CHARACTERIZING THE STATISTICAL DISTRIBUTION OF ORGANIC CARBON AND EXTRACTABLE PHOSPHORUS AT A REGIONAL SCALE

Greater awareness of potential environmental problems has created the need to monitor total organic carbon (TOC) and extractable phosphorus (P) concentrations at a regional scale. The probability distribution of these soil properties can have a significant effect on the power of statistical tests and the quality of inferences applied to these properties. The objectives of this study were to: (1) evaluate the probability distribution of TOC and extractable P at the regional scale in three Major Land Resource Areas (MLRA), and (2) identify appropriate transformations that will result in a normal distribution. Both TOC and extractable P were non-normally distributed in all three MLRAs. Suggested power transformations did not result in normality, but a natural log and negative binomial transformation did produce distributions that met the assumptions of normality in most cases. Statistical analysis of TOC and extractable P data at the regional scale will need to take into account the non-normal distribution of these properties for accurate and precise estimates

Switchgrass Biomass Production in the Midwest USA: Harvest and Nitrogen Management

Information on optimal harvest periods and N fertilization rates for switchgrass (Panicum virgatum L.) grown as a biomass or bioenergy crop in the Midwest USA is limited. Our objectives were to determine optimum harvest periods and N rates for biomass production in the region. Established stands of \u27Cave-in-Rock\u27 switchgrass at Ames, IA, and Mead, NE, were fertilized 0, 60, 120, 180, 240, or 300 kg N ha-1. Harvest treatments were two- or one-cut treatments per year, with initial harvest starting in late June or early July (Harvest 1) and continuing at approximately 7-d intervals until the latter part of August (Harvest 7). A final eighth harvest was completed after a killing frost. Regrowth was harvested on previously harvested plots at that time. Soil samples were taken before fertilizer was applied in the spring of 1994 and again in the spring of 1996. Averaged over years, optimum biomass yields were obtained when switchgrass was harvested at the maturity stages R3 to R5 (panicle fully emerged from boot to postanthesis) and fertilized with 120 kg N ha-1. Biomass yields with these treatments averaged 10.5 to 11.2 Mg ha-1 at Mead and 11.6 to 12.6 Mg ha-1 at Ames. At this fertility level, the amount of N removed was approximately the same as the amount applied. At rates above this level, soil NO3-N concentrations increased

Comparison of two software programs used to determine the relative supersaturation of urine ions

IntroductionRelative supersaturation (RSS) values for urine crystals are a measure of the risk of urinary stone formation and have been shown to be lowered in foods shown to aid in the management of urolithiasis. In order to calculate RSS in pets, computer programs have been developed to calculate RSS and aid in the understanding of stone formation in veterinary medicine. However, some older programs have not been updated for use in animals, and the specific coefficients used are not publically available. One of the first RSS programs was developed in BASIC computer language and published in 1985 which was called EQUIL2. The EQUIL2 program was updated to a compiled version compatible with a PC platform. However, the formulas could not be read or altered.MethodsThis study evaluates a new program with known coefficients to the original EQUIL2 program. The RSS values of the two programs were compared through a t-test, calculating the r2 from correlation analysis, Lin’s concordance correlation coefficient, and by a Bland–Altman analysis of outputs from the two programs using urine samples from healthy dogs and cats.Results and DiscussionOur results show that for both magnesium ammonium phosphate (struvite) and calcium oxalate, the RSS values of the original program could be calculated from the new programs RSS values. Although the actual RSS values were different (as might be expected through the use of the updated coefficients and different thermodynamic stability constants in the calculations) the results were highly correlated, finding elevations and reductions in RSS proportionally in the same urine samples. The current work creates a foundation for using the modernized program to calculate RSS and provides a shared method for understanding the risk of struvite and calcium oxalate stone formation

Adding a polyphenol-rich fiber bundle to food impacts the gastrointestinal microbiome and metabolome in dogs

