La incorporación de prácticas de conservación en cultivos herbáceos extensivos de secado en la región mediterránea

[spa] La intensificación de las actividades agrícolas en los últimos años ha supuesto un uso excesivo de insumos externos y un intenso laboreo del suelo que ha provocado contaminaciones a veces de carácter irreversible, el empobrecimiento y la degradación de los suelos y la pérdida de la biodiversidad de estos sistemas. La tesis doctoral va dirigida al desarrollo de sistemas agrícolas de secano más sostenibles en la región mediterránea con el fin de minimizar los efectos negativos de las prácticas agrícolas como son el laboreo intensivo y los aportes externos de fertilizantes y herbicidas. Los experimentos que forman parte de esta tesis doctoral se han llevado a cabo en el Parc de l’Espai d’Interès Natural de Gallecs, un espacio agrario periurbano situado a 15 kilómetros al norte de Barcelona. El capítulo I abarca un experimento de dos años de duración en campos de cereales de invierno con gestión convencional y comprende la introducción de prácticas agrícolas menos intensivas como son el laboreo mínimo y el control mecánico de la flora arvense. Para ello se evaluó el efecto del uso del arado de vertedera comparado con el arado de cincel, y el control mecánico respecto al control químico de la flora arvense sobre el rendimiento del cultivo trigo de invierno, y la abundancia y diversidad de la flora arvense. Los capítulos II, III y IV resumen los resultados de un experimento de cuatro años de duración enfocado al diseño de un sistema de producción de cultivos ecológicos herbáceos extensivos sostenible. En este experimento se estudiaron los efectos del laboreo mínimo, la fertilización orgánica con estiércol y la incorporación de cultivos de cobertura como abono verde en el suelo sobre: a) el rendimiento de los cultivos, la abundancia de la flora arvense, el contenido de carbono orgánico y nitrógeno, la densidad aparente y la biomasa microbiana del suelo (Capítulo II); b) la abundancia y diversidad de lombrices de tierra (Capítulo III); c) y los balances de nitrógeno y los parámetros de la eficiencia del uso del nitrógeno (Capítulo IV), en una rotación de cereales y leguminosas en la región mediterránea. El estudio de las distintas estrategias para disminuir la intensidad de las actividades agrícolas pone de manifiesto que es necesario llevar a cabo experimentos a largo plazo para poder obtener resultados concluyentes sobre cuáles son las mejores prácticas en los cultivos de secano de la región mediterránea. Asimismo, a la hora de aplicar distintas prácticas agrícolas es importante tener en cuenta las condiciones climáticas de la zona, la calidad y fertilidad del suelo y las prácticas de gestión previas. Los suelos de los cultivos de secano de la región mediterránea se caracterizan generalmente por un pobre contenido de nutrientes y una alta tasa de mineralización de la materia orgánica, por ello es imprescindible mantener los niveles de nutrientes en los suelos a través de una adecuada fertilización.[eng] The agricultural intensification in recent years has led to excessive use of external inputs and intensive soil tillage resulting in water pollution, soils degradation and loss of biodiversity of these systems. The aim of this thesis is the design of more sustainable rainfed agricultural systems in the Mediterranean region in order to minimize the negative effects of agricultural practices such as intensive tillage and chemical inputs (fertilizers and herbicides). The experiments comprising this work have been carried out in the Parc de l'Espai d'Interès Natural de Gallecs, a peri-urban agricultural area in Catalonia. Chapter I comprises a short-term experiment of 2 years in winter cereal fields with conventional management and includes the introduction of more sustainable agricultural practices such as reduced tillage and mechanical weed control. In this experiment we evaluated the effect of the use of mouldboard plough vs. chisel plough and the use of mechanical weed control vs. herbicide application on winter wheat crop yields and on weed abundance and diversity. Chapters II, III and IV comprise a medium-term experiment focused on the design of a sustainable organic cereal-legume rotation in Mediterranean dryland arable fields. The effects of reduced tillage, fertilization with farmyard manure and the incorporation of cover corps as green manure was evaluated on a) crop yields, weed abundance and organic carbon content, nitrogen total content and microbial biomass in the soil (Chapter III); b) the abundance and diversity of earthworms (Chapter III); c) and the balance of nitrogen and nitrogen efficiency parameters in the system (Chapter IV). The study of different strategies to reduce the intensity of agricultural practices reflects that it is necessary to perform long-term experiments in order to obtain solid results on which are the best practices in dryland agrosystems in the Mediterranean region. Furthermore, the arable soils of the Mediterranean region are generally characterized by a poor nutrient content and a high rate of mineralization of organic matter, therefore is crucial to maintain soil nutrients levels through a proper fertilization

