Browsing by Author "Andales, Allan, committee member"
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Item Open Access Comparative profitability of irrigated cropping activities for temporary water transfers(Colorado State University. Libraries, 2019) Kelley, Timothy, author; Mooney, Daniel, advisor; Goemans, Christopher, committee member; Andales, Allan, committee memberIn response to a projected gap in water supply and demand, Colorado's Water Plan calls for up to 50,000 acre-feet of temporary water transfers from agricultural to municipal and industrial uses by 2030. Water stakeholders, however, want to avoid buy and dry scenarios, implying that a portion of agricultural water-right holders' consumptive use (CU) should remain available for on-farm agricultural production. Alternative Transfer Methods (ATMs) represent the regulatory mechanisms that enable temporary water transfers without permanent drying of agricultural land. To participate in an ATM, water-right holders must first establish a historical consumptive use (HCU) baseline which can then be allocated to agricultural production or temporary transfer. When faced with less water, producers may pursue several management options, including: rotational fallow, deficit irrigation, changes to crop mix, or changes to other practices like harvest timing. Yet, previous research on the risk profile of these options and their effect on producers' expected adaptation behavior is limited. This research develops a framework to compare the expected profitability of irrigated cropping activities, and in doing so, accounts for differences in risk and water-leasing potential. The framework is applied to a case study of twelve selected irrigated cropping activities on a well-drained silt loam soil in northeastern Colorado using stochastic enterprise analysis. Specifically, we compare gross margins for two corn (grain and silage) and two alfalfa (two cut and three cut) cropping enterprises on a per water-unit basis (one unit equals 12.94 acre-inches of CU); each under full irrigation, deficit irrigation, and partial fallow water management strategies. First, we simulate producers' expectations about gross margins based on empirical distributions of precipitation, price, and cost data for 1992 – 2017 and the FAO crop water production function. Second, we employ econometric analysis of the first, second, and third moments of the simulated gross margin distributions to estimate a risk premium for each activity. Fully-irrigated corn is set as the reference activity (one acre requires 1 water-unit of irrigation or 12.94 acre-inches of CU) and we find that crop choice, harvest timing, and deficit/fallow strategies all significantly affect producers' risk exposure relative to the reference activity. Activities remaining in the efficient set are primarily the rotational fallow strategies which would enable 3.24 – 7.14 acre-feet of CU to be leased for every twelve water-units of their HCU baseline enrolled in an ATM at a breakeven cost of $386.05 to $791.51 per acre-foot. More land could be maintained in agricultural production for an identical amount of transferable water under deficit irrigation, but it would typically come at a higher breakeven cost of $381.95 to $850.19 per acre foot depending on the producers' choice of crop and harvest strategies. The results should be of interest to academic, producer, and policy audiences, respectively, as they provide insight on (i) a novel methodology for comparing irrigated cropping activities that incorporates expected profitability, risk, and leasable water into a single metric, (ii) a ranking of potential adaptation strategies for producers who participate in ATMs, and (iii) insight into the economic tradeoffs between maintaining agricultural working land while also allowing for temporary water transfers to other beneficial uses.Item Open Access Comparison of soil properties and Kentucky bluegrass shoots mineral composition prior to and after 10-11 years irrigation with recycled water(Colorado State University. Libraries, 2016) Lin, Yuhung, author; Qian, Yaling, advisor; Davis, Jessica, committee member; Klett, James E., committee member; Andales, Allan, committee memberIn Colorado, fresh water is one of the most valuable and limited natural resources. Due to population growth, an increase of fresh water withdrawal has been reported by U.S. Geological Survey. Irrigation with recycled water has been utilized as a means to alleviate the stress on potable water supplies and facilitate the reuse of treated wastewater. Recycled water irrigation is taking place at landscape sites such as public parks, golf courses, and school playgrounds. Research information is needed to better understand the long-term effects of recycled water irrigation on urban landscapes. Therefore, the objectives of this research were to: 1) assess changes in soil chemical properties after 5 and 11 years of recycled water irrigation, 2) determine if there is any heavy metal accumulation in soil