Market Garden Crops Research Articles

Plant Agrobiodiversity, Agricultural and Phytosanitary Practices of Market Garden Crops in the Centre‐East Region of Burkina Faso

ABSTRACTIntroductionIn West Africa, market gardeners use various agricultural practices to increase yields. However, many of these practices do not comply with agroecological standards and cause intoxication, pollution, soil degradation and biodiversity loss. This study characterizes the plant agrobiodiversity of market garden crops grown during the rainy season and the agricultural and phytosanitary practices used for their management.Materials and MethodsThe study was carried out in Burkina Faso. Plant agrobiodiversity was assessed in 100 market gardens. Agricultural and phytosanitary practices were characterized using semi‐structured interviews. A Sankey diagram was used to highlight the relationships among market garden crops, bioaggressors and diseases. Principal component analyses were applied to highlight the agricultural and phytosanitary practices used.ResultsThe results revealed rich agrobiodiversity, including 16 market garden crops, 15 local agroforestry species, 17 planted species and 37 weed species. The main market garden crops grown in the rainy season were cabbage (20.30%), lettuce (16.62%), tomato (11.69%), and amaranth (10.15%). The most frequent agroforestry species were Azadirachta indica (18.20%) and Mangifera indica (15.03%). The most common weeds were Eleusine indica (11.02%) and Cyperus reduncus (9.70%). Eleven pests were identified, and the most frequently recorded were caterpillars (39.06%). Sixteen diseases were reported, the most common being leaf yellowing (15.67%) and leaf wilt (11.67%). Numerous market gardeners use mineral fertilizers such as Yaramila (NPK 23‐10‐5), NPK (14‐23‐14), urea (46.00% nitrogen), and liquid fertilizer as well as compost and organic manure. The most common agricultural practice was crop rotation (79.00%). To protect crops, 89.00% of producers used synthetic chemical pesticides in an uncontrolled manner, most of which are purchased on the local market. Only 11.00% of the market gardeners practiced the natural phytosanitary treatments.ConclusionThis study provides important information that can be used for the sustainable management of market gardens. Agroecological standards should be popularized to ensure food security for market garden crops.

Study on the rate of pesticide use in market gardening to promote more sustainable and healthier farming practices in the Médéa region, Algeria

This study was carried out in the region of Médéa with the aim of finding out the rate of pesticide use in market garden crops, which are widely consumed by people in Médéa. In fact, this work aims to raise awareness among all pesticide sellers, farmers and consumers to minimise as far as possible the use and consumption of products treated with pesticides because they are very harmful to human, animal and environmental health in the short and long term. To this end, a survey of 49 farmers was carried out in the field on 30 farms in eight major stations, namely Tablat, Bouchrahile, Chahbounia, Suaghi, Sidi naamane, Beni sliman, Sidi rabie and Si mahjoub, using an appropriate questionnaire. The results of this study show that the majority of farmers report the presence of fungal diseases, in particular scab and mildew. In addition, there were parasitic pests such as aphids, mites and caterpillars, unlike weeds, whose presence depended on the farm. Farmers also use pesticides incorrectly, failing to observe the safety period and not wearing protective equipment when applying these substances. Pesticide sellers, farmers and consumers also suffer from a number of illnesses, including cancer (various types), skin diseases, eye diseases, stomach pains and coughs.

Spatio-temporal dynamics of agricultural and built-up areas in the Niaye area of Pikine urban wetland (Dakar, Senegal)