Crop yield, weed infestation and soil fertility responses to contrasted ploughing intensity and manure additions in a Mediterranean organic crop rotation

Conservation agriculture and organic farming are two alternative strategies that aim to improve soil quality and fertility in arable cropping systems through reducing tillage intensity, maintaining soil cover and increasing nutrient recycling, using farmyard and green manures. However, these practices can increase weed infestation or decrease nutrient availability. The objectives of this study were to evaluate the effects of tillage type (mouldboard vs. chisel ploughing), fertilization and green manure on soil parameters (SOC, N, bulk density, carbon stocks, and soil microbial biomass Cmic and Nmic), weed abundance and crop yields in a four-year rotation of spelt, chickpea, winter wheat and lentil in the Mediterranean region (Catalonia, Spain). Tillage and green manure did not affect crop yields or weed biomass, although during the last year of the experiment, plots with mouldboard ploughing had less weed biomass and higher lentil biomass. Fertilization was the most important factor, increasing the cereal yields, SOC, N and soil microbial biomass (Cmic and Nmic) content of the soil. However, fertilization did not favour chickpea and lentil crops because weed competition limited legume crop growth. Overall, there was a loss of SOC and a reduction of carbon stocks over the four years of the trial in the soil because of the deep soil tillage (25 cm) and low crop productivity irrespective of tillage type. In contrast, N content increased in all of the plots and was enhanced by fertilization. The use of chisel plough stratified the distribution of SOC and N in the surface layers (0-10 cm). Both Cmic and Cmic/SOC ratio increased in fertilized treatments, suggesting an increased lability of SOC. The application of more stabilized organic matter may be a better practice to build up soil organic matter and to maintain crop yields in organic farming systems

Nitrogen Utilization in a Cereal-Legume Rotation Managed with Sustainable Agricultural Practices

Optimization of the nitrogen (N) inputs and minimization of nutrient losses strongly affect yields in crop rotations. The aim of this research was to evaluate the effect of agricultural practices on yield and N use in a 4-year cereal-legume rotation in organic farming and to identify the best combination of these practices. The following treatments were compared: conventional plough (P) vs. reduced chisel (RC) tillage; composted farmyard manure (F) vs. unfertilized control (NF); and green manure (GM) vs. no green manure (NoM). No significant differences were found for N use efficiency between P and RC in each crop. The results suggested that legumes in the tested rotation do not need supplemental N fertilization, particularly if combining GM and F. The use of composted farmyard manure should be considered in a long-term fertilization plan for cereals, to allow a higher efficiency in N use. The residual effect of fertilization over time, along with the site-specific pedo-climatic conditions, should also be considered. In both tested tillage approaches, soil N surplus was the highest in plots combining GM and F (i.e., more than 680 kg N ha−1 in combination with RC vs. about 140 kg N ha−1 for RC without fertilization), with a risk of N losses by leaching. The N deficit in NoM⁻NF both combined with P and RC would indicate that these treatment combinations are not sustainable for the utilized crops in the field experiment. Therefore, the combination of the tested practices should be carefully assessed to sustain soil fertility and crop production

Nitrogen utilization in a mid-term cereal-legume rotation managed with sustainable agricultural practices

