Grain sorghum in the hybrid-era, 1957-2008: yield with hybrid advancement and improved agronomic practices

dc.contributor.authorAssefa, Yared
dc.date.accessioned2010-04-28T16:11:07Z
dc.date.available2010-04-28T16:11:07Z
dc.date.graduationmonthMayen_US
dc.date.issued2010-04-28T16:11:07Z
dc.date.published2010en_US
dc.description.abstractGrain sorghum yield has notably increased from the beginning of hybrid production and commercialization in the late 1950s. The yield increases were the result of improved agronomic practices and hybrid advancement. The objectives of my research were: (1) to determine the magnitude of yield change in the hybrid era in irrigated and rain fed sorghum production, (2) to determine the contribution of agronomic and hybrid changes for yield in the hybrid era, (3) to investigate changes in sorghum morphology, physiology, and water use that contributed to yield increases, (4) to investigate changes that accompanied yield increase with hybrid improvement, and (5) to understand sorghum water and nutrient use and variations between hybrids in these regards. Fifty-two years of grain sorghum hybrid performance trial data (1957-2008), were analyzed and greenhouse and field studies were conducted on five selected hybrids to meet our objectives. The greenhouse and field studies were conducted from the summer of 2007 to the fall of 2009 on five selected hybrids, each representing a decade from the past fifty years. Results indicated that there was an increase in hybrid yield of nearly 50 kg ha-1 yr-1 in dryland sites over the 52 yrs (1957-2008) analyzed. Irrigated grain sorghum yields, however, remained unchanged over the same period. Agronomic practices such as planting date, phosphorus fertilizer use, and planting density changed over these years but were not found to contribute to increased dryland sorghum yields. There was no difference found between old and new hybrids tolerance to different densities. Hybrid advancement and increased nitrogen fertilizer application were responsible for changes in dryland yields. Total water use changed with hybrid advancement. New hybrids used the greatest total water and also had greater root-to-total biomass ratio than the old hybrids. Leaf biomass was also greater for the newest hybrid. There was a difference in amount of total nutrients extracted by hybrids, and there were differences among hybrids in allocation of nutrients to different tissues. In general the yield focus of sorghum hybrid development was effective in dryland sorghum production, likely because of intentional or inadvertent selection of hybrids with better drought tolerance. Results indicated that breeding programs created hybrids with improved morphological characteristics that might have resulted in better resource use (water and nutrient) and ultimately increased yield.en_US
dc.description.advisorScott A. Staggenborgen_US
dc.description.degreeDoctor of Philosophyen_US
dc.description.departmentDepartment of Agronomyen_US
dc.description.levelDoctoralen_US
dc.description.sponsorshipKansas Sorghum Commission; Kansas Center for Sorghum Improvementen_US
dc.identifier.urihttp://hdl.handle.net/2097/3753
dc.language.isoen_USen_US
dc.publisherKansas State Universityen
dc.subjectSorghumen_US
dc.subjectHybrid advancementen_US
dc.subjectWater useen_US
dc.subjectMorphologyen_US
dc.subjectPhysiologyen_US
dc.subject.umiAgriculture, Agronomy (0285)en_US
dc.subject.umiAgriculture, Soil Science (0481)en_US
dc.subject.umiBiology, Plant Physiology (0817)en_US
dc.titleGrain sorghum in the hybrid-era, 1957-2008: yield with hybrid advancement and improved agronomic practicesen_US
dc.typeDissertationen_US

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