Browsing by Author "Davis, Jessica G., advisor"

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Open Access
Alfalfa reference crop evapotranspiration in Colorado and its use for irrigation scheduling
(Colorado State University. Libraries, 2015) Aljrbi, Abdulkariem Mukhtar, author; Davis, Jessica G., advisor; Andales, Allan A., advisor; Qian, Yaling, committee member; Hansen, Neil, committee member
The goal of irrigation scheduling is efficient use of water such that water is applied to the field for optimal crop production. Previous studies have optimized irrigation scheduling using different models to manage sprinkler irrigation. This research evaluated approaches for obtaining alfalfa reference evapotranspiration (ETr) and its use in a new irrigation scheduling model for a furrow irrigation system. The objectives of this research were to: 1) Compare seasonal trends of daily ETr from the American Society of Civil Engineers Standardized Penman-Monteith (ASCE-SPM) equation and the Penman-Kimberly (PK) equation along a climatic gradient in Colorado, 2) Verify the agreement between calculated ETr from the ASCE-SPM equation and measured ETr from a lysimeter during the 2010 season for the Arkansas Valley of Colorado and correct the lysimeter ETr for alfalfa overgrowth, and 3) Test the ASCE-SPM ETr along with a locally adapted Kcr curve for corn in an irrigation scheduling spreadsheet tool for simulating the daily soil water deficit of furrow irrigated corn in northeast Colorado. The two reference ET equations were compared using R2, Root-Mean-Square Error (RMSE), Relative Error (RE), and index of agreement (d). The R2 values ranged from 0.93 to 0.99; d ranged from 0.98 to 0.99, RMSE ranged from 0.29 to 0.75 mm/d, and RE ranged from -6.35 to 1.91 %. In a comparison of the ASCE-SPM and PK equations at the Fort Collins and Rogers Mesa sites in 2011, differences were observed between the energy balance and aerodynamic terms of each equation. The energy budget calculated by the ASCE-SPM was generally 28% lower than the energy budget calculated by the PK equation at both locations for 2011. On the other hand, the aerodynamic term calculated by the ASCE-SPM equation was from 27 - 28 % higher than the aerodynamic term calculated from PK during most of 2011 at both locations. The second objective of this research compared alfalfa ET measured with a lysimeter in the center of a 4.06 ha furrow irrigated field at the Colorado State University Arkansas Valley Research Center in Rocky Ford, CO to the calculated values from the ASCE-SPM equation in periods of reference conditions in 2010. Four days were selected when alfalfa in the lysimeter was 50 - 55 cm tall, unstressed, completely covering the ground, but with its canopy extending beyond the outer walls of the lysimeter. On these dates, hourly lysimeter ETr was 0.08 to 0.11 mm/h higher than ASCE-SPM ETr. The theoretical surface area of the lysimeter was 9.181 m², while the observed effective canopy area was up to 12.461 m² due to overgrowth. Surface area corrections for the overgrowth increased the index of agreement (d) between hourly lysimeter ETr and ASCE-SPM ETr from the 0.96 - 0.98 range to the 0.99 - 1.0 range. These results showed that it is important to use the correct effective canopy area when computing ETr from a weighing lysimeter. The CIS model for calculating water deficit under a furrow irrigation system with the addition of some data from field measurements such as soil moisture content, gross irrigation, climate data, and plant height and leaf area index generated good results. The water deficit under corn was simulated at the Limited Irrigation Research Farm (LIRF) located near Greeley, Colorado during the years 2010, 2011 and 2012. Daily corn crop ET (ETc) calculated from daily ASCE-SPM ETr and a locally-derived crop coefficient curve (Kcr) were used by the CIS for daily soil water deficit calculations via water balance. This data was used to test a furrow irrigation system via the CIS model and to simulate the field irrigation by predicting the time and the amount of water for the next irrigation. The results showed good agreement between calculated and measured deficits where index of agreement (d) ranged from 0.5 to 0.99 for most years of this study, specifically when measurements of soil water content (SWC) were inserted bi-weekly or monthly. The RMSE did not exceed 2.54 mm when using SWC once per season in 2011, while bi-weekly measurements recorded d to be 0.96 in 2010, 0.99 in 2011 and 0.70 in 2012. Also, the CIS showed that irrigation water usage could be reduced by 30 to 50% through use of CIS.