Optimization of the nitrogen (N) inputs and minimization of nutrient losses strongly affect yields in crop rotations. The aim of this research was to evaluate the effect of agricultural practices on yield and N use in a 4-year cereal-legume rotation in organic farming and to identify the best combination of these practices. The following treatments were compared: conventional plough (P) vs. reduced chisel (RC) tillage; composted farmyard manure (F) vs. unfertilized control (NF); and green manure (GM) vs. no green manure (NoM). No significant differences were found for N use efficiency between P and RC in each crop. The results suggested that legumes in the tested rotation do not need supplemental N fertilization, particularly if combining GM and F. The use of composted farmyard manure should be considered in a long-term fertilization plan for cereals, to allow a higher efficiency in N use. The residual effect of fertilization over time, along with the site-specific pedo-climatic conditions, should also be considered. In both tested tillage approaches, soil N surplus was the highest in plots combining GM and F (i.e., more than 680 kg N ha1 in combination with RC vs. about 140 kg N ha1 for RC without fertilization), with a risk of N losses by leaching. The N deficit in NoM-NF both combined with P and RC would indicate that these treatment combinations are not sustainable for the utilized crops in the field experiment. Therefore, the combination of the tested practices should be carefully assessed to sustain soil fertility and crop production

Nitrogen utilization in a mid-term cereal-legume rotation managed with sustainable agricultural practices

Optimization of the nitrogen (N) inputs and minimization of nutrient losses strongly affect yields in crop rotations. The aim of this research was to evaluate the effect of agricultural practices on yield and N use in a 4-year cereal-legume rotation in organic farming and to identify the best combination of these practices. The following treatments were compared: conventional plough (P) vs. reduced chisel (RC) tillage; composted farmyard manure (F) vs. unfertilized control (NF); and green manure (GM) vs. no green manure (NoM). No significant differences were found for N use efficiency between P and RC in each crop. The results suggested that legumes in the tested rotation do not need supplemental N fertilization, particularly if combining GM and F. The use of composted farmyard manure should be considered in a long-term fertilization plan for cereals, to allow a higher efficiency in N use. The residual effect of fertilization over time, along with the site-specific pedo-climatic conditions, should also be considered. In both tested tillage approaches, soil N surplus was the highest in plots combining GM and F (i.e., more than 680 kg N ha 1 in combination with RC vs. about 140 kg N ha 1 for RC without fertilization), with a risk of N losses by leaching. The N deficit in NoM-NF both combined with P and RC would indicate that these treatment combinations are not sustainable for the utilized crops in the field experiment. Therefore, the combination of the tested practices should be carefully assessed to sustain soil fertility and crop production

Nitrogen utilization in a mid-term cereal-legume rotation managed with sustainable agricultural practices

Optimization of the nitrogen (N) inputs and minimization of nutrient losses strongly affect yields in crop rotations. The aim of this research was to evaluate the effect of agricultural practices on yield and N use in a 4-year cereal-legume rotation in organic farming and to identify the best combination of these practices. The following treatments were compared: conventional plough (P) vs. reduced chisel (RC) tillage; composted farmyard manure (F) vs. unfertilized control (NF); and green manure (GM) vs. no green manure (NoM). No significant differences were found for N use efficiency between P and RC in each crop. The results suggested that legumes in the tested rotation do not need supplemental N fertilization, particularly if combining GM and F. The use of composted farmyard manure should be considered in a long-term fertilization plan for cereals, to allow a higher efficiency in N use. The residual effect of fertilization over time, along with the site-specific pedo-climatic conditions, should also be considered. In both tested tillage approaches, soil N surplus was the highest in plots combining GM and F (i.e., more than 680 kg N ha 1 in combination with RC vs. about 140 kg N ha 1 for RC without fertilization), with a risk of N losses by leaching. The N deficit in NoM-NF both combined with P and RC would indicate that these treatment combinations are not sustainable for the utilized crops in the field experiment. Therefore, the combination of the tested practices should be carefully assessed to sustain soil fertility and crop production

Earthworm abundance response to conservation agriculture practices in organic arable farming under Mediterranean climate