after 11 years of recycled water irrigation, 3) evaluate Kentucky bluegrass (Poa pratensis L.) (KBG) turf quality grown on golf courses irrigated with recycled water, and 4) determine the relationship of turf quality to shoot mineral concentrations and soil chemical properties. To address Objectives 1 and 2, soil samples were collected and analyzed at the commencement (in 2004) and 11 years after recycled water irrigation on three golf courses, 5 metropolitan parks, 1 school ground, and 1 zoo. Samples were taken at 0-20, 20-40, 40-60, 60-80, and 80-100 cm depths on golf courses and at 0-20 and 20-40 cm depths at other locations. Soil was analyzed for texture, soil pH, soil organic matter, soil salinity [soil electrical conductivity (EC)], exchangeable sodium percentage (ESP), cation exchange capacity (CEC), nitrate-N, chloride (Cl), boron (B), and AB-DTPA extracted phosphorus (P), iron (Fe), manganese (Mn), arsenic(As), chromium (Cr), cadmium (Cd), cobalt (Co), nickel (Ni), lead (Pb), zinc (Zn) and copper (Cu). Averaging over all sites, soil pH was 0.25-0.3 higher in 2015 and 2009 than in 2004. The increase was greater at deeper depths. Soil salinity (EC) was 0.84, 0.88, and 0.98 dS m-1in 2004, 2009 and 2015, respectively. The magnitude of increase in ESP after recycled water irrigation indicated potential sodicity problems. Calcium based product applications reduced ESP at soil surface depths. In contrast, significant increase in ESP was found at deeper soil depths. No increase in soil nitrate-N was observed over 5 and 11 years with recycled water irrigation, therefore, leaching of nitrogen to the groundwater was not a great concern. AB-DTPA extracted As, Co, and Ni decreased after 11 years of recycled water irrigation. Soil Cd, Cr, Cu, Pb, and Zn did not show significant change from 2004 to 2015. Results revealed that there was no sign of heavy metal accumulation. To address Objectives 3 and 4, research was conducted on eight golf courses, including three courses in Denver after 10 years of recycled water irrigation, three courses in the nearby cities receiving recycled water for more than 10 years, and two courses receiving fresh surface water for irrigation. Results indicated that Na concentration in KBG shoot tissues increased by 4.3-9.9 times, Cl by 1.5-1.3 times, B by 1.3-3.5 times whereas K/Na ratio was reduced by 74-90%. Multiple regression analysis indicated shoot Na accumulation had the highest association to turf quality decline (R2= 0.65). Soil sodium adsorption ratio (SAR) in 0-20 cm depth was highly associated with KBG shoot Na concentration (R2= 0.70).Item Open Access Developing a modified SEBAL algorithm that is responsive to advection by using limited weather data(Colorado State University. Libraries, 2014) Mkhwanazi, Mcebisi, author; Chávez, José, advisor; Andales, Allan, committee member; Ham, Jay, committee member; Trout, Thomas, committee memberThe use of Remote Sensing ET algorithms in water management, especially for agricultural purposes is increasing, and there are more models being introduced. The Surface Energy Balance Algorithm for Land (SEBAL) and its variant, Mapping Evapotranspiration with Internalized Calibration (METRIC) are some of the models that are being widely used. While SEBAL has several advantages over other RS models, including that it does not require prior knowledge of soil, crop and other ground details, it has the downside of underestimating evapotranspiration (ET) on days when there is advection, which may be in most cases in arid and semi-arid areas. METRIC, however has been modified to be able to account for advection, but in doing so it requires hourly weather data. In most developing countries, while accurate estimates of ET are required, the weather data necessary to use METRIC may not be available. This research therefore was meant to develop a modified version of SEBAL that would require minimal weather data that may be available in these areas, and still estimate ET accurately. The data that were used to develop this model were minimum and maximum temperatures, wind data, preferably the run of wind in the afternoon, and wet bulb temperature. These were used to quantify the advected energy that would increase ET in the field. This was a two-step process; the first was developing the model for standard conditions, which was described as a healthy cover of alfalfa, 40-60 cm tall and not short of water. Under standard conditions, when estimated ET using modified SEBAL was compared with lysimeter-measured ET, the modified SEBAL model had a Mean Bias Error (MBE) of 2.2 % compared to -17.1 % from the original SEBAL. The Root Mean Square Error (RMSE) was lower for the modified SEBAL model at 10.9 % compared to 25.1 % for the original SEBAL. The modified SEBAL model, developed on an alfalfa field in Rocky Ford, was then tested on other crops; beans and wheat. It was also tested on well-irrigated corn and also corn under deficit irrigation. The modified SEBAL model performed fairly well in wheat and