<p> Soil moisture sensor use in crop production systems has the potential to give inference on plant water status for the purpose of irrigation scheduling and site-drought characterization. These processed measurements could serve as the framework on which to compile trial results across locations, thereby more accurately defining varietal yield response to drought. Still, the ability to characterize drought within a given field or initiate irrigations from these data hinge upon the ability of the instrument to characterize soil moisture at the sampled point and extrapolate that information across the landscape and time. Therefore, the objectives of this research were to: (1) test the response of the Watermark 200SS (Irrometer Company, Inc., Riverside, CA) and Decagon 10HS (Decagon Devices, Inc., Pullman, WA) to changes in water content of three dissimilar soils representing common soils in row-crop production under variable environmental conditions; (2) develop a soil moisture-based index to quantify drought stress in dryland cotton cultivar trials; and (3) determine if a limited number of soil moisture sensors deployed into a dryland cultivar trial could accurately characterize the VWC at a given point within the field and if this measurement could be extrapolated out to the field scale from the very small sphere of influence characterizing the utilized soil moisture sensors. During the 2012 and 2013 growing seasons soil moisture sensors were deployed into over 14 cotton cultivar trials across the U.S. Cotton Belt and into a water-input controlled container study. Tested sensors' inability to accurately predict container VWC emphasized the relatively small quantity of soil on which these sensors rely and the variability in soil moisture within a very limited volume. Results from the drought-index studies suggested both the Accumulated Soil Moisture Stress Index (ASMSI) and the relative reduction in evapotranspiration (1-(ET_{c adj}/ET_c)) appear to have potential in characterizing the amount of stress experienced within dryland cultivar trials. Analysis of spatial and temporal stability suggested trends between sensors were consistent, but absolute node readings varied. Optimism concerning the potential of these measurements/approaches for increasing water use efficiency is coupled with a call for more arbitrary, universal methods of measurement analysis.</p>

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2007. / Source: Dissertation Abstracts International, Volume: 68-11, Section: B, page: 7521. Adviser: Julie L. Zilles. Includes bibliographical references. Available on microfilm from Pro Quest Information and Learning.

Digitization note: pgs. 62 & 91 missing from paper copy and not available for rescanning. / Effects of three levels of irrigation frequency; five levels of increasing NaCl (max 8000 ppm) in the irrigation water; and, two different soil types on the growth and survival of Italian Cypress Cupressus sempervirens, Oriental Arborvitae Thuja orientalis, and She-Oak Casuarina equisetifolia tree seedings were studied under greenhouse conditions. There were significant differences between the species throughout the stress period with regard to the evaluated parameters. Height, diameter growth, and leaf water potential in all species were reduced by increasing water and salt stress throughout the stress period. Reductions in total, shoot and root dry weight by water and salt stress were significant. Higher reductions were associated with higher water or salinity stress level. However, the species differed in their response to the stress treatments. Thuja had the lowest reductions in all measured growth parameters, followed by Casuarina and Cupressus. Water and salt stress treatments affected foliage tissue ion concentrations in all seedlings. N, P, K, Ca, Mg, Na, and Cl decreased as water stress level increased (except for, Na and Cl in Brazito soil). However, Ca, Mg, Na and Cl ion concentrations increased as the salinity level in the irrigation water increased. N and P decreased with increasing salinity and K was selectively accumulated. The seedlings' health declined with increasing stress treatment level. NaCl treatments caused foliar injury, which increased as the concentration of NaCl in the irrigation water increased. Thuja showed the least injury followed by Casuarina. Mortality was limited to Cupressus seedlings on both soil types. More mortality was noted with the increase in irrigation frequency and salinity level of the irrigation water. Thuja and Casuarina seedlings survived to the highest salinity level (8000 ppm NaCl), but with visible injury. Soil types affected all seedlings morphological parameters, total water potential, and foliage ion concentrations, except for P and Ca. All seedlings (except for Casuarina root dry weight) planted in Pima soil maintained higher growth and better overall health condition than on Brazito soil. Also, total water potential reached lower values in all species planted in Brazito soil rather than on Pima soil. Foliage Na and Cl concentrations on Brazito soil exceeded those on Pima soil. Survival of Cupressus seedlings was less on Brazito soil than on Pima soil. Overall, Cupressus growth was reduced the most on Brazito soil as compared with Pima soil. Growth of Casuarina was the least adversely affected on Brazito soil.

