Structure-biodegradation relationships of polymeric materials. 1. Effect of degree of oxidation on biodegradability of carbohydrate polymers

The biodegradability of oxidized starch and inulin has been studied in relation to the degree of periodate oxidation to dialdehyde derivatives, by measuring oxygen consumption and mineralization to carbon dioxide. A higher degree of oxidation of dialdehyde starch and dialdchyde inulin results in a lower rate at which the polymers are biodegraded. It is demonstrated that the biodegradation rate of dialdehyde inulin derivatives decreases more than that of equivalent starch derivatives. The differences in biodegradation behavior between dialdehyde starch and dialdehyde inulin, resulting from comparable modifications, are discussed in terms of conformational structure.     

Perennial filter strips reduce nitrate levels in soil and shallow groundwater after grassland-to-cropland conversion

Many croplands planted to perennial grasses under the Conservation Reserve Program are being returned to crop production, and with potential consequences for water quality. The objective of this study was to quantify the impact of grassland-to-cropland conversion on nitrate-nitrogen (NO3-N) concentrations in soil and shallow groundwater and to assess the potential for perennial filter strips (PFS) to mitigate increases in NO3-N levels. The study, conducted at the Neal Smith National Wildlife Refuge (NSNWR) in central Iowa, consisted of a balanced incomplete block design with 12 watersheds and four watershed-scale treatments having different proportions and topographic positions of PFS planted in native prairie grasses: 100% rowcrop, 10% PFS (toeslope position), 10% PFS (distributed on toe and as contour strips), and 20 PFS (distributed on toe and as contour strips). All treatments were established in fall 2006 on watersheds that were under bromegrass (Bromus L.) cover for at least 10 yr. Nonperennial areas were maintained under a no-till 2-yr corn (Zea mays L.)--soybean [Glycine max. (L.) Merr.] rotation since spring 2007. Suction lysimeter and shallow groundwater wells located at upslope and toeslope positions were sampled monthly during the growing season to determine NO3-N concentration from 2005 to 2008. The results indicated significant increases in NO3-N concentration in soil and groundwater following grassland-to-cropland conversion. Nitrate-nitrogen levels in the vadose zone and groundwater under PFS were lower compared with 100% cropland, with the most significant differences occurring at the toeslope position. During the years following conversion, PFS mitigated increases in subsurface nitrate, but long-term monitoring is needed to observe and understand the full response to land-use conversion.     

Predicting Satisfaction with Smart Irrigation Controllers and Their Long‐Term Use among Homeowners in Central Florida

Studies throughout Florida have shown smart controllers can substantially reduce irrigation under residential high‐water use conditions. However, successful promotion requires understanding the link between controller performance and the mechanisms by which they are adopted. This article compares irrigation water‐use and survey data collected from households installed with soil moisture sensor and evapotranspiration controllers. The study investigated whether the relative change in irrigation use between two years preceding and two years following installation was a reliable predictor of a homeowner's satisfaction with the device and likelihood of continuing to use it. Results indicated relative changes in irrigation use were only significantly associated with the quality of controller programming. Satisfaction with the controller was largely attributable to satisfaction with the appearance of the landscape and the perceived water‐saving effectiveness of the controller whereas the likelihood of its continued use was only significantly predicted by the level of technical knowledge regarding its functioning and whether or not challenges were experienced with it. Targeting homeowners with supplemental user‐friendly information may best support their long‐term adoption of smart controllers while providing irrigation contractors with training in implementation techniques would represent an integrated strategy for added reductions in residential outdoor water use.     

Alfalfa rapidly remediates excess inorganic nitrogen at a fertilizer spill site

By 19%, standard remediation techniques had significantly reduced the concentration of nitrate nitrogen (NO3- -N) in local ground water at the site of a 1989 anhydrous ammonia spill, but NO3- -N concentrations in portions of the site still exceeded the public drinking water standard. Our objective was to determine whether local soil and ground water quality could be improved with alfalfa (Medicago sativa L.). A 3-yr study was conducted in replicated plots (24 by 30 m) located hydrologically upgradient of the ground water under the spill site. Three alfalfa entries ['Agate', Ineffective Agate (a non-N2-fixing elite germplasm similar to Agate), and MWNC-4 (an experimental germplasm)] were seeded in the spring of 1996. Corn (Zea mays L.) or wheat (Triticum aestivum L.) was seeded adjacent to the alfalfa each year. Crops were irrigated with N-containing ground water to meet water demand. During the 3-yr period, about 540 kg of inorganic N was removed from the aquifer through irrigation of 4.9 million L water. Cumulative N removal from the site over 3 yr was 972 kg N ha(-1) in Ineffective Agate alfalfa hay, compared with 287 kg N ha(-1) for the annual cereal grain. Soil solution NO3- concentrations were reduced to low and stable levels by alfalfa, but were more variable under the annual crops. Ground water quality improved, as evidenced by irrigation water N concentration. We do not know how much N was removed by the N2-fixing alfalfas, but it appears that either fixing or non-N2-fixing alfalfa will effectively remove inorganic N from N-affected sites.     