beans, just slightly underestimating ET, and it performed well with irrigated corn. However, modified SEBAL, similar to the original SEBAL and also METRIC, could not accurately estimate ET for drier conditions or at early stages of plant growth.Item Open Access Estimating farmers' willingness to pay for improved irrigation: an economic study of the Bontanga Irrigation Scheme in northern Ghana(Colorado State University. Libraries, 2012) Alhassan, Mustapha, author; Frasier, Marshall, advisor; Loomis, John, advisor; Davies, Stephen, committee member; Andales, Allan, committee memberThis thesis estimates the willingness of farmers under the Bontanga Irrigation Scheme (BIS) in Northern Ghana to pay for improved irrigation services. The Contingent Valuation Method (CVM) was used in this study and farmers were randomly selected for interviewing based on the location of their farms (upstream, middle, and downstream) within the scheme. The payment card elicitation format was used and the data were analyzed using Maximum Likelihood Estimation (MLE) procedure that is capable of accommodating the intervals in payment card data. The mean willingness to pay was found to be GHC 16.32 (US$ 8.50) per ha per year and the median was GHC 14.00 (US$ 7.29) per ha per year. Tobit regression model was also used to estimate the mean number of labor days farmers under the scheme would be willing to contribute to improve the project. The mean labor days was found to be 5.26 days per year and the median was 5.28 days per year.Item Embargo Evaluation of salinity tolerance of pinto bean varieties(Colorado State University. Libraries, 2024) Paul, Winie Sharsana, author; Davis, Jessica G., advisor; Qian, Yaling, committee member; Andales, Allan, committee memberSalinity is an abiotic stress restricting agricultural crop production globally, primarily in arid and semi-arid areas. Saline soils are characterized by the accumulation of dissolved salts in the soil solution, which inhibits a plant's ability to absorb water and nutrients. Many crops are affected by high concentrations of salt in the soil. Dry edible pinto beans (Phaseolus vulgaris), very important in human nutrition around the world, are sensitive to salinity, and yield losses can occur in saline soils greater than 2 dS/m. The objective of this study was to assess the salinity tolerance of regular and slow darkening pinto bean varieties by evaluating the effect of different salt types on pinto bean germination, growth, and production. This project included three experiments: germination, greenhouse, and field studies. For the first two experiments, six varieties of pinto beans were evaluated: three slow-darkening pinto beans (Gleam, Mystic, Lumen) and three regular pinto beans (Othello, Cowboy, SV6139). In the germination experiment, treatments were arranged in a randomized complete block design with five replications, three saline solutions (NaCl, CaCl2, MgSO4.7H2O (MgSO4)), and control (distilled water) at 0.05 M, 0.1 M, and 0.15 M concentrations for each salt. For the greenhouse experiment, saline solutions with the same electrical conductivity (ECe) (dS/m), control (distilled water) and the six pinto bean varieties were organized in a Complete Random Design (CRD) with 10 replicates. The field experiment was an observational study where six pinto bean varieties: three slow-darkening pinto beans (Gleam, Mystic, Vibrant) and three regular pinto beans (Othello, Cowboy, SV6139) were planted in a field with a subsurface irrigation system to correlate yield to ECe for each variety. The results demonstrated that germination percentage, speed of germination and hypocotyl length decreased as the salt concentrations increased. Othello's vegetative and reproductive parameters were significantly higher compared to the other varieties in the greenhouse under the saline conditions. There was no significant correlation between yield and ECe in the field experiment. Results indicated that Othello's early maturity may have enabled it to perform better under salt stress conditions than the other tested varieties.Item Open Access Investigating the salinity impacts on current and future water use and crop production in a semi-arid agricultural watershed(Colorado State University. Libraries, 2024) Hosseini Ghasemabadian, Pardis, author; Bailey, Ryan T., advisor; Arabi, Mazdak, committee member; Smith, Ryan, committee member; Andales, Allan, committee memberSoil salinity can have a significant impact on agricultural productivity and crop yield, particularly in arid and semi-arid irrigated watersheds wherein irrigation and inadequate drainage often combine to increase salt ion concentrations in soil water. In conjunction with intense irrigation in semi-arid agricultural regions, increasing population resulting in boosted water demand, adverse impacts of climate change on water availability, in other words, water scarcity, future land use and land cover changes, changes in applied irrigation practices, and introducing new point-sources and