IntroductionPet foods fortified with fermentable fibers are often indicated for dogs with gastrointestinal conditions to improve gut health through the production of beneficial post-biotics by the pet's microbiome.MethodsTo evaluate the therapeutic underpinnings of pre-biotic fiber enrichment, we compared the fecal microbiome, the fecal metabolome, and the serum metabolome of 39 adult dogs with well-managed chronic gastroenteritis/enteritis (CGE) and healthy matched controls. The foods tested included a test food (TF1) containing a novel pre-biotic fiber bundle, a control food (CF) lacking the fiber bundle, and a commercially available therapeutic food (TF2) indicated for managing fiber-responsive conditions. In this crossover study, all dogs consumed CF for a 4-week wash-in period, were randomized to either TF1 or TF2 and fed for 4 weeks, were fed CF for a 4-week washout period, and then received the other test food for 4 weeks.ResultsMeaningful differences were not observed between the healthy and CGE dogs in response to the pre-biotic fiber bundle relative to CF. Both TF1 and TF2 improved stool scores compared to CF. TF1-fed dogs showed reduced body weight and fecal ash content compared to either CF or TF2, while stools of TF2-fed dogs showed higher pH and lower moisture content vs. TF1. TF1 consumption also resulted in unique fecal and systemic metabolic signatures compared to CF and TF2. TF1-fed dogs showed suppressed signals of fecal bacterial putrefactive metabolism compared to either CF or TF2 and increased saccharolytic signatures compared to TF2. A functional analysis of fecal tryptophan metabolism indicated reductions in fecal kynurenine and indole pathway metabolites with TF1. Among the three foods, TF1 uniquely increased fecal polyphenols and the resulting post-biotics. Compared to CF, consumption of TF1 largely reduced fecal levels of endocannabinoid-like metabolites and sphingolipids while increasing both fecal and circulating polyunsaturated fatty acid profiles, suggesting that TF1 may have modulated gastrointestinal inflammation and motility. Stools of TF1-fed dogs showed reductions in phospholipid profiles, suggesting fiber-dependent changes to colonic mucosal structure.DiscussionThese findings indicate that the use of a specific pre-biotic fiber bundle may be beneficial in healthy dogs and in dogs with CGE

Evaluation of arbuscular mycorrhiza populations for enhancing switchgrass yield and nutrient uptake

To enhance the economic viability of switchgrass (Panicum virgatum L.) as a forage or biomass crop, rapid stand establishment and high yields are needed using low inputs, particularly nitrogen (N) and phosphorus (P) fertilizer. Arbuscular mycorrhizal fungi (AMF) form symbiotic relationships with mycotrophic species, and can increase water and nutrient uptake by their host, and colonization by AMF may be essential for plant establishment and survival with mycorrhizal dependent plant species. Arbuscular mycorrhizal fungal inoculum was collected from native and seeded switchgrass stands in Nebraska, Kansas, Iowa, Missouri, Virginia, and North Carolina. Four switchgrass cultivars were inoculated with AMF from each collection, and grown in sand cultures for 12 wk. Mycorrhiza inoculated plants produced 15-fold greater shoot and root yields, and recovered six-fold more N and 36-fold more P than non-mycorrhizal plants, indicating that switchgrass is highly mycorrhizal dependent. Plants inoculated with AMF from seeded switchgrass stands averaged 1.5-fold greater shoot and root yields than plants inoculated with AMF from native prairies. Switchgrass, big bluestem (Andropogon gerardii Vitman), sorghum (Sorghum bicolor L. Moench) and soybeans (Glycine max (L.) Merr.) were grown for 12 wk in sand cultures inoculated with three highly or three moderately effective AMF populations. Switchgrass and big bluestem responded similar to inoculation with the different AMF. However, sorghum and soybeans responses were different from switchgrass, suggesting that highly effective AMF associated with seeded switchgrass stands are not highly effective for these crops. Switchgrass seedlings were inoculated with highly effective, moderately effective, or indigenous AMF populations, and grown in cone-tainers for 12-wk prior to transplanting in a Sharpsburg silty clay loam (fine montmorillonitic mesic typic Argiudoll) and an Ortello loam (coarse loamy mixed mesic udic Haplustoll) near Mead, NE. Switchgrass yield or N- and P-uptake were not significantly different between the introduced and the indigenous AMF at either site. This may have resulted from the inability of the introduced AMF to compete with the indigenous AMF for colonization of new switchgrass roots