Open Access
Azolla biofertilizer growth and utilization for vegetable production
(Colorado State University. Libraries, 2017) Widiastuti, Dwi P., author; Davis, Jessica G., advisor; Stromberger, Mary E., committee member; Bartolo, Michael E., committee member; Storteboom, Heather, committee member; Gafur, Sutarman, committee member
To view the abstract, please see the full text of the document.
Open Access
Cyanobacteria biofertilizer solubilizes soil phosphorus and alters soil microbial communities
(Colorado State University. Libraries, 2022) Afkairin, Antisar, author; Davis, Jessica G., advisor; Stromberger, Mary E., committee member; Storteboom, Heather, committee member; Weir, Tiffany, committee member
To view the abstract, please see the full text of the document.
Open Access
Effect of organic nitrogen fertilizer source, application method, and application rate on ammonia volatilization from drip irrigated vegetables
(Colorado State University. Libraries, 2018) Erwiha, Ghazala M., author; Davis, Jessica G., advisor; Ham, Jay M., committee member; Collett, Jeffrey L., committee member
To view the abstract, please see the full text of the document.
Open Access
Effects of agricultural management on greenhouse gas emissions, carbon and nitrogen sequestration, and DAYCENT simulation accuracy
(Colorado State University. Libraries, 2017) Toonsiri, Phasita, author; Davis, Jessica G., advisor; Cotrufo, M. Francesca, committee member; Conant, Richard T., committee member; Del Grosso, Stephen J., committee member
Agricultural activities affect greenhouse gases (GHGs) sources and sinks in terrestrial ecosystems. Organic fertilizer provides nitrogen (N) and organic carbon (C) to soil, resulting in enhanced N and C substrates for nitrification and denitrification which produce nitrous oxide (N2O) and for heterotrophic activity which generates carbon dioxide (CO2). Therefore, reduction of N and C substrates for N2O and CO2 production can reduce these emissions. Proper organic fertilizer application can regulate or reduce the loss of N2O from soil. In addition to reducing GHG production, increasing the potential of soil to sequester soil organic matter (SOM) is a key strategy for mitigating GHG emissions. Increasing organic inputs and reducing SOM turnover rate are keys for this mitigation. The persistence of SOM in agricultural soils is largely associated with the level of protection of C in stable aggregates. Therefore, applying proper practices to increase the stable aggregates can decrease the SOM decay rate, resulting in reduced loss of GHGs such as N2O and CO2 from soil. The focus of my dissertation is the study of (i) N2O and CO2 emissions from a lettuce field which received different organic fertilizer applications, (ii) SOM persistence and stable aggregates in organic and conventional farming systems, and (iii) simulation of N2O and CO2 emissions in organic lettuce using the DAYCENT model. The first study was performed in the summers of 2013 and 2014 at the Colorado State University Horticulture Research Center in Fort Collins, CO to determine the effects of environmental factors and four organic fertilizers (feather meal, blood meal, fish emulsion, and cyano-fertilizer) applied at different rates (0, 28, 56, and 112 kg N ha-1) on N2O and CO2 emissions from a lettuce field (Lactuca sativa L.). Feather meal and blood meal were applied at the full rate (single application) prior to transplanting lettuce, and fish emulsion and cyano-fertilizer were applied five times (multiple applications) after transplanting. The results showed that single application treatments significantly increased cumulative N2O emissions as compared with control, but multiple application treatments did not. However, single application treatments could be overestimated due to chamber placement over fertilizer bands. Cumulative CO2 emissions from single application and multiple application treatments in 2013 were not different, while in 2014, single application treatments presented higher CO2 emissions than multiple application treatments. The second study evaluated the effect of management on aggregate stability and SOM protection and persistence. The study was conducted by collecting soil samples from conventional and organic vegetable fields in different locations (California, Colorado, and New York) and at different soil depths (0-10, 10-20, and 20-30 cm) and analyzing their properties, microbial biomass, and aggregate size distribution. The results showed that organic farming systems have more microbial biomass, thus resulting in enhanced aggregate stability and the formation of organo-mineral bonding of microbial products, thereby storing higher C and N stocks than conventional farming systems. The last study compared N2O and CO2 emissions from field measurements with DAYCENT simulation. The data from the first study in 2014 was used to test the DAYCENT model. The result showed that DAYCENT simulated N2O and CO2 emissions from feather meal and blood meal (single application) better than for fish emulsion and cyano-fertilizer (multiple applications). In addition, the DAYCENT model had low potential to simulate soil water content and soil temperature in irrigated organic lettuce. Overall, the results of these studies show (i) multiple applications of cyano-fertilizer reduced N2O and CO2 emissions while maintaining lettuce yields, (ii) organic farming practices resulted in higher C inputs, microbial biomass, aggregate stability, and protected SOM relative to conventional farming practices, and (iii) DAYCENT reasonably simulated N2O and CO2 emissions from an irrigated organic lettuce field receiving solid organic fertilizers in single applications. These results should be used to support agricultural management decisions.
