Evaluation of promising technologies for soil salinity amelioration in Timpaki (Crete): A participatory approach

Soil salinity management can be complex, expensive, and time demanding, especially in arid and semi-arid regions. Besides taking no action, possible management strategies include amelioration and adaptation measures. Here we apply the World Overview of Conservation Approaches and Technologies (WOCAT) framework for the systematic analysis and evaluation and selection of soil salinisation amelioration technologies in close collaboration with stakeholders. The participatory approach is applied in the RECARE (Preventing and Remediating degradation of soils in Europe through Land Care) project case study of Timpaki, a semiarid region in south-central Crete (Greece) where the main land use is horticulture in greenhouses irrigated by groundwater. Excessive groundwater abstractions have resulted in a drop of the groundwater level in the coastal part of the aquifer, thus leading to seawater intrusion and in turn to soil salinisation. The documented technologies are evaluated for their impacts on ecosystem services, cost, and input requirements using a participatory approach and field evaluations. Results show that technologies which promote maintaining existing crop types while enhancing productivity and decreasing soil salinity are preferred by the stakeholders. The evaluation concludes that rainwater harvesting is the optimal solution for direct soil salinity mitigation, as it addresses a wider range of ecosystem and human well-being benefits. Nevertheless, this merit is offset by poor financial motivation making agronomic measures more attractive to users.

Actions of the International Union of Soil Science towards a global agenda for the sustainable use of soils

In a multi-level stakeholder approach the international level is of primordial importance not only in terms of legal frameworks, but also in terms of scientific analysis of the needs, options and constraints, as well as related to monitoring and evaluation systems. The Working Group on 'International Actions for the Sustainable Use of Soils' (IASUS) of the International Union of Soil Science (IUSS) identified a number of issues and measures in preparation of the 17thWorld Congress of Soil Science held in Bangkok, Thailand, in August 2002, and prepared a resolution in support of a 'global agenda for the sustainable use of soils', which was adopted on 21st August 2002 on the closing day of the congress.

Influence of sample matrix on the alkaline extraction of Cr(VI) in soils and industrial materials

An accurate and efficient determination of the highly toxic Cr(VI) in solid materials is important to determine the total Cr(VI) inventory of contaminated sites and the Cr(VI) release potential from such sites into the environment. Most commonly, total Cr(VI) is extracted from solid materials following a hot alkaline extraction procedure (US EPA method 3060A) where a complete release of water-extractable and sparingly soluble Cr(VI) phase is achieved. This work presents an evaluation of matrix effects that may occur during the hot alkaline extraction and in the determination of the total Cr(VI) inventory of variably composed contaminated soils and industrial materials (cement, fly ash) and is compared to water-extractable Cr(VI) results. Method validation including multiple extractions and matrix spiking along with chemical and mineralogical characterization showed satisfying results for total Cr(VI) contents for most of the tested materials. However, unreliable results were obtained by applying method 3060A to anoxic soils due to the degradation of organic material and/or reactions with Fe2+-bearing mineral phases. In addition, in certain samples discrepant spike recoveries have to be also attributed to sample heterogeneity. Separation of possible extracted Cr(III) by applying cation-exchange cartridges prior to solution analysis further shows that under the hot alkaline extraction conditions only Cr(VI) is present in solution in measurable amounts, whereas Cr(III) gets precipitated as amorphous Cr(OH)3(am). It is concluded that prior to routine application of method 3060A to a new material type, spiking tests are recommended for the identification of matrix effects. In addition, the mass of extracted solid material should to be well adjusted to the heterogeneity of the Cr(VI) distribution in the material in question.

