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The sunflower was introduced in Europe (in Spain) in the 15th century, and later in Italy in the second half of the 16th century by Giacomo Antonio Cortuso who was the head of the Botanical Garden in Padua. He and Andrea Mattioli published a detailed description of the species. The sunflower was mainly used for ornamental and medicinal purposes in the following two centuries. In the early 1800s, its cultivation area expanded as a consequence of two new, divergent uses and breeding programs: oilseed production and seed consumption. Nowadays, sunflower is cropped for many uses, mainly food, feed, and biodiesel. Beyond the global interest in this crop, it is extremely difficult to predict its cultivation and productivity in the short/medium term because of the current geopolitical and climate change scenarios. In this last perspective, sunflower cropping should foresee the integration of (i) crop breeding for improving quali-quantitative traits and biotic and abiotic stress tolerance; (ii) agronomic practices to increase the resilience of this crop through anticipated sowing dates and scheduled irrigation according to its phenological phases; and (iii) exploration of new cultivation areas towards higher latitudes.

Modern viticulture cannot be practiced without the use of plant protection products to control diseases like downy mildew, powdery mildew, and pests. In severely sloping vineyards, where mechanization is not possible, pesticide application is realized using spray guns, which is a laborious, expensive, and dangerous application technique. In these vineyards, where viticulture is defined as “heroic viticulture,” vine-growers could seriously take advantage of innovation in spray-technique applications. For this reason, several prototypes of a fixed spraying system (FSS) were realized in recent years. Two prototypes of a fixed spraying system were built in 2019 in two different vineyards in the Veneto region (north-eastern Italy). In both vineyards, the fixed spraying systems were used to perform pesticide application during the 2020 season to control downy mildew, powdery mildew, and pests. With this solution, both vineyards were successfully protected, resulting in comparable infection degrees and yields as the ones protected with airblast sprayers and spray guns. This study contributes to assert fixed spraying systems as an innovation that could improve working conditions, safety, timing, and performances of plant protection products’ application in heroic viticulture areas.

Summary Modelling weed seedling emergence pattern appears to be a promising approach in the development of effective weed management programmes based on the selection of optimal timing of control operations. Thermal and hydrothermal time models propose that seed germination rates are proportional to the amount by which temperature and water potential exceed threshold values for these environmental factors. Hence, base temperature for seed germination is a fundamental biological parameter for the prediction of weed emergence. A series of laboratory experiments were conducted to estimate base temperature in three weed species belonging to the Asteraceae family, predominant in conservation tillage fields in north-eastern Italy. The traditional method based on germination assays at constant temperatures was compared with a method based on assays at alternating temperatures. The latter might represent an alternative to the former for those species which do not germinate or only poorly under constant temperatures. Base temperature was estimated by regressing the reciprocal of the median germination time on temperature comparing two functions, a broken-stick and an exponential-type model. Both models showed good fit to all data in the whole temperature range and in almost all cases provided similar estimates of base temperature. The main result is that, for the weed species examined in this study, the use of alternating temperatures for base temperature estimation appears to be possible. However, further research is required to test if the use of germination assays performed at alternating temperatures can be a suitable method to estimate base temperature of species that have too low germination at constant temperatures.

The role played by organic farming as an alternative system to conventional farming is widely questioned, since conflicting results on crop yields sometimes greatly affect system efficiency. As a result, prolonged monitoring studies on organic (OF) and conventional farming (CF) systems are still required, especially in real-life farm conditions, in which the entire production process is quantified. In this context, this study reports crop yields (winter wheat, maize, soybean) and energy efficiency, over a 13-year monitoring period, on a farm in north-east Italy in which two sectors are farmed following OF and CF practices. Results showed that organic yields were always lower than conventional ones, averaging 69%, although their range varied greatly over the years (from 45% to 90%) and depended on crop type. Several management constraints had effects on the lower yields, especially reduced available nutrients and cropping season, but also the timings and types of tillage operations. By contrast, OF practices usually had positive effects on the environment, due to reduced energy input mainly fertilisation (−33.4% MJ ha −1 y −1 ) and the generally higher productivity of invested energy (E Out E In −1 = 4.53 in OF and 4.28 in CF); energy use differences per product unit were mainly equal. Other factors, such as local climate and soil variability, may have influenced system performance, but as the two experimental sites were located at a distance of 3.5 km from each other, the data reported here are still valuable, in that they represent the results of 13 years of monitoring, during which farm management played a major role. This case study, although conducted in two separate sites, did not highlight the best overall solution at farm level, it does indicate that the agricultural systems applied would be better suited for different situations and targets (e.g., productive, energetic, ecologic).

Glyphosate-resistant biotypes of Eleusine indica (L.) Gaertn. have been detected in Asia, the Americas but not in Europe. The aim of this study was to evaluate resistance levels and possible target site resistance mechanisms of an E. indica biotype (19-1) collected from a plant nursery in Southern Italy where poor glyphosate efficacy was reported. Two dose-response experiments were conducted to evaluate the sensitivity of biotype 19-1 to glyphosate in comparison with two susceptible checks. 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) sequencing was performed to identify possible mutations conferring the resistance. The susceptible biotypes were completely controlled at the glyphosate recommended field dose of 360 g ae ha&minus, 1, while 50% of the plants of biotype 19-1 survived at 1440 g ae ha&minus, 1. The resistance index of biotype 19-1 ranged between 5.8 and 7.3 for the response variables of fresh weight reduction and plant survival, respectively. All the plants surviving glyphosate application and sampled for DNA analyses had the point mutation P106A. The biotype 19-1 can be confirmed as glyphosate-resistant, representing the first glyphosate-resistant population of E. indica in Europe.

Weeds account for losses in crop yields, and this event might be exacerbated by salinity. Therefore, we investigated the responses of Chenopodium album L. and soybean (Glycine max (L.) Merr.) to salt stress, as well as interferences between species. Ten-day old plants were grown for 1 week in a single- or mixed-species set-up, either with or without 100 mM of NaCl. C. album reduced the biomass of soybean similarly to salt stress, while its growth was unaffected under any condition. C. album decreased the crop protein content when salinity was applied. This effect was ascribed to altered protein metabolism and/or N usage to produce other N metabolites, including osmolytes. The two species did not reciprocally affect the capacity to accumulate Na+, but the weed contained two-fold more Na+ in the leaves. Elevated initial K+ concentration and high K+ delivery to the shoot likely explained the better acclimation of C. album to salinity. C. album produced more phenolics and proline and exhibited greater antioxidant activity, but low lipid peroxidation, in the mixed set-up under salinity. Thus, it is possible that the weed could become more resilient to salinity when growing in a soybean field. In the long term, this might cause significant losses in soybean productivity as expected by the dramatic decline in crop protein content.

Weed emergence models require biological parameters such as base temperature for germination, determination of which is costly and time-consuming. Transferability of these parameters across different populations may therefore represent one of the main constraints for the development and practical use of emergence models at a large scale. A collaborative project was undertaken to assess the interpopulation variability of base temperature for germination in different European populations of velvetleaf and jimsonweed and evaluate possible applicative consequences in terms of weed control. Seeds were collected in Italy, Portugal, and Spain, and each population was then sown in every country, obtaining nine seed batches named as experimental lots. Base temperature for germination was estimated for each experimental lot to calculate lot-specific accumulation of growing degree days (GDD) under three dissimilar climatic scenarios. Threshold date (TD50) was calculated as the date when GDD accumulation of a given experimental lot surpassed the values corresponding to 50% of cumulative field emergence of seedlings. GDD accumulation and TD50were then used as indicators to identify differences among experimental lots within each climatic scenario. No significant differences were detected among base temperatures estimated for velvetleaf experimental lots or among their patterns of accumulation of GDD and TD50values within climatic scenarios. Each value of base temperature determined for a single experimental lot could therefore be adopted to model germination for all the lots regardless of the population of origin or cultivation site. In contrast, the population of origin affected the base temperature for jimsonweed, with significantly higher values for experimental lots of the Portuguese population. From an applicative perspective, differences among patterns of accumulation of GDD and TD50of several experimental lots within each climatic scenario suggest the need to use population-specific values as base temperature for germination and emergence modeling of jimsonweed.