non-point sources of salinity in the region all can govern the salinity and crop yield consequently. Taking into account the aforementioned impactful components on crop reduction via salinity increase, the overall objective of this dissertation is to provide insights for policymakers to better address the current and future salinity issues to sustain crop production in semi-arid regions under progressive salinity. This will be accomplished by i) investigating the controlling factors on salinity in the soil, groundwater, and river water using the SWAT-Salt model which simulates the reactive transport of 8 major salt ions in major hydrological pathways applied to a 1118 km2 irrigated stream-aquifer system located within the Lower Arkansas River Valley (LARV) in southeastern Colorado, USA ii) Assessing the salinity impacts on crops production blue and green water footprint as a measurable indicator for water being used per unit of a given crop production using the SWAT-MODFLOW-Salt model applied to a 732 km2 irrigated stream-aquifer system located in the LARV, iii) quantify the impact of environmental factors alteration including changes in climatic and irrigation practices in the LARV on future salinity content and its impact on crop production in the region using the SWAT-MODFLOW-Salt model. To control salinity, more importantly in semi-arid irrigated areas, the principal step is to identify the key environmental and hydrologic factors that govern the fate and transport of salts in these irrigated regions. To accomplish this objective, global sensitivity analysis was applied to the newly developed SWAT-Salt model (Bailey et al., 2019), which simulates the reactive transport of 8 major salt ions (SO4, Ca, Mg, Na, K, Cl, CO3, and HCO3) in major hydrologic pathways in a watershed system. The model was applied to a saline 1118 km2 irrigated stream-aquifer system located within the Lower Arkansas River Valley in southeastern Colorado, USA. Multiple parameters including plant growth factors, stream channel factors, evaporation factors, surface runoff factors, and the initial mass concentrations of salt minerals MgSO4, MgCO3, CaSO4, CaCO3, and NaCl in the soils and in the aquifer were investigated for control on salinity in groundwater, soils, and streams. The Morris screening method was used to identify the most sensitive factors, followed by the Sobol' variance-based method to provide a final ranking and to identify interactions between factors. Results showed that salt ion concentration in soils and groundwater was controlled principally by hydrologic factors (evaporation, groundwater discharge and up flux, and surface runoff factors) as well as the initial amounts of salt minerals in soils. Salt concentration in the Arkansas River was governed by similar factors, likely due to salt ion mass in the streams controlled by surface runoff and groundwater discharge from the aquifer. Sustainable agriculture in intensively irrigated watersheds, especially those in arid and semi-arid regions, requires improved management practices to sustain crop production. This depends on factors such as climate, water resources, soil conditions, irrigation methods, and crop types. Of these factors, soil salinity and climate change are significant challenges to agricultural productivity. To investigate the long-term impact of salinity and climate change on crop production from 1999 to 2100 in irrigated semi-arid regions, we applied the water footprint (WF) concept using the hydro-chemical watershed model SWAT-MODFLOW-Salt, driven by five General Circulation Models (GCMs) and two climate scenarios (RCP4.5 and RCP8.5), to a 732 km2 irrigated stream-aquifer system within the Lower Arkansas River Valley (LARV), Colorado, USA. In this study we estimated the green (WFgreen), blue (WFblue), and total (WFtotal) crop production WFs for 29 crops in the region, both with and without considering the impact of salinity on crop yield. The results indicate that during the baseline period (1999-2009), the total annual average WFgreen, WFblue, and WFtotal increased by 7.6%, 4.4%, and 6.5%, respectively, under salinity stress, with crop yields decreasing by up to 4.6%, 1.6%, and 2.3% for green, blue, and total crop yield. The combined impact of salinity and the worst-case climate model (IPSL_CM5A_MR) under the higher emission scenario (RCP8.5) resulted in increases of 3.3%, 1.9%, and 3% in green, blue, and total crop production WFs. Additionally, the study found that the proportion of green, blue, and total crop production WFs in the LARV exceeded the world average. This discrepancy was attributed to various factors, including different spatial and temporal crop distribution, irrigation practices, soil types, and climate conditions. Notably, salinity stress had a more significant impact on green crop yield and green WF compared to blue crop yield and blue WF across all GCM models. This finding highlights the need to prioritize management practices that address salinity-associated challenges