Evaluation of Switchgrass Rhizosphere Microflora for Enhancing Seedling Yield and Nutrient Uptake

Many rhizosphere microorganisms enhance nutrient uptake and plant growth, but their effectiveness can vary with host species and with genotype within species. This study evaluated the effectiveness of rhizosphere microflora indigenous to the rhizosphere of switchgrass (Panicum virgatum L.) for enhancing seedling yield and nutrient uptake. Switchgrass roots and rhizosphere soil were collected from native prairies and seeded stands in Nebraska, Kansas, Iowa, Missouri, Virginia, and North Carolina. Seedlings of four switchgrass cultivars were inoculated with root fragments and rhizosphere soil from each collection, fertilized with a nutrient solution, and gown in steamed sand for 12 wk in a greenhouse. Seedlings inoculated with rhizosphere microflora produced up to 15-fold greater shoot and root yields, and recovered up to 6-fold more N and %fold more P than seedlings inoculated with rhizosphere bacteria only. These responses were consistent for all four switchgrass cultivars and were probably due to arbuscular mycorrhizal fungi. Switchgrass rhizosphere populations were highly variable in their ability to recover N and P and stimulate seedling shoot and root yields. Seedlings inoculated with rhizosphere populations from seeded switchgrass stands averaged 1.5-fold greater shoot and root yields than seedlings inoculated with rhizosphere populations from native prairies. Rhizosphere populations that stimulated the greatest N uptake differed from pop;la;ions that resulted in the greatest P uptake. Highly effective microbial populations appear to develop in the rhizosphere of seeded switchgrass stands

Rhizome and Tiller Development of Three Nebraska Sandhills Warm-Season Grasses

Rhizome and tiller development of ungrazed switchgrass (Panicum virgatum L.), prairie sandreed [Calamolvilfa longifolia (Hook) Scribn.], and sand bluestem [Andropogon gerardii var. paucipilus (Nash) Fern.] were studied for two years in the Nebraska Sandhills. Rhizome growth of switchgrass began at the 4- to 5-leaf stage. Following tiller elongation, no new rhizomes developed but rhizome elongation continued. Many of the prairie sandreed tillers were biennial similar to those of indiangrass [Sorghastrum nutans (L.) Nash]. Spring tiller development on prairie sandreed came from both vertical and horizontal rhizomes and continuing growth of late emerging tillers from the previous year. New rhizomes began growth at the 4- to 5-leaf stage. Prairie sandreed was the only grass to have rhizomes deeper than 10 cm. In sand bluestem, buds on rhizomes that were underneath the previous year\u27s tiller lived over winter. In the spring after a tiller emerged through the soil and reached the 4- to 5-leaf stage meristematic tissue below the shoot apex elongated forming a rhizome which pushed the shoot apex to the soil surface. The newly formed rhizome initiated buds which served as the site of the following year\u27s tiller development. Normal tiller elongation and inflorescence formation occurred later in the season. Prairie sandreed and sand bluestem are adapted to sand burial while switchgrass requires a more stable soil

Switchgrass Biomass Production in the Midwest USA: Harvest and Nitrogen Management