Loddo D, Masin R, Otto S & Zanin G (2011). Estimation of base temperature for Sorghum halepense rhizome sprouting. Weed Research 52, 42–49. Summary Sorghum halepense is a rhizomatous perennial summer weed. It spreads by seeds and rhizomes that form ramets. The development of predictive models for ramet emergence (RE) from rhizomes may provide important information about their seasonal dynamics and consequently for the timing of control operations. The aim of this work was to analyse the effect of temperature on S. halepense rhizome sprouting (RS) and to estimate its base temperature, which is the first step for creating mathematical models to predict RE. Rhizomes collected from two North Italian populations were incubated at several constant temperatures. The total number of ramets, sprouted rhizomes and their ratio (ramet/sprouted rhizome) were calculated. The influence of temperature on sprouting performances was analysed. Base temperature was calculated using two methods: the reciprocal time of 50% RS (method) and RE (method). Confidence limits (at 0.95 level) were defined for each estimated base temperature using a bootstrap method. Base temperatures were compared to verify whether there were differences between populations and methods. Results indicated a significant stimulating effect of temperature on S. halepense rhizome performances. Estimated base temperatures did not differ between populations, nor between methods within a population (Padova RS 9.7 ± 1.25°C (confidence limits), RE 10.0 ± 1.28°C, Mantova RS 8.0 ± 1.89°C and RE 9.7 ± 1.23°C). The same thresholds may consequently be adopted for thermal time models for the two populations. These results also suggest that both methods (RE and RS) can be used without distinction to estimate the rhizome base temperature.

Summary We reviewed studies aimed at understanding functional relationships between weeds and arthropods in agroecosystems as influenced by biodiversity at different scales, with the main goal of highlighting gaps in knowledge, research methods and approaches. We first addressed: (i) the regulation of arthropod communities by weed diversity at genetic, species and habitat levels, (ii) the regulation of weed communities by arthropods through seed predation and dispersal and (iii) belowground weed-insect interactions. We then focussed on methodologies to study weed–arthropod interactions in agricultural landscapes and discuss techniques potentially available for data analysis and the importance of joint weed–arthropod trend detection. Lastly, we discuss the implications of research findings for biodiversity conservation policies (agri-environmental schemes) and suggest some priorities for future work. Results showed that to date research has largely ignored weed–arthropod interactions in agricultural landscapes. No information is available on the role of weed genetic diversity as driver of weed–arthropod interactions, whereas studies on effects of species and habitat diversity often lack a functional perspective and ⁄ or a spatial component. Also, information on how management of the wider agricultural biotope might express positive weed– arthropod functional interactions is scarce. Another area worth being explored is the relationship between weed-leaf ⁄ root herbivores and beneficial arthropods. Tools for spatial data analysis might be useful for elucidating weed–arthropod interactions in agricultural landscapes, but some methodological aspects, e.g. the definition of the most appropriate experimental design and sampling scale ⁄ frequency, must be refined. New studies on weed–arthropod interactions should encompass an explicit spatial component; this knowledge is particularly important for improving IPM ⁄ IWM systems and designing more targeted agri-environmental

Otto S, Loddo D & Zanin G (2010). Weed-poplar competition dynamics and yield loss in Italian short-rotation forestry. Weed Research50, 153–162. Summary In recent years there has been increasing interest in short-rotation poplar plantations for biomass production and cropping techniques and weed control strategies are being developed. Slow initial poplar growth can favour weed infestation and so there is a need for appropriate timing of weed control, based on an understanding of the competitive relationship and dynamics between poplar and weeds. A field experiment with annual and biennial crop cycles was conducted over two years. A 35 cm wide within-row weedy strip was allowed to develop as the basis for competition. Yield data were fitted with sigmoidal equations, in order to find the critical point (CP) and critical period of weed control (CPWC), using thermal time as the independent variable. Results showed that poplar is very sensitive to weed competition, especially in the first growing season after planting or cutting, and that competition can cause important yield losses. In the annual cycle, the CP corresponds to a yield loss of 26% and 8% in the first and second growing season respectively; in the biennial cycle the CP corresponds to a yield loss of 29%. Furthermore, the CPWC is long. For example, in the first year, based on a 5% yield loss, it lasts from 30 to 84 days after planting. This makes effective weed control difficult to achieve only using a pre-emergence herbicide, and thus necessitates a post-emergence treatment, either with herbicides or inter-row cultivation. These results, together with the inability of the crop to recover from damage, mean that resources must be invested in weed control soon after the beginning of the cropping cycle.

Summary Seventeen Italian experiments relating to maize, soyabean and durum wheat were used to analyse the variability of duration of tolerated competition (DTC) and weed-free period (WFP) curves across reasonably homogeneous areas. The data sets were analysed by regression analysis using four models relating yield loss to weed density, time of emergence and removal. These models differ in the way they account for the effect of time of weed removal on potential competitiveness. A sigmoidal relationship between these two variables appears necessary. The model with the best overall performance was then used to test the stability of the parameters that give the shape of the curve in relation to time of emergence and removal. This was done by comparing a full model with shape parameters specific to each experiment and a reduced model with a common set of parameters for all the experiments referring to a specific crop. For all three crops, the residual sum of squares of the reduced model did not increase significantly, indicating that, across tested environments, the yield loss caused by mixed weed infestations can be expressed by a single set of parameters relating weed competitivity to time of emergence and removal. For a given area, it should therefore be possible to predict yield loss on the basis of a quite limited set of experiments, thus greatly simplifying the development and use of decision support systems (DSS).

The efficacy of superficial tillage as a sustainable tool to reduce the emergence of Digitaria sanguinalis, Setaria viridis, and Sorghum halepense was evaluated with field experiments. Seeds were buried at 1, 2, 5, and 10 cm of depth to simulate seed vertical distribution caused by autumn superficial tillage. Seedling emergence was monitored weekly for two years after sowing. The highest emergence was obtained in the first year after sowing and from 1 and 2 cm. Sorghum halepense was only slightly affected by seed burial, with 15% of emergence from 10 cm of depth, while D. sanguinalis was strongly affected, with 4% of emergence from 5 cm. The efficacy of superficial tillage as control tool could vary according to local weed flora.

Summary Digitaria sanguinalis, Eleusine indica, Setaria glauca and S. viridis are troublesome summer annual weeds in turf. For taking rational decisions on the necessity for the level and type of weed management, it is important to know when weeds are ready to emerge (dormancy status) and also how long weed seeds can survive in the soil. Seeds of these four species were buried 4.0–4.5 cm deep in steel mesh net bags placed under permanent turf and periodically exhumed for 3 years to evaluate viability and determine the dormancy/non-dormancy cycle. D. sanguinalis, S. glauca and S. viridis showed the typical dormancy cycle of summer annual species, and their seed viability declined completely after 3 years of burial. In contrast, E. indica demonstrated unusual behaviour, with long persistence and no dormancy.

Buffer strips are an efficient and economical way to reduce agricultural nonpoint source pollution. Local researches are necessary to gain information on buffer performance, with particular emphasis on narrow buffers. The effect of a 6 m buffer strip (BS) in reducing runoff, suspended solids and nutrients from a field growing maize, winter wheat and soybean was assessed in a field experiment conducted in North-East Italy during 1998–2001. The BS was composed of two rows of regularly alternating trees (Platanus hybrida Brot.) and shrubs (Viburnum opulus L.), with grass (Festuca arundinacea L.) in the inter-rows. The BS reduced total runoff by 78% compared to no-BS, in which cumulative runoff depth was 231 mm over 4 years. With no-BS runoff appeared to be influenced mostly by total rainfall, while with BS maximum rainfall intensity was more important. The filtering effect of the BS reduced total suspended solids (TSS), particularly after the second year, when the median yearly concentrations ranged from 0.28 to 0.99 mg L−1 and were smaller than 0.14 mg L−1, with no-BS and with BS respectively. The combination of lower concentrations and runoff volumes significantly reduced TSS losses from 6.9 to 0.4 t ha−1 over the entire period. A tendency to increased concentrations of all forms of N (total, nitrate and ammonium) while passing through the BS was observed, but total N losses were reduced from 17.3 to 4.5 kg ha−1 in terms of mass balance. On the contrary, P concentrations were unmodified (soluble P), or lowered (total P) by the BS, reducing total losses by about 80%. The effect on total P, composed mainly of sediment-bound forms, was related to particulate settling when passing through the BS. A numerical index (Eutrophic Load Index), integrating water quality and runoff volumes, was created to evaluate the eutrophication risk of runoff with or without the BS. It showed that the BS effect was mostly due to a reduction of runoff volumes rather than improving the overall water quality.

