Soil phosphorus fractions after 111 years of animal manure and fertilizer applications

Accumulated soil P in agricultural soils is a major source of soluble and particulate forms of P entering water resources and degrading water quality. However, few research sites are currently available to evaluate the long-term effects of different cropping systems and fertility practices on soil inorganic and organic P accumulation. The objectives of this study were: (1) to compare the forms and quantity of different inorganic and organic soil P fractions in plots on Sanborn Field, which has been cultivated for 111 years; and (2) to assess the use of standard soil test P extractants for determining changes in soil P dynamics over time. A modified sequential P extraction procedure was used to separate labile and stable inorganic and organic P pools from surface soils collected on Sanborn Field in 1915, 1938, 1962, and 1999 from plots in continuous corn, continuous wheat, continuous timothy, and a corn-wheat-clover rotation amended with either manufactured fertilizers, horse or dairy manure or receiving no fertilization since 1888. Additional samples were collected from a native grass prairie site of a similar soil series to estimate soil characteristics at Sanborn Field before initial cultivation in 1888. Observed accumulation of Bray-1 P among fertilizer and manure treatments was attributed to over-application of P due to unrealistically high yield goals for each cropping system. Long-term cultivation of Sanborn Field increased soil bulk density and lowered soil pH and total organic C compared with native prairie. Fertilization either by addition of manufactured fertilizer or manure significantly increased inorganic resin-P and inorganic NaOH-extractable P. Applications of animal manure also significantly increased most organic P fractions compared with the unfertilized treatment. The native prairie had a larger proportion of total P in organic forms compared with cultivated plots, especially in organic NaOH-extractable P, but no significant decreases in either residual or total P were observed due to cultivation. This study confirms that soil P availability in cropping systems that are amended with predominantly organic P amendments may differ from conventional cropping systems relying on manufactured P fertilizers. However, no direct evidence was found to support the hypothesis that any individual inorganic or organic soil P fraction has a better relationship than conventional soil test P extractants with plant P uptake under contrasting organic and conventional fertility practices.     

Lepidium latifolium: plant nutrient competition-soil interactions

Exotic weeds are invading rangelands of the western United States at unprecedented rates. Understanding plant-soil relationships and competitive interactions of invasive weeds is crucial in long-term control strategies. In a greenhouse experiment, we investigated the influence of soil nutrient depletion on plant growth and plant competition between the exotic invasive weeds, Lepidium latifolium (invading wetlands) and Bromus tectorum (invading a multitude of habitats). Plants were grown individually and in combination until L. latifolium flowered, then roots and aboveground mass were harvested. Soil in individual pots was homogenized, subsamples collected for nutrient analyses, and the soil was re-planted to the same species, grown, and harvested twice more for a total of three growth cycles. As nutrient supplying capacity of the soil declined through growth cycles, aboveground mass of L. latifolium decreased significantly (PА.05) and growth potential of B. tectorum surpassed that of L. latifolium. Only bicarbonate-extractable soil ortho-P positively correlated with plant mass of L. latifolium. A separate experiment demonstrated that L. latifolium has a narrow window of soil water potentials for optimal growth; greatest growth at -20 kPa with significantly declining growth at saturation and -400 kPa. Our data suggest that L. latifolium primarily invades wetlands because the high soil water content reduces tortuosity and allows efficient transport of nutrients to this sparsely rooted species. When soil moisture and/or the nutrient supplying capacity of the soil declines, plants with greater root density can out-compete L. latifolium. Monocultural stands of L. latifolium may be self-limiting in time as available nutrients, particularly P, are biocycled to drier upper soil layers.     

Heavy metal, total arsenic, and inorganic arsenic contents of algae food products

The total arsenic, inorganic arsenic, lead, cadmium, and mercury contents of 18 algae food products currently on sale in Spain were determined. The suitability of the analytical methodologies for this type of matrix was confirmed by evaluating their analytical characteristics. The concentration ranges found for each contaminant, expressed in milligrams per kilogram of dry weight, were as follows: total arsenic, 2.3-141; inorganic arsenic, 0.15-88; lead, < 0.05-1.33; cadmium, 0.03-1.9; and mercury, 0.004-0.04. There is currently no legislation in Spain regarding contaminants in algae food products, but some of the samples analyzed revealed Cd and inorganic As levels higher than those permitted by legislation in other countries. Given the high concentrations of inorganic As found in Hizikia fusiforme, a daily consumption of 1.7 g of the product would reach the Provisional Tolerable Weekly Intake recommended by the WHO for an average body weight of 68 kg. A more comprehensive study of the contents and toxicological implications of the inorganic As present in the algae food products currently sold in Spain may be necessary, which might then be the basis for the introduction of specific sales restrictions.     