REMOVAL OF FLOODWATER SEDIMENTS BY A CLEARCUT TUPELO-CYPRESS WETLAND1

ABSTRACT: A palustrine water tupelo (Nyssa aquatica L.)-baldcy-press (Taxodium distichum (L.) Rich.) swamp in southwestern Alabama was subjected to three types of disturbance, including helicopter logging, rubber-tired skidder logging simulation, and helicopter logging followed by an herbicide application. An adjacent undisturbed stand served as a control area. Post-harvest collection of sedimentation data revealed that the herbaceous and woody vegetation regrowth within the helicopter and skidded clearcut areas trapped more sediments than did the control or herbicide treatment areas. Clearcutting, followed by plant regrowth, improved the wet-land's capacity to remove sediments from overbank flow flood waters.     

Spatial contrasts of seasonal and intraflock broiler litter trace gas emissions, physical and chemical properties

Comprehensive mitigation strategies for gaseous emissions from broiler operations requires knowledge of the litters' physical and chemical properties, gas evolution, bird effects, as well as broiler house management and structure. This research estimated broiler litter surface fluxes for ammonia (NH3), nitrous oxide (N2O), and carbon dioxide (CO2). Ancillary measurements of litter temperature, litter total N, ammonium (NH4+), total C content, moisture, and pH were also made. Grid sampling was imposed over the floor area of two commercial broiler houses at the beginning (Day 1), middle (Day 23), and end (Day 43) of a winter and subsequent summer flock housed on reused pine shavings litter. The grid was composed of 36 points, three locations across the width, and 12 locations down the length of the houses. To observe feeder and waterer (F/W) influences on the parameters, eight additional sample locations were added in a crisscross pattern among these automated supply lines. Color variograms illustrate the nature of parameter changes within each flock and between seasons. Overall trends for the NH3, N2O, and CO2 gas fluxes indicate an increase in magnitude with bird age during a flock for both summer and winter, but flux estimates were reduced in areas where compacted litter (i.e., caked litter or cake) formed at the end of the flocks (at F/W locations and in the fan area). End of flock gas fluxes were estimated at 1040 mg NH3 m(-2) h(-1), 20 mg N2O m(-2) h(-1), and 24,200 mg CO2 m(-2) h(-1) in winter; and 843 mg NH3 m(-2) h(-1), 18 mg N2O m(-2) h(-1)), and 27,200 mg CO2 m(-2) h(-1) in summer. The results of intensive sample efforts during winter and summer flocks, reported visually using contour plots, offer a resource to the poultry industry and researchers for creating new management strategies for improving production and controlling gas evolution. Particularly, efforts could focus on designing housing systems that minimize extremes in litter compaction. The extremes are undesirable with more friable litter prone to greater gas evolution and more compacted litter providing a slippery, disease-sustaining surface.     

Changes in the rhizosphere of metal-accumulating plants evidenced by chemical extractants

The plants Salix viminalis L. (common osier) and Thlaspi caerulescens J. Presl & C. Presl have been studied often because of their high potential to extract heavy metals from soils. The soil properties favoring this phytoextraction are not yet fully known. In this study we compared three frequently used single-extracting agents (NaNO3, diethylenetriaminepentaacetic acid [DTPA], and ethylenediaminetetra-acetic acid [EDTA]) with a sequential extraction procedure to describe changes in the different Cd, Cu, and Zn pools in the rhizosphere of S. viminalis and T. caerulescens grown on calcareous and acidic Swiss soils in a pot experiment. The sequential extraction was used to assess the chemical affinities of these heavy metals (HM) in the soil whereas the single extractants were used for estimating the bioavailable HM pools in the soils. Cadmium depletion in several pools was most apparent in the acidic soil, with a significant decrease observed in the NaNO3-, DTPA-, and EDTA-extractable fractions following T. caerulescens growth compared with control pots. The sequential extraction showed that most Cd extracted by the plant from the acidic soil originated from the organic pool, which implies that heavy metals bound to organic matter may constitute a significant part of the bioavailable Cd pool in soils. In the calcareous soil only a small amount of Cd was taken up by T. caerulescens, and this came mainly from the carbonate-bound fraction. This study shows that T. caerulescens, and to a lesser extent S. viminalis, can alter the heavy metal distribution in different soil pools within 90 d.     

The first Neanderthal tooth found North of the Carpathian Mountains

An upper second permanent molar from a human was found alongside numerous tools of the Micoquian tradition and was excavated in Stajnia Cave, which is located over 100 km North of the Carpathian Mountains in southern Poland. The age of these finds has been established within a time-span of late Saalian to early Weichselian, most likely to OIS 5c or 5a, according to the palaeontological, geological, archaeological and absolute dating of the layer from which they were obtained. An examination of the morphology of the human molar indicates that this tooth exhibits many traits frequently occurring in Neanderthal upper molars. Although the occurrence of derived Neanderthal traits in the Stajnia molar cannot be firmly established because of degradation of its cusps, the presence of the above-mentioned features allows the assertion that this tooth belonged to a Neanderthal. The age of the Stajnia tooth and the archaeological context of this find also indicate that this molar is of Neanderthal origin.