The Niaye area of Pikine, a wetland with favorable physical and climatic conditions, is a rich and varied ecosystem that guarantees a supply of water and fertile soil, conducive to market gardening. This plays an important socio-economic role in the Dakar region. However, this sensitive and fragile ecosystem is often affected by poor farming practices. The aim of the study was to analyze the spatial evolution of agricultural areas and built-up areas in order to identify related environmental problems. Interview guides, aerial photographs from 1966 and 1978 and Digital Globe Over view 2 satellite images from 2004 and 2022 were used. The interview guides were used to obtain data on the management of the market gardening activity, and also to identify the environmental problems it generates. Satellite data processing revealed, through cartographic analysis, a progressive market gardening dynamic of +5.07%. In addition, the built-up area around the lake has increased by over 200%, resulting in a 68.4% decline in upland vegetation and a migration of market gardeners to the lake. This situation leads to the destruction of market garden crops in the rainy season as the water rises. What's more, the intensification of market gardening in response to the population's growing demand for vegetables has not failed to encourage bad practices, including the use of pesticides and sewage, which is a public health problem and a threat to the future of this wetland.

Identification and Characterization of Market Garden Crops Grown Near Landfills in Abidjan District

Abstract: Market garden crops constitutes an important source of food and is one of the most income-generating activities in Côte d'Ivoire. In the Abidjan district, several market gardening sites are located near illegal landfill sites, therefore representing a danger for consumers.
 Aims: This study was carried out to map these different sites, inventory the plant species cultivated and characterize the cultivation practices with a view to highlighting the constraints and identifying prospects for improvement.
 Methodology: Semi-structured individual interviews were carried out in 4 communes of Abidjan (Abobo, Bingerville, Cocody and Port-bouët) to collect information from 400 residents including 280 men and 120 women. The statistical analysis of the survey results was carried out using Google Form and Excel software.
 Results: The results revealed six (6) market garden sites with landfills distributed in four (4) different communes (Abobo - Akeikoi village; Bingerville - Bingerack city; Cocody - M'pouto village and M'badon village; Port-bouët - 4th bima and Mafiblé village). Thirteen (13) market garden species which are divided into eight families. Lettuce and basil are grown on all identified sites and represent the most cultivated species (40%). Market garden crops is practiced by young people aged 10 to 30 (70%) with a relatively low level of education. Pests (insects, rodents, fungi) and heavy metals from illegal dumps constitute the main obstacles to production and are vectors of frequent diseases.
 Conclusion: It would be wise to adopt an integration policy for market gardening, in urban development plans, and to combat the proliferation of uncontrolled landfill sites, this will help to improve the quality and yield of market garden crops in Abidjan.

Market garden efficiency and farmer empowerment in the urban and peri-Urban area of San Pedro for food security in Côte d'Ivoire

The aim of the study was to assess the effectiveness of market garden crops in the urban and peri-urban area of San Pedro, Côte d'Ivoire, and to determine their contribution to the empowerment of market gardeners and to food security in the region. The sample was carried out on 50 market gardeners spread over 5 production sites, with a cumulative cultivated area of 16.6 hectares. The results show that thirteen (13) crops are grown, of which four are specifically grown by women, six are specifically grown by men and three are grown jointly by women and men. Short cycles are predominantly managed by women, while long cycles are dominated by men. The best gross margins were observed for eggplant cultivation in periods of scarcity and abundance. The study also revealed constraints linked to market gardening practices, as well as to fertilizer types and use. These results could be useful for improving market gardening practices in the region and boosting food security. This should help public policy-makers to make the right decisions.

Identification of Salmonella in Market Garden Products and Irrigation Sources in the City of N'djamena