Open Access
Effects of cyanobacterial fertilizer, commonly-used organic fertilizers, and plant growth regulators on yield and growth characteristics of carrots (Daucus carota var. sativus), cucumbers (Cucumis sativus), and bell peppers (Capsicum annuum)
(Colorado State University. Libraries, 2016) Wickham, Allison, author; Davis, Jessica G., advisor; Schipanski, Meagan, committee member; Bartolo, Michael, committee member
Nitrogen (N) is arguably the most important agricultural nutrient. More money and resources are spent on N management in agricultural systems than any other nutrient. Producing N fertilizer for agricultural use accounts for more than half of the carbon footprint of crop production. Nitrogen plays a crucial role in plant growth, and adding N fertilizers to agricultural systems can lead to noticeable increases in productivity. Nitrogen fertilizers commonly used in organic production are often energy intensive to produce and expensive to transport. Cyanobacteria fertilizer (cyano-fertilizer) produced on-farm could decrease fertilizer impacts on the environment as well as reduce production costs for organic farmers. In addition, cyanofertilizer may perform similarly to products marketed to increase production via plant growth hormones such as seaweed extract, which is shipped all over the world from coastal regions. The effects of common organic fertilizers as well as organic liquid cyano-fertilizer on carrot (Daucus carota var. sativus) and cucumber (Cucumis sativus) growth and yield characteristics were tested during field experiments at the Horticulture Field Research Center in Fort Collins, CO in 2014 and 2015. Bell peppers (Capsicum annuum) were grown in a greenhouse experiment in 2015 at the Colorado State University Plant Growth Facility. Cyano-fertilizer was produced and evaluated in this study to compare effects of farm-grown cyano-fertilizer and commonly-used organic fertilizers. The purpose of this study was to identify fertilizer and foliar seaweed application effects on yield, stress, and growth characteristics of all three plant species. In all experiments, hydrolyzed and non-hydrolyzed fish fertilizers, and cyano-fertilizer treatments were applied at prescribed N rates throughout the growth period approximately every 10 days. Control treatments received no supplemental N. Each treatment, including the control, was repeated with the addition of two forms of concentrated organic seaweed extract applied foliarly. Neptune’s Harvest and Seacom PGR brand seaweeds were used for their lack of N content. Seaweeds were applied at the manufacturers’ recommended rates. Phytohormones were detected in all N fertilizers and in the PGR seaweed. No phytohormones were detected in the Neptune’s Harvest seaweed. In 2014, carrot length and yield were increased by the addition of cyano-fertilizer compared to the unfertilized control. All fertilizers increased post-season soil N compared to the control. Nitrogen fertilizers increased carrot leaf tissue Mg concentrations compared to the control. Nitrogen fertilizers and foliar seaweed influenced the number of carrots with deformities, and a significant interaction between N fertilizers and seaweed with regard to stress indicated a stress response to the addition of both fish fertilizer and a foliar seaweed application. In 2015, cyano-fertilizer produced a higher carrot yield than hydrolyzed fish fertilizer. Nitrogen fertilizers impacted the total number of cucumbers harvested as well as total cucumber yield, but the results were not consistent across years. The majority of significant differences occurred in the pepper study. Nitrogen fertilizer had an effect on leaf tissue nutrient concentrations as well as phytohormone content. Nitrogen fertilizer also impacted flower death and leaf abscission as well as plant stress. Foliarly applied seaweed treatments had very little significant influence in the carrot or cucumber field studies, but did have an effect on pepper shape and color (crop quality). Pepper yield was impacted by the addition of N fertilizers. Foliar seaweed impacted pepper branching behavior as well as fruit color and shape. Based on these experiments, it can be concluded that cyano-fertilizer can be used as a N source in place of commonly-used organic fertilizers. With regards to plant growth characteristics, it is unclear that any of the products applied consistently impacted plant growth characteristics in a way that improved yield or quality.
