Browsing by Author "Davis, Jessica, advisor"
Now showing 1 - 6 of 6
Results Per Page
Sort Options
Item Open Access A guide for small-scale organic vegetable farmers in the Rocky Mountain region(Colorado State University. Libraries, 2009) Stonaker, Frank, author; Stushnoff, Cecil, advisor; Davis, Jessica, advisor; Cranshaw, Whitley, advisorThe steady growth over the last twenty-five years in the organic agriculture sector has been paralleled by growth in the number of farmers' markets and community-supported agriculture (CSA) operations, reflecting increased consumer interest in "buying locally". Small organic farms represent the core of the local growers involved and invested in this trend in Colorado and yet have had little research to direct or support their forays into organic agriculture. Agricultural research focusing on organic systems and the challenges in soil fertility management, pest and disease management, and plant breeding appropriate for organic production has lagged. The research in organic production that has been done in the US has occurred largely on the east and west coasts and upper Midwest where climatic conditions are different from that of the arid, inter-mountain west. In 2002 the Horticulture and Landscape Architecture Department at Colorado State University initiated the Specialty Crops Program, and soon after the Rocky Mountain Small Organic Farm Project (RMSOFP) was established to address issues relevant to small-scale organic farmers in Colorado and the region. Within this context a prototypic small organic farm was developed on certified organic land at the Horticulture Field Research Center (HFRC) neat Ft. Collins, Colorado. A variety of research projects have been undertaken ranging from cultivar trials of vegetables, to evaluations of phytochemicals of vegetables grown on organic and conventional plots. This production guide for small-scale organic farmers provides a basis for future research, education, and outreach efforts that can be made available to farmers, extension workers, teachers and students. It is a comprehensive production guide for small-scale organic farmers in the climatic zones similar to those found in Colorado. Topics included are: soil fertility management, tillage, irrigation, and pest management. Detailed production recommendations for melons, tomatoes, spinach and lettuce are presented, with cultivar trial results of melons, tomatoes and spinach. Fifteen organic vegetable farmers from Colorado were interviewed about their production practices, and their comments are included.Item Open Access Development of an organically certifiable growth medium for N-fixing cyanobacteria in a raceway biofertilizer production system(Colorado State University. Libraries, 2014) Barminski, Rosalyn, author; Davis, Jessica, advisor; Storteboom, Heather, committee member; Peers, Graham, committee memberThe on-farm cultivation of N-fixing cyanobacteria in raceway ponds may provide an alternative N source in organic farming systems. The cultivation of cyanobacteria in an organic farming system requires an organically certifiable growth medium. Additionally, efficient cyanobacterial cultivation depends on production methods that reduce the severity of the three growth limiting factors present in outdoor raceway cultivation: inefficient solar irradiance, growth medium nutrient depletion, and day-night temperature fluctuations. The purpose of this work was two-fold, first to develop and test an organically certifiable growth medium, and secondly to test four specific production methods so as to optimize cyanobacterial growth and N-fixation. The four raceway production methods tested separately included: batch (B) versus semi-continuous (SC) operation mode, a culture depth of 20-cm versus 25-cm, bicarbonate supplementation in the growth medium, and four different cover plastics over raceways. All studies used a cyanobacterium cultured from a Fort Collins, CO lake, with 99% similarity to Anabaena cylindrica. Cyanobacterial growth was estimated by optical density (OD) and chlorophyll content and cyanobacterial N-fixation was estimated by net Total Kjeldahl Nitrogen (TKN). In chapter 2, "Comparison of cyanobacterial growth and nitrogen fixation in a newly developed organically certifiable growth medium and Allen and Arnon growth medium", a laboratory and raceway study were conducted. In the lab study, the nutrients of Allen and Arnon (AA) that were not organically certifiable were replaced with organically certifiable nutrients to compose the organic medium (RB). The exponential growth rate was significantly higher in the RB medium compared to AA. Conversely the net TKN in the RB medium was 37% lower than that of AA. The lower N-fixation in the RB medium was attributed to the presence of N in the P source used for RB medium (bone meal). In the raceway study, there was no significant difference in growth between the two treatments despite lower concentrations of P, Co, Zn, and B in the RB medium. An overarching limiting factor evident in both treatments such as light limitation or C depletion could explain why there was no observed growth effect due to the low