Objective: Irrigation of market garden crops in the city of N'Djaména is done through wastewater often heavily soiled by human and animal faeces. The aim of this study was to identify salmonella in market garden products and irrigation sources in the city of N'Djaména. Methodology and Results: Samples of water and lettuce (Lactuca sativa L.) were taken from market gardens in 16 sites covering 7 districts (1, 3, 5, 7, 8, 9 and 10) of the city of N'Djaména. Microbiological analysis was done according to ISO 6579:2002. Salmonella strains were isolated according to the standard microbiology method and confirmed by the Api 20 E bacterium. Market gardening is practiced by 87.87% of men and 12.12% of women, most of whom are illiterate (53.03%). However, 84.84% of producers have no knowledge of biosafety; 80.30% do not know what salmonellosis is; 78.78 recognize that the use of wastewater in market gardening constitutes a danger to the health of producers and consumers. The rate of contamination of water by salmonella by district was: 94.44% in the 1st ; 91.66% in the 9th; 81.57% in the 7th; 80% in the 10th; 78.26% in the 3rd; 69.69% in the 5th and 68.96% in the 8th. According to the seasons: the prevalence was 85% in the dry season, 76% in the rainy season. The prevalence of salmonella in the different types of irrigation water was: 88.48%; 86.40%; 83.33% and 35.71% in pond water, wastewater, river water and borehole water respectively. The contamination rate in lettuce was: 93.10% in the 9th; 92.10% in the 1st; 92.% in the 7th; 91.66% in the 3rd; 90.90% in the 10th; 88.88% in the 5th, and 86.95% in the 8th. According to the seasons, salmonella contamination was 92.59% in the dry season and 89% in the rainy season. For fertilizers, the prevalence was 88% for simple dung, while for dung associated with synthetic fertilizer, it was 86%.

Description of the Gap between Local Agricultural Practices and Agroecological Soil Management Tools in Zerhoun and in the Middle Atlas Areas of Morocco

Agroecology is an agricultural, holistic, and innovative approach, which aims to increase the effectiveness, efficiency, and sustainability of agricultural systems. This approach is very rewarding for agriculture in developing countries, mainly in arid zones where water resources are in sharp decline. In this study, we examined farmers’ knowledge by studying existing agricultural production systems and agricultural practices in Moulay Driss Zerhoun (S1) and the Middle Atlas (S2) in central Morocco, to assess the gap between them and the principles and recommendations of agroecology. Data were collected through a survey of 64 farmers, and through field trips and observations. Collected data were analyzed with Chi-square tests and canonical correspondence analysis. Most farms (63.3% in S1 and 52.9% in S2) have an area between 0 and 5 ha. Both areas frequently opt for agroforestry. Olive trees and annual crops (85%), olive trees and fodder crops (10%), and olive trees and market garden crops (5%) are the most recorded associations. Olive trees were used frequently in association with other fruit trees, such as almond trees (15%), carob trees (13%), and fig trees (5%). Of farmers practicing agroforestry, 70% use only organic fertilizers. Thus, 53% of the farmers interviewed at the level of the S2 zone cultivate vegetable crops, against 17% at the level of S1, and only 40% of the farmers of S1 use irrigation, while 60% depend on rainfall. On the other hand, 83.3% of farmers in S1 adopted a two-year rotation—cereals and legumes—against 30% in S2. Tillage or plowing is considered by farmers a necessary procedure before sowing, and, only in S2, 71% of farmers opt for annual tillage of their land for agroforestry. Based on multivariate analysis, the choice of crops was significantly influenced by region and type of organization. However, it was not influenced by topography or farmland size, and the land and area played an important role in the selection of crop types. Raising awareness and introducing agroecological practices in the two study areas based on local knowledge seems essential, with the aim of strengthening the resilience of agroecosystems, respecting the environment, and guaranteeing the sustainability of small farmers through the diversification of their productions. The obtained results from this work are the first in this field of study and constitute a basis for comparative investigations.

CROP PERFORMANCES AND GENETIC VARIABILITY ANALYSIS OF SEVEN TOMATO GENOTYPES CONDUCTED UNDER AGRO ECOLOGICAL FARMING MANAGEMENT

Tomato crop occupies a predominant place after that of potatoes in market garden crops in Algeria. The main purposes of this study were to evaluate crop performances, variability of some morphologic and phenologic traits, and correlations with the yield of seven (07) genotypes of tomato. The trials were carried out on Random Complete Blocs Design (RCBD) with three replications at the local unheated greenhouse during the period from November to June 2018. The most important morphological markers used were stem growth rate, inflorescence (Number of flowers, length of peduncle) and fruit characters (length and circumstance), phenologic stages, and average yield. The effect of the genetic material on the observed variability was significant for all the traits considered. Additionally, we noticed positive values of correlation coefficients of yield with stem length between every two clusters and the number of leave under cluster, average fruit weight, and earliness to flowering. Additionally, earliness to flowering shows very high and stable correlations (above 0.8) with yield during the crop cycle. The principal component analysis showed that the first two components generated 62.17 % of variability, while the first four components accumulated more than 93 % (93.51 %) of the total diversity. Moreover, the dendrogram analysis classified the genotypes within 03 groups.