in the region. The adverse effects of salinity on soil health, crop yield, and environmental ecosystem require comprehensive strategies for managing salinity in agricultural watersheds by adopting improved irrigation practices and effective salinity management strategies for mitigating these impacts and sustaining agricultural productivity in salinity-affected regions. The complex dynamics between various irrigation practices and soil salinity play a pivotal role in shaping agricultural productions and managing soil salinity. In semi-arid regions like the LARV, salinity poses a significant threat to agriculture, exacerbated by climate change and historic irrigation practices. To evaluate the interplay between salinity, climate change, and irrigation management in affecting crop yields within the Lower Arkansas River Valley (LARV), focusing on corn and alfalfa, we utilized the SWAT-MODFLOW-Salt model to examine how changes in irrigation management influence crop production under various scenarios projected through the year 2100. This study addresses the differential responses of corn and alfalfa to the impact of incremental increases and reductions in irrigation efficiency and irrigation water loss (5%, 10%, 15%, and 20%) on corn and alfalfa yields dynamics under salinity stress, utilizing projections from five global climate models under two distinct Representative Concentration Pathway (RCP) scenarios, RCP4.5 and RCP8.5 and two irrigation scenarios. The findings from irrigation practice scenario (1), maintaining a constant amount of irrigation water, revealed that corn yields improved by up to 13.8% under salinity stress and 16.5% under non-salinity conditions with a 20% increase in irrigation efficiency and a 20% reduction in water loss under RCP4.5. Alfalfa, demonstrating greater salinity tolerance, showed similar benefits, with yield increases of 9.1% under salinity stress and even higher improvements under non-salinity conditions. These results highlight the effectiveness of tailored irrigation practices in mitigating environmental stresses. In contrast, scenario (2), which involved reducing irrigation water by half, resulted in more pronounced negative outcomes. Corn yields exhibited greater sensitivity to salinity stress, with yield reductions ranging from -9.8% under salinity stress to -9.3% under non-salinity conditions, particularly under the RCP8.5 scenario. Alfalfa yields also declined, though less severely than corn, with reductions ranging from -8.9% under salinity stress to -8.3% under non-salinity conditions. Despite improvements in irrigation efficiency and reduced water loss, the adverse effects of salinity stress were not fully mitigated in scenario (2), emphasizing the need for adequate water availability to sustain crop yields under salinity and climate change pressures. The research highlights the importance of adopting advanced irrigation technologies and practices that not only counteract the adverse effects of salinity but also adapt to evolving climatic conditions. This study offers valuable insights for policymakers and agricultural managers on strategic water resource management to sustain crop yields in salinity-affected and water-limited agricultural systems. The results of this study can be used in decision-making regarding the most impactful land and water management strategies for controlling salinity transport and build-up in soils, both for this watershed and other similar semi-arid salinity-impacted watersheds for present and future purposes.Item Open Access Irrigation effects on growth, stress, visual quality and evapotranspiration of ornamental grasses(Colorado State University. Libraries, 2016) Hagopian, Sam R., author; Klett, James E., advisor; Qian, Yaling, committee member; Andales, Allan, committee memberDeficit irrigation research has proven extremely effective for reducing the amount of irrigation applied to various types of landscape plants including trees, shrubs, and herbaceous ornamental plants. This research has yet to delve into one of the most common classes of drought tolerant plants, ornamental grasses. Deficit irrigation treatments were based on evapotranspiration of a short reference crop (Kentucky bluegrass evapotranspirtation, ETo). In 2012 three ornamental grass species were planted, and an on-site atmometer was used to estimate ETo. The three species used for trialing were Panicum virgatum ‘Rotstrahlbusch’ (Rotstrahlbusch Switchgrass), Schizachyrium scoparium ‘Blaze’ (Blaze Little Bluestem), and Calamgrostis brachytricha (Korean Feather Reed Grass). Treatments were applied and data was collected in 2014 and 2015 on two separate studies. The first study was in-ground and consisted of four treatments based on ETo (0%, 25%, 50%, and 100%). The second study was a mini-lysimeter and consisted of three treatments based on ETo (25%, 50%, and 100%). Only Schizachyrium scoparium ‘Blaze’ (Blaze Little Bluestem) was used in the lysimeter study. Data collected in both studies included plant water