Ellagitannins,flavonoids, and other phenolics in red raspberries and their contribution to antioxidant capacity and vasorelaxation properties

Analysis of extracts of Glen Ample raspberries (Rubus idaeus L.) by gradient, reverse phase HPLC with diode array and tandem mass spectrometry identified eleven anthocyanins, including cyanidin-3-sophoroside, cyanidin-3-(2(G)-glucosylrutinoside), cyanidin-3-glucoside, cyanidin-3-rutinoside, pelargonidin-3-sophoroside, pelargonidin-3-(2(G)-glucosylrutinoside), and pelargonidin-3-glucoside. Significant quantities of an ellagitannin, sanguiin H-6, with an M(r) of 1870 were detected along with lower levels of a second ellagitannin, lambertianin C, which has an M(r) of 2804. Other phenolic compounds that were detected included trace levels of ellagic acid and its sugar conjugates along with one kaempferol- and four quercetin-based flavonol conjugates. Fractionation by preparative HPLC revealed that sanguiin H-6 was a major contributor to the antioxidant capacity of raspberries together with vitamin C and the anthocyanins. Vasodilation activity was restricted to fractions containing lambertianin C and sanguiin H-6.     

Nitrate leaching losses and their control in a mixed farm system in the Cotswold Hills, England

Abstract. Nitrate leaching was measured for four years at the Royal Agricultural College 's Coates Farm in the Cotswolds, England. Coates is a typical Cotswold mixed farm with thin, well-drained calcareous soils especially prone to leaching. Over the duration of this study there were dairy, sheep and arable enterprises on the farm. A 'Farm Gate' nitrogen (N) budget was constructed. Small 120 m × 20 m 'farmlets' were sited in ten fields across the farm, covering all parts of the rotation, as the sites for detailed measurements. Each farmlet received the same management as the rest of the field in which they were situated. Using ceramic probes inserted to 60 cm, soil water was sampled every two weeks throughout the winter drainage season. The annual drainage varied from 135 mm under grassland in 1996/7 to 600 mm under cereals in 1998/9. Average N losses by leaching were determined mostly by rainfall and were 65 kg N ha^–1 yr^–1, accounting for 25% of the N inputs. Especially leaky parts of the rotation were the ploughing out of a lucerne ley and the grazing of stubble turnips with sheep, both typical Cotswold farm practices. The research highlights some of the difficulties in developing practicable, profitable management practices to decrease nitrate losses.     

Does butterfly diversity predict moth diversity? Testing a popular indicator taxon at local scales

Indicator taxa are often proposed as efficient ways of identifying conservation priorities, but the correlation between putative indicators and other taxa has not been adequately tested. We examined whether a popular indicator taxon, the butterflies, could provide a useful surrogate measure of diversity in a closely related but relatively poorly known group, the moths, at a local scale relevant to many conservation decisions (10⁰-10¹ km²). We sampled butterflies and moths at 19 sites representing the three major terrestrial habitats in sub-alpine Colorado: meadows, aspen forests, and conifer forests. We found no correlation between moth and butterfly diversity across the 19 sites, using any of five different diversity measures. Correlations across only meadow sites (to test for correlation within a single, species-rich habitat) were also not significant. Butterflies were restricted largely to meadows, where their host plants occur and thermal environment is favorable. In contrast, all three habitats contained substantial moth diversity, and several moth species were restricted to each habitat. These findings suggest that (1) butterflies are unlikely to be useful indicators of moth diversity at a local scale; (2) phylogenetic relatedness is not a reliable criterion for selecting appropriate indicator taxa; and (3) a habitat-based approach would more effectively conserve moth diversity in this landscape and may be preferable in many situations where indicator taxa relationships are untested.     

Rehabilitation of degraded Calluna vulgaris (L.) Hull-dominated wet heath by controlled sheep grazing

Many upland areas of the British Isles have seen declines in the area and condition of heather (Calluna vulgaris)-dominated heathland vegetation. To reverse this decline, management regimes must be designed to rehabilitate areas that have seen this decline. As most of this heathland vegetation is primarily managed by grazing, such management has to determine what stocking levels can maintain the vegetation in a desired state. This paper describes how to reverse this decline through suitable grazing management.A degraded ‘wet-heath’ system, previously grazed at 2.1 sheep ha⁻¹, was subject to a range of grazing treatments over a 5-year period. Treatments varied in intensity (0-1.4 sheep ha⁻¹) and timing (summer only, winter only, or year round) of grazing. Grazing levels were maintained at 2.1 sheep ha⁻¹ outside the fenced areas. Vegetation composition remained stable outside the fenced treatments. All the fenced treatments showed an increase in the relative frequency of the evergreen Calluna vulgaris, with the greatest increase being in the ungrazed treatment, and the least in the year round 1.4 sheep ha⁻¹ treatment. This increase was in line with a reduction in heather utilisation to relatively low and sustainable levels. Other species that benefited from reduced grazing included Carex nigra, Deschampsia flexuosa and to a lesser extent Galium saxatile and Erica tetralix, whereas a range of moss species including Hypnum jutlandicum and Rhytidiadelphus loreus were more frequent at higher grazing levels. Though the recovery of heather was similar in the two seasonally grazed treatments, the vegetation showed different overall trajectories. Winter only grazed allowed a substantial increase in the cover of the deciduous Molinia caerulea, whereas this species was kept in check by summer only grazing. A stocking level of between 0.7 and 1.4 sheep ha⁻¹ appears to be appropriate to maintain and even enhance the cover of heather on degraded wet heath. Complete removal is not necessary. Grazing restricted to the winter period is inappropriate in areas where M. caerulea occurs. Setting appropriate stocking levels to maintain the condition of the vegetation must take into account site conditions, especially the presence of species that can affect the utilisation of heather.     

