Loss of pendimethalin in runoff and leaching from turfgrass land under simulated rainfall

A field study was undertaken to investigate runoff and leaching loss of the herbicide pendimethalin in turfgrass land of loamy sand soil. A series of plots constructed in a golf course fairway were surface-applied with pendimethalin SC formulation at the rate of 2. 25 or 4.50 kg a.i./ha and subjected to simulated rainfall at 2.0 cm/day for 10 consecutive days. Runoff losses of pendimethalin were the highest at the first rainfall and then gradually decreased with time. The first runoff event contained pendimethalin in its highest concentration, and in subsequent runoff samples the concentration decreased exponentially. The ranges of pendimethalin concentration were 80.9-18.2 and 177.4-48.6 microgram/L in the standard and double doses, respectively. Total losses by 20 cm of rainfall for 10 days reached 0.81 and 1.22% of the initial deposits at 2.25 and 4.50 kg a. i./ha, respectively. Pendimethalin concentration in the leachate collected at 30-cm soil depth was quite lower than that in the runoff, and the concentration rapidly decreased from 4.3-4.7 to 0. 2-0.4 microgram/L during the 10 days of rainfall treatment. Soil residue analysis at 45 and 90 days after pendimethalin treatment showed that more than 90% of the residue remained at the top 10 cm of soil depth. Low runoff and leaching confirmed that lateral and downward movement of the herbicide should be limited in turf soil. The half-life of pendimethalin under field conditions was 23-30 days and was not affected by application dose and rainfall treatment, but longer persistence was observed under laboratory conditions. Considering low runoff and leaching, as well as relatively short persistence in soil, it is concluded that little environmental carryover of pendimethalin would be expected in turfgrass land.     

Simplified fat extraction with sulfuric acid as cleanup procedure for residue determination of chlorinated hydrocarbons in butter

A new cleanup procedure is described for chlorinated hydrocarbon residues in butterfat. The method is based on the dropwise addition of H2SO4 to a fat solution column and continuous removal of the lipids and the acid. The cleanup of 0.25-2.0 g fat requires only 10-40 ml sulfuric acid and 12-17 ml petroleum ether. There is no need for any further cleanup step, solvent evaporation, or centrifugation. The method is easy to standardize and is suitable for automation. At least 30 fat samples can be cleaned up manually by one analyst in one day. Recoveries were complete (greater than 90%) for polychlorinated biphenyl compounds and for 13 chlorinated pesticides of 16 examined. The method was tested on chlorinated hydrocarbon residues in commercial butter and the results were compared with those obtained with the acetonitrile method. The versatility and limitations of the method were investigated by varying the sulfuric acid strength, initial fat solution concentration, and column dimensions.     

Elemental deposition downwind of a coal-fired power plant

Dry deposition of fly ash emitted by a coal-fired power plant has been calculated using a surface depletion Gaussian plume model. The subject plant is located in the southwestern United States. Soil samples collected downwind of this power plant have been chemically analyzed for selected trace elements (As, B, F, Hg, Se, Sr, U, and V) to determine concentration vs. distance trends. Gaussian plume deposition calculations predict very little increase of trace element concentrations in soils, except for those elements highly concentrated in fly ash emissions compared to soils. Trace element soil concentrations as a function of downwind distance generally confirm these predictions, with the possible exception of Se.     

Laboratory research on the compressibility of four topsoils from grassland

A laboratory technique is described that was developed to investigate the effects of hoof pressure on grassland topsoil. The effects of a vertically-applied pressure (300 kPa) of short duration on 4 soils equilibrated at 0, 5 and 10 kPa water tension are reported. Less vertical deformation and compression were produced at the lower water tension in 2 of the soils. In general, there was a greater recovery from deformation, measured immediately after the transient pressure, at lower water tensions. The most severe structural damage was recorded at depths of approximately 100 mm rather than at the surface.     

Overload-controlled cultivation shanks under static loads

Cultivators for stony soils have to be protected to prevent breakage. Draft forces of cultivator shanks in hard clod-forming soils are higher than in the temperate soils of wet areas. Load-control devices are used to prevent breakage, but most of them cannot maintain constant depth in hard soils.

Load-controlled light cultivator shanks and chisel plows were tested to define their behaviour under high soil resistances and obstacles. The shanks were loaded with horizontal forces to simulate soil resistances as found in cultivating hard clod-forming soils.

The variations in the depth, the lift angle and the backward deflection were measured. The maximum stresses on the shanks were calculated.

It was found that only the light cultivator shank with a pre-loaded special design moment control device can till hard soils with small reasonable depth variations and still run over an obstacle without being broken.

Only the heavy chisel plow with the rear spring load control device can run over an obstacle without being broken, but it loses cultivation depth under too low a soil resistance, compared with the maximum draft that it can hold.     