potential, biomass accumulation, green up date, flowering date, height, width, circumference, floral impact, landscape impact, overall habit, self-seeding, and color. The in-ground component also measured infrared canopy temperature and soil water content, while the lysimeter study included daily weight measurements which were then transferred to evapotranspiration readings. Plants in the 0% treatment were smaller and not considered visually suitable for landscape use. All three species in the 25% treatment performed equivalent to the 50% and 100% treatments in all categories. The only exception was plants in the 25% mini-lysimeter study were more stressed than the 50% or 100% treatments during periods of drought. These plants were all considered visually suitable for landscape use based on visual ratings. This suggests that as long as ornamental grasses are kept on a strict weekly regiment of 25% ETo, and are never exposed to periods of drought, they will be physiologically as well as aesthetically usable in the landscape trade. A weekly amount of 0.25 inches of irrigation on weeks without precipitation was determined to be a usable number for those installing and maintaining ornamental grasses.Item Open Access Mapping evapotranspiration at a high resolution using the surface aerodynamic temperature model and airborne multispectral remote sensing data(Colorado State University. Libraries, 2016) Barlak, Melahat Semin, author; Chávez, José L., advisor; Andales, Allan, committee member; Schipanski, Meagan, committee memberIrrigation is the largest single consumer of water in the world, and with the increasing population, limitation of natural resources, climate change, and global warming, the pressure on water resources has become more significant and attention to agriculture is increasing daily. The limitation of agricultural areas requires efficient use of these areas to obtain a maximum yield. Evapotranspiration (ET) is a major component of the water budget and energy balance. Therefore, exact measurement of plant water use (and thus ET) is vital for efficient use of water resources, planning, and management purposes, especially for arid and semiarid regions. Many methods have been developed for estimating crop ET on a small field scale, such as the Bowen Ratio (BR), the Eddy Covariance (EC), and Lysimeter systems; however, remote sensing-based ET methods have been developed for estimating crop water needs on a regional scale. The energy balance (EB)-based ET algorithms require the computation of net radiation (Rn), soil heat flux (G), and sensible heat flux (H) to solve for latent heat flux or ET as a residual. Values of Rn and G can be estimated with an acceptable accuracy. However, estimation of H is not straightforward. This is because surface aerodynamic temperature (To) is difficult to measure or estimate. Instead, radiometric surface temperature (Ts) is generally used in the estimation of H. However, using Ts may cause overestimation of H, and thus underestimation of ET. To account for those differences between To and Ts, several remote sensing-based algorithms have been developed for mapping ET. The Surface Aerodynamic Temperature (SAT) model is one of them, and was used in this study to estimate sensible heat flux (H) for cotton fields and calculate ET as a residual of the EB for research fields located at the USDA-ARS Conservation and Production Research Laboratory (CPRL) near Bushland, Texas in 2008. By using the SAT model, ET results obtained from the multispectral airborne remote sensing data were compared with ET calculated with model input data collected at the large weighing lysimeters site . Resulting SAT ET values were obtained with a Mean Biased error (MBE) and a Root Mean Squared error (RMSE) of 2.67% and 8.61%, respectively. Then, actual crop ET from the SAT model were compared to measured values from the large lysimeter mass balance. This evaluation resulted in 25.9% MBE and a 44.07% RMSE for the east irrigated fields while for the west dryland fields the error obtained was 42.13% MBE and 42.91% RMSE. In addition, the crop water stress index (CWSI) was used to calculate actual ET using remote sensing inputs and results were also compared to lysimeter measured ET values. Results indicated that the errors were MBE value of 3.77% and an RMSE value of 10.76% for the east fields and 0.89% MBE and 6.0% RMSE for the west fields of the research area, respectively. The results show that the SAT model that was used in this study may not be appropriate for sparse vegetation and heterogeneous surface conditions and that further improvement of the model is required with the application of remote sensing data. On the other hand, the CWSI method performed better than the SAT model for estimating ET and crop water stress levels.Item Open Access Spatial modeling of site productivity and plant species diversity using remote sensing and geographical information system(Colorado State University. Libraries, 2011) Mohamed, Adel Ahmed