Open Access
Evaluation of cyanobacterial biofertilizer as a supplemental or solitary fertilizer on peach yields, leaf tissue nutrient concentration, and trunk growth
(Colorado State University. Libraries, 2016) Sterle, David, author; Davis, Jessica G., advisor; Caspari, Horst, committee member; Fonte, Steven, committee member
Nitrogen (N) is the nutrient applied in the greatest quantities to peach trees and is a necessary component of proteins. As a result, carbon assimilation is dependent upon adequate levels of N in leaf tissue. Cyanobacteria are a type of bacteria which can fix gaseous N from the atmosphere enzymatically. This N fixation can be exploited in a cyanobacterial biofertilizer (cyano-fertilizer) production raceway, which allows farmers to grow their own source of N with relatively small energy inputs. Cyano-fertilizer was grown on three peach farms in Western Colorado, and applied to peach orchards in combination with a chicken feather meal (mixed with meat and bone meal), a dried chicken manure, and separately in comparison to a conventional foliar fertilizer, fish emulsion fertilizer foliarly applied, and a soil application of fish emulsion fertilizer. Treatments were assigned to experimental units across three separate farms (Farms A, B, and C) and arranged using Randomized Complete Block Designs. Peach fruit yield, trunk cross sectional area, leaf tissue nutrient concentrations, soil nutrient concentrations, SPAD and fruit juice quality characteristics were measured. A significant fruit yield increase was seen on Farm B in treatments which included cyano-fertilizer and manure (Cyano-Manure), versus manure alone (No-Cyano). Trunk cross sectional area showed less growth in treatments including cyanobacteria on Farm B. Significantly higher leaf tissue S, P, and Cu concentrations were found in Cyano-Manure treatments on Farm B; however, significantly greater Ca concentrations were found in the No-Cyano treatment. Chlorosis was present throughout Farm B and so relative leaf chlorophyll content was estimated by measuring Soil Plant Analysis Development (SPAD). SPAD readings were positively correlated with leaf Fe concentration. In the 2015 fertilization section, SPAD readings were higher in Cyano-Manure treatments despite the relatively low amount of Fe present in the cyano-fertilizer, suggesting that cyano-fertilizer may have increased Fe uptake by the trees. Significant differences in leaf micronutrient concentrations were found among treatments in Farm C. Across all farms, treatment effects were masked by three unforeseen events. First, a large infestation of aphids on Farm A caused the death of young vegetative tissue and also killed young peach fruit. Second, a freezing event during bloom, killed most of the fruit on two of the farms. Lastly, there were prior fertilizations earlier in the season on Farm C which lowered the impact additional fertilizer had on the trees.
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 member
Salinity 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.
Open Access
Nitrogen mineralization from biofertlizer Azolla mexicana compared to traditional organic fertilizers
(Colorado State University. Libraries, 2018) Jama, Aisha, author; Davis, Jessica G., advisor; Stromberger, Mary, committee member; Uchanski, Mark, committee member
Organic agriculture has become an essential approach to meeting the growing global food production demand and long-term soil sustainability, as well as addressing environmental problems connected with the use of synthetic agrochemicals. As a result, biofertilizers (biological fertilizers) have become promising resources to meet the growing demands for healthy and safe food production. Biofertlizers supply nutrients and take advantage of microorganisms that contribute to sustainable practices. One such biofertilizer is the aquatic pteridophyte Azolla mexicana which can be found in both tropical and temperate climates. Azolla can multiply rapidly, ensuring year-round biomass, and has also been found to have fast and high rate of N fixation. Azolla strains have been successfully exploited as effective biofertilizers in Asia but strains native to the Great Plains have not. There is no literature that assesses N mineralization (Nmin) rates of Azolla mexicana compared to other organic fertilizers in Colorado soils. A laboratory soil incubation was conducted to determine the rates of Nmin, N availability and total C and N of Azolla mexicana applied to soils compared to commonly-used organic fertilizers. Then, a greenhouse study was conducted to assess the organic fertilizer and urea treatment responses on kale growth and yield, leaf and petiole N percentage, total N uptake and percentage N recovery. In this study, we hypothesized that Azolla biofertilizer application will enhance soil inorganic nitrogen (soil