Runoff-Related Pesticide Input into the Lourens River,South Africa: Basic Data for Exposure Assessment and Risk Mitigation at the Catchment Scale

The characterization of runoff-related pesticide input and the identification of areas of concern in the field are essential for a comprehensive assessment of risk and the planning of mitigation measures. To this end, the agriculturally-derived aqueous and particle-associated pesticide contamination of the Lourens River and its tributaries was measured in a comprehensive design. Sampling was performed in the beginning of April prior to the first rainfall of the wet season and in the middle of April during high water conditions following the first rainfall of 9.6 mm d^-1. Pre-runoff samples indicated contamination with endosulfan at levels up to 0.06 μg L^-1, while no other pesticides were detectable. Rainfall-induced runoff resulted in an increase in the levels of the pesticides endosulfan, deltamethrin, azinphos-methyl, chlorpyrifos, and procymidone up to levels of 0.35, 1.4, 0.6, 0.19 and 9 μg L^-1, respectively in water samples. Endosulfan, azinphos-methyl, and chlorpyrifos were detected at maximum concentrations of 273, 152, and 245 μg kg^-1 in suspended sediments. No increased pesticide levels were detected at a control site upstream of the agricultural area. The Lourens River received its contamination via the tributaries discharging the surrounding farming area. Contamination of the six tributaries depended on landuse and slope characteristics and enabled the identification of target sites for risk reduction approaches. Transient pesticide levels exceeded the target water quality limit proposed by the South African Department of Water Affairs and Forestry (DWAF). The Lourens River site downstream of the farming area has been identified as a site where potential toxic conditions could arise.     

Simplified Dilute Acetic Acid Based Extraction Procedure for Fractionation and Analysis of Wheat Flour Protein by Size Exclusion HPLC and Flow Field‐Flow Fractionation

A simple, highly efficient and reproducible two‐step extraction procedure using dilute acetic acid without (AN) and then with sonication (AS) has been developed for the fractionation of wheat flour protein. Approximately 97% of total protein was extracted from a Canadian hard red spring wheat flour; an additional 1.2% protein could be recovered by further extraction with 1% DDT and 50% 1‐propanol (AR). Size‐exclusion HPLC (SE‐HPLC) and flow field‐flow fractionation (flow FFF) showed that the AN extract, which accounted for most of the total extractable protein (AN + AS + AR), consisted primarily of monomeric protein. The AS extract was composed primarily of polymeric proteins. Flow FFF showed that AN polymeric protein, including that eluting at the SE‐HPLC void volume, showed smaller Stokes diameters than AS polymeric protein. Flow FFF profiles of AS SE‐HPLC subfractions showed that the void volume subfraction contained monomeric and small polymeric protein in addition to large polymeric protein, indicating formation of larger complexes through interaction between some or all of the components. AN and AS extracts, as well as SE‐HPLC and flow FFF fractions thereof, showed a fairly wide range of values among 12 Canadian hard red and white spring wheat cultivars. The proportion of total protein in the AS extract and in the larger sized polymeric protein fractions from SE‐HPLC and flow FFF were highly positively correlated to farinograph mixing time.     

伊朗西部不同土地利用方式下钙质土壤疏水性研究

Soil wettability and water repellency, two important soil physical properties, play an important role in water retention and water conductivity in arid and semi-arid regions. To date, there is a lack of information on soil water repellency in calcareous soils of western lran. In this study, soil water repellency and its affecting factors were studied using 20 soil series collected from Hamadan Province~ western Iran. The effects of soil properties including organic carbon content （SOC）, total nitrogen （TN）, C：N ratio, texture, CaCO3 content, and both fungal and bacterial activities on water repellency were investigated using air-dried, oven-dried and heated soil samples. Water repellency index （WRI） was determined using the short-time sorptivity （water/ethanol） method. To distinguish the actual effects of SOC, a set of soil samples were heated at 300 ~C to remove SOC and then WRI was measured on the heated samples. Relative water repellency index （RWRI） was defined as the change of WRI due to heating relative to the oven-dry WRI value. Results of the WRI values showed that the soils were sub-critically water-repellent. Pasture soils had higher WRI values compared to tilled soils, resulting from high SOC and TN, and high activities of bacteria and fungi. It was observed that SOC, TN, fungal activity, and SOC：clay ratio had significant positive impacts on WRI. Strong positive correlations of RWRI with SOC, TN and fungal activity were also observed. Pedotransfer functions derived for predicting WRI showed that the WRI values had an increasing trend with the increases in fungal activity, salinity, alkalinity and fine clay content, but showed a decreasing trend with increasing bacterial activity.