P, Co, Zn, and B concentrations of RB medium. The net TKN between the two treatments was not statistically different, which suggests similar N-fixation. The conclusion of similar N-fixation was questioned due to the contribution of dissolved N from bone meal. Together, the studies support that the RB medium supports growth similar to that of the AA medium in raceway cultivation. However, since N was present in the RB medium, it is possible that maximal N- fixation was not achieved. Recommendations to increase nutrient concentrations in RB medium are discussed in chapter 4, "Future recommendations". In chapter 3, "Biomass yield and nitrogen fixation of cyanobacteria in outdoor raceways under batch versus semi-continuous operation", a SC treatment was operated under a 25% harvest regime every other day beginning on day 6. The B treatment was grown for 14 days, then 85% of the treatment was harvested and the remaining 15% was used as seed to begin a second B set. At the end of four weeks, biomass yield and total N fixed was calculated for the B and SC treatments. There was no difference in biomass yield or N yield between the two treatments. More than likely the SC was harvested when the culture density was above the optimal cell density range, resulting in a lower total biomass and N yield than what could have been achieved within the optimal cell density range. Determination of the optimal cell density and a specific harvest regime that maintains the SC within the optimal cell density would result in a higher total SC biomass and N yield compared to that of B. Possible experiments to determine the optimal cell density are discussed in chapter 4, "Future recommendations". In Appendix II, "Cyanobacterial growth and nitrogen fixation in response to depth, bicarbonate supply, and hoop house coverings in outdoor culture", three separate batch studies were conducted in 1.2-m (l) by 0.6-m (w) by 0.3-m (h) tanks. The first experiment compared the growth and N-fixation of batch cultures grown at two different depths (20-cm and 25-cm). Raceway depth did not have an effect on total growth or net N-fixation. The second experiment compared cyanobacterial growth and N-fixation in AA medium supplied with 0 mM (control), 0.2 mM (low treatment), and 2.0 mM (high treatment) of potassium bicarbonate (KHCO3). There was no increase in growth or N-fixation due to addition of KHCO3. It was concluded that inadequate KHCO3 was added to significantly increase growth and that the addition of NaHCO3 rather than KHCO3 is necessary to assure adequate Na concentrations needed for maximal bicarbonate uptake. The third experiment compared the growth and N-fixation of cultures grown under different hoop house plastics (Thermax, Luminance, Dura-film Super 4, and 4 mil Husky construction plastic) and a no-cover control. None of the covers tested in the study increased the growth compared to the no-cover control. Zn slowly leached from the cultivation tanks, so that by the end of the third study, Zn toxicity clouded the interpretation of results.Item Open Access Effects of cyanobacterial fertilizers compared to commonly-used organic fertilizers on nitrogen availability, lettuce growth, and nitrogen use efficiency on different soil textures(Colorado State University. Libraries, 2013) Sukor, Arina, author; Davis, Jessica, advisor; Stonaker, Frank, committee member; Storteboom, Heather, committee member; Stromberger, Mary, committee memberNitrogen plays a crucial role in synthesis of amino acids and proteins, plant growth, chlorophyll formation, leaf photosynthesis, and yield development of lettuce. Generally, organic farmers use composted manure, legume cover crops, and off-farm fertilizers such as fish emulsion to meet the nitrogen (N) demand of crops. However, the nutrient composition of off-farm fertilizers such as composted manure and fish emulsion varies widely depending on animal species and often have higher transportation costs. Therefore, an evaluation of the application of cyanobacteria in comparison to the commonly-used organic fertilizers was conducted as an alternative potential N biofertilizer. The laboratory soil incubation and greenhouse studies were conducted to evaluate the effect of N availability from potentially mineralizable N on different types of soil textures. Then, a greenhouse study was conducted to assess the effect of N availability from cyanobacterial fertilizers compared to the commonly-used organic fertilizers on lettuce growth, fertilizer recovery and lettuce root response on N use efficiency. Lettuce (Lactuca sativa) is a shallow-rooted crop and requires an extensive amount of N fertilizer to produce yield. The aims of the soil incubation study were to determine the rates of mineralization for different organic fertilizers, influence of soil texture on N mineralization, and to evaluate changes in soil microbial biomass from fertilizer application to sandy and clayey soils. In this study, N mineralization potential of cyanobacterial fertilizers were compared with traditional organic fertilizers in two soils with contrasting textures in a laboratory incubation study at constant temperature (25 degrees C) and