The Role of Forest Soils in a Northern New England Effluent Management System

The Carrabassett Valley Sanitary District in Carrabassett Valley, Maine has utilized both a forest spray irrigation system and a Snowfluent™ system for the treatment of their wastewater effluent. This study was designed to evaluate potential changes in soil properties after approximately 20 years of treatment in the forested spray irrigation site and three years of treatment in the field Snowfluent™ site. In addition, grass yield and composition were evaluated on the field study sites. After treatment with effluent or Snowfluent™, soils showed an increase in soil exchangeable Ca, Mg, Na, and K, base saturation, and pH. While most constituents were higher in treated soils, available P was lower in treated soils compared to the controls. This difference was attributed to higher rates of P mineralization from soil organic matter due to an irrigation effect of the treatment, depleting available P pools despite the P addition with the treatment. Most of the differences due to treatment were greatest at the surface and diminished with depth. Depth patterns in soil properties mostly reflected the decreasing influence of organic matter and its decomposition products with depth as evidenced by significantly higher total C in the surface compared to lower horizons. There were decreasing concentrations of total N, and exchangeable or extractable Ca, Mg, Na, K, Mn, Zn, and P with depth. In addition, there was decreasing BS with depth, driven primarily by declining exchangeable Ca and Mg. Imgation with Snowfluent™ altered the chemical composition of the grass on the site. All element concentrations were significantly higher in the grass foliage except for Ca. The differences were attributed to the additional nutrients and moisture derived from the Snowfluent™. The use of forest spray imgation and Snowfluent™ as a wastewater treatment strategy appears to work well. The soil and vegetation were able to retain most of the applied nutrients, and do not appear to be moving toward saturation. Vegetation management may be a key tool for managing nutrient accumulation on the grass sites as the system ages.

Bentgrass response to K fertilization and K release rates from eight sand rootzone sources used in putting green construction.

There is a lack of plant response to fertilizer K in some sandy soils even though routine soil tests for soil available K are shown to be low. This lack of plant response to K fertilizer application may be explained by K release from nonexchangeable forms. Greenhouse and laboratory experiments were conducted to evaluate (a) response of bentgrass (Agrostis palustris [Agrostis stolonifera var. palustris]) cv. Pencross grown in rootzones with different sand sources to K fertilizer application and (b) K release from nonexchangeable forms from the different sand sources as an index to K availability. Experimental variables in the greenhouse were 2 K levels (0 and 250 mg K/kg soil) and 8 sand rootzone sources. Rootzone soils were sub-irrigated to ensure no K loss from leaching. Two laboratory methods (boiling 1 M HNO3 extraction and continuous leaching with 0.01 M HCl) and total K uptake by the bentgrass were employed to index K release from nonexchangeable forms for each rootzone source. K fertilizer application significantly increased bentgrass yield growing in one rootzone source and root weight in 3 rootzone sources. K uptake by bentgrass and the 2 laboratory methods showed important differences in K release from the sand rootzones. The K removed by the 2 laboratory methods was closely related to leaf tissue K and K uptake, with the 1 M HNO3 extraction method providing the closest fit. The release of K from primary minerals in some rootzones with high sand content is proceeding at rates to satisfy bentgrass requirements for K. The 1 M HNO3 extraction method may provide an alternative to the routine laboratory procedures presently being used to measure the extractable K in sand-based constructed putting greens by measuring K contributed by nonexchangeable forms.

(Table 1) Cation exchange capacity and other characteristics of soils common in Lower Saxony, Germany

The chemical and biochemical processes associated with the filtration of rainwater through soils, a step in groundwater recharge, were investigated. Under simulated climatic conditions in the laboratory, undisturbed soil columns of partly loamy sands, sandy soils and loess were run as lysimeters. A series of extraction procedures was carried out to determine solid matter in unaltered rock materials and in soil horizons. Drainage water and moisture movement in the columns were analysed and traced respectively. The behaviour of soluble humic substance was investigated by percolation and suspension experiments. The development of seepage-water in the unsaturated zone is closely associated with the soil genetic processes. Determining autonomous chemical and physical parameters are mineral composition and grain size distribution in the original unconsolidated host rock and prevailing climatic conditions. They influence biological activity and transport of solids, dissolved matter and gases in the unsaturated zone. Humic substances, either as amorphous solid matter or as soluble humic acids play a part in diverse sorption, solution and precipitation processes.

