Impact of conservation management practices on greenhouse gas emission in semi-arid, intensively cropped regions of Texas

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Título:
Impact of conservation management practices on greenhouse gas emission in semi-arid, intensively cropped regions of Texas
Autor: McDonald, Mark David
Assuntos: Agriculture ; Carbon dioxide (CO2) ; Cotton nitrogen management ; Cover crops ; Greenhouse gas emissions ; Nitrous oxide ; No-tillage
Notas: http://hdl.handle.net/2346/74382
Descrição: The Texas High Plains (THP) region is known for cotton (Gossypium hiristum L.) production and the Dust Bowl. Cotton production on the THP is massive, producing about 15% of USA cotton. With large areas under agricultural production, tillage is often used to manage the soil. Tillage is effective at controlling weeds on the THP and for preparing and making beds, however wind erosion is a problem on the THP, and often intensive tillage is not well suited to the sandy soil and semi-arid climate of the THP. Following the events of the Dust Bowl, conservation tillage and cover crop use has increased on the THP, with about 48% of land in Texas being under some form of the two practices in 2012. There are numerous benefits to conservation tillage and cover crop use, namely reduced wind erosion and greater water holding capacity of the soil on the THP. The potential to reduce or mitigate greenhouse gas (GHG) emissions from the soil and increases in cotton lint yield and fiber quality are also benefits that have been seen in other areas of the USA. Even with the potential benefits of conservation tillage and cover crop use regarding wind erosion, water holding capacity, mitigation of GHG emissions, and increases in cotton production, producers can still be reluctant to implement these practices due to a lack of information regarding the changes that occur in cotton production due to implementation of these systems on the THP. This study aimed to quantify the changes in carbon dioxide (CO2-C) and nitrous oxide (N2O-N) emissions, cotton lint yield, and cotton fiber quality within the first two years of implementation of no-tillage with (NTW) and without (NT) a winter cover crop compared to a conventional tillage (CT) system, and nitrogen (N) fertilizer application management within these tillage systems. In addition, changes in soil nutrient concentrations, cover crop N uptake and carbon (C) assimilation, microbial community structure, and cotton plant N uptake and partitioning were determined to provide a whole system evaluation of no-till and cover crop implementation on the THP. The fluxes of CO2-C and N2O-N were affected by the time of year in which the data was collected as well as a response to the addition of N fertilizer in some cases. Tillage affected CO2-C and N2O-N flux as well, with a generally greater flux occurring in the NTW system. Cumulative emissions of CO2-C and N2O-N were affected by N treatment in 2016 and CO2-C emissions were affected by tillage in 2017. Cotton lint yield differed between years due to climatic conditions that also affected the lint yield and fiber quality in 2017. The NTW system provided protection from high temperatures and winds early in the 2017 growing season, resulting in a better stand and more mature cotton with stronger fibers compared to NT and CT systems. Carbon assimilation in the wheat cover crop was greater than the amount of C lost due to the increase in CO2-C emissions in 2017, which may be a potential avenue of mitigation. Vegetative uptake of N was greater in treatments with a pre-season application of N fertilizer, while seed assimilation of N was generally greater in treatments with a mid-season application. Microbial abundance was greater in 2016 than in 2017, and a negative linear relationship was determined between fungal and bacterial abundance in 2017. Soil parameters were largely unchanged, although differences in pH, nitrate-N and sulfur due to tillage were determined, while total N was affected by the interaction of tillage and N treatment. Through this study, it was determined that the implementation of an NTW system will not directly mitigate CO2-C and N2O-N fluxes or gross cumulative emissions but may indirectly affect net CO2-C emissions through C sequestration in the wheat herbage mass. Use of a cover crop and no-till increased lint yield in the second year of this study due to climatic mitigation and should be continued to be examined in subsequent years to determine further effects on cotton lint yield and fiber quality with a changing climate. Overall, some trends were observed regarding no-tillage and cover crop use with differing N fertilizer timings, although rarely was there an interaction effect between them. The lack of interaction suggests the need for further study of cover crops and conservation tillage systems in subsequent years to better characterize the effects these systems have on soil and cotton growth dynamics on the THP.
Data de criação/publicação: 2018
Idioma: Inglês

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Impact of conservation management practices on greenhouse gas emission in semi-arid, intensively cropped regions of Texas

McDonald, Mark David

2018

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