The purpose of this research is to investigate the environmental remediation and energy potential of anaerobic digesters on pig and dairy farms and to demonstrate how incorporating those benefits into a cost-benefit analysis would make biodigester projects more financially feasible. By assigning dollar values to the emissions and water pollution avoided by this technology, I sought to update the traditional cost-benefit analyses (CBAs) to demonstrate that this technology is more widely applicable. The study took place In the Lake Champlain Drainage Basin, USA and the Lake Tai Drainage Basin, China. Dairy and pork production are high density endeavors and produce large quantities of waste which make them ideal candidates for biodigesters. Using standard emissions estimates and gas production rates from past research and from the current Cow Power Program in Vermont, the methane and nitrous oxide emissions averted by adding a biodigester to a particular farm were estimated. Additionally, using past research, the total nitrogen and phosphorous collected by the biodigesters and diverted from becoming classified as non-point source pollution was calculated, valued, and incorporated into a CBA tool. The results from this study show that the incorporation of environmental benefits in a CBA for Green Mountain Dairy increased profitability by 60% and reduced the payback period by two years. Overall, projects that include environmental benefits are 72% more profitable and the payback period is cut in half. Further development of the CBA tool is needed to strengthen results. This study points to the need for more experimental data on the environmental benefits of biodigesters.

Penguin colonies from permanently cold environments have a strong impact on their surrounding ecosystem because their excrements provide ample nutrients to the soils and sediments. The high phosphate content of the penguin guano directly affects primary productivity. However, phosphate solubility is dependent on the presence of iron and other metals, which can form stable PO4-rich minerals. Phosphate can also be sorbed onto minerals, including iron oxides. The present study investigated the biogeochemistry of phosphorus in a 42 cm-deep soil profile on Gardiner Island in Antarctica in order to assess the effect of penguin excrements on P partitioning in the solid and aqueous phases. The results indicate that the porewaters were slightly acidic (pH 5-6) and contained extremely high levels of dissolved organic carbon (DOC; 120 mM), PO4 (120 mM), SO4 (27 mM), NO3 (18 mM), Cl (320 mM), F (2 mM), Sr (0.10 mM), Ca (18 mM) and Mg (150 mM) at the top of the soil profile. Dissolved iron concentrations were generally low (&lt; 0.04 mM) and increased at a depth of 15-20 cm and at the bottom of the profile. Chemical extraction revealed the presence of two zones of reactive phosphorus (P-ascorbate extractable fraction) in the soil profile, i.e., at the surface and between 16 and 20 cm. Enriched reactive and crystalline iron fractions were also present at a depth of 16-20 cm, but fluctuated throughout the profile. The Fe(II)/Fe(III) molar ratio of the soil was greater than 1 at the surface of the profile and declined with depth. X-ray diffraction analysis showed that the soil likely contained berlinite, strengite and vivianite, along with silicates and quartz. Saturation index calculations also indicated that Ca and Mg-rich phosphate minerals were likely present in the soil. Based on the above results, the presence of penguin colonies on Gardiner Island strongly impacted the geochemical and mineralogical composition of the soil, as observed in other studies on bird guano impacted (ornithogenic) soils. In addition, the presence of both Fe(II) and Fe(III) points to the fact that the soil undergos redox changes, likely as a result of seasonal water table fluctuations. Microcosm experiments with selected samples from the soil profile and an iron-reducing bacterium indeed showed that iron and phosphorus were released into solution as a result of microbial iron reduction. However, abiotic systems also showed a release of phosphorus indicating that non Fe-rich phosphate minerals are soluble under the conditions prevailing in the growth medium.

No description available.

