Cover crops management as conservation system and improvement of soil quality and runoff water in the andalusian olive grove

The majority of the world’s olive production is concentrated in the Mediterranean basin. Problems of erosion and loss of soil fertility pose a particular threat to the sustainability of this crop. In comparison to tillage systems, cover crops have proven to be an effective way of protecting the soil and producing improvements in its organic matter content. The aim of this thesis is to gain a better understanding of cover crops, in particular in terms of which species most reduce runoff and erosion losses, and which have the most positive effect on soil fertility. The study was carried out with plant species typically used as covers: graminoids, crucifers and legumes. Dead mulches, which to date have been the focus of limited study, were also analysed. Such covers include pruning residues and their benefits were examined in relation to different amounts and residue size. The existence of a vegetation cover, whether sown or spontaneous, reduces runoff and erosion losses. The study carried out using a sprinkler rainfall simulator on 50 m2 plots with a 20% slope showed that the cover crop system significantly reduces soil loss and loss of soil organic carbon (SOC) associated with sediment wash-off. The experiment was carried out over two years with two rainfall intensities (40 mm h-1 and 15 mm h-1) and at two different times of the year (when the cover crop is growing and after it has been mechanically mowed). The results showed that with a cover crops system runoff was reduced by more than 60% compared to a tillage system, and that there were reductions of soil and SOC loss of more than 90%. In addition to protecting the soil against erosion and the associated loss of organic matter, cover crops offer other advantages such as improved physical and chemical properties of the soil as well as contributing to the capture and fixation of atmospheric carbon in the soil. A study was carried out over three seasons on a farm in southern Spain in order to assess the degree of protection during the period of decomposition of the cover after mechanical mowing, and the release of C to the soil. Three species, a gramineous plant (Brachypodium distachyon) and two cruciferous (Eruca vesicaria and Sinapis alba), were compared with the spontaneous vegetation in the area, which is the cover most widely used by farmers. The decomposition of the cover crops released between 2.4 y 4.7 t ha-1 of C, depending on the species, with B. distachyon being the species that generated most biomass and best protected the soil throughout the decomposition period. The climate of the area exerts a significant influence on the growth of the cover crops and thus on the benefits they provide. In fact, meteorological conditions in the third season meant that the gramineous species did not develop as it had in previous seasons, leaving S. alba as the species that fixed the most C as SOC in the soil profile studied. A dead mulch of pruning residues protects the soil for a longer period of time, as it decomposes more slowly. Our study confirms that coverage did not drop below 60% in any of the different treatments tested in an experiment carried out over two seasons (704 days). The treatments involved the use of fine chopped residue (leaves and twigs of up to 8 cm) from spur pruning, as well as both fine and thick residue from a renewal pruning...En la cuenca mediterránea se concentra la mayor parte de la superficie mundial de olivar. La sostenibilidad de este cultivo está amenazada especialmente por problemas de erosión y pérdida de fertilidad de sus suelos. Las cubiertas han demostrado ser un sistema de cultivo eficaz para proteger el suelo del olivar y favorecer la mejora de su contenido en materia orgánica en comparación con el sistema de laboreo. El objetivo que se pretende con esta tesis doctoral es tener un mayor conocimiento sobre las cubiertas vegetales, en concreto qué especies reducen más la escorrentía y las pérdidas por erosión, y cuáles son más favorables para mejorar la fertilidad del suelo. El estudio se ha desarrollado con especies vegetales típicamente empleadas como cubierta: gramíneas, crucíferas y leguminosas. Se ha trabajado también con cubiertas inertes, poco estudiadas hasta la fecha, como son los de restos de poda, valorándose los beneficios del uso de distintas dosis y tamaño de restos. La existencia de una cobertura vegetal, ya sea sembrada o espontánea, reduce las pérdidas por escorrentía y erosión. El estudio desarrollado mediante un simulador de lluvia por aspersión en parcelas de 50 m2 y una pendiente del 20% demostró que el sistema de cubiertas reduce de forma significativa las pérdidas de suelo y las pérdidas de soil organic carbon (SOC) asociadas al sedimento arrastrado. En el experimento, desarrollado durante dos años con dos intensidades de lluvia (40 mm h-1 y 15 mm h-1) y en dos momentos del año (con la cubierta en su desarrollo y tras su desbroce mecánico), la escorrentía se redujo más de un 60% con el sistema de cubierta y las pérdidas de suelo y SOC en más de 90% respecto al sistema de laboreo. Además de la protección del suelo contra la erosión y la pérdida de materia orgánica que ésta supone, las cubiertas vegetales tienen otras ventajas como la mejora de las propiedades físicoquímicas del suelo y contribuir a la captura de carbono atmosférico y su fijación en el suelo. Para evaluar el grado de protección en el periodo de descomposición de la cubierta tras su desbroce mecánico y la liberación de C al suelo, se realizó un estudio desarrollado durante tres campañas en una finca del sur de España. Se emplearon tres especies, una gramínea (Brachypodium distachyon) y dos crucíferas (Eruca vesicaria y Sinapis alba), que fueron comparadas con la hierba espontánea de la zona, la cual es la cubierta más ampliamente utilizada por los agricultores..

