Suchergebnisse

In western Africa, soil organic matter is a source of fertility for food provision and a tool for climate mitigation. In the Savannah region, strong soil degradation linked to an increase in population threatens organic matter conservation and agricultural yield. Soil degradation is also expected to impact biodiversity and, with it, increase the vulnerability of ecosystem goods and services, including the storage of soil organic carbon. Studies of land use, plant species composition and soil fertility were conducted for a conservation project at a demonstration farm in Northern Togo (West Africa), host to various management regimes. Results showed a low organic matter content of the surface soil horizons, often around 0.5%. The highest values were found in a sacred forest within the farm (2.2%). Among crops, rice had the highest soil organic matter, around 1%. In a survey of grasslands, pastures showed the highest organic matter content, with vegetation composition differing from grazed fallows and abandoned grasslands. Plant species richness showed a positive relationship with soil organic matter (R2adj=41.2%), but only by the end of the wet season, when species richness was also highest. Sampling date had a strong effect on vegetation composition. Results showed a strong influence of human activity on soil formation and distribution, and also on plant diversity. The soil characteristics found under the permanent forest suggest a high potential of the soils of the region for improvement of both agricultural yields and as a potential carbon sink relevant to global change policies. ; The authors want to thank Anna Comellas and Josep Miquel Ubalde for their help in field work and sample processing, and to the Centre de Formation Rurale de Tami in Togo and his director Felipe Garc´ıa for invaluable help in all areas; this work would not have been possible without his collaboration. Funding from the Universitat de Lleida, PROIDE and 15 the Agencia Espan˜ola de Cooperacio´n Internacional para el Desarrollo made the work possible. APPLUS-Agroambiental S.A. provided soil analyses. Work within the CARBOPAS (REN2002- 04300-C02-01) and CARBOAGROPAS (CGL2006-13555-C03-01/BOS) projects, both from the Spanish Science Foundation (FECYT), and the PASTUS-INTERREG (I3A-4-147-E) project from the EU programme INTERREG III-A contributed to the development of ideas in this paper.

The aim of this work was to identify the most sensitive soil quality indicators and assess soil quality after long-term application of sewage sludge (SS) and conventional mineral fertilization for rainfed cereal production in a sub-humid Mediterranean calcareous soil. The treatments included six combinations of SS at different doses (40 t ha−1 and 80 ha−1) and frequencies (every 1, 2 and 4 years), plus a control with mineral fertilization, and a baseline control without fertilization. Twenty-five years after the onset of the experiment, 37 pre-selected physical, chemical and biological soil parameters were measured, and a minimum data set was determined. Among these indicators, those significantly affected by treatment and depth were selected as sensitive. A principal component analysis (PCA) was then performed for each studied depth. At 0–15 cm, PCA identified three factors (F1, F2 and F3), and at 15–30 cm, two factors (F4 and F5) that explained 71.5% and 67.4% of the variation, respectively, in the soil parameters. The most sensitive indicators (those with the highest correlation within each factor) were related to nutrients (P and N), organic matter, and trace metals (F1 and F4), microporosity (F2), earthworm activity (F3), and exchangeable cations (F5). Only F3 correlated significantly (and negatively) with yield. From these results, we concluded that soil quality can be affected in opposite directions by SS application, and that a holistic approach is needed to better assess soil functioning under SS fertilization in this type of agrosystem. ; This project has received funding from the National Institute for Agricultural and Food Research and Technology (INIA) through the RTA2017-00088-C03-01 project and from the European Union's H2020 research and innovation programme under Marie Sklodowska-Curie grant agreement No. 801586