Salinidad del agua freática en el área regadía del río Mendoza

La provincia de Mendoza tiene la mayor superficie regada de Argentina y cuenta con una vasta infraestructura de riego y drenaje en los cinco ríos aprovechados. Los suelos son de origen aluvial, con perfiles que alternan capas de distintas texturas, observándose la presencia de estratos muy finos -casi impermeables- que impiden el libre drenaje del agua de riego. Esta situación dinámica es más evidente a medida que el río disminuye su pendiente coincidiendo con los sectores bajos de la cuenca. La acumulación de agua produce el ascenso de los niveles freáticos hasta aproximarse a la superficie del suelo, incrementando la salinización del mismo. El área de riego del río Mendoza, con valores de salinidad media del agua en su derivación hacia la red de riego menor de 1 dS.m-1, es una de las más intensamente explotadas del país y presenta dos sectores con problemas de freática cercana a superficie. Los mismos corresponden a una zona central llamada Área de Surgencia AS y a otra llamada Área Lavalle AL. En AS hay una red de 98 pozos de observación (freatímetros) para conocer las profundidades, direcciones de flujos y calidad del agua freática. El AL tiene una red de 100 freatímetros distribuidos en tres subáreas correspondientes a tres colectores de drenajes: Tres de Mayo-Jocolí TMJ, Villa Lavalle VL y Costa de Araujo-Gustavo André CG. El presente trabajo muestra los resultados de la evaluación de la salinidad del agua freática expresada como salinidad total a 25 °C (CE) para las dos áreas de estudio. Las muestras han sido extraídas en 2002 y 2004. Los resultados indican que en los dos momentos de muestreo la mediana es menor que la media correspondiente, lo que evidencia asimetría positiva en las distribuciones. Las medianas obtenidas fueron: 6180 μS cm-1 (2002) y 6195 μS cm-1 (2004). Además se observan cambios en las distribuciones entre los momentos de muestreo y entre las áreas: en 2004 aparecen valores extremos superiores mucho mayores que en 2002, y el área VL acusa frecuencias relativas más uniformes y los mayores incrementos de CE. Se distingue también que en los dos momentos de muestreo el área AS posee los valores de posición de CE más bajos, aunque también es la zona con mayor cantidad de outliers; las áreas TMJ, CG y AS no han sufrido cambios importantes en los valores de CE en dos años, pero sí se advierte un sensible aumento de la CE en VL. Con la base de datos depurados se realizaron isolíneas para diferentes intervalos de la variable analizada (CE) que muestran espacialmente los sectores afectados con los distintos intervalos de salinidad freática.

Determinación de la relación de expansión en suelos de Mendoza (Argentina)

El objetivo fue lograr Índices de Corte ajustados a los suelos de las regiones en estudio y relacionar los mismos con determinaciones sencillas de laboratorio como volumen de sedimentación. Se observó en la región una gran disparidad de métodos para calcular el plano proyecto a obtener y la aplicación de valores de relación corte/relleno sin validación local. El trabajo se realizó en la provincia de Mendoza. Se relevaron 22 parcelas en las zonas irrigadas por los ríos Mendoza y Tunuyán. Los valores promedio de relación de expansión obtenidos, de acuerdo con el tipo de suelo, fueron: arenoso 1,04; franco 1,4; arcilloso 1,71; franco-arenoso 1,29; francoarcillo- limoso 1,71; franco-arcilloso 1,64 y franco-limoso 1,34, respectivamente.

Propuesta metodológica para la evaluación de tierras periféricas al oasis irrigado de Lavalle, Mendoza (Argentina)

La factibilidad de obtener productos agrícolas de calidad, irrigados con agua salina, hace necesario evaluar áreas periféricas al oasis irrigado para determinar su aptitud para el cultivo. El objetivo es articular diversas metodologías para cartografiar y evaluar unidades ecológicamente homogéneas en tierras marginales de Mendoza utilizando las comunidades vegetales como indicador. Se relevó un área piloto mediante procesamiento de imagen LANDSAT/TM y se analizó la vegetación, suelo y freática. Las unidades evaluadas y sus respectivos rangos de salinidad, en dS m-1, hasta 50 cm fueron: estepa de Heterostachys ritteriana, 91-83; matorral de Allenrolfea vaginata con H. ritteriana, 83-48; matorral abierto de A.vaginata con Prosopis strombulifera, 62-55; estepa abierta de Suaeda divaricata con Atriplex argentina, 52-83; matorral de S. divaricata con Lycium tenuispinosum, 40-43; bosquecillo abierto de Prosopis flexuosa, 37-26; matorral denso de Prosopis alpataco, 7-6. La concentración de sales solubles sobrepasa los niveles críticos tolerados por las plantas cultivadas. No se detectaron niveles freáticos en los primeros 15 m de profundidad. Se considera que los suelos tienen buen drenaje interno, por lo que pueden ser recuperados sin inversiones elevadas. Este enfoque metodológico mostró una buena correspondencia entre las comunidades vegetales, su expresión espectral y las condiciones de salinidad y drenaje del suelo.