The mechanisms of herbicide resistance were investigated in two diclofop-methyl-resistant Lolium spp. populations from central Italy, Roma ’94 and Tuscania ’97. These two populations were compared with two susceptible Italian populations (Vetralla ’94, Tarquinia ’97) and a resistant and a susceptible population from Australia, SLR31 and VLR1. The activity of acetyl Co-A carboxylase (ACCase) extracted from susceptible (S) or resistant (R) individuals from the Italian populations was inhibited by both aryloxyphenoxypropanoate (diclofop acid and fluazifop acid) and cyclohexanedione (sethoxydim) herbicides. Diclofop-methyl was rapidly de-esterified to diclofop acid at a similar rate in both R and S populations. In all populations, diclofop acid was subsequently degraded to other metabolites. The rate of degradation of diclofop acid was not significantly faster in R than in S populations; however, diclofop acid was degraded more completely in Roma ’94 and Tuscania ’97 compared with the S populations. Application of the mixed-function oxidase inhibitor 1-aminobenzotriazole (ABT) significantly enhanced diclofop-methyl toxicity towards both R populations, but not in S populations. However, enhanced herbicide metabolism does not completely account for the measured resistance level. A mechanism other than an altered ACCase and enhanced herbicide metabolism appears to be responsible for resistance to diclofop-methyl in Roma ’94 and Tuscania ’97.

Populations of Lolium spp. collected in central Italy were screened for resistance to acetyl-coenzyme A carboxylase (ACCase)-inhibiting herbicides and compared with known susceptible and resistant Lolium rigidum (Gaud.) populations from Australia. Populations Roma’94 and Tuscania’97 were up to 8- and 7.5-fold more resistant to diclofop-methyl, respectively, than susceptible populations in pot experiments. However, populations Tarquinia’97 and Vetralla’94 were not resistant. Diclofop-methyl resistance levels in the Italian populations were lower than in the Australian populations SLR31 and WLR96 (16.5 and > 64 times more resistant than S respectively). In an agar germination test, Tuscania’97 showed low levels of cross-resistance to fluazifop-p-butyl, whereas no cross-resistance was found in the Roma’94 population.

Floral surveys were carried out on a field of 28 m x 100 m on the nodes of a regular 2 m x 2 m grid, using a rectangular sampling area of 25 cm x 30 cm. In total, 765 units were sampled, each one characterized by the spatial co-ordinates and the number of seedlings of different weed species. The spatial representation of the weeds was obtained with kriging. Simulations were carried out for Amaranthus spp., which had the highest frequency and density (221 plants m -2 ), and Portulaca oleracea L., a species that combined a more aggregated distribution with a medium-high density (27 plants m -2 ). The results obtained clearly indicated that the usefulness of geostatistical procedures depends on the type of question posed by the user. If the goal is to estimate weed density and, consequently, crop yield loss, kriging appears to overburden the decision-making process, without improving the estimates obtained. This procedure becomes useful for obtaining weed infestation maps to be used for intermittent spraying applications. The reliability of these maps increases with the number of samples used for kriging. With the more aggregated species, at least 50 samples are required to obtain an infestation map. The reduction in the area to be treated depends on the threshold level adopted and on the number of samples used for kriging. With a threshold around the break-even point for most post-emergence treatments, this reduction varies from 10% to 40% with maps obtained from 50 and 175 samples respectively. The usefulness of infestation maps obtained with kriging for improving the decision-making process is strictly dependent on the weed patch dynamics : if these patches remain relatively stable over time, kriging can be carried out periodically without overburdening the decision-making process, whereas, if they are not stable, maps need to be drawn up each year, with a significant increase in costs.

AlertInf is a recently developed model to predict the daily emergence of three important weed species in maize cropped in northern Italy (common lambsquarters, johnsongrass, and velvetleaf). Its use can improve the effectiveness and sustainability of weed control, and there has been growing interest from farmers and advisors. However, there are two important limits to its use: the low number of weed species included and its applicability only to maize. Consequently, the aim of this study was to expand the AlertInf weed list and extend its use to soybean. The first objective was to add another two important weed species for spring-summer crops in Italy, barnyardgrass and large crabgrass. Given that maize and soybean have different canopy architectures that can influence the interrow microclimate, the second objective was to compare weed emergence in maize and soybean sown on the same date. The third objective was to evaluate if AlertInf was transferable to soybean without recalibration, thus saving time and money. Results showed that predictions made by AlertInf for all five species simulated in soybean were satisfactory, as shown by the high efficiency index (EF) values, and acceptable from a practical point of view. The fact that the algorithm used for estimating weed emergence in maize was also efficient for soybean, at least for crops grown in northeastern Italy with standard cultural practices, encourages further development of AlertInf and the spread of its use.

In northern Italy, on soil managed with three different tillage systems (conventional tillage, ridge tillage, and no-tillage) and submitted to standard cultural practices (crop rotation, and chemical weed control), the weed vegetation was assessed at the beginning of the trial (1987) and after six, and eight years. The aims were to evaluate (1) the effect of tillage systems on the weeds; and (2) the possibility of linking the floristic changes under reduced disturbance to the theory of ecological succession. The weeds were categorised according to life-forms (biological groups), periodicity types (ecophysiological groups), dispersal types and seed longevity. Data were analysed using Sorenson's Indices of Similarity, the Independence test, and Principal Components Analysis. The tillage systems profoundly altered the weed community: in undisturbed soils the importance of the geophyte and hemicryptophyte species, and among the annuals, Digitaria sanguinalis, Conyza canadensis and Kickxia elatine increased, as well as that of the wind-dispersed weeds. The species linked to disturbance were annuals and in particular Amaranthus spp., Chenopodium album and Echinochloa crus-galli. After eight years the floristic evolution in the reduced tillage system can be interpreted on the basis of ecological succession. The community that has formed assumes, from the quantitative point of view, characteristics of a pioneer community of secondary succession with a predominance of annual species and a large number of wind-dispersed plants. Qualitatively there is a movement towards a more mature community that could become similar to that of the woodland edge, with more perennial species, shrubs, and bird-dispersed plants. The implications of these conclusions are discussed in terms of weed management.