Soil moisture regimes under different land uses were observed and modeled in a representative forest basin in the Catalonian Pre-Pyrenees, more specifically in the Ribera Salada catchment (222.5 km2). The vegetation cover in the catchment consists of pasture, tillage and forest. A number of representative plots for each of these land cover types were intensely monitored during the study period. The annual precipitation fluctuates between 516 and 753 mm, while the soil moisture content oscillates between 14 and 26% in the middle and low lying areas of the basin, and between 21 and 48% in shady zones near the river bed, and in the higher parts of the basin. Soil moisture and rainfall are controlled firstly by altitude, with the existence of two climatic types in the basin (sub-Mediterranean and sub-alpine), and further, by land use. Two models were applied to the estimated water moisture regimes: the Jarauta Simulation Newhall model (JSM) and the Newhall simulation model (NSM) were found to be able to predict the soil moisture regimes in the basin in the different combinations of local abiotic and biotic factors. The JSM results are more precise than the results obtained using another frequently used method, more specifically the Newhall Simulation Model (NSM), which has been developed to simulate soil moisture regimes. NSM was found to overestimate wet soil moisture regimes. The results show the importance of the moisture control section size and Available Water Capacity (AWC) of the profile, in the moisture section control state and variability. The mountain soils are dominated by ustic and occasionally xeric regimes. Land use changes leading to an increase in forest areas would imply drier soil conditions and therefore drier soil water regimes. These effects are most evident in degraded shallow and stony soils with low AWC. ; Los regimenes de humedad del suelo bajo diferentes usos del suelo fueron observados y modelados en una cuenca forestal modelo en el Prepirineo meridional Catalán, específicamente en la cuenca de la Ribera Salada (222.5 km2). La vegetación presente en la cuenca consiste en pasturas, cultivos y bosques. Un número representativo de parcelas experimentales por cada uso del suelo fueron monitoreados de forma intensiva durante el periodo estudiado. La precipitación anual fluctúa entre 516 y 753 mm, mientras el contenido de humedad del suelo oscila entre 14 y 26% en la parte baja y media de la Cuenca y entre 21 y 48% para zonas de umbría cerca de las riberas, y en las partes altas de la cuenca. La humedad del suelo y las lluvias están controladas en primer lugar por la altitud, con la existencia de dos pisos climáticos en la cuenca (sub-Mediterrano y subalpino), y además por los usos del suelo. Dos modelos fueron implementados para estimar los regimenes de humedad del suelo: El Modelo de Simulación Jarauta (JSM) y el Modelo de Simulación Newhall (NSM) encontrando que pueden predecir los regimenes de humedad del suelo en la cuenca para diferentes combinaciones de factores bióticos y abióticos a escala local. Los resultados usando JSM son más precisos que los obtenidos mediante el modelo mas usado, concretamente NSM, el cual ha sido específicamente desarrollado para la simulación de los regimenes de humedad del suelo. El NSM tiende a sobre estimar los regimenes de humedad del suelo, tendiendo hacia regimenes húmedos. Los resultados muestran la importancia de la profundidad de la sección control del suelo y la capacidad de retención de humedad del suelo, en el estado y variabilidad de la sección control de humedad del suelo. Los suelos en zonas de montaña mediterránea están dominados por regímenes ústicos y excepcionalmente xericos. Los cambios en los usos del suelo están direccionados hacia un incremento de las áreas forestales lo cual implica una disminución en la humedad del suelo. Estos efectos son más evidentes en suelos superficiales degradados y pedregosos con baja retención de humedad. ; The research was partly funded by the Spanish Government grant MAE AECI 2004-2006 and the project REN2001-1590/HID (Ministry of Science and Technology, Spain).