GEOSPATIAL TREND ANALYSIS OF RAIN-FED AND IRRIGATION PRACTICES FOR CROPS YIELD IMPROVEMENT IN KURA AND MINJIBIR, KANO SATE, NIGERIA

One of the advancements in Agriculture in recent time is the boost of crop yield to increase the number of output and feed the growing Nigerian population. The higher the output the less cost of food items and the more the food security. Kano State is one of the focal point not only on rain fed Agriculture alone but in irrigation farming. Irrigation was adopted coupled with soil fertility. most major crops such as Sorghum Bicolor, Maize, Millet, Beans and Groundnuts are typically grown during rainy season, while market garden crops such as Tomatoes, Pepper, Onion and Rice are now cultivated during the dry period in large hectares of land. This study focuses on different crops yield and its spatial distribution; to calculate the total crop yield per hectare and ascertain the duration of bumper harvest using trend analysis and normal probability. The result indicated more turn-out of farmers with double output of both rain fed and irrigation crops from 2019 and 2020 in two major local government area of Kano State Nigeria

Analysis of Pesticide Residues in Some Market Garden Crops in Santa, North West Cameroon

The increased use of pesticides in crop production, especially in Santa, has left consumers with great fear and uncertainty regarding the fate of residues after consumption in the human body. This study was aimed at performing a multi-residue analysis of crop samples to detect and quantify pesticide residues present, and thus determine their level of contamination. Twelve (12) crop samples (4 samples each of Solanum tuberosum (Irish potato), Solanum lycopersicum (tomato), Capsicum annum (sweet pepper) and Apium graveolens (celery)), were randomly collected from four villages in Santa. The samples were analyzed using the QuEChERS Buffered AOAC 2007.01 method. The results showed the presence of pesticide residues in 58.3% of the samples. Cypermethrin and chlorpyrifos insecticides were detected, though cypermethrin was found in traces. After quantification, the concentration of chlorpyrifos was determined to be far above the CODEX Maximum Residue Limits (MRLs) in 28.6% of the samples. Samples with this high concentration of chlorpyrifos were: tomato from Pinyin and Baligham (2.0 and 1.8 μg/g respectively), whereas the Codex MRLs for tomato is 1.0 μg/g. This study raised concerns on the contamination of some garden crops by pesticide residues and calls for the assessment of the health situation of consumers and the analysis of pesticide residues in drinking water resources in this area.

Varying Effects of Organic Waste Products on Yields of Market Garden Crops in a 4-Year Field Experiment under Tropical Conditions

Controlling organic and mineral fertilisation is a major concern in tropical environments. An experiment was conducted on an arenosol in the Dakar region, the main market gardening area of Senegal, to evaluate treatments commonly used by farmers. Seven treatments were repeated three times: A mineral fertilisation (MF) treatment based on N-P2O5-K2O (10-10-20), and three organic treatments at two doses (dried sewage sludge (SS), poultry litter (PL) and a digestate from an anaerobic digestion (AD) of cow manures). Each of the organic treatments were supplemented with a normal dose (1) and a double dose (2) of mineral N and K fertiliser. A lettuce, carrot and tomato rotation was grown in four campaigns (2016–2020) on all of the plots. Yields of all three crops in all of the organic treatments were statistically similar (p > 0.05) to the MF in all four campaigns, except for the yield of the lettuce crop under treatment PL-2 in campaigns 2 and 3. The tomato yields were statistically similar under all of the organic treatments in all four campaigns. In contrast, the yields of the lettuce and carrot crops differed statistically from each other and under the different organic treatments in all four campaigns. The yields of all three crops differed in the campaigns with the fertilisation treatment. In each campaign, the yields of each crop were not correlated with the total amounts of N, P and K applied. These differences or similarities in yields are explained by the nature of the organic waste products, the accumulation of nutrients after several applications, the type of crop and interannual differences in temperature.