Master of Science / Department of Agronomy / Charles W. Rice / Biotic interactions among mycorrhizal fungi, nematodes, plants and other microbial communities can have significant effects on the dynamics of C and nutrient cycling. The specific objectives of this study were (1) to evaluate the effects of grazing and mycorrhizal symbiosis on the allocation and storage of C, especially for plant above-and belowground biomass, (2) evaluate the biotic rhizosphere interactions and their role in C cycling, (3) determine the soil microbial community structure as a result of the plant-mycorrhizal symbiosis, and (4) determine the effect of mycorrhizal fungal abundance on soil aggregation. The soil for the experiment was sampled from the Ap horizon of a fine-silty, mixed, superactive, mesic Cumulic Hapludolls located at Konza Prairie Biological Station, Manhattan KS. The experiment was a three-way factorial in a complete randomized block design with four replications. The three factors were mycorrhizae (M), nematodes (N), and phosphorus (P). In a greenhouse study, 96 microcosms (52×32×40cm) were planted to Andropogon gerardii Vit. so that a third of the microcosms could be destructively sampled at the end of each growing season for three years. Plant biomass was separated into aboveground, rhizomes, and roots. All components were dried and weighed at harvest. Mycorrhizal fungi and P increased plant aboveground biomass, while nematodes decreased plant aboveground biomass compared to non-inoculated controls. As expected, P increased plant root biomass, while mycorrhizae increased plant rhizome biomass. Nematodes decreased both above- and belowground biomass. Phospholipid and neutral lipid fatty acid (PLFA and NLFA) analysis were determined for both soil and roots. Water-stable aggregates were separated using a modified Yoder wet-sieving apparatus and analyzed for mass, total C and N, and the isotopic composition of C. There was a positive relationship between AM fungal abundance in the soil and the mass of the largest macroaggregates (>2000µm) after the 3rd year (r=0.67). The effect of roots on the macroaggregate (>2000µm) fraction was not apparent. Phosphorus significantly increased smaller macroaggregates (250-2000µm), along with significantly enhanced plant root biomass, which indirectly demonstrated the effect of roots on the formation of macroaggregates (250-2000µm). The addition of P induced more plant derived C into the aggregates than the non-P amended microcosms as suggested by the [superscript]13C content of the aggregates. Our results confirmed the importance of biotic and abiotic interactions among mycorrhizae, nematodes, and phosphorus on plant growth and the resulting effect on the soil C cycle and soil aggregation.

Doctor of Philosophy / Department of Horticulture, Forestry, and Recreation Resources / Edward E. Carey / A series of four investigations was conducted from 2005 to 2007 focusing on vegetable or high tunnel production. In the first study (chapters 1 & 2), the effect of high tunnels on soil quality was investigated. Grower perceptions of soil quality were assessed from 81 responses to a questionnaire. Indicators of soil quality were evaluated at two KSU research centers. Soil quality was then quantified in high tunnels and adjacent fields at 79 farms, where high tunnels ranged in age from two to fifteen years. Particulate organic carbon as a fraction of soil total carbon was used as an indicator of soil quality. At 80 % of locations, particulate organic matter carbon was greater under high tunnels than adjacent fields. Soil quality was not adversely affected by the continuous presence of high tunnel covering. Management and cropping history in high tunnels was also collected and reported as this information is of interest to growers and the universities and agricultural industries that serve them. Tomato was the most common high tunnel crop. It was grown by 86 % of survey respondents in the previous four year period. Organic soil amendments were applied by 89 % of growers; 35 % use organic soil amendments exclusively. In the second study (chapter 3), two microbial tea solutions were applied to collard green (Brassica oleracea L. var. acephala cv. Top Bunch) or spinach (Spinacea oleracea L. cv. Hellcat) crops at Olathe and Haysville, Kansas, without significant effects on crop yield or soil microbial biomass. Finally, preliminary results from two studies were formatted for reporting as extension publication (chapters 4 and 5). Autumn production, over-wintering, and spring bolting were assessed for 26 spinach cultivars in a 3-season multi-bay Haygrove high tunnel. Also, the effect of autumn planting date on harvest date and yield was observed for two spinach cultivars (cv. Avenger and PVO172) planted on six dates in October and November, under high tunnels at Olathe, Kansas. Spinach planted in the first half of October was harvested in the winter, without loss of spring yield for both cultivars.