A methodological approach to determine the opti- mum time to control weeds that integrates aspects of weed biology, weed-crop competition, and economics is presented. The approach is based on the concept of Time Density Equivalent: this is defined as the density of weed plants that germinate with the crop and compete until harvest that causes the same yield loss caused by a group of weeds with a given density, time of emergence, and time of removal. A model was developed that accounts for pattern of weed emer- gence and permits determination of timing of weed control that minimizes economic loss due to weeds emerging both before and after treatments. The outcomes of the model are presented with two examples: corn in competition with velvetleaf and soybean in competition with Amaranthus cruentus. For both crops, six different weed control strategies involving preemergence, chemical, and mechanical poste- mergence treatments are considered. The results obtained with the model are compared with the calculation of net margin based on assumptions of simultaneous emergence of crop and weeds and no effect of different times of control. Different control strategies are compared considering not only maximum net margin but also its dependence on time of control, because a strategy with a lower value of maximum net margin, but a flatter net margin curve, allows more flexibility of time of control. Nomenclature: Dicamba, 3,6,di- chloro-2-methoxybenzoic acid; fomesafen, 5-(2-chloro-4

When a pesticide is applied in a vineyard, the fraction can drift away from the target and affect the abundance of beneficial arthropods in adjacent crops or hedgerows. A field experiment was conducted in north-eastern Italy using an air-assisted sprayer in order to evaluate the spatial distribution of etofenprox drift in a vineyard-hedgerow system and its effect on the predatory mite Kampimodromus aberrans. Three scenarios of decreasing potential drift were compared, all in still wind conditions. In the worst case of free expansion of drift, 12% of the applied rate drifted for 6–7 m with minor effect on K. aberrans abundance, according to the dose–response assay results; the presence of a hedgerow reduced the drift by about 80%. The hedgerow was also effective when good agronomic practices were followed, and the effect of drift on K. aberrans was not significant, its abundance being mainly linked to the patchiness of the natural population. Because of lateral drift, i.e. not in the direction of air-flow from sprayer, spray was detected at very low concentration in the contiguous untreated vineyard. This had no effect on K. aberrans but had the capacity to contaminate organic crops and provide a risk to surface water and bystanders. This suggests that an environmental regulatory scheme taking hedgerows into account should be supported and implemented on a catchment or regional scale.

The relationship between weed control cost in soybean and the risk of groundwater contamination was evaluated for five typical pedo-floristic situations of the Po Valley. For the weed control treatments, a ‘GroundWater Danger Index’ (GWDI) was calculated as the proportion of the active ingredient applied which leaches downwards, relative to the guidelines for drinking water calculated according to the World Health Organisation methodology. The fraction of the active ingredient which can leach was estimated with the Pesticide Root Zone Model (PRZM) and by means of the Attenuation Factor (AF) and the Groundwater Ubiquity Score (GUS). For each chemical option a total cost was calculated adding the treatment cost to the value of the yield loss caused by residual weeds. The optimal treatments were very different depending on the pedo-climatic and floristic situations. A large number of options had higher values of GWDI than those of atrazine under the same conditions, indicating a potential risk of groundwater contamination in soybean weed control. The GWDI calculated with the PRZM were then compared to those obtained with the other simplified indices, AF and GUS. Using the AF gave a good correlation with the values obtained on the basis of the PRZM, while with GUS the correlation, even where significant, was poor.

A hydrothermal time model was developed to simulate field emergence for three weed species in maize (common lambsquarters, johnsongrass, and velvetleaf). Models predicting weed emergence facilitate well-timed and efficient POST weed control strategies (e.g., chemical and mechanical control methods). The model, called AlertInf, was created by monitoring seedling emergence from 2002 to 2008 in field experiments at three sites located in the Veneto region in northeastern Italy. Hydrothermal time was calculated using threshold parameters of temperature and water potential for germination estimated in previous laboratory studies with seeds of populations collected in Veneto. AlertInf was validated with datasets from independent field experiments conducted in Veneto and in Tuscany (west central Italy). Model validation resulted in both sites in efficiency index values ranging from 0.96 to 0.99. AlertInf, based on parameters estimated in a single region, was able to predict the timing of emergence in several sites located at the two extremes of the Italian maize growing area.

Summary: Resume: Zusammenfassung A method to evaluate potential crop damage from multi-species weed infestations is presented. The method is based on the hyperbolic relationships between density of a single weed species and crop yield loss. When considering a mixed weed population, the density of each species is transformed into a Density Equivalent, defined as the density that is equal to the density of a reference species giving the same yield loss. A hypothetical species with i and a parameters both equal to 100 was adopted to describe the relationship between yield and reference density. The method has been evaluated with data from a 2-year experiment on soybean (Glycine max (L.) Merril) grown in mixtures with Xanthium strumarium L. subsp. italicum, Polygonum persi-caria L. and Panicum miliaceum L. The mixtures included seven weed densities with different proportions of the three weed species. The model described the data well, but it showed an average 7–5% overestimation of crop damage. The reasons for this overestimation and the utility of the model in weed management is discussed. La densiteequivalente: une methode pour predire les penes de rendement causees par des populations melangees de mauvaises herbes Une methode est presentee qui permet d'evaluer le dommage potentiel causea une culture par des infestations multi-specifiques de mauvaises herbes. Elle est basee sur les relations hyperboliques entre la densite d'une mauvaise herbe donnee et la perte de rendement de la culture. Quand on considere une population de mauvaises herbes melangees, la densite de chaque espece est con-vertie en une DensiteEquivalente, definie comme la densiteegale a la ensite de la mauvaise herbe de relerence qui occasionne la meme perte de rendement. Une espece hypothetique avec des parametres 'i' et 'a' tous deux egaux a 100 a ete definie pour decrire la relation entre le rendement et la densite de reference. La methode a eteevaluee avec des donnees tirees d'une experimentation de deux ans sur soja (Glycine max. (L.) Merril) en cultures melangees avec Xanthium strumarium L. subsp. italicum, Polygonum persicaria L. et Panicum miliaceum L. Les melanges comprenaient 7 densites de mauvaises herbes avec des proportions differen-tes des trois especes. Le modele decrivait bien les donnees mais il surestimait d'environ 7.5% le dommage a la culture. Les raisons de cette sures-timation et 1'utilite du modele dans la lutte centre les mauvaises herbes sont discutees. Eine Methode zur Vorhersage von Ertragsver-lusten durch Unkrautmischbestande mil Hilfe des Dichte-Aquivalents Die Methode zur Bestimmung moglicher Ertragsverluste durch Verunkrautungen mil mehreren Arten basiert auf dem hyperbolischen Verhaltnis zwischen der Dichte einer einzelnen Unkrautart und dem Ertragsverlust. Bei Unkrautbestanden mil mehreren Arten wird die Dichte jeder einzelnen Artinein Dichte-Aquiva-lent transformiert, das als die Dichte definiert ist, die der Dichte einer Referenz-Art gleich ist, die zu demselben Ertragsverlust fuhrt. Es wurde eine hypothetische Art mit den Parametern ‘i’ und ‘a’, beide gleich 100, angenommen, um die Beziehung zwischen Ertrag und Referenz-Dichte zu beschreiben. Die Methode wurde anhand von Daten aus einem 2 ahrigen Versuch in Sojabohne (Glycine max (L.) Merril) und Mischbestanden mit Xanthium strumarium L. ssp. italicum, Polygonwn persicaria L. und Panicum miliaceum L. uberpruft. Mit den 3 Unkrautarten wurden durch verschiedene Anteile 7 Unkrautdichtungen in den Mischungen eingestellt. Mit dem Model] konnten die Daten gut beschrieben werden, doch wurden die Ertragsverluste im Durchschnitt um 7.5 %uberbewertet. Die Grunde fur dies uberbewertung und die Brauchbarkeit des Modells fur die Unkrautbekampfung werden diskutiert.

Decision-making processes must indicate if, how, and when weed control should be practiced. So far, Decision Support Systems (DSSs) for weed control to prevent crop yield losses can guide decisions on “if” and “how.” Experience shows that farmers need a DSS that can also guide when to treat, but this can only be done if the actual weed density observed in the field is known during the crop cycle. Emergence models allow the prediction of daily density, but precision depends on the survey date. This study focuses on the estimation of the date of the survey for the best prediction of the daily density throughout the crop cycle. The predicted daily density of each species can be used by DSSs without any further survey, saving time and money and improving the use of the DSSs. Results showed that the best date is when the actual density of each weed reaches or exceeds 50% emergence, and this is earlier than the critical point date, supporting the validity of the date estimation method. The possibility to provide specific advice for farmers considering a proper mortality rate of weed seedlings is then discussed. The ability to optimize the date of sampling can improve the reliability of decision-making tools for integrated weed management, in agreement with the European Union goal of sustainable use of pesticides and more environmentally sustainable cropping systems through the use of integrated pest management.

