Browsing by Subject "Sustainability and the environment"
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Item Agroecology of three integrated crop-livestock systems in the Texas High Plains(2012-05) Zilverberg, Cody; Allen, Vivien G.; Johnson, Phillip N.; Galyean, Michael L.; Moore-Kucera, Jennifer; Villalobos, Carlos; Kellison, RickTechnological advances have enabled agriculture to feed and clothe a growing global population with great success. It is now imperative that we remain productive while halting the natural resource degradation that often accompanies high productivity. In the semi-arid Texas High Plains, sustainability of current agricultural practices is threatened by depletion of the Ogallala aquifer and soil erosion. Perennial grasses, the region’s historic vegetation, can build soil rather than lose it and require little or no supplemental irrigation. We designed and tested three agroecosystems that integrated crop and livestock production using a base of perennial forages. All systems were designed to decrease water withdrawals from the Ogallala aquifer relative to conventional irrigated agriculture. The experiment covered a total of 42 ha in a randomized block design with three blocks. The non-irrigated system, DRY (evaluated from 2004 to 2008), included a paddock of native perennial grasses and a rotation of cotton (Cynodon dactylon [L.] Pers.) and foxtail millet (Setaria italica [L.] P. Beauv.). The buffer-irrigated system, LOW (evaluated from 2009 to 2011), was the same as DRY except that LOW added an irrigated paddock of ‘WW-B. Dahl’ old world bluestem (Bothriochloa bladhii [Retz] S.T. Blake; hereafter bluestem), which was harvested for grass seed as well as grazed. The limit-irrigated system, MED (evaluated from 2007 to 2011), included two irrigated paddocks of bermudagrass that were grazed and harvested for hay, and one paddock of bluestem that was grazed and harvested for grass seed. Angus beef stocker steers (Bos taurus L.; initial BW: 245 kg) sequence-grazed each system. We evaluated these systems with a variety of criteria, including forage and animal production, water use, crop yields and quality, forage quality, soil C fractions, soil penetration resistance, forage species stability, economic performance, fossil fuel energy use, and C emissions associated with fossil fuel use. We found that each system had strengths and weaknesses. Annual irrigation water use by each system was: DRY, 0 mm; LOW, 44 mm; and MED, 229 mm. The MED system was the most productive, yielding 446 kg steer live weight gain ha-1, compared with 107 for LOW and 57 for DRY. Bermudagrass yielded the most animal unit grazing days ha-1 (644; bluestem: 246; native grasses: 90; annuals: 41) of any forage and was the highest quality forage with the exception of the annual, foxtail millet. Bermudagrass also had the highest soil concentration of particulate organic matter C (3.1 g kg-1 soil in top 5 cm; native grass: 2.5; bluestem: 2.1), an indicator of higher potential nutrient mineralization and soil C accumulation. The annual fields had the lowest levels (1.3 g kg-1 soil in top 5 cm); however, the MED system was the worst economic performer and emitted the most C (774 kg C ha-1; LOW: 226; DRY: 205) as a consequence of fossil fuel use. In contrast, DRY produced the least amount of grazing (72 animal unit grazing days ha-1; LOW: 76; MED: 434), but was the most profitable and used no irrigation water. Although productivity of DRY and LOW were less than MED, LOW and MED beef carcasses were of equivalent quality (68% USDA Choice; DRY was not evaluated) and cotton lint from DRY and LOW received price premiums in all years (mean $0.024 and 0.106 kg-1, respectively). The lessons learned from this experiment should be used to design future agroecosystems that conserve soil and water while producing agricultural goods. Relative to annual and perennial non-irrigated paddocks, applying irrigation and N to introduced forages increased productivity and accelerated soil C sequestration, but the additional inputs were not justified economically. It may be more profitable to integrate, at the farm or landscape scale, large areas of non-irrigated native grasses in combination with smaller areas of intensively farmed, high-value crops that receive irrigation and fertilizer. Ley farming, which includes long rotations of perennial grass with annual crops, is one option that may hold promise for the future.Item Optimal groundwater use and dryland adoption utilizing the hotelling framework in the southern high plains(2012-05) Principe, Jonathaniel; Farmer, Michael; Benson, Aaron G.; Ellingson, Leif; Wang, ChenggangInterest in nonrenewable resources has ignited numerous economic and public policy debates on long-term sustainability issues. On the Southern High Plains (SHP), functionally nonrenewable groundwater for agricultural irrigation has received significant attention given the central role of the agricultural sector to the regional economy. Current policies center on conservation, which is not equivalent to a policy of sustainability. Currently irrigation restrictions are being implemented under the so-called 50/50 Management Goal for the SHP where 50 percent of the saturated thickness of the Southern Ogallala Aquifer will be maintained in 50 years. This evades the central issue and causes several unintended consequences that interfere with true overall economic stability in the long run. Over draft of the aquifer is inevitable. Recharge cannot support even minimal levels of pumping for agriculture. So from an agricultural and economic perspective, the economic centrality of irrigated agriculture to the local economy which cannot be sustained classifies the Ogallala as a nonrenewable resource. This work then treats aquifer management directly as a nonrenewing resource and looks to the Hotelling nonrenewable resource model adapted to the SHP conditions. Groundwater research in the SHP has increasingly focused on the relevance of long-term issues. With a few exceptions, studies