Master of Science / Department of Agronomy / Charles W. Rice / The sequestration of atmospheric CO[subscript]2 into soil through no-till management is an economic and viable method for reducing greenhouse gases, but maintaining no-till practices are necessary to sequester C in the long-term. Our study focused on the effects of a single tillage operation on soil organic C and N and aggregation in no-till soils when no-till practices are immediately resumed after tillage. Three locations in western Kansas were selected that had been in continuous dryland no-till for at least 5 years – Wallace, Tribune, and Spearville. Tillage treatments were administered in 2004 and consisted of no-till (NT), disk plow (DP), sweep plow (SwP), and chisel plow (CP). Treatments were arranged in a randomized complete block design with four replications. Soil samples were taken at 0-5, 5-15, and 15-30 cm depths. Composite samples were taken from each block prior to tillage and tested for whole soil organic C and N. Further soil samples were collected in spring 2005 at approximately nine months after tillage (MAT) and again in fall 2005 at approximately 12 MAT and tested for whole soil organic C and N and aggregate size distribution. Bulk density was measured for each plot and depth prior to sampling at 12 MAT. Twelve MAT samples were also tested for aggregate-associated C and N. The DP tillage had a greater C concentration than NT and CP when averaged over depth and time, but C mass did not vary between tillage systems. Changes in whole soil C and N over time varied by location, but the differences were similar between tillage treatments. Tillage treatments DP and SwP also had a greater mass of macroaggregate (250-1000 [Mu]m) associated C relative to CP (but not to NT) for Wallace in the surface 0-5 cm at 12 MAT. No other differences between tillages in aggregate-associated C were observed. A single tillage event did not have a significant impact on aggregate size distribution. The greatest amount of aggregate-associated C and N existed in the large microaggregate (53-250 µm) fraction. Changes in aggregate distribution or aggregate-associated C or N did not directly correlate to changes in whole soil C and N. We therefore conclude that a single tillage operation using these implements will not result in a measurable loss in sequestered C over time for dryland soils in a semi-arid climate such as western Kansas.

Master of Science / Department of Agronomy / David B. Mengel / Grain Sorghum (Sorghum bicolor) is one of the most drought and stress tolerant crops grown in Kansas. For this reason, much of the sorghum is grown in high risk environments where other crops are more likely to fail or be unprofitable. Efficient sorghum cropping systems should not only produce high yields and use inputs such as nitrogen efficiently, but they should also remove as much risk as possible for a successful crop, and give farmers more flexibility in making input decisions. The price of nitrogen (N) fertilizer has increased substantially in recent years. Current retail prices for commonly used N fertilizers range from $0.88 to $1.50 per kilogram of N in Kansas. Thus, a farmer could easily invest $50-$100 per hectare in N, depending on the rate of N needed and the source used. Practices which allow farmers to assess crop potential as late as possible after planting before applying costly inputs like fertilizer, can increase the potential for a profitable return on those inputs in risky environments. Currently, most sorghum growers routinely apply all the N fertilizer prior to planting, sometimes as much as 6 months prior. The current Kansas State University (KSU) nitrogen recommendation is yield goal based and performs well when the grower is able to predict yield six months or more in advance of harvest. However, yield is quite variable and difficult to predict. Because long range weather and yield predictions are not very reliable, could deferring making N application decisions until later in the season when yield can be more accurately predicted reduce risk? Can the use of active sensors provide a better estimate of yield potential and nitrogen needs sometime after planting? If they can, how late can the decision be made and how best should the fertilizer N be applied? Several studies were conducted throughout Kansas to look at the effect of N rate, N application timing (pre-plant, side dress, or combinations of the two) and method of application on sorghum yield and N use efficiency. The studies were also designed to examine the potential of using optical sensors to predict optimum N rate for post-planting applications as a means of avoiding the use of soil tests to estimate soil N contributions. The objectives of this research were: a. to validate the KSU N fertilizer recommendations for grain sorghum grown in rotation with crops such as soybeans and wheat, b. to determine the effect of both preplant and midseason N applications on the growth and yield potential of grain sorghum, and to determine the optimal timing and method for midseason N applications on grain sorghum, and, c. to assess the potential of optical sensing of the growing crop to refine N recommendations using in-season applications during the growing season. This thesis will summarize the results from the various experiments we completed to achieve these objectives. The KSU N fertilizer recommendations for grain sorghum may need some revisions. This research suggests that including coefficients relating to N use efficiency may be necessary to get more accurate N recommendations. Both pre-plant and midseason N applications increased the yield of grain sorghum whenever a response to N was observed. There was no negative effect of applying all the nitrogen midseason at 30-40 days after planting when compared to pre-plant applications. Injecting nitrogen fertilizer below the soil surface had higher yields than other methods of midseason N applications such as surface banding or surface broadcasting, especially when a significant rainfall event did not occur within a few days of application. The optical sensors used in this study were very effective at making N recommendations 30-40 days after planting. These sensors will provide for more accurate N recommendations compared to the current soil test and yield goal method.