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In addition to a survey of the soils under 150 forest stands on non-calcareous sandy soils, the chemical composition of the soils under 40 stands on non-calcareous loess soil, 30 stands on non-calcareous clay soils and 30 stands on oligotrophous peat soils have been examined, to assess the current status with repect to acidification and eutrophication, and the provide data for further studies. Only the clay soils are not yet seriously affected by the atmospheric inputs. The loess soils are generally considerably acidified, except the alluvial loess soils. The peat soils show a considerable eutrophication, especially in the topsoil, whereas anthropogenic acidification can hardly be separated from their natural acidity. Most investigated heavy metals show elevated concentrations, both in the humus layer and in the top soil, but serious pollution is not found.

A simple one-dimensional stochastic model was developed for quantifying groundwater dynamics and model accuracy. Due to its soil physical backbone, the model is somewhere between pure empirical models on the one hand, and complex physical-mechanistic models on the other. Hence, it is envisaged that it is more effective in scenario studies than pure empirical models, and more easily to operate than complex physical-mechanistic models. A case study showed that the model was capable of predicting various groundwater characteristics.

The Pesticide Leaching and Accumulation (PESTLA) model is used to evaluate the leaching of pesticide to the groundwater on a national and a European scale. A description of all processes and factors taken into account in version 3.4 of the PESTLA model is given. The hydrological data needed to run the PESTLA model are obtained using version 2.0 of the Soil Water Atmosphere Plant (SWAP) model. Guidance is given on the preparation of the PESTLA input files under DOS. A description is also given of the Graphical User Interface of PESTLA, which has been developed to make PESTLA more user friendly. One example is given which is based on the Dutch Standard Scenario. Instructions are given for installation of the PESTLA model.

The TOXSWA model calculates the acute exposure concentration and the average exposure concentrations (AECs) of pesticides in ditches after 4, 21 and 28 days. In a (global) sensitivity analysis based on the Monte Carlo method the most sensitive processparameters (pesticide properties) and the most sensitive system parameters (e.g. ditch dimensions) with respect to AECs were determined. The process parametes "transformation rate in the water layer", "coefficient for sorption to macrophytes" and "Henry coefficient" were identified as contributing most to the varation in the AECs. The full range of pesticides was characterized by these three parameters and subsequently the flow velocity, water depth and dry weight of macrophyutes were identified sas sensitive system parameters with respect to the AECs. Analytically, the water depth, bottom width of the ditch and the sorption coefficients for sorption to macrophytes and suspended solids were identified as sensitive parameters with respect to the acute exposure concentration.

The relationship between parameters of autoregressive moving average exogenous variable (ARMAX) models and physical information that can be derived from databases such as digital topographical maps, digital elevation maps and soil profile descriptionswas investigated at 51 sites with open sandy soils in the Pleistocene part of the Netherlands, The ARMAX parameters appeared to be weakly related with physical information. Water-table depth predicted with ARMAX models which were guessed using physical information have large systematic errors but relatively small random errors. It is concluded that the relationships between time series model paremters and physical information can be improved with respect to the modelling as well as the quality of the data used.

The regional hydrological model SIMGRO of SC-DLO is used for solving various kinds of water management problems, specifically those where the interaction between groundwater and surface waters plays a crucial role. The model code has been thorougly revised, both technically and conceptually. The new version, V3.0, contains many new features, notably concerning water management measures. This manual contains comprehensive information regarding theoretical concepts, technical features of the modules, installation, program use and error handling.

Rainfall, water, sediment yields and evaporation were quantified in three catchment areas with undisturbed rain forest, selectively logged forest, and forest with shifting cultivation respectively. Despite a considerable regional variation in rainfall(1700-2300 mm/a), annual evaporation rates were similar (1209-1314 mm/a). The impact of land use practices on water yield is negligible compared to the effect of rainfall. The sediment yield increased from 56 kg per ha per year for undisturbed forest to 105 kg per ha per year for forest with agriculture and to 564 kg per ha per year for selective logging. The simulated soil erosion increased by more than 1000 kg/ha when skid tracks were constructed on slopes exceeding 10°.