that have modeled the SHP aquifer decline tend to use the conventions to pre-set the planning period, thereby fixing a final groundwater target exogenously at some period. Targets may be a 50/50 Management Goal or depletion of the aquifer at a set, pre-fixed time. However, these modeling conveniences do not endogenize the terminal and transition period out of irrigated agriculture to other systems, such as dryland farming or other renewable energy systems. A pre-fixed end date used to compare policies misses many of the responses of producers and thereby over-estimates or under-estimates the long run impacts of a policy, such as the 50/50 rule. In this study, we develop a simple and surprisingly tractable behavioral model under certainty and with some attention to risk on groundwater utilization in the SHP. This groundwater model retains the main features of the Hotelling framework: that producers will consider the economic effects of the last quantities of applied irrigation today on the profitability of irrigation tomorrow, and producers try to balance these economic trade-offs. What is perhaps surprising is that the assumed decision process is a lot less complex than more standard or classical exemplars of the Hotelling framework. Guided by the Hotelling insight, we model economic decisions that fully endogenize the terminal period for irrigated agriculture (the time period when producers choose to discontinue irrigation applications). We use this decision rule to conduct policy analysis on irrigated agriculture conversion to evaluate several social outcomes of interest: timing of abandonment of irrigated agriculture, welfare of farmers today and in the future, and groundwater levels remaining after transition. Finally, we evaluate by illustration the benefits of specific timetables for research and development to increase dryland profitability as a direct sustainability program rather than the current conservation focus, an alternative public program that takes non-renewability seriously. Evaluation of a groundwater use restriction shows that the objective of water conservation is clearly attained in terms of water left in the aquifer on transition; but at the expense of welfare of producers in the future. This is because the restriction does not retain producers in irrigated agriculture longer but the reduced income induces producers to leave sooner, experiencing not a ‘soft’ transition but a much more disruptive and abrupt economic decline. Restrictions abbreviate rather than extend irrigated agriculture. Compared to the optimal groundwater use of producers operating under market conditions, the potential loss in incomes has the greatest adverse impact in the long-run on farmers that have lower levels of initial groundwater stock. So a restriction policy mostly injures the worst off farmers in terms of water stocks i.e. initial saturated thickness overlying their land. Results also show that providing a more profitable dryland alternative early on mitigates the adverse economic and economic and long run social disruption of a restriction policy over time. An example of a modest research and development strategy reveals that farmers will do far better with dryland research that commences immediately; the sooner they know or form expectations with regard to clear and more tangible outcomes of research and development, the more stable is their economic performance. Research and development discoveries that arrive in a ‘just in time’ fashion for transition are shown to be far less effective since it arrives too late to stabilize the regional economic activity. This study has ramifications on policy formulation in the future for managing groundwater resources such as questions on continuing irrigation and water use efficiency as a conservation policy or pursuing more aggressive dryland research as a direct sustainability policy for the nonrenewable groundwater resource. These are important aspects to consider in the long-run given that agriculture is a pivotal industry here in the SHP and the sense of urgency in current policy debates and allocation of resources towards these policies.Item Tracing the roots of the sustainable sites initiative(2012-05) Casanova, Christine; Kvashny, Alon; Klein, Charles H.; Cox, Robert D.It is a commonly held that there is a powerful triumvirate to a perfect storm: High pressure, low pressure and that which is at risk. In the year 2011, on planet earth, it is profoundly true that mankind is in the midst of a perfect storm. This storm is challenging him to examine modern life as he knows it, is provoking him to meet change, and is most certainly shifting him to a new paradigm of existence. This storm is the sustainability movement. While architecture and structural disciplines currently have a formalized working framework to evaluate sustainability in building, Landscape Architecture has not previously used a ratified or professional method of evaluating conservation and sustainability efforts in performance. In 2009 The American Society of Landscape Architects (ASLA) in a collaborative effort with The Lady Bird Johnson Wildflower Center and The United States Botanical Garden developed the Sustainable Sites Initiative (SSI or SITES) offering an index for measuring sustainability in landscape practices. The purpose of this study is to track the winds of this perfect storm, to investigate pressures brewing in this revolution, to look at the environmental risks we face, to analyze the codependence between the factors and to prove how they influence the guiding principles of this SITES initiative. In a cursory exercise the author will examine the utility of this rating system as applied to a design on a given site based on a demanding program for capturing sustainable opportunities. This exercise should approximate the experience of an entry level professional using the new criteria and guidelines and offer insight to the SITES program as it emerges to encourage and impact sustainable outcomes in land planning and development.