Comparación de sistemas de manejo de suelo en olivar en ensayos de simulación de lluvia

El objetivo de este estudio es comparar la influencia de dos sistemas de manejo de suelo utilizados en olivar, cubierta vegetal y laboreo convencional, en la generación y calidad de las aguas de escorrentía y la erosión asociada a estos fenómenos. Se parte de la convicción de que la cubierta vegetal, al reducir el flujo superficial y la pérdida de suelo, ha de disminuir en principio la contaminación de las aguas superficiales

Study of C, N, P and K Release from Residues of Newly Proposed Cover Crops in a Spanish Olive Grove

Cover crops (CC)s are increasingly employed by farmers in olive groves. Spontaneous soil cover is the most commonly used CC. Its continuous utilization changes ruderal flora. It is necessary to study new CCs. Living CCs provide C and nutrients to soil during decomposition. Information on this issue in olive groves is scarce. A 4-year field study involving grab sampling of Brachypodium distachyon, Sinapis alba and spontaneous CC residues was conducted to study C and nutrient release from cover crop residues. Throughout the decomposition cycles, C, N and P release accounted for 40 to 58% of the C, N and P amounts in the residues after mowing. Most K was released (80–90%). Expressed in kg per hectare, the release of C and N in Brachypodium (C: 4602, N: 181, P: 29, K: 231) and Sinapis (C: 4806, N: 152, P: 18, K: 195) was greater than that in spontaneous CC (C: 3115, N: 138, P: 21, K: 256). The opposite results were observed for K. The Rickman model, employed to estimate the amount of C, N and P in residues, yielded a good match between the simulated and measured values. In comparison to spontaneous CC, the newly proposed CCs have a higher potential to provide soil with C and N

Soil Management, Irrigation, and Fertilisation Strategies for N2O Emissions Mitigation in Mediterranean Agricultural Systems

Feeding a growing population, which will reach 10 billion in 2050, is a major challenge. Another major challenge is to increase crops’ productivity in a sustainable way, as the increase in agricultural inputs may lead to greenhouse gas emissions, including N2O fertiliser. Several factors can influence N2O emissions such as irrigation, the soil management system, or the type of fertiliser used. The aim of this research is to study the impact of each above-mentioned factor on N2O emissions during three growing seasons in a maize field, considering three nitrogen fertilisers: urea (U), ammonium nitrate (AN), and a fertiliser with the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP); two irrigation strategies: on demand (100%) and deficit irrigation (75% of demand); and a comparison of two soil management systems: conventional tillage (T) systems and no-tillage (NT) system. The interactions among the three factors and their effects on emissions were analysed through a principal component analysis. Higher emissions were recorded in plots that received the highest irrigation dose. The most favourable management to reduce N2O emissions derived from agricultural activity for maize crops under a Mediterranean climate was the NT soil management, using a fertiliser with nitrification inhibitor and an irrigation dose of 75% of conventional irrigation

Effects of Multifunctional Margins Implementation on Biodiversity in Annual Crop

The most suitable land for agricultural use has been gradually occupied by crops around the world. Large, uninterrupted croplands have been created, while disproportionate amounts of fertilizers, insecticides, fungicides and herbicides are applied on them. As a result, agricultural activity has a negative impact on biodiversity the ecological intensification of cultivated lands has become necessary. Multifunctional Margins (MFM), the establishment of native flora margins adjacent to croplands, provide a semi-natural habitat for food and wildlife refuge. Three different species mixtures sown in MFM were studied in this paper. The large capacity of six species used in MFM (Borago officinalis, Glebionis coronaria, Coriandrum sativum, Sinapis alba, Trifolium resupinatum and Vicia sativa) was determined. Reductions of up to 65% in the appearance of weeds and increases of 36% in pollinator biodiversity in sown MFM with respect to the MFM of spontaneous flora were observed. The biodiversity of the epigeal fauna increased by 15% in the MFM of spontaneous flora and by 32% in sown MFM, with respect to annual crops

Application effects of Oil Mill Effluents on Agricultural Soils

The extraction of olive oil by physical methods produces large amounts of washing water for oils and olives. Being stored in large rafts for evaporation, lacking any use. In this sense, a study has been developed on the agricultural, environmental and business benefits and limitations of its use as irrigation in olive orchards and on arable land. Specifically, the study has a double aspect. The first one, which has consisted in a complete characterization of the composition and variability of the liquids coming from the washing of the olives and oils in the mills. And a second, aimed at studying the effects of irrigation, evaluating its agricultural utility, as well as the possible generation of residues on the soil, the plant and the environment in general. In view of the data collected during the study, we have obtained a series of conclusions about the benefits that the farmer can obtain when irrigating with effluents, in addition to the obvious contribution of humidity in periods of low rainfall. Allowing in turn, offer recommendations on when to perform such irrigation.La extracci&oacute;n del aceite de oliva por m&eacute;todos f&iacute;sicos produce grandes cantidades de aguas de lavado de aceites y aceitunas. Siendo almacenadas en grandes balsas para su evaporaci&oacute;n, careciendo de cualquier aprovechamiento. En este sentido, se ha desarrollado un estudio sobre los beneficios y limitaciones agr&iacute;colas, ambientales y empresariales de su utilizaci&oacute;n como riego en olivar y en tierra calma. En concreto, el estudio ha constado de una doble vertiente. Una primera, que ha constado en una completa caracterizaci&oacute;n de la composici&oacute;n y variabilidad de los l&iacute;quidos procedentes del lavado de las aceitunas y aceites en las almazaras. Y una segunda, encaminada a estudiar los efectos del riego, evaluando su utilidad agr&iacute;cola, as&iacute; como la posible generaci&oacute;n de residuos sobre el suelo, la planta y el medio ambiente en general. A la vista de los resultados recopilados durante el estudio realizado, se han obtenido una serie de conclusiones sobre los beneficios que puede obtener el agricultor al regar con efluentes, adem&aacute;s del aporte obvio de humedad en periodos de bajas precipitaciones. Permitiendo a su vez, dar recomendaciones sobre cuando realizar dicho riego.</p