Master of Science / Department of Agronomy / David B. Mengel / This study was initiated to determine if potassium (K) deficiencies seen in soybeans (Glycine max (L.) Merr.) under no-till and strip-till production systems are impacting soybean yields, and if so, what fertilizer application practices including: rate of K application; broadcast or deep band methods of application; and the use of starter fertilizer at planting; could be used to correct the problem. The residual impacts of K fertilization and placement were also evaluated on corn (Zea mays L.) grown in rotation with soybeans. This research was conducted on-farm in cooperation with local producers. Soybeans sites in 2007 were near Harris, Ottawa and Westphalia, Kansas with corn planted in 2008 at the sites near Ottawa and Westphalia. Soybean sites in 2008 were located near Ottawa and Welda, Kansas. Selected sites were generally near or below the current soil test K critical level of 130 mg per kg extractable K, based on sampling histories provided by the cooperators. Sampling in the spring of 2007 confirmed these soil test (ST) K levels. Soybean leaf tissue potassium levels in 2007 were less than the critical level of 17 mg per kg in the unfertilized control plots, and were significantly greater when potassium fertilizer was deep banded or a high-rate of K fertilizer was broadcast. No significant difference in yield of soybeans due to K fertilization was seen, likely due to significant water stress during the grain fill period, which severely limited soybean yield in 2007. Soil test K levels at all the research sites increased dramatically between 2007 and 2008, even where no K was applied. Different weather conditions experienced these two years may have contributed to this occurrence. No residual impacts of K fertilization in 2007 on soybeans were seen in soil tests, corn leaf tissue K levels or corn yield in 2008. Soybean sites in 2008 also showed a dramatic increase in K ST levels in 2008 as compared to farmer records. No effects of K fertilization on soybean growth or yield were seen in 2008. The 2008 Ottawa soybean site had very low P soil tests. A significant response to P fertilization contained in the starter treatments was observed. This suggests that the dominant farmer practice of applying P and K fertilizer to corn, and not applying fertilizer directly to soybeans, even at low soil test levels, may not be supplying adequate P to soybeans, and is likely costing farmers yields and profits.

Master of Science / Department of Agronomy / David B. Mengel / The increasing price of phosphorus (P) fertilizers has created interest among producers in ways to enhance the efficiency of applied P fertilizers. Research has long focused on increasing phosphorus efficiency through the use of fertilizer placement techniques (banding, strip applications, and in furrow placement with the seed). Recently, various products have been introduced and marketed claiming to increase efficiency of applied P or increase availability of native soil P. The objective of this study was to test the use of two such widely advertised products: Avail®, a long chain, organic polymer created to reduce the fixation of fertilizer P by aluminum and calcium, and JumpStart®, a seed inoculant containing a fungus (Penicillium bailii), which is said to increase the availability of fertilizer and native soil P to plant roots through the colonization of the root system and producing organic acid exudates. This study was conducted at multiple locations across Kansas with corn (Zea mays L.) in 2008 and 2009 and winter wheat (Triticum aestivum L.) in 2009. Selected sites varied in soil test P, with a majority of the locations having a Mehlich III P test of < 20mg kg-1, where a P response would be expected. Treatments consisting of P rates from 0 to 20 kg P ha-1 with and without the addition of Avail were applied at planting. At many locations, each of the fertilizer/Avail treatments were planted with and without Jumpstart seed treatment. Plant samples were collected at early and mid-season growth stages. Harvest data consisting of grain yield, grain moisture content at harvest, test weight or bushel weight and grain P content also were collected to measure treatment response. Plant samples for both trials failed to show consistent responses to the addition of either product. Excellent corn grain yields were obtained at seven of eight site years with location averages above 12,500 kg ha-1. One location displayed a significant grain yield response to P in both 2008 and 2009. There were no significant responses to enhancement products where a response to P was seen. At two of the five wheat trials, a significant tissue P response to the addition of P was seen. At one location with very low soil test, 6 mg kg-1, P fertilization increased rate of maturity. No effect on growth or yield at either P responsive or unresponsive sites was seen in wheat due to the use of enhancement products. A series of 20 single replications sites were conducted with the JumpStart product in cooperation with County Extension Agents as a part of wheat variety demonstrations. Analysis of this data showed a significant decrease in wheat yield with the addition of JumpStart in 2009. Overall, this study showed a lower than expected frequency of response to applications of P fertilizer based on soil test and the KSU P fertilizer recommendations. It also showed no response across locations, years and crops to the use of P fertilizer enhancement products.

