A FIELD TECHNIQUE FOR WEIGHING BEDLOAD SAMPLES1

ABSTRACT: A technique for weighing bedload samples that was developed for laboratory use has been modified for field application. The technique involves determining the submerged weight of bedload samples as they are collected. The submerged weights are converted to dry weights from a knowledge of the specific gravity of the bedload material. The technique makes bedload transport data available immediately and eliminates costly and time-consuming steps involved with saving samples for laboratory analysis. Only samples designated for particle-size or other lab analyses need to be saved.     

SIMULATION OF HERBICIDE CONCENTRATIONS IN STORMFLOW FROM FORESTED WATERSHEDS1

The breakpoint rainfall hydrology and pesticide options of the field scale model CREAMS (Chemicals, Runoff, and Erosion from Agricultural Management Systems) were used to predict average concentrations of hexazinone [3 cyclohexyl-6-(dimethyl-amino)-1-methyl-1,3,5-triazine-2,4(1H,3H)-dione] in stormflow from four forested watersheds in the upper Piedmont region of Georgia. Predicted concentrations were compared with measured concentrations recorded over a 13-month period. CREAMS accurately predicted hexazinone concetrations in the initial stormflow events which also contained the highest concentrations. The model underestimated the hexazinone concentrations in stormflow two months and greater following pesticide application. In a companion study, the daily rainfall option of the CREAMS model was used to evaluate the reltive risk associated with the maximum expected concentration of hexazinone, bromacil (5-bromo-3 sec-butyl-6 methyuracil), picloram (4-amino-3,5,6 trichloropicolinic acid), dicamba (3,6-dichloro-0-anisic acid), and triclopyr {[(3,5,6-trichloro-2-pyridinyl)oxy] acetic acid} in stormflow from small forested watersheds. The model predicted the following order of potential residue appearance in stormflow: bromacil>triclopyr>hexazinone>picloram>dicamba. Subsurface movement of residues via interflow and deep leaching losses are not simulated by the version of CREAMS used in these studies.     

Insect habitat management in pasture systems

Two important habitat management strategies in pasture systems involve controlled burning and effective grazing manipulation schemes to maintain native climax grassland vegetation These climax grasslands have historically suffered less insect pest pressure than imported systems However, these types of grasslands are difficult to reestablish after relatively severe disruption by man Also, the proper diversity and stability is difficult to capture in developing imported systems. Imported pastures can exhibit substantial yields per land unit but are often composed of vegetation that rapidly mines nutrients stored by the native vegetation, and often need considerable inputs of fossil fuel, manufactured fertilizers and pesticides, because they are or become very susceptible to pestiferous insects. Habitat manipulation efforts can be effective in regulating forage pest populations below economic levels in imported pasture systems Such efforts include: 1) land use (coupled with plant diversity, grazing, and harvest manipulations), 2) sanitation (including controlled burning), 3) planting dates and harvest times (including grazing manipulations), 4) tillage methods, 5) fertilization, 6) trap crops, 7) water management, and 8) fire management for insect pest suppression and augmentation of natural enemies.     

From the Editors

Editorial Introduction

From the Editors     

Measuring agricultural sustainability in terms of efficiency: the case of Dutch sugar beet growers

Sustainability embraces socio-economic and bio-ecological dimensions or attributes. This paper presents a conceptual framework for quantifying sustainability on the basis of efficiency theory commonly used in economics. The conceptual model is implemented using Data Envelopment Analysis (DEA). Sustainability is measured for a sample of Dutch sugar beet growers. The average technical efficiency was only 50%. A positive correlation was found between technical efficiency and sustainable efficiency. Differences in efficiency among farmers were persistent within and between years. We conclude that there is considerable scope for improving the sustainability of arable farming by better management.     

Mass movements and conservation management in Malta

Mass movements at an environmentally sensitive but very popular leisure site in Malta were investigated in order to establish whether they were naturally occurring or whether they might in some way have resulted from the chronic long-term degradation of the site. Field surveys of the slopes were undertaken and physical and geotechnical properties of the Maltese Blue Clay Formation, which forms the slopes, were determined from laboratory analysis of samples. Slope stability was analysed using the infinite slope model; analysis of two 1996 mudflows indicates that these mass movements are natural processes. A landslide hazard analysis based on this finding suggested that whilst future mudflows constitute a small hazard, the risk of harm arising from them is even smaller. The implications of this for conservation management of the site are important, given the objective of restoring and then maintaining a natural ecological environment at the site. The mudflows are integral components of this natural environment, shaping the landscape and the ecological communities. The provision of information to visitors constitutes a valuable education and management tool that should further reduce the risk of harm and promote responsible recreational use of the site. However, it is essential that managers understand the nature of all relevant components of an environmentally sensitive site, in order that appropriate management strategies are devised. In the case discussed, these might include avoiding unnecessary future intervention on the clay slopes.     

