M.R. Cameira

Integrating system modeling with field research in agriculture: applications of the root zone water quality model (RZWQM)

Publisher Summary Models provide a ready means of translating research to other locations and thus minimize duplication of field research. They also provide a ready means to transfer the integrated knowledge and technology to farmers and other users. This chapter focuses on root zone water quality model (RZWQM), an agricultural system model that integrates the state-of-the-science knowledge of agricultural systems into a tool for agricultural research and management, environmental assessment, and technology transfer. RZWQM has been tested for different aspects of water movement, several pesticides, crop growth, nitrogen dynamics, and several agricultural management practices. The model has been used nationally and internationally and the degree of success in RZWQM application depends on the agricultural system simulated, data availability and quality, processes of interest, and, to some extent, the modeling experience of users. Both the successes and failures of the model have provided information to improve the model and data collection. During these numerous calibration and validation exercises, many new ideas have been developed on model application. Moreover, RZWQM applications have furthered understanding of agricultural systems and promoted the integration of models with field research.

Monitoring water and NO3-N in irrigated maize fields in the Sorraia Watershed, Portugal

The Sorraia Watershed has a long history of continuous irrigated maize. Imprecise water and fertiliser management has contributed to increase nitrate in the groundwater. Solving this problem requires the identification of problem sources and the definition of alternate management practices. This can be performed by an interactive use of selective experimentation and modelling. This paper presents the experimentation phase, where the field experiments were conducted under the irrigation and fertilisation management commonly found in the watershed. Two different soil representatives of the watershed were selected, presenting different water and solute transport properties. One is a silty loam alluvial soil, with a shallow water table, and the other is a sandy soil with a very low water retention capacity. The various terms of the water (consumption, drainage, soil storage) and nitrogen balance (plant uptake, mineralisation and leaching) were obtained from intensive monitoring in the soil profile up to 80 cm, corresponding to the crop root zone. The results showed that in the alluvial soil, up to 70 kg N ha-1 was produced by mineralisation. Current fertiliser management fail in that it does not consider the soil capability to supply mineral nitrogen from the organic nitrogen stored in the profile at planting. This leads to a considerable amount of NO3-N stored in the soil at harvesting, which is leached during the winter rainy season. In the sandy soil, the poor irrigation management (45% losses by deep percolation), leads to NO3-N leaching during the crop season and to inefficient nitrogen use by the crop. Author Keywords: Water and nitrogen balance; Experimental methods; Nitrate leaching

Evapotranspiration estimation performance of root zone water quality model: evaluation and improvement

Abstract Root zone water quality model (RZWQM) has proven to be useful in evaluating the agricultural systems. However, it has previously been recognized that its evapotranspiration estimates somewhat depart from the measured values indicating the potential for some improvement in this module. Estimation procedure is based on the dual surface approach of Shuttleworth and Wallace, that although having a solid theoretical basis, it is greatly empirical in its application due to the lack of accurate quantitative knowledge of the resistance terms that control the heat fluxes in the canopy. Analysis of the formulation used in RZWQM allowed to detect some weakness in the calculation of bulk surface resistance (rsc), which is based on stomatal resistance averaged by effective leaf area index (LAIeff). In this work, an alteration to the definition of LAIeff is proposed, which leads to an improvement of the estimates. It is also discussed that a greater improvement could be obtained by introducing a model of stomatal resistance response to environmental conditions, which would increase the complexity of the model and be difficult to apply given the lack of adequate knowledge of the quantitative behavior of stomata. Alternatively, the simple crop coefficient approach could be incorporated to define an upper limit to evapotranspiration fluxes and avoid some otherwise unrealistically high estimates of the current version of the model.

Spatial variability of trace elements in allotment gardens of four European cities: assessments at city, garden, and plot scale

PurposeUrban allotment gardens (UAGs) are expanding worldwide, especially in large cities. Environmental pressures (direct and diffuse pollution, gardener practice, geogenic contamination) often result in the accumulation of potentially harmful trace elements in garden soils. The objectives of this study were to assess the spatial variability of trace element distribution in UAGs from city, garden, and plot scale in four European cities; to provide a baseline understanding and identify abnormal values under environmental pressures; and to evaluate the potential of portable X-ray fluorescence screening as a useful tool in soil management.Materials and methodsThe four cities (Ayr and Greenock (Scotland), Lisbon (Portugal), Nantes (France)) provided a wide range of environmental pressures on soils. The locations of the 14 allotment gardens were identified in consultation with the local municipality in each city to reflect various land uses or according to previous evaluation of soil quality. Soil sampling was carried out in 66 plots in total, from which 3 datasets were produced: (i) basic soil properties and trace element concentrations from a composite sample of topsoil for each plot (trace elements quantified by inductively coupled plasma–optical emission spectrometry/mass spectrometry (ICP-OES/MS) or using in-lab portable X-ray fluorescence (PXRF); (ii) in situ PXRF measurement on composite samples (263 plots in Nantes); and (iii) composite samples from 32 small areas within 4 plots in one garden of Nantes.Results and discussionThe results were analyzed to assess the spatial variability of soil properties. At city and garden scale, the variability observed for basic soil properties and major elements is dominated by local geology/parent material (pH, CaCO3, Fe) and gardening practice (OM, CaCO3), which vary between each country. The range of trace element concentrations is similar between each city except for Greenock. Extreme values are observed for Cu, Pb, and Zn reflecting human disruption. In most situations, the trace element contamination was explained through the historical and environmental situations of the site. The PXRF screening method proved useful in providing detailed mapping for hot spot detection or delineation, providing support for soil management at plot and garden scale.ConclusionsAs anticipated, basic soil properties appear to be controlled by the parent material. At plot and garden scale, the trace element variability shows the influence of land use history and background and strong inputs from external factors (e.g., by industrial activity or traffic emission). The PXRF screening method appears to be an efficient solution for soil management as it can be used to discriminate zones which may require restriction on cultivation.

Environmental Quality in Urban Allotment Gardens: Atmospheric Deposition, Soil, Water and Vegetable Assessment at LISBON City

The purpose of this study was to analyze the quality of atmospheric deposition, soil, vadose zone water, and plant species in several Urban Allotment Gardens (UAG) in the city of Lisbon, and to correlate its nature and characteristics with their location within the city pressures and with the farming practices, comparing results with similar studies elsewhere. Twenty one metals or metalloids (Ag, Al, As, B, Ba, Be, Cd, Co, Cr, Cu, Fe, Li, Mn, Mo, Ni, Pb, Sb, Se, Ta, V, Zn) and 16 PAHs (acenaphthene, acenaphthylene, anthracene, fluorene, phenanthrene, naphthalene, benzo[a]anthracene, benzo[a]pyrene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[g,h,i]perylene, chrysene, dibenzo[a,h]anthracene, fluoranthene, indeno[1,2,3-c,d]pyrene), pyrene) were analyzed in the atmospheric deposition, and some of these elements/compounds were further analyzed in soils, water, and vegetables. Results show a wide range of concentrations in the city resulting from different soil types and contamination sources. Indexes based on ratios of selected PAHs suggest pyrogenic origins for the PAHs. Metals and metalloids have both anthropogenic and petrogenic origins, the latter mainly for soils with vulcanic origin. Despite the fact that concentrations in soils and waters have exceeded the recommended values in some areas, the lettuce and cabbage rarely presented contamination, with the measured metal values generally under legislated limits, where this exist.