The dispersal of Avena spp. (A. fatua and A. sterilis) by natural dissemination and by agricultural operations was studied in four experiments conducted in Spain and Britain. Natural dispersal was very limited, with a maximum dispersal distance of 1.5 m. Dispersal was higher in the geographic direction that was downwind than in any of the other three geographic directions. Although plant movement was very small under notillage, an annual patch displacement of 2-3 m in the tillage direction was observed under conventional soil tillage. Ploughing downhill resulted in much larger dispersal distances than ploughing uphill. In the crops studied, combine harvesters dispersed few Avena spp. seeds, because of the fact that the plants had shed most of their seeds (>90%) before harvest. The percentage of seeds available to be dispersed by the combine was dependent on the harvest time. Although combine harvesting may not contribute much to short-distance dispersal, it may play an important role in long-distance dispersal. In our studies, isolated plants were located up to 30 m from the original sources. This small proportion may have a significant effect on the distribution of the weed within a field, acting as foci for new patches.

Corn poppy is the most abundant broad-leaved weed in winter cereals of Mediterranean climate areas and causes important yield losses in wheat. Knowledge of the temporal pattern of emergence will contribute to optimize the timing of control measures, thus maximizing efficacy. The objectives of this research were to develop an emergence model on the basis of soil thermal time and validate it in several localities across Spain. To develop the model, monitoring of seedling emergence was performed weekly during the growing season in a cereal field located in northeastern Spain, during 3 yr. Cumulative thermal time from sowing date was used as the independent variable for predicting cumulative emergence. The Gompertz model was fitted to the data set of emergences. A base temperature of 1.0 C was estimated through iteration for maximum fit. The model accounted for 91% of the variation observed. Model validation in several localities and years showed general good performance in predicting corn poppy seedling emergence ( values ranging from 0.64 to 0.99 and root-mean-square error from 4.4 to 24.3). Ninety percent emergence was accurately predicted in most localities. Results showed that the model performs with greater reliability when significant rainfall (10 mm) occurs within 10 d after crop sowing. Complemented with in-field scouting, it may be a useful tool to better timing control measures in areas that are homogeneous enough regarding climate and crop management.

Summary Lolium rigidum is an extremely competitive and prevalent grass weed in cereal fields of Mediterranean areas. The proper timing of control measures is a prerequisite to maximising herbicide efficacy, in terms of both improved control and reduced herbicide inputs. The development of models to predict emergence flushes will contribute to this goal. Pooled cumulative emergence data obtained during three seasons from a cereal field were used to develop a Gompertz model. This explained relative seedling emergence from crop sowing onwards as a function of: (i) standard soil thermal time accumulation (TT) with a base temperature of 1.8°C and (ii) soil thermal time accumulation corrected for soil moisture (cTT). For the latter, no thermal time accumulation was computed for days in which the soil water balance within the upper 10‐cm soil layer indicated no water available for plants, because evapotranspiration was greater than rainfall plus the stored water remaining from the previous day. The model was validated with six datasets from four different sites and seasons. Compared with TT, the model based on cTT showed better performance in predicting L. rigidum emergence, particularly in predicting the end of emergence. Complemented with in‐field observations to minimise deviations, the model may be used as a predictive tool to better control this weed in dryland cereal fields of Mediterranean climate areas.

Determination of the soil coverage by crop residues after ploughing is a fundamental element of Conservation Agriculture. This paper presents the application of genetic algorithms employed during the fine tuning of the segmentation process of a digital image with the aim of automatically quantifying the residue coverage. In other words, the objective is to achieve a segmentation that would permit the discrimination of the texture of the residue so that the output of the segmentation process is a binary image in which residue zones are isolated from the rest. The RGB images used come from a sample of images in which sections of terrain were photographed with a conventional camera positioned in zenith orientation atop a tripod. The images were taken outdoors under uncontrolled lighting conditions. Up to 92% similarity was achieved between the images obtained by the segmentation process proposed in this paper and the templates made by an elaborate manual tracing process. In addition to the proposed segmentation procedure and the fine tuning procedure that was developed, a global quantification of the soil coverage by residues for the sampled area was achieved that differed by only 0.85% from the quantification obtained using template images. Moreover, the proposed method does not depend on the type of residue present in the image. The study was conducted at the experimental farm “El Encín” in Alcalá de Henares (Madrid, Spain).

Gonzalez‐Andujar JL, Fernandez‐Quintanilla C, Bastida F, Calvo R, Gonzalez‐Diaz L, Izquierdo J, Lezaun JA, Perea F, Sanchez Del Arco MJ & Urbano JM (2010). Field evaluation of a decision support system for herbicidal control of Avena sterilis ssp. ludoviciana in winter wheat. Weed Research50, 83–88. Summary Two field studies were conducted in Central and Northern Spain over a total of five seasons to assess the usefulness of a decision support system (AVENA‐PC) from agronomic, economic and environmental points of view on herbicidal control of Avena sterilis ssp. ludoviciana in winter wheat. The control treatments evaluated were: (i) AVENA‐PC‐based recommendations, (ii) full herbicide dose (standard farmer practice), (iii) half herbicide dose and (iv) no herbicide. The herbicide rates used in the AVENA‐PC treatment averaged 65% and 30% lower than the full and half dose treatments respectively. AVENA‐PC implementation controlled A. ludoviciana with similar efficacy as standard herbicide treatments. Nevertheless, it did support a reduction in relation to the non‐herbicide treatment. Yields obtained with AVENA‐PC were, in general, not statistically different to those obtained with herbicide treatments and were on average 69% higher than those in the no herbicide application strategy. Comparing AVENA‐PC economic performance with the other treatments there were, in general, no significant statistical differences in Central Spain. In Northern Spain, all herbicide treatments had similar net returns, with there being no statistical differences between AVENA‐PC and the herbicide treatments. However, there were differences recorded with the non‐herbicide treatment. The results of this research indicate that AVENA‐PC, due to its flexibility, may recommend less herbicide than the standard farmer practice, providing clear environmental benefits and adequate weed control with maintained crop yield and net returns similar to standard farmer practice.