Estimation of soil strength properties for critical rooting conditions

Methods to aid in the large-scale testing and characterization of Coastal Plain soils based on their susceptibility to root-limiting strength problems were developed and analyzed. They were basically regression equations modeled after a Taylor series expansion. The equations relate changes of soil strength, bulk density and soil water content between field and “critical rooting conditions”. Once equations wered eveloped from a data set of 426 laboratory samples, critical rooting bulk density was predicted for a separate set of laboratory and field samples. All laboratory samples and appropriate field samples were equilibrated at — 100 kPa soil-water potential. Soils used were sandy Ultisols, which may limit the scope of equations.

In many cases, changes in the water contents were not a significant factor in the prediction of soil strength. This may be a reflection of the limited capabilities of the equations, the uniform equilibration of soil-water potential of the soils, or the fact that the slope of the strength vs. bulk density curve is independent of water content over the range of samples considered. Nevertheless, it does simplify the equations and may suggest that a series of several equations for different soil types would be better than a single equation that requires soil-water content.     

Phytoextraction of Cd and Zn with Salix viminalis in field trials

Abstract. Use of high biomass crops such as the willow Salix viminalis to extract metals for soil remediation has been proposed as an alternative to the low biomass-producing hyperaccumulating plants. High yields compensate for the moderate heavy-metal concentrations in the shoots of such species. We report the first long-term trials using Salix viminalis to extract heavy metals from two contaminated soils, one calcareous (5 years) and one acidic (2 years). Total metals extracted by the plants were 170 g Cd ha⁻¹ and 13.4 kg Zn ha⁻¹ from the calcareous soil after 5 years, and 47 g Cd ha⁻¹ and 14.5 kg Zn ha⁻¹ from the acidic soil after 2 years; in the first year outputs were negligible. After 2 years, Salix had performed better on the acidic soil because of larger biomass production and higher metal concentrations in shoots. Addition of elemental sulphur to the soil did not yield any additional benefit in the long term, but application of an Fe chelate improved the biomass production. Cd and Zn concentrations were significantly higher in leaves than stems, highlighting the necessity to collect leaves as well as shoots. On both soils, concentration in shoots decreased with time, indicating a decrease in extraction efficiency.     

Estimates of minimum viable population sizes for vertebrates and factors influencing those estimates

Population size is a major determinant of extinction risk. However, controversy remains as to how large populations need to be to ensure persistence. It is generally believed that minimum viable population sizes (MVPs) would be highly specific, depending on the environmental and life history characteristics of the species. We used population viability analysis to estimate MVPs for 102 species. We define a minimum viable population size as one with a 99% probability of persistence for 40 generations. The models are comprehensive and include age-structure, catastrophes, demographic stochasticity, environmental stochasticity, and inbreeding depression. The mean and median estimates of MVP were 7316 and 5816 adults, respectively. This is slightly larger than, but in general agreement with, previous estimates of MVP. MVPs did not differ significantly among major taxa, or with latitude or trophic level, but were negatively correlated with population growth rate and positively correlated with the length of the study used to parameterize the model. A doubling of study duration increased the estimated MVP by approximately 67%. The increase in extinction risk is associated with greater temporal variation in population size for models built from longer data sets. Short-term studies consistently underestimate the true variances for demographic parameters in populations. Thus, the lack of long-term studies for endangered species leads to widespread underestimation of extinction risk. The results of our simulations suggest that conservation programs, for wild populations, need to be designed to conserve habitat capable of supporting approximately 7000 adult vertebrates in order to ensure long-term persistence.     

Factors contributing to guidance performance when using a camera-based guidance aid

A guidance aid is a device that provides guidance information to the driver rather than replacing the driver. With a camera-based guidance aid, the view seen by a forward-looking video camera is displayed on a monitor situated within the operator station of the vehicle. As the vehicle moves forward, images of the ground scroll vertically across the monitor. The rate at which the image scrolls, the image velocity, is related to the forward velocity of the vehicle, the placement of the camera (height and tilt angle), and the optical characteristics of the guidance camera. When tested with a tractor at forward velocities between 1.6 and 12.8 km/h, lateral error increased linearly as image velocity increased. Driver self-confidence decreased linearly as image velocity increased. Based on subjective feedback, drivers preferred a camera tilt angle of 20 degrees (over either 30 degrees or 40 degrees) because it yielded the greatest look-ahead distance. Statistically, a tilt angle of 30 degrees was best for a camera with a narrow field of view (narrow FOV, 20 degrees in the lateral direction). For a camera with a wide field of view (wide FOV, 39 degrees in the lateral direction), there was no statistical difference. For the narrow FOV camera, a camera height of 1.1 m yielded statistically smaller lateral errors than a camera height of 1.5 m. There was no statistical difference for the wide FOV camera. Overall, the lateral error was statistically smaller for the narrow FOV camera than for the wide FOV camera due to the difference in the lateral ratio for each camera, where the lateral ratio is the ratio of the lateral field of view of the camera to the fixed monitor width.