Dpto. de Química Agrícola y Edafología Facultad de Ciencias (Universidad de Córdoba) Edificio Marie Curie. 3ª Planta. Campus de Rabanales 14014, Córdoba, Spain
Abstract: Application of crop residues to soil and reduced or no tillage are current management practices in order to achieve better water management, increase soil fertility, crop production and soil erosion control. This study was carried out to quantify the effect of wheat straw mulching in a no tilled Fluvisol under semi-arid conditions in SW Spain and to determine the optimum rate in terms of cost and soil protection. After a 3-years experiment, mulching application significantly improved physical and chemical properties of the studied soil with respect to control, and the intensity of changes was related to mulching rate. The organic matter content was generally increased, although no benefit was found beyond 10 Mg haâ1 yearâ1. Bulk density, porosity and aggregate stability were also improved with increasing mulching rates, which confirmed the interactions of these properties. Low mulching rates did not have a significant effect on water properties with respect to control, although the available water capacity increased greatly under high mulching rates. After simulated rainfall experiments (65 mm hâ1 intensity), it was found that the mulch layer contributed to increase the roughness and the interception of raindrops, delaying runoff generation and enhancing the infiltration of rain water during storms. Mulching contributed to a reduction in runoff generation and soil losses compared to bare soil, and negligible runoff flow or sediment yield were determined under just 5 Mg haâ1 yearâ1 mulching rate. It was observed that during simulations, the erosive response quickly decreases with time after prolonged storms (30 min) due to the exhaustion of available erodible particles. These results suggest that the erosive consequences of intermediate intensity 5-years-recurrent storms in the studied area could be strongly diminished by using just 5 Mg haâ1 yearâ1 mulching rates.
Abstract: Rock fragments are a key factor for determining erosion rates, particularly in arid and semiarid environments where vegetation cover is very low. However, the effect of rock fragments in non-cultivated bare soils is still not well understood. Currently, there is a need for quantitative information on the effects of rock fragments on hydrological soil processes, in order to improve soil erosion models. The main objective of the present research was to study the influence of rock fragment cover on run-off and interrill soil erosion under simulated rainfall in Mediterranean bare soils in south-western Spain. Thirty-six rainfall simulation experiments were carried out at an intensity of 26.8 mm hâ1 over 60 min under three different classes of rock fragment cover (<50%, 50â60% and >60%). Ponding and run-off flow were delayed in soils with high rock fragment cover. In addition, sediment yield and soil erosion rates were higher in soils with a low rock fragment cover. The relationship between soil loss rate and rock fragment cover was described by an exponential function. After this first set of experiments, rock fragments were removed from sites with the highest cover (>60%) and the rainfall simulation experiments were repeated. The steady-state run-off rate and soil loss increased significantly, showing that run-off and soil erosion were partly conditioned by rock fragment cover. These results have significant implications for erosion modelling and soil conservation practices in areas with the same climate and soil characteristics.
Abstract: This paper describes the changes in soil water repellency and soil hydrological and erosional responses to rainfall at small-plot scale, arising from a prescribed fire immediately following burning and one year later in a Mediterranean heathland in the area of the Strait of Gibraltar (southern Spain). Very little research has been carried out about the modifications on the ground surface after fire immediately after burning. A prescribed fire was conducted to study short-term changes of the ground surface immediately and one year following burning. After a prescribed fire, a homogeneous charred litter layer and ash-bed covered the mineral soil surface. This cover stayed stable on the soil surface during a period of seven days, until strong winds redistributed litter and ashes. The hydrophobicity of the exposed surface (litter and ashes) decreased considerably in relation with the litter layer properties before the fire. Ponding, runoff coefficients and soil loss were determined using simulated rainfall over the litter layer, the ash-bed and the bare soil. Significant differences were not detected between pre- and post-fire soil loss rates while a charred litter and thick ash layer were present on the ground surface. Runoff and erosion rates increased and time to ponding and runoff decreased when the charred litter and ash layers were artificially removed and the bare soil was exposed. Although wildfires will increase soil erodibility, the trends observed in this study suggest that this increased susceptibility to erosion from rainsplash processes may be limited to some degree while an intact ash and charred litter layer is still present.
Abstract: This paper describes an experiment performed in order to study the possibility of using zeolite in organic olive groves. Soil and leaf analysis was performed and an increase in soil N levels was observed. Furthermore, higher levels of K in the soil and the trees point to the improved nutritional potential of these soils in terms of K, as a result of adding zeolite. The results obtained under experimental conditions can be extrapolated for real plantations in the area and will also lead to significant water savings, greater efficiency, decreased use of fertilizers and less contamination of underground water supplies, which can then be used elsewhere.
Abstract: The relationships between structural stability (as measured by the Henintest and the USLE erodibility index) and various physical and chemical parameters for 28 agricultural soils from southern Spain developed on calcareous materials was investigated. Results revealed that erodibility in these soils, which is closely related to structure, decreases with increasing proportion of clay and permeability values. The structural stability was found to depend on exchangeable sodiunm and magnesium, carbon from fulvic acids, active lime and pH. An analysis of the relationships observed suggests that aggregates are formed by bonding of active groups of fulvic acids with exchangeable sodium and magnesium ions, and that active lime stabilizes them by preventing their biodegradation.
Abstract: This paper presents a proposal for a parametric model of forestry assessment for Mediterranean Mountains based upon the chemical properties of the soil. In addition, an informatic program, calles "Evaluator", has been developed and alloes to assess systematically and automatically as well as to store information within a data base.
Abstract: The authors study the land suitability of soils from Natural Park "Sierra de Grazalema" for forestal use of Abies pinsapo B., Mediterranean species of high ecological value, by applying the "Evaluator· informatic program, wich attains additive parametric evaluation of selected physico.chemical properties of soils. The results indicate that edaphic formations with calcaric and/or mollic horizons show a major suitability for development of this forestal with either a gley horizon horizon or a limited development to soil profile.
Abstract: The relationship between various physical and chemical properties of Mediterranean soils and their erodibility expressed as KUSLE was investigated. Based on the results, soils with a large proportion of particles sized from 0.002 to 0.1 mm (ie, the fraction containing most of the calcareous material) are specially erodible. Also, soils with an aggregate fraction containing abundant lime and low level of organic matter are scarcely permeable and hence more readily erodible.