A hybrid representation of the environment to improve autonomous navigation of mobile robots in agriculture

This paper considers the problem of autonomous navigation in agricultural fields. It proposes a localization and mapping framework based on semantic place classification and key location estimation, which together build a hybrid topological map. This map benefits from generic partitioning of the field, which contains a finite set of well-differentiated workspaces and, through a semantic analysis, it is possible to estimate in a probabilistic way the position (state) of a mobile system in the field. Moreover, this map integrates both metric (key locations) and semantic features (working areas). One of its advantages is that a full and precise map prior to navigation is not necessary. The identification of the key locations and working areas is carried out by a perception system based on 2D LIDAR and RGB cameras. Fusing these data with odometry allows the robot to be located in the topological map. The approach is assessed through off-line data recorded in real conditions in diverse fields during different seasons. It exploits a real-time object detector based on a convolutional neural network called you only look once, version 3, which has been trained to classify a considerable number of crops, including market-garden crops such as broccoli and cabbage, and to identify grapevine trunks. The results show the interest in the approach, which allows (i) obtaining a simple and easy-to-update map, (ii) avoiding the use of artificial landmarks, and thus (iii) improving the autonomy of agricultural robots.

Assessment of the Health Risks Associated with the Ingestion of Heavy Metals (As, Cd, Cr, Pb, Ni, Zn, Hg) in Vegetable Crops in the City of Daloa (Ivory Coast)

In order to assess the health risks associated with the ingestion of heavy metals or trace metal elements (TME) contained in foodstuffs from market garden crops, we sampled the tomato, cabbage, onion and leaves of 'onions and lettuce grown in the lowlands of the town of Daloa. The concentrations of ETM contained in these market garden products were determined by an Atomic Absorption Spectrophotometer (AAS) using three methods such as the flame method (Zn), the oven method (Pb, Cd, As, Cr, Ni) and the hydride (Hg) method. The results obtained showed that the heavy metals studied are present in fruits and vegetables with the most important Zn, Cr and Ni contents. However, metals such as arsenic, mercury and zinc present a concentration higher than that of the standard in force for the foodstuffs studied. Thus, the consumption of market garden products from cultivated soils in the areas studied could present dangers for the exposed population. Indeed, the study of the health risks associated with the ingestion of these vegetables has shown that for arsenic and zinc the determined Danger Quotient are all greater than 1. Which means that these vegetable crops present risks. related to the ingestion of zinc and arsenic. this means that the exposed population is theoretically out of danger. The values obtained from the Health Impact (SI) are all less than 1 for the population surveyed. On the other hand, for the estimated population of the city of Daloa we observe an IS> 1.

Diversity of experimentation by farmers engaged in agroecology

Agroecology questions the production of generic knowledge. Rather than searching for the best practices for large-scale transfer, it would be more efficient to help farmers find their own solutions. A promising activity for farmers is experimentation because it answers their needs and helps them learn. However, how agroecological practices are tested by farmers in their own experiments is still poorly known. In this study, we examined the short-term experimental activity, i.e., experiments carried out at a yearly scale in pre-defined fields. Seventeen farmers in south eastern France were surveyed. The farmers practiced conventional or organic farming and cultivated either arable or market garden crops. Experiments on agroecological practices were characterized, located along a timeline, and discussed with them. To conduct the interviews with the farmers, each experiment was described in three stages: (1) designing the experiment, (2) managing it in real time, and (3) evaluating the results of the experiment. The data collected in the interviews were first analyzed to build a descriptive framework of farmers’ experiments, after which hierarchical cluster analysis was used to analyze the diversity of the farmers’ experiments. Here, we propose for the first time a generic framework to describe farmers’ experiments at a short time scale based on the consistency between the Design, Management, and Evaluation stages. We used the framework to characterize the diversity of farmers’ experiments and identified four clusters. The originality of this work is both building a descriptive framework resulting from in-depth analyses of farmers’ discourse and using statistical tools to identify and interpret the groups of experiments. Our results provide a better understanding of farmers’ experiments and suggest tools and methods to help them experiment, a major challenge in the promotion of a large-scale agroecological transition.