Master of Science / Department of Agronomy / Johnathon D. Holman / Kraig L. Roozeboom / Replacing fallow periods with cover crops can provide many benefits including soil quality improvements and reduced nitrogen fertilizer requirements. Field experiments were established near Garden City, KS with winter wheat and fallow phases as main plots, thirteen legume or non-legume cover crops, continuous winter wheat, and fallow as subplots, and cover crop termination method as sub-subplots. Treatments containing triticale had greatest water use efficiency (19.9 kg ha[superscript]-1 mm[superscript]-1) and aboveground biomass (3550 kg ha[superscript]-1), but subsequent winter wheat yields were reduced due to a reduction in volumetric water content. Increased soil residue through greater cover crop biomass resulted in increased precipitation storage efficiency during the fallow period, but water requirements to produce biomass depleted soil moisture more than growing a low biomass crop or fallow. In years of above-average precipitation, low biomass cover crops might be grown with little to no negative effect on subsequent wheat yields. A second field experiment was established near Manhattan, KS with fallow, double crop soybean, and four cover crop treatments planted after wheat harvest in a winter wheat-grain sorghum-soybean no-till cropping system, with five nitrogen treatments applied to the sorghum crop to estimate nitrogen contribution of the cover crops. Greatest above ground biomass production and nitrogen accumulation was observed with sorghum-sudan grass. At the 0 kg ha[superscript]-1 N rate, grain sorghum yields were reduced 1200 kg ha[superscript]-1 following sorghum-sudan grass, while all other cover crop treatments provided a 20-30 kg ha[superscript]-1 N equivalent benefit. Sorghum yields might be reduced following large biomass producing cover crops when nitrogen is limiting, but a small nitrogen benefit might be realized following low C:N ratio cover crops. Cover crop productivity and their subsequent effects on grain sorghum performance were evaluated in field studies established near Manhattan and Hutchinson, KS in 2008 and 2009. Sixteen summer or fall cover crop species were planted in no-tillage winter wheat stubble and evaluated for biomass production, nitrogen concentration, and nitrogen accumulation. Summer annual grass species produced the greatest biomass, 3392 kg ha[superscript]-1 and greater, and legume species accumulated the greatest amounts of nitrogen, averaging 43 kg ha[superscript]-1. Grain sorghum yields were 867 kg ha[superscript]-1 greater following summer cover crops compared to fall cover crops. Cover crops had a significant effect on sorghum performance, with yields 1240 kg ha[superscript]-1 greater following legume cover crops.

The objective of this research was to determine the effects of conventional inputs on soil chemical and biological properties compared to organic systems in a four year vegetable rotation. Tillage and cover crops were the same in all treatments to avoid confounding factors often present in similar research. Additional experiments investigated plant gene expression in organic and conventional management systems and in soils with decreased microbial diversity. Experimental plots were prepared in the spring of 2004; four replications of three management treatments, organic, low-input and conventional, were arranged in a randomized complete block design. The rotation consisted of edamame soybean, sweet corn, fallow (pastured poultry in organic plots), and potatoes. Soil samples were taken in the spring and fall of each year, along with data for pest damage, weed control, yield and quality. Soil samples were analyzed for enzyme activity (maximum activity under substrate saturation) and basic soil chemical properties. Treatments were compared over time using 2-Way ANOVA. Multiplex terminal-restriction fragment length polymorphism (M-TRFLP) profiles of the soil microbial community were compared using Multiple Response Permutation Procedures (MRPP). Multi-way ANOVA detected significant treatment effects over time in total carbon, nitrogen, Mehlich III K, Exchangeable K and exchangeable Na (p=0.05). Many significant changes in soil properties over time could not be attributed to treatment effects. All treatments produced similar yields, indicating that successful organic production of these vegetables is possible in Kentucky. Input costs for organic were 37% higher than conventional, due to the cost of organic fertilizer. The organic system required nearly 50% more labor hours than conventional or low-input. The low-input system was the most cost effective, with 58% less input expenses than the conventional system. Microarray analysis of approximately 37,500 Glycine max transcripts did not show significant differences in the gene expression between plants grown organically and conventionally, in plots with significant soil chemical and microbial differences. An experiment in progress is investigating changes in plant gene expression using real time RT-PCR in tomatoes grown in autoclaved soil and native field soil.