ammonium-N and nitrate-N) concentrations and that soil amended with Azolla will also enhance vegetable plant growth parameters (plant height, leaf and petiole N percentage, total N uptake and percentage N recovery). In the incubation study, soil NH4+-N for all treatments tended to increase until day 56 where they all peaked then subsequently decreased until the end of the incubation period. Compost treatment recorded higher initial soil NH4+-N while Azolla + Watanabe treatment recorded higher soil NH4+-N concentration towards the end of the study. The soil NO-3-N concentrations in all treatments increased throughout the 140-day study. The Azolla + Watanabe treatment showed highest average soil NO-3-N concentration at day 140 while the Control treatment had the lowest soil NO-3-N concentration throughout the experiment. The decline in soil NH4+-N concentration formed during ammonification was followed by an increase in soil NO-3-N concentration because of nitrification. In the greenhouse study, Azolla + Watanabe treatments had taller kale, significantly higher leaf fresh weight as well as significantly higher leaf dry weight. Both Azolla + Watanabe and Urea treatments recorded significantly higher yields compared to the other treatments. The Azolla + Watanabe and both Cyano treatments recorded significantly higher root dry weights compared other treatments. Control treatment had significantly higher root to shoot ratio. There were no significant differences in leaf N (%) among Azolla + Watanabe, Azolla, Cyano and Cyano + Moringa treatments. Azolla + Watanabe treatment also had significantly higher total N uptake among the organic fertilizers but was not significantly different from Azolla. Urea treatment recorded significantly higher N recovery and showed a similar pattern as the total N uptake whereby Azolla + Watanabe had significantly higher N recovery.
Open Access
Organic nitrogen fertilizers influence nutritional value, water use efficiency, and nitrogen dynamics of drip irrigated lettuce and sweet corn
(Colorado State University. Libraries, 2016) Sukor, Arina, author; Davis, Jessica G., advisor; Schipanski, Meagan E., committee member; Qian, Yaling, committee member; Argueso, Cristiana, committee member
Farmers usually rely on off-farm sources (fish emulsion, feather meal, blood meal) for the additional N needed during the growing season, and they are willing to pay the extra shipping cost. However, there is another fertilizer option being developed that could allow farmers to produce N on-farm, which is cyanobacteria, formerly known as the blue green algae. The general objectives of this study were to assess effects of organic N fertilizer application and N rates on nutritional value, water use efficiency, N dynamics of sweet corn and lettuce. A two-year field study was conducted in the summers of 2013 and 2014 at the Colorado State University Horticulture Research Center, Fort Collins, CO. The fertilizers used in this study were blood meal, feather meal, fish emulsion, and cyano-fertilizer. Both fish emulsion and cyano-fertilizer were supplied in four split applications over the growing season through drip irrigation, while the blood meal and feather meal were subsurface banded prior to planting. Lettuce and sweet corn were used as an indicator to evaluate effects of organic nitrogen (N) fertilizers on nutritional value, water use efficiency, and N dynamics. The aims of this study were to evaluate the effect of different types of organic N fertilizer on nutritional value; β-carotene, iron (Fe), zinc (Zn), marketable yield, water use efficiency (WUE), residual soil nitrate-N, N content, and N use efficiency (NUE) of horticultural crops, particularly lettuce and sweet corn. All fertilizer treatments in 2013 increased β-carotene concentration in leaf tissue compared to control, while only fish emulsion had a higher β-carotene concentration compared to other treatments in 2014. The high indole-3-acetic acid (IAA) applied in the fish emulsion treatment could have increased β- carotene concentration in lettuce in both years. Amount of IAA applied in the fish emulsion treatment was positively correlated with β-carotene concentration in both years. A significant negative correlation was found between marketable yield and β-carotene concentration in leaf tissue in 2014. High salicylic acid (SA) applied in the cyano-fertilizer treatment had a higher total leaf area compared to other fertilizers in both years. In lettuce, the blood meal treatment had a lower leaf Fe and Zn concentrations than other fertilizer treatments at 112 kg N ha-1. The cyano-fertilizer treatment had a higher leaf Fe concentration at 56 kg N ha-1. Leaf N concentration was positively correlated with Leaf Fe and Zn concentrations. Amount of NO3- -N applied in organic N fertilizers was negatively correlated