The main issue that European agriculture is facing is related to maintaining and if possible increasing yields while reducing inputs - especially pesticides, including herbicides. Society is paying increasing attention to the quality of products as well as to the sustainability of the productive system. Control of weeds is necessary to achieve economically acceptable yields. The main tool is chemical weed control. This practice spread quickly after its introduction, due its efficacy and simplicity, but it also generated a series of agronomic and environmental issues. One of the solutions to maintain yields, while reducing herbicide use is the adoption of the Integrated Weed Management (IWM). IWM is based on the knowledge of weeds and their response to cropping practices, weed-crop competitive relationships and chemical and non-chemical means of control. IWM has had a quite remarkable success among researchers, politicians and public opinion, but has rarely been applied by farmers. The limited implementation of this management approach may have different explanations: i) IWM is more complex than conventional management as it requires greater skill and is more time consuming; ii) there is a lack of financial support and demonstration farms, necessary to convince the farmers to adopt it; iii) IWM is considered riskier than conventional management; iv) research has not succeeded in transferring scientific knowledge to the productive systems.The paper includes an analysis of several examples of IWM application in Italy in recent years (development of decision support systems, predictive models, formation of GIRE (Italian Herbicide Resistance Working Group) with the objective of defining their benefits and drawbacks and finding new solutions for the future. It is also underlined that the main difficulty in IWM development is the lack of integration between means of control and proactive agronomic practices that are suitable to prevent the spread and evolution of weeds in the fields.

The integration of environmental issues into agricultural policies has attracted significant attention in recent years. The objective of this paper is to discuss the (past and future) research questions in this area and the role of economic analysis in supporting decisions regarding the integration of environmental issues into agricultural policies, with a special focus on the Common Agricultural Policy (CAP) of the European Union (EU). The paper first examines the evolution of the process integrating environmental concerns into the CAP. Then, the role of economic analysis is discussed with reference to selected major issues, including: the evaluation of the relationship between agriculture and environmental impacts, and the economic value of such effects; the evaluation of policy effectiveness and efficiency; optimal policy design; the effects on markets and farm structures; and the coordination and governance of policy measures. The contents of these study areas are discussed and the research priorities required to meet future needs are identified. The work concludes by highlighting the need to develop more detailed policy analysis studies while, at the same time, developing a wider and more innovative vision of the role of agricultural policy in the global context.

The introduction of herbicide-resistant crops and postemergence herbicides with a wide action spectrum shifted the research focus from how to when crops should be treated. To maximize net return of herbicide applications, the evolution of weed–crop competition over time must be considered and its effects quantified. A model for predicting the yield trend in relation to weed removal time, considering emergence dynamics and density, was tested on data from glyphosate-resistant soybean grown in cropping systems in Italy and Argentina. Despite an ample variation of weed emergence dynamics and weed load in the four trials, the model satisfactorily predicted yield loss evolution. The estimated optimum time for weed control (OTWC) varied from about 18 d after soybean emergence in Argentina to 20 to 23 d in Italy, with time windows for spraying ranging from 14 to 28 d. Within these limits a single glyphosate application ensures good weed control at low cost and avoids side effects like the more probable unfavorable weed flora evolution with double applications and the presence of residues in grains. Despite the apparent simplicity of weed control based on nonselective herbicides, the study outlines that many variables have to be considered to optimize weed management, particularly for the time evolution of the infestation and, subsequently, a proper timing of herbicide application.

Masin R, Berti A, Otto S & Zanin G (2010). Validation of a model relating yield loss to weed time of emergence and removal in traditional and early-sown maize. Weed Research50, 120–126. Summary In northern Italy, there has been a tendency in recent years to advance maize sowing from mid-April to mid-March. This may lead to many agronomic advantages but can strongly influence weed flora composition, density, time of emergence, and crop and weed relative growth. Altering the maize sowing date thus requires a better understanding of the competitive relationship between crop and weeds. This study evaluates an existing model expressing crop yield as a function of maximum yield of the weed-free crop, weed competitive load and time of weed emergence and removal. The model can predict the yield loss caused by mixed infestations with a single set of parameters. The aim of this study was to validate this model with independent data from experiments on early and traditionally sown maize, in support of the idea that the model is robust enough to be used as a prediction tool for forecasting yield losses in a variety of conditions created by different sowing dates. In traditional sowing, the plot of expected versus observed yields showed that the model gives a good fit. However, for early sowing, the model accuracy in predicting crop yields was improved when the curve intercepts were shifted by 60 growing degree days (d °C). This shift corresponded to the difference between the onset of weed emergence in traditional and early sowing, which suggests that weeds may be less competitive when maize is sown earlier.

Predicting weed emergence dynamics can help farmers to plan more effective weed control. The hydrothermal time concept has been used to model emergence as a function of temperature and water potential. Application of this concept is possible if the specific biological thresholds are known. This article provides a data set of base temperature and water potential of eight maize weeds (velvetleaf, redroot pigweed, common lambsquarters, large crabgrass, barnyardgrass, yellow foxtail, green foxtail, and johnsongrass). For five of these species, two ecotypes from two extreme regions of the predominant maize-growing area in Italy (Veneto and Tuscany), were collected and compared to check possible differences that may arise from using the same thresholds for different populations. Seedling emergence of velvetleaf and johnsongrass were modeled using three different approaches: (1) thermal time calculated assuming 5 C as base temperature for both species; (2) thermal time using the specific estimated base temperatures; and (3) hydrothermal time using the specific, estimated base temperatures and water potentials. All the species had base temperatures greater than 10 C, with the exception of velvetleaf (3.9 to 4.4 C) and common lambsquarters (2.0 to 2.6 C). All species showed a calculated base-water potential equal or up to −1.00 MPa. The thresholds of the two ecotypes were similar for all the studied species, with the exception of redroot pigweed, for which the Veneto ecotype showed a water potential lower than −0.41 MPa, whereas it was −0.62 MPa for the Tuscany ecotype. Similar thresholds have been found to be useful in hydrothermal time models covering two climatic regions where maize is grown in Italy. Furthermore, a comparison between the use of specific, estimated, and common thresholds for modeling weed emergence showed that, for a better determination of weed control timing, it is often necessary to estimate the specific thresholds.

The frequency distribution of yield loss due to weeds in winter wheat, sugar beet, maize and soybean has been studied using the available data of weed control trials undertaken in north-central Italy in the last 30 years. The breakeven yield loss and the probability of obtaining a positive net return from chemical weed control were calculated, considering different treatment options and different weed-free yields. The mean value of yield loss varies from 23 to 30% in winter wheat and from 33.9 to 37.5% in maize, depending on the type of weed flora, and is 50.2% for sugar beet and 33.3% for soybean. The breakeven yield loss falls between 1.4 and 15% in winter wheat, 4.0 and 12.2% in maize, 5.1 and 12.6% in sugar beet and 3.3 and 17.7% in soybean. Even with the higher treatment costs and the lower yields, the probability of a positive net return is always > 80% and, for sugar beet, > 95%.

According to Grime's model, velvetleaf can be classified as a competitive-ruderal species. Its biological and ecological characteristics make it particularly competitive and persistent in cultivated fields. Herbicide control is difficult and, once established, it is almost impossible to avoid seed production. The economic threshold, on a single year basis, varies between 0.3 and 1.7 plants m–2. When the competitive relationships and their effects are evaluated, it is very difficult to apply a weed management system based on a single-season threshold. When one considers the agronomic implications of the ecological characteristics of velvetleaf over a longer period, it can be concluded that the use of a single-season economic threshold is probably not the best management strategy.