Between all-for-one and each-for-himself: On-farm competition for labour as determinant of wetland cropping in two Beninese villages

In sub-Saharan Africa, unexploited land and water resources in wetlands represent an important potential for intensified, sustainable and food-secure farms through rice production and market gardening. The lack of uptake of cropping in wetlands may be related to the ways in which resources are divided between family fields and individual fields. The management system on sub-Saharan African farms comprises a family management unit or a combination of a family management unit and one or more individual management units. The family management unit or the farm head controls production in family fields to satisfy family needs while the individual management units control production in individual fields to satisfy individual needs. Our objective was to investigate the diversity in farm management systems and the resulting uptake of cropping in wetlands for different farm types, as the first step towards suggestions for enhancing rice production and market gardening in wetlands. We studied farms in two case-study villages in Benin: Zonmon in the southern part and Pelebina in the north-western part.Farm typologies were developed based on random samples of 51 out of 134 farms (38%) from Zonmon and 50 out of 146 farms (34%) from Pelebina by combining principal component analysis and Ward's minimum variance clustering. Variables included in the PCA were related to levels of resource endowment (e.g., amounts of land, family labour, cash for purchasing chemical inputs and hiring labour) and to resource-use strategies including resource division between family fields and individual fields, and between uplands and wetlands.We identified 3 farm types in Zonmon and 5 farm types in Pelebina based on differences in resource-use strategies and in resource endowment. We found no trade-off between the existence of individual fields and the area under rice and market garden crops in wetlands. Labour abundance was the main factor driving both the occurrence of individual fields and the expansion of cropping in wetlands. Differences in labour division strategies between family and individual fields among farm types reflected differences in food and cash division strategies. Land use appeared strongly motivated by food self-sufficiency objectives and labour productivity, leading to prioritisation of upland over wetland areas. In wetlands, most farm types opted for cultivating market garden crops during the dry season when labour demand for upland fields was low. Our results indicate that increasing labour productivity in food crops and in rice and market garden crops would enhance the uptake of rice and market garden crops in wetlands. Creating credit facilities would increase the labour resource and allow farmers to hire labour, further contributing to wetland use. We discuss the relevance of a systemic farm analysis that enables distinguishing family and individual fields for understanding farm uptake of rice and market garden crops in wetlands.

The Implications of Climate Variability on Market Gardening in Santa Sub-Division, North West Region of Cameroon

If Cameroon maintains its position as the “bread basket” of the Central African sub-Region, one of the areas to be credited is the Santa Sub-Division which is one of the major agricultural production basins, particularly market gardening. Apart from grappling with the conventional pre and post-harvest problems which plague the agricultural sector in Cameroon, observed variability in climate has aggravated the scenario. Using climatic records temperature and rainfall) for a 10 year period, including the output of market garden crops (carrots, leeks, tomatoes and cabbage), complemented by field observations and interviews, we established a correlation between climatic variations and variations in output of market garden crops The results showed both direct and inverse relationships between climate variability and market gardening resulting in differential implications for market gardeners. The implications of this results is that in the future, market gardeners could logically shift their focus to some specific crops; this could reduce the output of these crops leaving a bearing on demand and price. As a logical way forward, we suggest some adaptation options which can help farmers to “climate –proof” the market gardening sector which remains a source of livelihood for many farmers in Santa Sub-Division.