Earthworms are one of the most important soil macrofaunal groups, and they play a major role in agricultural ecosystems. Agricultural practices, such as reduced tillage, the use of green manures and organic fertilization, can be beneficial for earthworm populations in agricultural systems. However, under a Mediterranean climate, not much is known regarding their response to agricultural management. The aim of this study was to analyse the effects of tillage type, organic fertilization, and green manures on the density and biomass of earthworms in organic arable dryland. The trial was conducted in a four-year crop rotation with a complete factorial design that combined tillage system (mouldboard ploughing vs. chisel), fertilization (composted farmyard manure vs. no fertilizer) and green manures (green manures vs. no green manures). Earthworms were assessed in each plot by the extraction of all individuals in three soil areas of 33 cm × 33 cm that were excavated to a depth of 25 cm. Only five earthworm species were found in this trial, and the earthworm community was dominated by such endogeic ecotypes as Aporrectodea roseaand Allolobophora georgii, and the anecic ecotype Aporrectodea trapezoides.Endogeic species can benefit from soil inversion because of the incorporation of organic matter, but the anecic ones can be negatively affected by it. The results show that plots with farmyard manure had higher density and biomass of earthworms. We observed that the type of tillage significantly affected earthworm populations: plots that had been ploughed with mouldboard ploughing (soil inversion) the year prior to sampling presented more juveniles. The biomass of earthworms was significantly lower in plots with green manures and chiselling. Our results indicated that the combination of chiselling and green manures were not optimal for earthworm populations, but organic fertilization played a considerably more important role and enhanced their abundances

Earthworm abundance response to conservation agriculture practices in organic arable farming under Mediterranean climate

Earthworms are one of the most important soil macrofaunal groups, and they play a major role in agricultural ecosystems. Agricultural practices, such as reduced tillage, the use of green manures and organic fertilization, can be beneficial for earthworm populations in agricultural systems. However, under a Mediterranean climate, not much is known regarding their response to agricultural management. The aim of this study was to analyse the effects of tillage type, organic fertilization, and green manures on the density and biomass of earthworms in organic arable dryland. The trial was conducted in a four-year crop rotation with a complete factorial design that combined tillage system (mouldboard ploughing vs. chisel), fertilization (composted farmyard manure vs. no fertilizer) and green manures (green manures vs. no green manures). Earthworms were assessed in each plot by the extraction of all individuals in three soil areas of 33cm×33cm that were excavated to a depth of 25cm. Only five earthworm species were found in this trial, and the earthworm community was dominated by such endogeic ecotypes as Aporrectodea rosea and Allolobophora georgii, and the anecic ecotype Aporrectodea trapezoides. Endogeic species can benefit from soil inversion because of the incorporation of organic matter, but the anecic ones can be negatively affected by it. The results show that plots with farmyard manure had higher density and biomass of earthworms. We observed that the type of tillage significantly affected earthworm populations: plots that had been ploughed with mouldboard ploughing (soil inversion) the year prior to sampling presented more juveniles. The biomass of earthworms was significantly lower in plots with green manures and chiselling. Our results indicated that the combination of chiselling and green manures were not optimal for earthworm populations, but organic fertilization played a considerably more important role and enhanced their abundances

Crop yield, weed infestation and soil fertility responses to contrasted ploughing intensity and manure additions in a Mediterranean organic crop rotation

Conservation agriculture and organic farming are two alternative strategies that aim to improve soil quality and fertility in arable cropping systems through reducing tillage intensity, maintaining soil cover and increasing nutrient recycling, using farmyard and green manures. However, these practices can increase weed infestation or decrease nutrient availability. The objectives of this study were to evaluate the effects of tillage type (mouldboard vs. chisel ploughing), fertilization and green manure on soil parameters (SOC, N, bulk density, carbon stocks, and soil microbial biomass Cmic and Nmic), weed abundance and crop yields in a four-year rotation of spelt, chickpea, winter wheat and lentil in the Mediterranean region (Catalonia, Spain). Tillage and green manure did not affect crop yields or weed biomass, although during the last year of the experiment, plots with mouldboard ploughing had less weed biomass and higher lentil biomass. Fertilization was the most important factor, increasing the cereal yields, SOC, N and soil microbial biomass (Cmic and Nmic) content of the soil. However, fertilization did not favour chickpea and lentil crops because weed competition limited legume crop growth. Overall, there was a loss of SOC and a reduction of carbon stocks over the four years of the trial in the soil because of the deep soil tillage (25 cm) and low crop productivity irrespective of tillage type. In contrast, N content increased in all of the plots and was enhanced by fertilization. The use of chisel plough stratified the distribution of SOC and N in the surface layers (0-10 cm). Both Cmic and Cmic/SOC ratio increased in fertilized treatments, suggesting an increased lability of SOC. The application of more stabilized organic matter may be a better practice to build up soil organic matter and to maintain crop yields in organic farming systems