Hassan, author; Reich, Robin M., advisor; Khosla, Rajiv, advisor; Andales, Allan, committee member; Wei, Yu, committee memberThe primary objective of this study was to describe the variability in site productivity of the diverse forests found in the state of Jalisco, Mexico. This information is fundamental for the management and sustainability of the species-rich forests in the state. The study also contributes to developing conservation-management program for the plant species diversity in Elba protected area in Egypt. The objective of chapter 1 was to develop site productivity index (SPI) curves for eight major forest types in the state of Jalisco, Mexico, using the height-diameter relationship of the dominant trees. Using permanent plot data, selected height-diameter functions were evaluated for their predictive performance within each of the major forest types. An important finding of this study was that a simple linear model could be used to describe the height-diameter relationship of the dominant trees in all of the major forest types considered in this study. SPI varied significantly among forest types, which are largely determined by the trends in temperature and precipitation. SPI decreased with increasing temperature and increased with increasing precipitation. The height-diameter relationship of the dominant trees was independent of stand density, and the more productive sites are able to sustain higher levels of basal area and volume, than the less productive sites. Trees on more productive sites had less taper than trees on less productive sites; and stand density did not influence the form or taper of the dominant trees. Chapter 2 evaluates methods to model the spatial distribution of site productivity in eight major forest types found in the state of Jalisco, Mexico. A site productivity index (SPI) based on the height-diameter relationship of dominant trees was used to estimate the site productivity of 818 forests plots located throughout the state. A combination of regression analysis and a tree-based stratified design was used to describe the relationship between SPI and environmental variables which included soil attributes (pH, sand, and silt), topography (elevation, aspect, and slope), and climate (temperature and precipitation). The final model explained 59% of the observed variability in SPI. GIS layers representing SPI for each forest type, along with associated estimates of the prediction variance are developed. Chapter 3 characterizes plant species richness on four major transects in Elba protected area in Egypt. Species data recorded on 63 sample plots were used to characterize the plant species richness by species group (trees, shrubs and subshrubs). Poisson regression was used to identify explanatory variables for estimating species richness of each species group. Important variables included the location of the line transect (A, B, C, and D), soil texture (gravel, sand, silt and clay), pH, and elevation. The final model explained 23%, 58%, and 52% in the variability of species richness for shrubs, subshrubs, and trees, respectively. The results of the study will contribute to the development of an inventory and monitoring program aimed at the conservation and management of species diversity in Elba protected area of Egypt.Item Open Access Water replenishment through agricultural water conservation: an economic analysis of deficit irrigation(Colorado State University. Libraries, 2013) Sidwell, Jenny, author; Pritchett, James, advisor; Goemans, Christopher, advisor; Andales, Allan, committee memberAvailable freshwater supplies are under growing pressure due to climate variability and expanding development. Water-intensive companies are becoming increasingly aware of the importance of managing their water use due to the impact it has, both on corporate profitability and local ecosystems. Many corporations have calculated the water footprint of their products to determine where reductions might be made. Water neutrality is an extension of a water footprint audit, and involves a consumer or producer reducing their water use as much as possible and then using additional measures to offset any remaining water use. Those additional measures include working with other water users to reduce their water use. For instance, a third party could contract with an agricultural producer and pay them reduce their own water use and then lease a portion of their water right. The objective of this thesis is to determine whether agricultural water conservation can be used to offset a business's residual water use, and more specifically, whether deficit irrigation can be a profit-maximizing option for that conservation. To that end, an optimization model was created and run in Excel's Solver using data from a USDA deficit irrigation research farm to estimate crop water production functions. The results of the model illustrate a range of profit maximizing crop mixtures and indicate potential lease quantities given a range of crop prices and lease payments.