<p>Land use histories affect the rate and pattern of soil nutrients at regional and global scale. However, former studies have rarely focused on soil trace elements (B, Mn, Zn, Cu and Fe). In this study, we aimed at the long-term biogeochemical cycling pattern and spatial heterogeneity of soil trace elements in response to land use changes. We conducted experiment at Calhoun experiment forest in SC and surrounded relic hardwood forest, cultivated land and secondary pine forests with contrasting land use histories in a statistically rigorous and spatially explicit design. Our first study indicated that spatial heterogeneity is greatly reduced in many soil properties by agricultural practices, but that successional forest growth on previously cultivated soils re-structures heterogeneity of soil properties within a few decades. We document cases in which land use alters both the soil property's central tendencies and their heterogeneity (C, N, CN, Ca, K), and cases in which changes are apparent in central tendency but much less so in their heterogeneity (Db). In our second study, samples of the upper 0.6-m mineral soil archived in 1962 and 1997 revealed three cycling patterns: 1) Extractable B and Mn were significantly depleted because tree uptake of B and Mn from mineral-soil greatly outpaced resupplies from atmospheric deposition, mineral weathering, and deep-root uptake. 2) Extractable Zn and Cu changed little during forest growth, indicating that nutrient resupplies kept pace with accumulations by the aggrading forest. 3) Oxalate-extractable Fe increased substantially during forest growth, by about 10-fold more than accumulations in tree biomass. This study indicated that forest Fe cycling is qualitatively different from that of other macro- and micro-nutrients. Thirdly, our results revealed that long-term cultivation substantially diminished the activity of soil iron oxides relative to forest growth. Forest Fe cycling is derived from mineral soil weathering, which suggests a need to explore the underlying mechanisms by which bioturbation (e.g.earthworms) mediates transformations of iron bioavailability and oxidation of organic matter in soils. Overall, the wide range of responses to land use changes among the ecosystem's trace elements and other biogeochemical features illustrates the great dynamics of the soil system over time scales of decades to centuries.</p> / Dissertation

<p>The Piedmont region of the southeastern United States has undergone considerable land-use change since settlement by Europeans and Africans. Forests were cleared for agriculture, followed centuries later by land abandonment. Following abandonment, natural recruitment, plantings for erosion control, and plantation forestry have resulted in a large area of the region covered by loblolly pine, Pinus taeda. Today, the Piedmont is a mosaic of farm fields, pastures, pine forests, and relic woodlots. The Calhoun Experimental Forest, located in Union County, SC, has provided a unique history of land use change's alteration of soil properties and processes, the ability of reforestation to restore or deplete soil fertility, and provided insights into the effects this change has on biological diversity.</p><p>In this work, the diversity of fungi living in soil is examined in the context of land-use change and soil biogeochemical change in and around the Calhoun Forest. This study uses molecular tools to identify fungal species from soil and to identify mycorrhizal associates of loblolly pine in a bioassay of propagule diversity, and proposes a novel use of quantitative PCR to quantify the relative abundance of major fungal families affected by land-use change.</p><p>Fungal diversity in soils is high in all land uses, but fungal communities shift from agricultural field communities largely comprised of unicellular ascomycetes and basal lineages to forest communities dominated by saprophytic and symbiotic basidiomycetes. In addition to this shift across a land use gradient, fungal communities are also responding to changes in carbon quantity and quality, biologically available nitrogen and phosphorus, pH, acidity and texture.</p><p>ECM propagule communities also differ across a land use gradient of cultivated fields, grasslands, pine forests, and mixed hardwood stands. There are few ECM propagules able to associate with loblolly pine in cultivated and grassland soils. There is a trend towards higher ECM diversity in the hardwood and pine soils, and both of those soil communities are distinct from each other as well as from soils from field treatments.</p><p>Quantitative PCR, coupled with a nested set of taxon-specific, fungal primers, is a potential way to estimate the abundance of the given taxon relative to all fungi in an environmental DNA. Primers specific to several taxonomic level of fungi were tested to confirm amplification in PCR, then were tested for taxonomic specificity by generating clone libraries with environmental DNA. Several of the successful primers were tested with soil DNA extracts in QPCR and the calculated ratios of fungal abundance varied widely by method of analysis. The results suggest that many repeated measurements and many replicates are required for a robust estimate of the relative abundance of a specific taxon.</p> / Dissertation