moisture content (60% water-filled pore space) for 140 days. Soils were destructively sampled over the course of 140 days and analyzed for NH4+-N, and NO3--N, soil microbial biomass C, soil organic C, and soil total C and N. In both soils, soil NH4+-N was the highest at day 56 and decreased from day 56 to 140 due to its conversion to soil NO3--N. Compost treatment significantly increased soil microbial biomass C (207.5 mg C kg-1 soil) compared to fish emulsion (115.42 mg C kg-1 soil) in sandy soil. The N availability was 9% greater from fish emulsion than liquid cyanobacteria, and 6% greater from solid cyanobacteria than compost in sandy soil. The fish emulsion treatment showed 5% higher N availability compared to the solid and liquid cyanobacterial fertilizers. In the greenhouse study, percentage fertilizer recovery (PFR) was quantified to assess the efficiency of N uptake by lettuce to produce yield. A greenhouse study was conducted for 63 days to evaluate cyanobacterial and traditional organic fertilizers application on lettuce N response. Total leaf area, fresh yield, leaf dry weight, and leaf total N content were measured at the end of the greenhouse study. Total N uptake in lettuce tissue and PFR were calculated based on the analyses results. Soil applied fish emulsion recorded significantly higher fresh yield at 112 kg N ha-1 (147 g) compared to 56 kg N ha-1 (117 g) in clayey soil relative to sandy soil. Soil-applied liquid cyanobacteria recorded significantly higher yield compared to composted manure by 58%. Solid cyanobacteria recorded significantly higher total N uptake at 56 kg N ha-1 compared to 112 kg N ha-1 in clayey soil. In conclusion, soil applied fish emulsion treatment recorded higher PFR (99%) than soil applied composted manure (44%) at 56 kg N ha-1 on clayey soil. Soil applied fish emulsion has significantly higher PFR (57%) compared to the combination soil and foliar fertilizer (FFCom and FLScyb) at 56 kg N ha-1 in sandy soil. Nitrogen is also acquired from the soil by the plant roots. In the greenhouse study, root response to N fertilization was assessed to determine the efficiency of N uptake by lettuce to produce yield. A greenhouse study was conducted for 63 days to evaluate cyanobacterial and traditional organic fertilizers application on lettuce root response. Root: shoot ratio, root dry weight, root surface area, and root length density were measured at the end of the greenhouse study. Nitrogen use efficiency (NUE) was calculated based on the analyses results. There was no significant difference observed in root dry weight. The composted manure (Com) treatment recorded significantly higher root: shoot ratio at 56 kg N ha-1 while foliar and soil applied liquid cyanobacteria (FLScyb) treatment recorded lower root: shoot ratio at 112 kg N ha-1. The foliar applied fish emulsion and soil applied composted manure (FFCom) treatment recorded the highest root surface area compared to other treatments at 112 kg N ha-1 on clayey soil . The FLScyb treatment recorded higher root surface area compared to the Com treatment at 112 kg N ha-1 on sandy soil. The fish emulsion (Fish) treatment recorded higher root length density at 112 kg N ha-1 on clayey soil while FLSCyb recorded higher root length density on sandy soil at 112 kg N ha-1 compared to the Fish and solid cyanobacteria (Scyb) treatments. In conclusion, the Fish treatment recorded 35 % higher NUE at 56 kg N ha-1 on clayey soil while Scyb treatment has significantly 24% higher NUE compared to Com treatment at 56 kg N ha-1 in sandy soil. Overall, the soil applied fish emulsion treatment recorded higher percentage fertilizer recovery and NUE compared to the solid and liquid cyanobacterial fertilizers at 56 kg N ha-1 on clayey soil. However, the combined soil and foliar cyanobacterial fertilizer and soil applied solid and liquid cyanobacterial fertilizers recorded higher percentage fertilizer recovery and NUE at 56 kg N ha-1 compared to the composted manure which correspond to lettuce yield component which was higher in fish emulsion compared to the composted manure.Item Open Access Effects of topdressing established Kentucky bluegrass with composted manure(Colorado State University. Libraries, 2005) Johnson, Grant A., author; Qian, Yaling, advisor; Davis, Jessica, advisor; Koski, Anthony J., committee memberConcerns about water quality issues surrounding nutrient loading into surface and ground water from agricultural manure applications have contributed to the increasing interest in composting manure and topdressing it on turfgrass to alleviate manure pollution. Little information is available regarding the effects of composted dairy manure topdressings on established turfgrass. The objectives of this research were to evaluate the effects that topdressing composted manure has on: (i) turfgrass growth and quality, (ii) soil physical and chemical properties, (iii) turfgrass quality and soil moisture content during periods of dry down, and (iv) nutrient runoff and leaching during simulated rainfall event. Compost was topdressed onto three cultivars ('Nuglade', 'Livingston', and 'Kenblue') of established Kentucky bluegrass (Poa pratensis L.) at rates of 0, 33, 66, and 99 m3 ha-1, twice in 2003 and once in 2004. A synthetic fertilizer (Urea 46-0-0) was added to help balance inorganic N rates among treatments. Compost treatments had 6-10% higher quality than the control during the growing seasons, produced 18-56% higher clipping yields in late summer months, and helped retain turfgrass color longer into the fall and allowed for faster spring green up. Compost treatment 99 m3 ha-1 reduced surface soil (0-3 cm) bulk density by 5.3% and increased water retention by an average of 14.2% over all tensions tested. Compost treatments increased soil P, K, Fe and Mn in the 0-10cm depth. During 10-day dry down periods, compost treatment increased soil moisture in the 15-30 cm soil depth during the first 2-3 days, which in turn, increased soil moisture in the 0-15 cm depth towards the end of dry down and led to 1.2-3.3 °C lower canopy temperatures compared to the control. Runoff collected revealed no differences in NO3-N or total phosphorus concentrations among treatments, and mean NO3-N concentrations (6.5 mg L-1) were below the EPA standards, while mean TP concentrations (1.1 mg L-1) slightly exceeded EPA standards. No differences in leaching potential occurred among treatments. From these results it is recommended that manure compost be topdressed to Kentucky bluegrass at an optimal rate 66 m3 ha-1, which provided good quality throughout most of the year.Item Open Access Microgreen production: an evaluation of types of growing media(Colorado State University. Libraries, 2018) Lake, Julie A., author; Davis, Jessica, advisorMicrogreens are edible vegetable, herb, and even flower plants that are harvested between 7 to 15 days after germination, when cotyledons and/or two ‘true’ leaves have emerged. Harvest parameters often vary depending on the type of plant being produced. The seedlings are harvested by cutting the hypocotyl just above the grow media, leaving the radicle behind. The hypocotyl, cotyledons, and often emerging first two 'true leaves' are the parts of the plant that are consumed. Plants in this early stage of development have a much higher nutritional content than their mature counterparts. Microgreens can be produced using a variety of growing methods, are easily grown in small or large quantities, and can be grown in almost any location. These factors make microgreens a quick growing source of nutritious food in the U.S. and globally. Researching different possible methods that can be used to grow microgreens could benefit future food supplies. Three separate, randomized replications were completed in a greenhouse setting. Each replication contained six different types of media, the grow media performance and microgreen production results were compared. Results showed the seed starter mix and the germinating media mix had the highest harvest volumes and required the least amount of water overall. Future research can include more media options, such as rockwool, vermicompost, perlite/vermiculite mix, coconut coir fibers/dust (not in a mat form), and sugarcane filter cake.Item Open Access Organic fertilizer comparison on kale (Brassica spp.) varietal growth and nutrient content(Colorado State University. Libraries, 2014) Yoder, Natalie, author; Davis, Jessica, advisor; Stonaker, Frank, committee member; Elliott, Adriane, committee memberSelecting supplemental N fertilizer for use on certified organic farms can be difficult and confusing. There are many options commercially available to farmers with similar N concentrations but widely different ingredients. Field experiments on three farms in Fort Collins, CO were conducted to evaluate the impact of a few commonly-used organic fertilizers on kale yield and nutrient concentrations. This study includes a fertilizer under development which is produced on-farm utilizing N-fixing cyanobacteria; this cyanobacterial bio-fertilizer may be a viable choice for farmers in the near future. The three fertilizer treatments (hydrolyzed fish, alfalfa meal and liquid cyanobacteria) were applied at rates calculated by subtracting soil nitrate-N concentration from a target 50 mg/kg. Cyanobacteria and hydrolyzed fish were applied in liquid form while alfalfa was incorporated dry into the soil pre-planting. Biweekly measurements of plant height and chlorophyll content were taken on three varieties of kale, Dinosaur, Red Russian, and Winterbor. Leaf weight, leaf area, N, Fe and Zn concentrations were measured during four monthly harvests. Organized in a split-plot experimental design, each farm had 3 treatment replications with subplots of different kale varieties. No significant effects were found on plant height, leaf weight, leaf area, N, Fe or Zn concentrations among fertilizer types. There were varietal differences in plant height, leaf area, and general performance as well as resistance to pest pressure. Residual N in each subplot was measured after this study and showed significant difference among varieties. Kale variety choice seems to have a much larger impact on yield and nutrient concentrations than fertilizer choice, as long as fertilizers are applied at similar N rates.