University of Valladolid. Valladolid (Spain)
May 5th, 2006
Original summary:
Tradicionalmente el laboreo ha sido una actividad insustituible en la agricultura que en muchas ocasiones conlleva los riesgos de erosión y compactación del suelo, contaminación de la atmósfera y acuíferos, etc. y aspectos tan importantes como el gasto energético, consiguiendo a corto plazo reducir la productividad. Surge entonces la agricultura de conservación para intentar paliar estos efectos. Con ella se establecen las bases para seguir viviendo de la tierra a la vez que se cuida el medio ambiente. Existen numerosas interacciones entre el sistema de laboreo, rotaciones, malas hierbas, cultivo y suelo. De estas interacciones dependerá el mayor o menor éxito de estos sistemas.
En este trabajo se ha estudiado la influencia del sistema de laboreo y de las rotaciones sobre las características químicas del suelo, la aparición y evolución de malas hierbas así como su diversidad, y el comportamiento agronómico del cultivo.
El diseño experimental fue un split-plot con cuatro repeticiones donde el factor principal fue el sistema de laboreo y el subfactor la rotación de cultivos. Los sistemas de laboreo ensayados fueron siembra directa, laboreo mínimo y laboreo tradicional y las rotaciones R-1 (Barbecho/Trigo/Cebada/Garbanzo/ Trigo), R-2 (Cebada/Barbecho/Cebada/Veza/Trigo), R-3 (Cebada/Cebada/ Garbanzo/Cebada/Trigo), R-4 (Cebada/Veza/Trigo/Cebada/Trigo) y R-5 (Veza/ Cebada/Veza/Trigo/Trigo).
Durante el ensayo se tomaron muestras de suelo a dos profundidades en tres estados del cultivo diferentes con las que se analizaron la materia orgánica, el pH los macronutrientes del suelo en los distintos sistemas de laboreo y rotaciones.
Durante el ciclo vegetativo del cultivo se realizó un seguimiento de la vegetación adventicia en varios estados fenológicos del cultivo identificándola y cuantificándola en número y biomasa seca.
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English summary:
Traditionally, tillage has been regarded as an essential agricultural practice. However, in many cases it entails risks such as soil erosion and compaction, atmospheric and groundwater pollution, as well as other important concerns such as energy consumption, all of which may ultimately reduce productivity, even in the short term. Conservation agriculture emerged as an approach aimed at mitigating these effects. It provides a basis for maintaining agricultural production while protecting the environment. Numerous interactions exist among tillage systems, crop rotations, weeds, crops and soil, and the success of these systems largely depends on such interactions.
This study investigated the influence of tillage systems and crop rotations on soil chemical properties, weed emergence and development, weed diversity, and crop agronomic performance.
The experimental design was a split-plot with four replicates, in which tillage system was considered the main factor and crop rotation the subplot factor. The tillage systems evaluated were no-tillage, minimum tillage and conventional tillage. The crop rotations were
R-1 (Fallow/Wheat/Barley/Chickpea/Wheat),
R-2 (Barley/Fallow/Barley/Vetch/Wheat),
R-3 (Barley/Barley/Chickpea/Barley/Wheat),
R-4 (Barley/Vetch/Wheat/Barley/Wheat) and
R-5 (Vetch/Barley/Vetch/Wheat/Wheat).
During the experiment, soil samples were collected at two depths and at three different crop growth stages. These samples were analysed to determine organic matter content, pH and soil macronutrient levels under the different tillage systems and crop rotations.
Throughout the crop growing cycle, weed vegetation was monitored at several phenological stages. Weed species were identified and quantified in terms of plant density and dry biomass.
Crop establishment was also assessed by monitoring biomass development at each phenological stage. At harvest, grain yield and yield components were determined.
The results regarding soil chemical properties showed a substantial increase in organic matter content, particularly within the upper five centimetres of soil, under conservation tillage systems compared with conventional tillage. A similar trend was observed for soil nitrogen content. Phosphorus and potassium contents also increased in the upper five centimetres under conservation tillage. A decrease in soil pH was also observed under these systems. The influence of crop rotations on these parameters was less pronounced than that of tillage systems; nevertheless, higher nitrogen levels were found in plots cultivated with legumes.
In general, conservation tillage systems promoted greater weed diversity and higher weed populations. However, not all species followed the same pattern. While most species were favoured by conservation tillage, particularly minimum tillage, others were favoured by conventional tillage. In general, monocotyledonous weeds were better adapted to conservation tillage, particularly Bromus spp., whereas dicotyledonous weeds were more closely associated with conventional tillage. Crop rotations also had a considerable influence. Thus, following vetch and chickpea crops, a significant increase in weed populations, including species such as Papaver rhoeas, was observed.
In plots affected by higher levels of weed infestation, crop yields decreased. This situation was generally associated with conservation tillage, and consequently barley yields were higher under conventional tillage in almost all growing seasons. During the first two seasons, wheat showed no differences in grain yield among tillage systems. However, during the final two seasons, when weed pressure was greater, grain yield under conservation tillage decreased, resulting in higher yields under conventional tillage. Regarding crop rotations, continuous barley cropping was found to be inadvisable under conservation tillage.
In any case, the results obtained cannot be fully extrapolated to all conditions. Therefore, field trials adapted to each specific area are required in order to properly assess the benefits and effects of different tillage systems.
Descriptors: Farm equipment, Agronomy, Crop breeding, Crop management, Cultural engineering, Field crops, Management for plant production, Soil behaviour under alternative uses, Soil fertility, Weed control, Soil chemistry, Soil conservation, Soil mechanics (agriculture)
Citation:
I. González Barragán, "Estudio de la influencia del sistema de laboreo y de las rotaciones de cultivo sobre la composición química del suelo, el desarrollo de la vegetación adventicia y el comportamiento agronómico de los cultivos en condiciones semiáridas", PhD. dissertation, University of Valladolid, Valladolid, Spain, 2006.