Aggregation in soils is the result of the interaction of the soil organic components and soil minerals. The reactivity of the mineral phase is acknowledged to interfere with aggregates formation and stabilization, but its influence on aggregation in semi-arid Mediterranean soils remains mostly unknown. In this study, we used micromorphological analysis of aggregates formed in a 28-d incubation in two agricultural soils differing only in the composition of the mineral phase in the upper Ap horizon (a carbonate-depleted Palexeralf with 21.5% clay, and a contiguous carbonate-rich Typic Calcixerept with 20.9% clay before decarbonation which was reduced to 10.4% upon decarbonation). The two soils belong to the same agricultural field and have had similar management for decades. Soil samples were completely disaggregated into their fractions 2 mm) formed during the incubation were separated at days 3, 7, 14, 21 and 28 and used to prepare thin sections. Macroaggregates were more abundant at day 3, and then decreased in number in the two soils, which indicates a dependency between organic matter decomposition and stable macroaggregates formation. They contained a greater proportion of smaller aggregates in the decarbonated soil. Micromorphological analysis revealed significant differences in the fabric and physical characteristics of these macroaggregates, in which bonds among primary particles were observed to be led by clays in the Palexeralf while the coarse fraction appeared embedded in a micromass with crystallitic b-fabric corresponding to carbonates in the Calcixerept. This resulted in a more compact fabric and less porosity in macroaggregates in the Calcixerept. Image analysis of thin sections was used to quantify and characterize the pore system of macroaggregates. Porosity (pores > 20 μm) was more than double (36.9% for 15.6%) within macroaggregates in the decarbonated soil, with more elongated pores. Although in both soils most pores were 20 to 150 μm in equivalent diameter, some porosity > 150 μm was observed only in macroaggregates from the decarbonated soil. These observations allow hypothesizing that the mechanisms responsible for aggregates stabilization and/or formation are different in the two soils, and that they result in different physical characteristics of soil aggregates. The implications of such differences on air and water flow rates within aggregates, and thus on the soil microbial activity and organic matter decomposition, as well as on soil erodibility, need to be studied and accounted for when evaluating the effect of soil management and other practices on soil quality in semi-arid Mediterranean agrosystems. ; We acknowledge the Basque Government for funding O. Fernández-Ugalde pre-doctoral research, and Lya Arpón for assistance in selecting soils and sampling. A. Gortari is thanked for assistance in image analysis and data processing

In the European Union, the maintenance of soil quality is a key point in agricultural policy. The effect of additions of dairy cattle (Bos taurus) manure (DCM) during a period of 11 years were evaluated in a soil under irrigated maize (Zea mays L.) monoculture. DCM was applied at sowing, at wet-weight rates of 30 or 60 Mg ha−1yr−1 (30DCM or 60DCM). These were compared with a mineral-N treatment (300 kg N ha−1, MNF), applied at 6–8 emerged leaves and with a control (no N, no manure). Treatments were distributed in a randomized block design. Factors analysed were stability against wetting stress disaggregation, porosity, soil organic carbon (SOC) fractions and earthworm abundance, studied eight months after the last manure application. The application rate of 30DCM increased aggregate stability and the light SOC fraction, but not the pore volume, nor the earthworm abundance, compared with MNF. The DCM rates did not result in unbalanced agronomic advantages versus MNF, as high yields (17–18 Mg ha−1 yr−1) were obtained. In Mediterranean environments, the use of DCM should be encouraged mainly because of its contribution to the light SOC fraction which protects dry macro-aggregates from implosion (slaking) during the wetting process. Thus, in intensive agricultural systems, it protects soil from physical degradation. ; The authors thank Elena González, Irma Geli and Albert Roselló for field assistance and Montse Antúnez and Nouha Gobber for laboratory assistance. This study was supported by the National Institute for Agricultural and Food Scientific Research and Technology of Spain-INIA (project RTA2013-057-C05-05) funds. The initial field maintenance was done through different Spanish projects from the National Institute for Agricultural and Food Scientific Research and Technology (INIA) and from the Interministerial Science and Technology Research commission (CICYT): AGL2001-2214-C06; RTA2003-066-C4, AGL2005-08020-C05-03.The subsequent field maintenance by IRTA-Mas Badia and the Department of Agriculture, Livestock, Fisheries, Food and Natural Environment from Generalitat de Catalunya, is fully acknowledged. This research article received a grant for linguistic revision from the Language Institute of the University of Lleida (2015 call).