The extent of revegetation in the Colorado River delta in Mexico is described, with emphasis on the return of native cottonwood (Populus fremontii ) and willow (Salix gooddingii) trees. Low-level aerial and satellite remote sensing methods were combined with ground surveys to census the vegetation in a 100 km reach of riparian corridor in Mexico. Although the invasive plant, saltcedar (Tamarix ramosissima), still dominates the riparian zone, native trees now account for 23% of the vegetation in the delta. Multi-band digital camera images obtained by aircraft were used to calculate the Normalized Difference Vegetation Index (NDVI) and scored for percent vegetation cover (NDVI:%C has r = 0.91***). A Thematic Mapper (TM) image taken concurrently with the aerial survey was similarly classified, and by comparing scenes on the TM and aerials, it was possible to calibrate NDVI with percent vegetation on the TM image. This information was used to conduct a change analysis relating flows in the Colorado River with summer vegetation patterns on TM images for the years 1992-1999. The results support the importance of pulse floods in restoring the ecological integrity of arid-zone rivers. This dissertation also compared transpiration rates of three Sonoran Desert riparian trees using sap flow and leaf temperature methods using constructed canopies (two of each species: Populus fremontii (cottonwood), Salix gooddingii (willow) and Tamarix ramosissima (saltcedar)) in an outdoor experiment in Tucson, Arizona. Canopies were measured over 11 days for both sap flow and canopy and air temperature differential (Tc-Ta) under non stressed and stressed conditions. Objective 1: to determine the strength of the relationship between transpiration (Et) and Tc-Ta to determine if Tc-Ta can be a useful remote sensing method to measure Et for these species. Objective 2: to compare Et rates among species, to determine if the invasive species, saltcedar, has higher Et rates or ecophysiological advantages over the native trees species. We conclude that the Tc-Ta method could be useful in estimating Et by remote sensing over riparian corridors, and that native trees are not at an ecophysiological disadvantage to saltcedar so long as sufficient non-saline soil moisture is available to support Et.

In desert grasslands of the southwestern United States, Prosopis velutina (mesquite), an N-fixing legume, has proliferated from historic drainage locations into more xeric grassland plains. This expansion is forming a more heterogenous soil nutrient topography in grasslands, N-pools are becoming localized under mesquite canopies, yet the rate and extent of this sequestration remains relatively unknown. Repeated prescribed burning has been used to control Prosopis distribution, but effects of fires on grassland soil nutrient distribution and aboveground plant biomass are also largely unknown. I examined recent research concerning P. velutina natural history, emphasizing characteristics that contribute to range expansion. I also evaluated Prosopis management practices---which include herbicide treatment, prescribed burning, grazing reduction, and mechanical removal---and management goals---which involve complete removal, no removal, and limited removal. Of these, limited removal is the most beneficial, using an herbicide application followed by periodic prescribed burning. In 1997 I established a study area at Fort Huachuca Military Reservation in southeastern Arizona, selecting two adjacent sites with similar soil composition and topography but different fire histories. I examined spatial and seasonal changes in composition and distribution of available soil N and litterfall. My results indicated these were more spatially and temporally heterogenous on sites with low fire frequency and high P. velutina stand development. In 1998 I selected nine sites at Fort Huachuca on two upland surfaces located < 1 km apart, with similar soil physical characteristics and fire frequencies ranging from 0 to 5 fires/decade. I evaluated relationships between fire frequency, soil nutrient status (pH, available P, organic C, total N, and available N), and aboveground plant biomass, including that of the non-native Eragrostis lehmanniana (Lehmann lovegrass). Soil pH and ammonium significantly decreased with increased fire frequency on one surface, and available P significantly decreased with increased fire frequency on the other surface. Available P and pH were significantly different between the 2 surfaces, but aboveground biomass was similar. Soil nutrient status and biomass were not related, suggesting plant-available soil nutrients may not control plant distribution or recovery following fire. E. lehmanniana biomass was negatively correlated with native grass and forb biomass, and tended to increase with increasing fire frequency. Surface litter and E. lehmanniana biomass were correlated, and may increase fire frequency, an important consideration when implementing grassland fire management practices.