Information on optimal harvest periods and N fertilization rates for switchgrass (Panicum virgatum L.) grown as a biomass or bioenergy crop in the Midwest USA is limited. Our objectives were to determine optimum harvest periods and N rates for biomass production in the region. Established stands of \u27Cave-in-Rock\u27 switchgrass at Ames, IA, and Mead, NE, were fertilized 0, 60, 120, 180, 240, or 300 kg N ha-1. Harvest treatments were two- or one-cut treatments per year, with initial harvest starting in late June or early July (Harvest 1) and continuing at approximately 7-d intervals until the latter part of August (Harvest 7). A final eighth harvest was completed after a killing frost. Regrowth was harvested on previously harvested plots at that time. Soil samples were taken before fertilizer was applied in the spring of 1994 and again in the spring of 1996. Averaged over years, optimum biomass yields were obtained when switchgrass was harvested at the maturity stages R3 to R5 (panicle fully emerged from boot to postanthesis) and fertilized with 120 kg N ha-1. Biomass yields with these treatments averaged 10.5 to 11.2 Mg ha-1 at Mead and 11.6 to 12.6 Mg ha-1 at Ames. At this fertility level, the amount of N removed was approximately the same as the amount applied. At rates above this level, soil NO3-N concentrations increased

Atrazine Dissipation and Off-Plot Movement in a Nebraska Sandhills Subirrigated Meadow

Atrazine [6-chloro-N-ethyl-N’-(1-methylethyl)-1,3,5-triazine-2,4-diamine] can be used to modify species composition of naturally subirrigated Sandhills meadows. The potential for ground water contamination exists as the water table depth ranges from 0 to 3 m. Atrazine was applied at 2.2 and 3.4 kg ha-1 in May 1984, August 1984, or May 1985 to a Gannett fine sandy loam (Typic Haplaquoll, coarse-loamy, mixed, mesic) in a Nebraska Sandhills subirrigated meadow. Residues of atrazine applied in 1984 and 1985 carried over into 1985 and 1986, respectively. Herbicide dissipation and off-plot movement were monitored in 1985 by sampling soil at 0 to 5 cm and 5 to 15 cm depths within and outside the experimental areas. Atrazine dissipation initially approached zero-order kinetics after May 1985 application, but generally followed first-order kinetics during the entire 320-day sampling period. Atrazine half-life in the entire 0 to 15 sampling zone was 46 ± 7 days. Herbicide concentrations at the 5 to 15 cm sampling depth did not exceed levels measured at 5 days after application. Low and highly variable atrazine concentrations detected in some of the untreated plots and in some off-plot soil samples indicated minimal lateral movement of the herbicide

Dependence of 3 Nebraska Sandhills Warm-Season Grasses on Vesicular-Arbuscular Mycorrhizae

Vesicular-arbuscular mycorrhizae (VAM) are rare or absent in actively eroding soils of the Sandhills. The objective of this study was to determine if 3 major Sandhills warm-season grasses used in reseeding eroded Sandhills sites are highly mycorrhizal dependent, and evaluate the response of VAM at different phosphorus (P) levels. In 2 greenhouse experiments, sand bluestem [Andropogon gerardii var. paucipilus (Nash) Fern.], switchgrass, (Panicum virgatum L.), and prairie sandreed [Calamovilfa longifolio (Hook) Scribn.] were grown in steam-sterilized sand in pots and inoculated with either indigenous Sandhills VAM, Glomus deserticola, or noninoculated. In the second experiment, VAM inoculated and control plants were treated with 5 P levels ranging from 5.4 to 27.0 mg P pot1. Increasing levels of P fertilizer caused an initial increase, then dramatic decrease, in percentage colonization by Glomus deserticola but had no effect on percentage colonization by indigenous Sandhills VAM. Mycorrhizal inoculated plants had a greater number of tillers, greater shoot weight, root weight, tissue P concentration and percentage P recovered, and a lower root/- shoot ratio and P efficiency than noninoculated plants. Non-inoculated sand bluestem had significantly lower shoot P concentration but greater P efficiency over all P levels than any other grass-VAM treatment combination. Phosphorus fertilizer and VAM effects were often complementary at P levels up to 16.2 to 21.6 mg P pot-1, with no change or a decrease in plant responses at higher P levels. These 3 major Sandhills warm-season grasses were highly mycorrhizal dependent. Successful reestablishment of these on eroded sites in the Sandhills may be greatly improved if soil reinoculation with VAM occurred prior to revegetation