In recent years, interest has increased in late-winter sowing of corn in northern Italy because of many agronomic advantages. However, cold and rainy weather slows initial crop growth, which can favor weed infestation. There is, therefore, a need for appropriate timing of weed control tactics based on an understanding of the competitive relationship and dynamics between crop and weeds. Five experiments were conducted over 4 yr, with a series of treatments increasing either duration of interference or length of weed-free period. Yield data were fitted with sigmoidal equations to find the critical point (CP) and critical period of weed control (CPWC). Although the CP is determined only by the competition between weed and crop, the CPWC is also market dependent. To quantify the effect of weed flora on the CP, a multiple regression model was tested, taking into account weed density, inflection point, and slope parameter of the Gompertz model of the cumulated infestation. The results confirmed that the late-winter sowing date increases the importance of late winter– and early spring–emerging weeds. In general, the precompetitive period was longer in the late winter–sown corn than in traditional midspring-sown corn. The delayed start of the CPWC makes control more difficult with a preemergence herbicide, which raises questions on the utility of this agronomic technique. Multiple regression analysis showed that the position of CP can be estimated with the density, earliness, and competitiveness of the infestation. Furthermore, the slope/inflection point ratio of the Gompertz model appears to be independent of sowing date. Results suggest that the weed–crop competition mechanism can be represented with simply the weed flora dynamic parameters and that a combination of crop–weed competition studies and emergence prediction models can predict the position of CP and give useful information about the CPWC and weed management.

When a pesticide is applied a proportion of the sprayed solution may become a cause of pollution in the surrounding environment, with ecotoxicological implications and phytotoxicity to other crops. In many countries buffer zones along field edges are recommended to shield surface waters, and hedgerows can play an important role in reducing pesticide risk. This study focuses on droplet drift, with the aim of evaluating the hedgerow efficacy in reducing drift from broadcast air-assisted sprayers and then to construct a simple model for estimating the spray drift level in surrounding fields. Three experiments were conducted in North-East Italy in 2004 and 2005, in winter, summer and autumn to obtain suitable optical porosity values in order to evaluate their effects. Three study situations (no hedgerow, single, double hedgerow) and two sprayer-hedgerow interaction scenarios (sprayer working perpendicular to or parallel with the hedgerow) were considered. Hedgerows were 7-8 m in height, while spray release height ranged from 1 to 2 m. The sampling method proved to be effective, with more than 73% of total amount sprayed being intercepted. Where there was at least one hedgerow, off-site spray reductions ranged from 82.6 (with optical porosity of 74.7%) to 97% (with optical porosity of 10.8%). The presence of a double hedgerow did not produce a higher interception rate. Analysis of the spatial pattern of drift showed that where there is a hedgerow with an optical porosity of 74-75%, the aerial drift caused by common broadcast air-assisted sprayers becomes negligible at a distance of 6-7 m. Hedgerows thus proved to be effective in intercepting spray drift leaving cultivated fields. In particular, low optical porosities provided high interception rates, even with very dense canopies, as no spray bypass was recorded. Spray drift profile was then modelled taking into account the effect of wind and optical porosity of a nearby hedgerow. A negative-exponential model is proposed. The model fits the experimental data quite satisfactorily and may be used to estimate spray drift magnitude in relation to wind speed and optical porosity of any hedgerow crossed by a droplets cloud spray drift.

Predicting weed emergence is useful for planning weed management programs. Unfortunately, our ability to anticipate initial emergence and subsequent levels of emergence from simple field observations or weather reports is often inadequate to achieve optimal control. Weed emergence models may provide predictive tools that help managers anticipate best management options and times and, thereby, improve weed control. In this study, the germination characteristics of four annual grass weeds (large crabgrass, goosegrass, green foxtail, and yellow foxtail) were investigated under different temperatures and water stresses to calculate base temperatures and base water potentials. These parameters were used to develop a mathematical model describing seedling emergence processes in terms of hydrothermal time. Hydrothermal time describes seed germination in a single equation by considering the interaction of soil water potential and soil temperature. The model, called WeedTurf, predicted emergence with some accuracy, especially for large crabgrass (lowest efficiency index [EF] value 0.95) and green foxtail (lowest EF value 0.91). These results suggest the possibility of developing interactive computer software to determine the critical timing of weed removal and provide improved recommendations for herbicide application timing.

A comprehensive research project was set up to characterize by different approaches some Italian populations of Lolium spp. susceptible and resistant to diclofop-methyl. The present study was aimed at the taxonomic identification of these Lolium populations on the basis of the electrophoretic analysis of seed reserve proteins. Electrophoresis confirmed the great range of variation detected by preliminary morphological analysis. Approximately half the individuals in each population could be classified as belonging to Lolium multiflorum or Lolium rigidum, the most common Lolium species present in the area. However, electrophoretic patterns revealed a significant number (40-60%) of hybrid individuals in all populations. The origin of these off-types was postulated as resulting from both intrageneric hybridization among different Lolium species and intergeneric hybridization between Lolium and Festuca genera. No significant differences were detected in the taxonomy of herbicide-susceptible and -resistant populations.

The competitive ability of 10 major soybean weeds (Abutilon theophrasti Medicus (ABUTH), Amaranthus cruentus L. (AMACR), Chenopodium album L. (CHEAL), Datura stramonium L. (DATST), Panicum miliaceum L. (PANMI), Polygonum persicaria L. (POLPE), Setaria viridis (L.) Beauv. (SETVI), Solanum nigrum L. (SOLNI), Sorghum halepense (L.) Pers. (SORHA), Xanthium strumarium L. (XANST)) was studied for two years in northern Italy. The economic thresholds for soybean weed control have been determined for different herbicides and mixtures. Economic thresholds were very low in 1989, when only SOLNI and PANMI showed a threshold higher than 1 plant m−2, while in 1990, values varied between 0.05 plants m−2 for XANST and 4.3 plants m−2 for ABUTH. The seed production — weed density relationships for five species (ABUTH, AMACR, CHEAL, DATST and XANST) were also determined and the long-term evolution of the potential infestations deriving from subeconomic threshold populations were calculated. The results of the calculation demonstrate the inadequacy in the medium-long-term of weed control decisions based on single year economic thresholds.

Pour estimer l'abondance des semences de mauvaises herbes dans un sol, il est necessaire de connaitre d'abord la variabilite de l'echantillonnage. A partir de l'analyse d'experimentations conduites par le groupe de travail de l'EWRS, il a ete montre que la variance d'echantillonnage (s 2 ) du nombre de semences augmente avec la moyenne d'echantillonnage (x) et peut etre determinee a partir de la forme logarithmique de la loi de Taylor : log 10 (s 2 )=a+b log 10 (x). Cette relation est constante dans le temps pour les moyennes superieures a 0,1 semence par prelevement sur les cinq sites differents etudies (variabilite temporelle) mais differe legerement entre les sites (variabilite geographique). Un essai d'utilisation d'une relation generale s 2 :x pour determiner le nombre d'echantillons en fonction de la precision et de la densite est propose.

Summary: Resume: Zusammenfassung Thresholds for winter wheat weed control have been determined for different herbicides or mixtures effective against individual weed species. For Avena sterilis L. subsp. ludoviciana (Durieu) Nyman the economic threshold was between 7 and 12 plants m−2, for Alopecurits myosuroides Hudson and Lolium multiflorum Lam. it varied between 25 and 35 plants m−2, while for Bromus sterilis L. the values were just under 40 plants m−2. For Galium aparine L. the threshold was as low as 2 plants m−2, while for Vicia sativa L. it was between 5 and 10 plants m−2. Within the same species the different values of economic threshold result from the different costs and efficacy of herbicides. Nitrogen fertilization was important: in its absence, the competitiveness of B. sterilis and G. aparine was negligible, and it was not possible to calculate an economic threshold for some of the treatments which could not be justified economically. Estimation de seuils economiqu.es de desherbage chez le ble d'hiver Les seuils economiques de desherbage du ble d'hiver ont ete determines pour differents herbicides, seuls ou en melanges, pour plusieurs especes demauvaises herbes. POUT Avena sterilis L. subsp. ludoviciana (Durieu) Nyman, le seuil economique etait compris entre 7 et 12 plantes m−2. PourAlopecurus myosuroides Hudson et Lolium multiflorum Lam., il variait entre 25 et 35 plantes m−2 et etait juste au-dessous de 40 plantes m−2 pour Bromus sterilis L. Pour Galium aparine L., le seuil etait2 plantes m−2 et etait compris entre 5 et 10 plantes m−2 pour Vicia sativa L. Les differences de seuil pour une meme espece sont dues aux differences de cout et d'ef-ficacite des herbicides. Le role de la fertilisation azotVe Vtait important: en son absence, le pou-voir compVtitif de B. sterilis et de G. aparineetait negligeable, et il n'etait pas possible de calculer de seuil economique pour certains traitements, qui ne pouvaient se justifier economiquement. Bestimmung von wirtschaftlichen Schadensschwel-lenfiirdie Unkrautbekdmpfung in Winterweizen Fur verschiedenen Herbizide und -mischungen wurden entsprechend ihrer Wirksamkeit gegenuber bestimmten Unkrautarten Schadensschwellen zur Unkrautbekampfung inWinterweizen bestimmt. Fur Avena sterilis L. spp. ludoviciana (Durieu) Nyman lag die Schadensschwelle zwischen 7 und 12 Pflanzen m−2, fur Alopecurus myosuroides Hudson und Lolium multiflorum Lam. variierte sie zwischen 25 und 35 Pflanzen m−2, wahrend die Werte fur Bromus sterilis L. bei knapp 40 Pflanzen m−2 lagen. Bei Galium aparine L. war die Schadensschwelle ganz niedrig, namlich 2 Pflanzen m−2, wahrend sie fur Vicia sativa L. zwischen 5 und 10 Pflanzen m2 betrug. Fiir ein und die-selbe Art ist die okonomische Schadensschwelle je nach den Kosten und der Wirksamkeit der Herbizide unterschiedlich. Die Stickstoffdun-gung ist zu beachten: wenn sie fehlt, ist die Konkurrenz durch Bromus sterilis und Galium aparine verachlassigbar, so das keine gerechtfertigten okonomischen Schadensschwellen berechnet werden konnten.

