is imposing increasing pressure on water demands in agriculture to meet future food and fiber demand of rapidly growing world populations. One of the viable alternatives to counter this challenge is cultivating new drought-tolerant hybrids/varieties/cultivars. Recently, new drought-tolerant maize (Zea mays L.) hybrids have been developed by major seed companies. However, it is essential to evaluate the performance of these hybrids, in terms of grain yield and crop water use (actual evapotranspiration) in various climatic and soil conditions under large production settings. Research was conducted at four locations across the state of Nebraska: Clay Center (SCAL), Concord (HAL), North Platte (WCREC) and Scottsbluff (MAL) during the 2010, 2011 and 2012 growing seasons to study such objectives. A total of four maize hybrids were investigated in the four-location study under three irrigation treatments: fully irrigated (FIT), early cutoff (ECOT) and rainfed treatments (RFT) with two planting populations: 59,300 and 84,000 plants ha-1. The maximum grain yields were 15.9, 14.8, and 18.0 Mg ha-1 which recorded under FIT across the four research sites for 2010, 2011, and 2012. Crop evapotranspiration

increased with irrigation amounts, seasonal cumulative ETa across the research sites ranged from 360 mm (under RFT at MAL site) to 755 (under FIT at MAL site) in 2010, from 301 mm (under RFT at MAL site) to 754 mm (under FIT at MAL site) in 2011, and from 220 mm (under RFT at HAL site) to 849 mm (under FIT at MAL site) in 2012.Crop water productivity was assessed to evaluate each hybrid performance, the highest CWUE and IWUE values were varied by site and years. The greatest CWUE of 3.46 kg m-3 was recorded for H3 hybrid (high population) under FIT at the SCAL in 2012. The greatest IWUE of 8.07 kg m-3 was recorded for H4 hybrid (high population) under ECOT at the SCAL in 2012.

Advisors: Suat Irmak and William Kranz