Volatilization rates of pesticides were measured with two micrometeorological methods. For fenpropimorph, the highest rates (1.3-3.0% per hour) were measured in the first hours after application. The rate gradually declined to less than 0.01% per houron the sixth day. Clopyralid had much lower volatilization rates. They were highest (0.1% per hour) on the day after the day of application and declined below the detection limit (less than 0.01% per hour) on the sixth day after application. Rates calculated with the aerodynamic method were slightly higher than those calculated with the Bowen ratio.

An overview is given of three dynamic soil acidification models for application on different spatial scales. NUCSAM, the model for the local scale, was validated on data from two intensively monitored research sites. Results of annual average soil solution concentrations and fluxes calculated with the validated NUCSAM model agreed well with those of the national-scale model RESAM and to a lesser extent with those of the European-scale model SMART. Various deposition scenarios for SOx, NOx and NHx on soils were evaluated with the three acidification models.

The effects on phosphate leaching to surface waters of two scenarios for net phosphate input to sandy agricultural soils were estimated. WATBAL and ANIMO simulations for manure surplus areas in the Netherlands were used. The methodology and models were verified by comparing model results with measured values of the Schuitenbeek catchment. Simulated values of phosphate loads to surface waters and phosphate concentrations were underestimated by 10 and 30% respectively. Phosphate leaching to surface waters and phosphate concentrations hardly increase in the lower scenario with a net P2O5 input or `loss' of 10 kg per ha per year. With a P2O5 surplus of 40 kg per ha per year both leaching fluxes and concentrations increase.

METRONIA is a set of computer programs for calculating the water retention characteristic and the unsaturated hydraulic conductivity from an evaporation experiment by Wind's method. This document describes the programs for screening and processing thedata of an evaporation experiment using the simple set-up for manual operation.

The effects of reusing drainage water have been evaluated and other options to increase the water utilization rate in Egypt explored. The results are an operational network for monitoring drainage water discharges and salinity along the major drains, a database for monitored drainage water discharges and chemical composition, and a complete series of data yearbooks. A mathematical model has been developed to evaluate the potentials for reusing drainage water in irrigation under arid conditions. The model has been calibrated and validated for the Nile Delta. It has been applied to evaluate water management alternatives related to water saving, increased reuse of drainage water and long-term effects of land reclamation.

At fourteen times after application of parathion and chlorothalonil to a potato crop their rates of volatilization were determined by the aerodynamic and Bowen ratio methods. The highest volatilization rate of parathion occurred shortly after application. In the first hours after application its volatilization rate decreased sharply; thereafter it decreased more gradually. The volatilization rate of chlorothalonil at one week after application did not differ much from that shortly after application. Weather conditions in the first twenty-four hours after application of both pesticides were simulated in a chamber. The volatilization of parathion in the chamber had the same order of magnitude as that determined in the field.

DRIP1 is an instrument for measuring and storing rainfall, air pressure and temperature data, which can be retrieved using a portable PC. DRIP1 can be used stand-alone or can be integrated in a measuring network thus allowing the measuring frequency of other network devices to depend on rainfall signalled by DRIP1. This will reduce the size of data sets measured by other instruments. DRIP1 is small, uses little power, and can be supplied by a small solar cell/battery combination. Its 512 Kb memory islarge enough to store data for a long period. This document describes its use, hardware and software.

This technical document presents a standardized data format, designed to promote the exchange of data of different field studies between research groups. The contents of a standardized set of field data and the contents and format of each individual data file are discussed.

Soil information for the EU soil map

The main function of the Crop Growth Monitoring System (CGMS) is to monitor the agricultural season conditions over the whole of the EC for time intervals of ten days. The system is built as a Geographic Information System (GIS) in which modules for interpolation of weather data, crop growth simulation, weather analysis, crop growth analysis and output generation are installed