Water management within the cropping system is a key factor for an integrated weed management. Soil moisture affects seed persistence and seed dormancy, thus influencing their germination, the establishment of seedlings as well as the competition at adult stage and the number, vitality and dormancy of the new seeds produced by the weeds. The interactions among water availability and competition are very complex and still not fully understood. A research effort in this sector should the be very relevant for the development of new approaches of weed management, such as “Ecological weed management”, aiming to reduce weed density and competitiveness and, in the medium term, to prevent undesired modifications of the weed flora.

Summary: Resume: Zusammenfassung Qualitative and quantitative surveys (biological and ecophysiological spectrum, structural organization, seed bank size) of the potential flora (PF) in maize (Zea mays L.) fields of the Po Valley are reported. Data were collected from 45 sites and two sampling depths (0–20 cm and 21–40 cm). Soil seed content was highly variable, ranging from 1660 to 53371 seeds m−2, with an average value of 10391 seeds m−2 and a median of 5500 seeds m−2. Seed stock was lower than 2000 seeds m−2 in 6.6% of the sites and over 10000 in 26.6%. Six species were found in more than 50% of the sites, representing 27.7% of the total stock: Anagallis arvensis L., Chenopodium album L., Stellaria media (L.) Vill., Echinochloa crus-galli (L.) P. Beauv., Amaranthus spp., Polygonum persicaria L. + P. lapathifolium > L. Overall, 63 species were recorded, the species number per site ranging from 4 to 25, with a median value of 11. Therophytes accounted for 90.6% of the species and 94.3% of individuals. Of the species, 39.8% were assignable to the summer, 21.9% to the spring, 8.1% to the winter and 5.3% to the autumn germinating group, and 24.9% were non-seasonal. Simpson's dominance index for PF ranged from 0.11 to 0.525, with an average value of 0.21 and a median of 0.195. The Shannon diversity index had a range of 1.15–2.43, with an average value of 1.93 and a median of 1.91. In some cases (13.3%) compensation phenomena are evident, sustained by different species from site to site. These results form the basis of a discussion on the effectiveness and the limits of management strategies designed to reduce soil seed stock. Un profil de la flore potentielle des champs de mais de la Vallee du Po Des enquetes quali-quantitatives (spectre biologique et ecophysiologique, organisation structurale, taille du stock grainier) de la flore potentielle (FP) dans les champs de mais (Zea mays L.) de la vallee du Po, sont rapportees. Les donnees ont ete collectees dans 45 sites a 2 profondeurs d'echantillonage (0–20 cm et 21–40 cm). La teneur en graines du sol etait fortement variable, allant de 1660 a 53371 graines m−2 pour une moyenne de 10391 et une mediane de 5500. Le stock grainier etait inferieur a 2000 graines m−2 dans 6,6% des sites et superieur a 10000 dans 26,6%. 6 especes ont ete trouvees dans plus de la moitie des sites, representant 27,7% du stock total: Anagallis arvensis L., Chenopodium album L., Stellaria media (L.) Vill., Echinochloa crus-galli (L.) P. Beauv., Amaranthus spp., Polygonum persicaria L., +P. lapathifolium L. Globalement, 63 especes ont ete inventoriees, avec le nombre d'especes par site allant de 4 a 25 avec une mediane de 11. Le groupe biologique des therophytes concernait 90,6% des especes et 94,3% des individus. Au sein des especes, 39,8%etaient estivales, 24,9% indifferentes, 21,9% des printanieres, 8,1% hivernales et 5,3% automnales. L'index de dominance de Simpson pour PF allait de 0,11 a 0,525 avec une moyenne de 0,21 et une mediane de 0,195. L'index de diversite de Shannon allait de 1,15 a 2,43 avec une moyenne de 1,93 et une mediane de 1,91. Dans quelques cas (13,3%) les phenomenes de compensation sont evidents, alimentes par differentes especes d'un site a l'autre. Ces resultats forment la base d'une discussion sur l'efficacite et les limites des strategies en vue de reduire le stock grainier du sol. Potentielle Flora in Maisfeldern der Po-Ebene Bei einer sowohl qualitativen als auch quantitativen Aufnahme der potentiellen Verunkrau-tung von Mais-(Zea-mays-)Feldern der Po-Ebene wurden Daten uber das biologische und okophysiologische Spektrum, die Struktur und den Umfang des Samenvorrats im Boden in 0–20 und 21–40 cm Tiefe an 45 Orten erhoben. Der Samenvorrat variierte erheblich und reichte von 1660 bis 53371 Samen m2 bei einem Mittelwert von 10391 und einem Median von 5500. An 6,6% der Orte war er 10000. 6 Arten wurden an > 50% der Orte gefunden und machten 27,7% des gesamten Samenvorrats aus: Anagallis arvensis L., Chenopodium album L., Stellaria media (L.) Vill., Echinochloa crusgalli (L.) P. Beauv., Amaranthus spp., Polygonum persicaria L. +Polygonum lapathifolium L. Insgesamt wurden 63 Arten gefunden, an den einzelnen Orten zwischen 4 und 25, im Mittel 11. Zur Lebensform der Therophyten zahlten 90,6% der Arten und 94,3% der Samen. 24,9% waren indifferente, 21,9% Fruhjahrs-, 39,8% Sommer-, 5,3% Herbst-und 8,1% Winterkeimer. Der Simpson-Dominanzindex der potentiellen Flora reichte von 0,11 bis 0,525 mit einem Mittelwert von 0,21 und einem Median von 0,195. Der Shannon-Diversitatsindex lag zwischen 1,15 und 2,43 mit einem Mittelwert von 1,93 und einem Median von 1,91. In einigen Fallen (13,3%) war eine deutliche Kompensation der Arten erkennbar. Anhand der Befunde werden die Wirksamkeit und die Grenzen einer Strategie zur Verringerung des Samenvorrats im Boden diskutiert.