Agriculture is the principal land use throughout Europe and agricultural intensification has been implicated in large reductions in biodiversity, with the negative effects on birds particularly well documented. The lapwing (Vanellus vanellus) is one such species where changes in farming practices has reduced the suitability and quality of breeding habitat, leading to a drop in population size that has been so severe as to warrant its addition to the Red List of Birds of Conservation Concern in the UK. Lowland areas, where agricultural intensification has generally been most pronounced, have been worst affected, however, more recently declines in marginal upland areas, previously considered refuges for breeding wader populations, have been identified. An upland livestock farm in Stirlingshire that uses an in-bye system of fodder crop management and has unusually high densities of breeding lapwings provides a basis for this project to test causal hypotheses for the decline of upland lapwing populations and to identify potential conservation management solutions. Specifically this farm plants a forage brassica in an in-bye field for two consecutive years, followed by reseeding with grass and seven, out of sixteen, in-bye fields have undergone this regime at the study site since 1997. Fields that had undergone fodder crop management supported almost 60% more lapwings than comparable fields that had not previously been planted with the fodder crop. Lapwing density was highest in the year after the fodder crop was planted, once it had been grazed, which results in a high percentage of bare ground, likely to be attractive to nesting lapwings. Lapwing densities remained above that which occurred in fields that had not undergone fodder crop management for a further four years after the field had been returned to grass. The effect of management on lapwing food resources and nesting structure was tested through a field experiment; liming increased the abundance of Allolobophora chlorotica, an earthworm species that was associated with chick foraging location at the study site, suggesting that lapwings may benefit from liming conducted as part of fodder crop management. The relationship between lapwings and soil pH is further explored across 89 sites on mainland Scotland, using soil property data to improve the predictive power of habitat association models, something which has not previously been done for any farmland bird. Adding soil and topographical data to habitat models, based on established relationships between breeding lapwings and their habitat, improved model fit by almost 60%, indicating that soil properties influence the distribution of this species. The density of breeding lapwings was highest at higher altitude sites, but only when the soil was relatively less peaty and less acidic, providing further support for the hypothesis that agricultural liming benefits lapwings. In addition to assessing the conservation benefit of fodder crop management, the economic costs are also considered. Fodder crop management provides a source of livestock fodder in the autumn and winter during a period when forage demands outstrip grass growth, and ultimately improves the grazing quality of the grass that is replaced; this system currently operates outside of any agri-environment scheme (AES). However, at the study site, planting of the fodder crop and grass is delayed to avoid agriculture operations during the breeding season, which reduces yield and hence profitability. An initial estimate of £200 ha-1 is suggested as an incentive to encourage wider adoption of fodder crop management in a “lapwing friendly” manner, although further work is required to determine if this payment level is appropriate and the current method of AES implementation may limit the suitability of fodder crop management as an AES. The results indicate that agricultural liming could benefit breeding lapwings in pasture fields where soil pH falls below pH 5.2, by increasing earthworm abundance. Where soil pH is below pH 5.2, liming should provide a cost effective mechanism for farmers to improve grass yields. Regular soil testing and liming in response to low pH, within improved or semi-improved grassland fields, where management activities such as use of nitrogen fertiliser can contribute to soil acidification, should be advocated to farmers in marginal areas as a mechanism for improving grass productivity whilst potentially benefitting breeding lapwing and other species where earthworms contribute significantly to their diet.

The effects of land-use history in the Animas Mountains, New Mexico (AM) and the Sierra los Ajos, Sonora (SLA) were studied in relation to morphological and soil chemical characteristics, radial and basal area growth, and forest structure. Litter depth, organic matter, total nitrogen, CEC, and exchangeable cations were greater in the AM than in the SLA, apparently as a result of differences in fire frequency and other land uses. Seasonal precipitation (October-January) was reconstructed for the AM. Annual precipitation (July-July) was reconstructed for the SLA. July PDSI was reconstructed for both mountain ranges. Fires in the AM were preceded by relatively wet conditions two years before the fire year. No significant climate-fire relationship was found in the SLA. Tree radial and basal area increase differed between mountain ranges, suggesting that annual growth was influenced by differences in land-use history. Fire suppression activities and other land uses in the AM apparently have produced an increase in tree density and dominance of shade-tolerant but less-fire resistant species (i.e. Douglas-fir, southwestern white pine, pinyon pine). More frequent fires and logging activities in the SLA apparently have produced lower tree densities and dominance by shade-intolerant ponderosa pine.