with leaf Fe concentration. The cyano-fertilizer, fish emulsion, and blood meal treatments increased Fe concentration in sweet corn compared to feather meal. Amount of NO3- -N, Fe, and Zn applied in organic N fertilizers were positively correlated with kernel Fe concentration, while amount of NH4+ -N applied was negatively correlated with kernel Fe concentration. There was no N rate or treatment effect on leaf and kernel N concentrations in sweet corn. The amount of phytohormone, Ca, and Fe applied in organic N fertilizers may have affected field water use efficiency (fWUE), instantaneous water use efficiency (iWUE), kernel number, and leaf gas exchange components of sweet corn. Cyano-fertilizer apparently had a higher WUE, likely due to the high amount of SA applied. A positive relationship was observed between the amount of SA applied with iWUE and fWUE. The amount of Fe applied in organic N fertilizers had a positive correlation with leaf VPD and transpiration rate. The amount of Ca applied in the feather meal treatment may have contributed to increasing leaf temperature and decreasing net photosynthetic rate. The amount of NH4+ -N and Ca applied in the feather meal treatments were negatively correlated with both iWUE and fWUE. N rate effect was only observed in lettuce marketable yield and NUE in both years. Blood meal and feather meal fertilizers with higher percentage of N applied as NO3- -N compared to other fertilizer treatments had a higher residual soil NO3- -N concentration in 2013. Greater residual soil NO3 - -N was observed in the 0-30 cm depth compared to the 30-60 cm depth in 2014. Organic growers could achieve higher marketable yield and NUE when applying fertilizers at rates between 28 kg N ha-1 and 56 kg N ha-1 compared with 112 kg N ha-1. In sweet corn, the feather meal and fish emulsion treatments had a higher residual soil NO3- -N compared with other treatments. The fish emulsion, cyano-fertilizer, and blood meal had a higher leaf and kernel N contents and NUE compared with feather meal at 56 kg N ha-1. The cyanofertilizer treatment had a higher marketable ear yield and NUE compared with other treatments at 112 kg N ha-1 in 2014. The amount of C inputs and crop species may have affected soil permanganate oxidizable carbon (POXC) concentration in a single season study. Soil POXC concentration was higher in the cyanofertilizer treatment compared to the control treatment in sweet corn, while the opposite trend was found in lettuce. Depth effect was observed in soil POXC concentration at 0-30 cm compared to 30-60 cm in lettuce. Soil POXC concentration was higher at 112 kg N ha-1 compared to 56 kg N ha-1 in sweet corn, but there was no N rate effect in lettuce. Greater soil POXC concentration and marketable ear yield of sweet corn were observed in the cyano-fertilizer treatment compared to others at 112 kg N ha-1. Overall, our results indicate that organic N fertilizer, particularly cyano-fertilizer influenced soil POXC concentration over a short-term growing season of horticultural crops.
Open Access
Soil carbon and nitrogen pools under perennial forage
(Colorado State University. Libraries, 2010) Widiastuti, Dwi P., author; Davis, Jessica G., advisor; Mikha, Maysoon M., committee member; Qian, Yaling, committee member
To view the abstract, please see the full text of the document.
Open Access
The effect of irrigation and cropping systems on soil carbon and nitrogen stocks and organic matter aggregation in semi-arid lands
(Colorado State University. Libraries, 2014) Abulobaida, Mohamed, author; Davis, Jessica G., advisor; Hansen, Neil, committee member; Cotrufo, M. Francesca, committee member; Conant, Richard T., committee member; Barbarick, Kenneth A., committee member
Demand for water is increasing as a result of population growth, economic activity and agricultural irrigation requirements. Thus, the balance between water demand and supply becomes unstable in countries suffering from water shortage. Therefore, overuse of non-rechargeable groundwater for irrigation in arid regions reduces the availability of water for other users. However, increasing drought periods, shortages of groundwater and urban competition for water have altered irrigated agriculture in Colorado. This may lead to changes in irrigated cropping practices such as alternative water conservation approaches from full irrigation to limited irrigation or dryland cropping systems to alleviate shortage. However, the risk of loss of soil C from dewatered cropland exists, because soil C levels may decline with reduced irrigation due to decreased C input into the soil. The overall goal of the study is to evaluate the impact of conversion from full irrigation to no- till limited irrigation or dryland cropping systems on soil carbon and nitrogen stocks and organic matter aggregation in semi-arid lands. This