Resume: Summary: Zusammenfassung Des simulations d'echantillonnage ont ete realisees sur des donnees provenant d'une experimentation commune du groupe de travail EWRS ‘Potentiels semenciers des sols agricoles’. Cinq parcelles agricoles ont ete choisies et leurs stocks semenciers analyses. Une etude par simulation de la relation liant la precision relative et le nombre de prelevements regroupes en composites a montre (1) que l'hypothfese de normalite des distributions des moyennes specifiques n'est realisee que pour environ 30% des series lorsque le nombre de prelevements est egal a 30 et pour 75% des series lorsque ce nombre est de 150; (2) que la precision relative est fonction d'une part de la taille du composite (nombre de prelevements) et d'autre part du nombre moyen de semences par prelevement; (3) I'existence d'une relation de type exponentiel liant la precision relative et le nombre moyen de semences par prelevement sur les differentes parcelles experimentales. EWRS collaborative study of seed bank estimation, II. Estimation of the relative accuracy of the mean using the compound sample procedures Sampling simulations were made using the data from a joint experiment of the EWRS working group ‘Seed banks of agricultural land’. Five agricultural plots were selected and the seed banks analysed. A simulation study of the relationship between the relative accuracy and the size of the compound sample (number of soil cores) showed (1) that the hypothesis of normality of the distribution of the species means was true for only about 30% of the sets when the compound sample size was 30 and for about 75% of the sets when the size was 150, (2) that the relative accuracy was dependent partly on the size of the compound sample and partly on the mean number of seeds per soil core, and (3) that there was an exponential relationship between relative accuracy and the mean number of seeds per soil core for the various experimental plots. EWRS-Ringsversuch zur Bestimmung der Samenbank im Boden. II. Schatzung der re-lativen Treffsicherheit des Mittelwerts von Sammelproben Mit Datenmaterial aus einem Ringversuch der EWRS-Arbeitsgruppe ‘Samenbank land-wirtschaftlich genutzter Boden’ wurden Pro-bennahme-Simulationen vorgenommen. Dazu wurden 5 Felder ausgewahlt und deren Samenvorrat analysiert. Eine Simulations-Studie uber die Beziehung zwischen der relativen Treffsicherheit und der Sammel-probengrose (Anzahl der Bodenproben) ergab zum einen, das die Hypothese der Normalverteilung der Mittelwerte von Arten nur in etwa 30% der Datensatze bei einer Sammelproben-grose von 30 und in etwa 75% bei einer Sammelprobengrose von 150 zutraf. Zum anderen hing die relative Treffsicherheit teils von der Grose der Sammelproben, teils von der mittleren Samenzahl pro Bodenprobe ab. Drittens bestand fur die einzelnen Versuchsflachen eine exponentielle Beziehung zwischen der relativen Treffsicherheit und der mittleren Samenzahl pro Bodenprobe.

Summary: Resume: Zusammenfassung Weed density was sampled in a number of quadrats in five crops and at eight locations in Italy. For every location and species of crop and weed, a mean/variance pair was calculated. The relationship between these two parameters was significantly influenced by crop and, to a lesser extent, by site, but not by species of weed. The goodness of fit of the negative binomial distribution to the samples was assessed. Its k exponent was estimated on the basis of the observed variance/mean regression. A good fit was found for weed populations with fewer than 10 plants m−2. The applicability of a sequential sampling procedure based on the negative binomial distribution to a weed control strategy that uses a threshold density is discussed. Denombrement de la frequence des adventices et applicabilite a une methode d'echantillonnage sequentiel pour un desherbage integre La densite en adventices a eteechantillonnee dans plusieurs cadres dans 5 cultures et a 8 endroits en Italic. Pour chaque lieu et espece de culture et de mauvaise herbe un couple moyenne/variance a ete calcule. La relation entre ces deux parametres etait tres dependante de la culture et a un degre moindre du lieu, mais n'etait pas influence par l'espece d'adventice. La validite de l'application de la distribution binomiale negative aux echantillons a ete estimee. Son coefficient k etait estime sur la base de la regression observee sur variance/ moyenne. Une bonne adequation a ete mise en evidence pour des populations inferieures a 10 plantes m−2 L'applicabilite d'un protocole d'echantillonnage sequentiel base sur la distribution binomiale negative, a une strategic de desherbage utilisant un seuil de densite est discutee. Frequenzverteilung in Unkraut-Vegetationsaufnahmen und Aufnahmemethode im Rahmen der integrierten Unkrautbekampfung Auf der Basis der Dichte von Unkrautern in 5 Kulturen an 8 Orten in Italien wurden Mittelwert und Varianz berechnet. Das Verhaltnis dieser beiden Parameter wurde durch die Kulturpflanzenart signifikant, weniger durch den Ort und gar nicht durch die Unkrautart beeinflust. Die Gute der Anpassung an dienegative Binomialverteilung der Erhebungsdaten wurde bestimmt. Ihr k-Exponent wurde nach der beobachteten Varianz/Mittelwerts-Regression bestimmt. Fur Populationsdichten von < 10 Pflanzen m−2 ergab sich eine gute Anpassung. Die sich aus der negativen Binomialverteilung ergebende Bekampfungsstrategie aufgrund von Schadensschwellen wird diskutiert.

National audience

(…) Dans les 186 series de donnees considerees, on n'a jamais observe de distribution normale. Les especes presentant les moyennes les plus basses (

Summary Four tests were carried out in 1980 and 1981 to determine: (a) the economic threshold density of Abutilon theophrasti Medicus (velvetleaf) in maize, and (b) seed production with varying densities of infestation, both in the presence and in the absence of maize. The infestation was artificially created, and the density of the weed ranged from 0 to 80 plants m−2. The economic threshold, calculated using the Cousens (1987) model, varied between 0⋅3 plants m−2 and 2⋅4 plants m−2, depending on the variables considered. The presence of maize reduced the seed-rain of A. theophrasti by 50%. This seed-rain reached its maximum level at 20–30 plants m−2 in maize, and at 30–35 plants m−2 in weed monoculture. However, with only 4–5 plants m−2 in competition with maize, A. theophrasti produced 8–10 thousand seeds m−2. The usefulness of threshold density in weed management is debatable when one considers the ecological characteristics of the A. theophrasti seed, and the great capacity of seed production of this weed. Resume Seuil de nuisibilite et production grainiere de l'abutilon (Abutilon theophrasti Medicus) en culture de mais Quatre experimentations ont ete conduites en 1980 et 1981 pour determiner: (a) la densite-seuil economique d'Abutilon theophrasti Medicus, en mais; (b) la production grainiere avec des densites variables d'infestation, soit avec, soit sans mais. L'infestation etait artificielle, et la densite d'adventice allait de 0 a 80 plantes m−2. Le seuil economique, calcule selon le modele de Cousens (1987), variait entre 0,3 et 2,4 plantes m−2 suivant les variables considerees. La presence de maiS reduit la production graniere de l'abutilon de 50%. Cell-ci est maximale pour 20–30 plantes m−2 en culture de mais et pour 30–35 plantes avec seulement des adventices. Cependant avec seulement 4 a 5 plantes m−2 en competition avec du mais, A. theophrasti a produit huit a dix mille graines m−2. L'utilite des densites seuils en desherbage est discutable quand on considere les caractetistiques ecologiques des graines d'A. theophrasti et la capacite considerable de production grainiere de cette adventice. Zusammenfassung Schadensschwelle und Samenproduktion der Linden blattrigen Schonmalve (A butilon theophrasti Medicus) im Mais Zur Bestimmung der okonomischen Schadensschwelle und der Samenproduktion von Abutilon theophrasti im Mais wurden 1980 und 1981 vier Versuche mit Bestandesdichten des Unkrauts von 0 bis 80 Pflanzen m−2 durchgefuhrt. Die Schadensschwelle wurde mit dem Modell von Cousens (1987) berechnet; sie betrug je nach den Variablen 0,3 bis 2,4 Pflanzen m−2. Die Samenproduktion war bei Konkurrenz mit Mais urn 50% herabgesetzt. Das Maximum lag bei einer Dichte von 20 bis 90 Abutilon-Pflanzen m−2 im Mais und bei 30 bis 35 Pflanzen m−2 im Reinbestand. Bei nur 4 bis 5 Abutilon-Pflanzen m−2 im Mais bildete das Unkraut 8000 bis 10 000 Samen m−2. Angesichts des keimungsoklogi-schen Verhaltens der Samen und der hohen Samenproduktion erseheint die Anwendung des Schadensschwellenprinzips bei der Bekampfung dieses Unkrauts zweifelhaft.