Fertilizer Management in Watersheds of Two Ramsar Wetlands and Effects on Quality of Inflowing Water

Two field experiments were carried out in the watersheds of two Ramsar wetland areas, Lakes Koronia and Volvi (area A) and Lakes Mikri and Megali Prespa (area B), to study the effect of application of N fertilizer on wheat yields, the quality of runoff water, and the quality of stream water. The treatments were a combination of two methods of fertilizer application (total amount in fall, and 2/3 in fall + 1/3 in spring) at three rates (0, 100, and 200 kg N/ha) with four replications. Concentrations of NH₄ ⁺, NO₃ ⁻, NO₂ ⁻, P, and Cl⁻ and pH were determined in all water samples. Runoff water quality was not influenced by fertilizer application in either area. Chemical parameters for water did not differ along the selected watercourses in area B, while in area A they were higher in the samples taken near Lake Koronia than in the samples taken upstream, indicating that the watercourses are polluted downstream by nonagricultural sources. The differences in wheat yields between the 100 and 200 kg N/ha application rates were not high. These results call for better fertilizer management in order to achieve better yields and to diminish the possibility to have negative effects to the environment.     

Environmental impact assessment of a proposed info-tech complex in East Calcutta wetlands

An info-tech complex is proposed for 286 acres (116 ha) of land within the East Calcutta wetlands. The proposed site is 15 km east of Kolkata city and only 8 km south of Dum Dum airport. The site is vacant, with pockets of agricultural land and a few degrading water-logged areas. In order to assess the likely impact of the proposed development on the environment, a rapid environmental impact assessment of an area of 10 km radius from the centre of the project site was carried out. The present status of the environment with respect to ambient air, surface water, groundwater, soil, landuse, noise, and socio-economics of the core and buffer zone has been documented and correlated with 24 project activities during construction, development and operational phases. The frequency of adverse impacts is greater than that of beneficial impacts. Out of the total adverse impacts 20 are short term, reversible and have a low magnitude. The total impact score for the proposed project is (–)468.75 and as per the Assessment Value Index Scale the environmental impact of the proposed project activities is no appreciable impact. But there are certain sectors where the environment will be adversely impacted. Therefore, appropriate measures have been suggested to ameliorate the adverse impacts. It is envisaged that if these measures are implemented then there will be an improvement in the quality of the environment, as well as life, by 687.5 units.     

Post-irrigation impact of domestic sewage effluent on composition of soils,crops and ground water--a case study

Long-term irrigation with sewage water adds large amounts of carbon, major and micro- nutrients to the soil. We compared the spatial distribution of N, P, K and other micronutrients and toxic elements in the top 0.6 m of an alluvial soil along with their associated effects on the composition of crops and ground waters after about three decades of irrigation with domestic sewage effluent as a function of distance from the disposal point. Use of sewage for irrigation in various proportions improved the organic matter to 1.24-1.78% and fertility status of soils especially down to a distance of 1 km along the disposal channel. Build up in total N was up to 2908 kg ha(-1), available P (58 kg ha(-1)), total P (2115 kg ha(-1)), available K (305 kg ha(-1)) and total K (4712 kg ha(-1)) in surface 0.15 m soil. Vertical distribution of these parameters also varied, with most accumulations occurring in surface 0.3 m. Traces of NO3-N (up to 2.8 mg l(-1)), Pb (up to 0.35 mg l(-1)) and Mn (up to 0.23 mg l(-1)) could also be observed in well waters near the disposal point thus indicating initiation of ground water contamination. However, the contents of heavy metals in crops sampled from the area were below the permissible critical levels. Though the study confirms that the domestic sewage can effectively increase water resource for irrigation but there is a need for continuous monitoring of the concentrations of potentially toxic elements in soil, plants and ground water.     

Characterisation of DNA probes for the analysis of metallothionein gene expression in the bank vole (Clethrionomys glareolus)

DNA probes have been developed for subsequent use in monitoring the exposure of animals to heavy metal pollution in terrestrial environments using metallothionein (MT) gene expression in the bank vole (Clethrionomys glareolus). Three different bank vole sequences were characterised corresponding to the cDNA and the genomic DNA for MT-I and the genomic DNA for MT-II. Nucleotide sequence analysis indicates that the coding sequences of the bank vole MT-I and MT-II genes exhibit a very high degree of similarity (greater than 92%) to the corresponding genes of the Chinese hamster, the mouse and the rat. In common with other mammalian MT genes, both the MT-I and MT-II genes in the bank vole are interrupted by two introns, which are at identical positions as those in other rodent MT genes; furthermore, the sizes of these introns are similar to those in other rodents with the first intron being larger than the second and those in the MT-I gene being larger than those in the MT-II gene. The predicted amino acid sequence for the proteins shows that both proteins contain 20 cysteine residues at positions identical to those in other known mammalian MTs. The availability of these DNA sequences now provides a good opportunity to investigate MT gene expression and possible gene amplification in bank voles exposed to metal pollution.