goal was achieved in the context of three studies that are included in this dissertation. First, the impact of irrigation and cropping systems management on SOC and TN stocks in a semi-arid environment was evaluated for wheat (Triticum aestivum), corn (Zea mays), and alfalfa (Medicago sativa) managed under various treatments of full irrigation, limited irrigation and dryland cropping systems. Second, the effect of different cropping systems with various irrigation levels and dryland cropping on soil aggregation and physical SOC stabilization in a semi-arid region was evaluated by measuring the aggregate size distribution, determining the C and N stocks in aggregate fractions and measuring the soil C mineralization rate in different cropping systems with various irrigation levels. Finally, the impact of conversion of irrigated farmland to limited irrigation or dryland cropping systems on SIC content was evaluated over a 3-yr period. The SOC and TN were analyzed at different depths from 0 to 60 cm depth in 2007 and 2010. Aggregate size distribution, SOC and TN contents for the aggregate size fractions [macro (M) and micro (m) aggregates, and silt & clay fractions] and for the isolated fractions from macroaggregates [coarse particulate organic matter (cPOM), microaggregate into macroaggregate (mM) and Silt&Clay-M)] were measured in soils from full irrigation alfalfa (Full-A), full irrigation corn (Full-C), limited irrigation forage alfalfa (Ltd-fA), limited irrigation forage corn (Ltd-fC), limited irrigation grain wheat (Ltd-gW), limited irrigation grain corn (Ltd-gC), dryland wheat (Dry-W) and dryland corn (Dry-C) treatments. SIC was measured in 2007 and 2010 for all treatments, and in 2013 for limited irrigation grain wheat-corn sorghum cropping system (Ltd-gWCFs). Soil pH was measured for all treatments in 2010 and for Ltd-gWCFs in 2013 in the different depths. The SOC and TN contents were significantly different among full irrigation and dryland treatments in the 0-20 cm layers of soil, but those differences were not significant below 20 cm depth. However, for all treatment comparisons, the differences remained significant throughout the soil profile in which crops rotated with alfalfa particularly limited irrigation systems (Ltd-fA and Ltd-fC) had higher SOC and TN stock compared with Ltd-gW. Our results showed the SOC and N stocks were significantly related to their concentrations not to bulk density for all depths. The SOC and TN distribution throughout the soil profile were stratified, and the SOM accumulation under the treatments almost occurred at similar C/N ratios. The amount of free microaggregates (m) under all treatments ranged from 69.4 to 75.6 % of the soil and the macroaggregates (M) comprised less than 18 % of the soil. The latter was higher under fully irrigated corn (Full-C), limited irrigation forage corn (Ltd-fC) and limited irrigation grain corn (Ltd-gC) compared to dryland corn (Dry-C). The SOC stock in the microaggregates occluded inside macroaggregates (mM) was higher under fully irrigated crops relative to dryland crops, especially in corn treatments. Conversion from full irrigation to dryland induced a reduction in macroaggregates. The Full-C treatment had higher SOC stocks in mM fraction relative to Dry-C. Our study indicates that irrigation and no-till management enhanced aggregate formation and increased C sequestration in mM fractions compared to dryland cropping systems. The SIC stock was significantly higher under limited irrigation grain wheat (Ltd-gW) treatments compared to full irrigation cropping systems (Full-C and Full-A) and limited irrigation forage cropping systems (Ltd-fC and Ltd-fA). However, there were no significant differences between Ltd-gW and other treatments (Ltd-gC, Dry-C and Dry-W). The Ltd-gW treatment gained more SIC compared to other treatments which accounted 19.4 % of total SIC sequestered under all treatments over the entire profile (0-60 cm) through the period of the study. Our results showed that the most important factor controlling the process of SIC formation in the 0-30 cm depth was soil pH which explains the high variation of SIC among treatments (R2 = 0.80, P <.01). This may be due to the effect of different cropping systems in which sunflower rotated into wheat-corn grain rotation (Ltd-gWCSf) consumed a greater amount of water than other summer crops and this may be effectively increasing soil pH in those crops rotated with sunflower.
Open Access
The influence of outdoor light on biomass, nitrogen, and phytohormone concentrations of a nitrogen-fixing Anabaena sp. Cyanobacterium
(Colorado State University. Libraries, 2017) Wenz, Joshua, author; Davis, Jessica G., advisor; Storteboom, Heather, committee member; Reardon, Kenneth, committee member
To view the abstract, please see the full text of the document.