INVESTIGATION OF TRACE ELEMENTS CONTENT IN ORGANIC WASTES USED FOR MARKET GARDENING

ISHS International Symposium on Urban and Peri-Urban Horticulture in the Century of Cities: Lessons, Challenges, Opportunitites INVESTIGATION OF TRACE ELEMENTS CONTENT IN ORGANIC WASTES USED FOR MARKET GARDENING

기후변화를 고려한 제주지역의 권역별 가뭄 평가 및 농업용수에의 영향 고찰

Recently, the occurrences of droughts have been increased because of global warming and climate change. Water resources that mostly rely on groundwater are particularly vulnerable to the impact of precipitation variation, one of the major elements of climate change, are very sensitive to changes in the seasonal distribution as well as the average annual change in the viewpoint of agricultural activity. In this study, the status of drought for the present and future on Jeju Island which entirely rely on groundwater using SPI and PDSI were analyzed considering regional distribution of crops in terms of land use and fluctuation of water demand. The results showed that the precipitation distribution in Jeju Island is changed in intensity as well as seasonal variation of extreme events and the amount increase of precipitation during the dry season in the spring and fall indicated that agricultural water demand and supply policies would be considered by regional characteristics, especially the western region with largest market garden crops. Regarding the simulated future drought, the drought would be mitigated in the SPI method because of considering total rainfall only excluding intensity variation, while more intensified in the PDSI because it considers the evapotranspiration as well as rainfall as time passed. Moreover, the drought in the northern and western regions is getting worse than in the southern region so that the establishment of regional customized policies for water supply in Jeju Island is needed.

Investigation of potentially toxic heavy metals in different organic wastes used to fertilize market garden crops

The benefits of using organic waste as fertilizer and soil amendment should be assessed together with the environmental impacts due to the possible presence of heavy metals (HMs). This study involved analysing major element and HM contents in raw and size-fractionated organic wastes (17 sewage sludges and composts) from developed and developing countries. The overall HM concentration pattern showed an asymmetric distribution due to the presence of some wastes with extremely high concentrations. HM concentrations were correlated with the size of cities or farms where the wastes had been produced, and HM were differentiated with respect to their origins (geogenic: Cr–Ni; anthropogenic agricultural and urban: Cu–Zn; anthropogenic urban: Cd–Pb). Size fractionation highlighted Cd, Cu, Zn and Pb accumulation in fine size fractions, while Cr and Ni were accumulated in the coarsest. HM associations with major elements revealed inorganic (Al, Fe, etc.) bearing phases for Cr and Ni, and sulfur or phosphorus species for Cd, Cu Pb and Zn.

Risk analysis for biological weed control - simulating dispersal of Sclerotinia sclerotiorum (Lib.) de Bary ascospores from a pasture after biological control of Cirsium arvense (L.) Scop.

Biological control of Cirsium arvense(L.) Scop. in pasture by the plurivorous plantpathogenic fungus Sclerotiniasclerotiorum (Lib.) de Bary mayresult in the formation, escape and aerialdispersal of ascospores, creating an additionaldisease risk in down-wind market garden crops. To determine the width of a safety zone for apasture subjected to this form of weed control,we simulated the spatial pattern in the ratioof added (due to biocontrol) to naturallyoccurring airborne ascospores (due to marketgarden crops) around a 1ha virtual biocontrolpasture under either sheep or dairy cattlegazing over a 91-day emission period in 1996 inCanterbury, New Zealand. This was achievedusing a unique combination of two computermodels; SPORESIM-1D (for spore escape from avegetation source) and PC-STACKS (a modernGaussian plume model for dispersal beyond asource). Plumes of dispersing ascospores weremodelled for each hour of the emission periodfor both the virtual market garden andbiocontrol sites, and the aerial density of theascospores was averaged over the period. Assuming that a 1:1 ratio of added to naturallypresent spores is acceptable, no safety zonewas necessary for either of the modeledpastures. A ten-fold ratio (1:10 added tonatural) necessitated safety zones of 300 and150 m for the sheep and dairy pasturerespectively. Uncertainties associated withextrapolation of this conclusion to individualpasture management scenarios, and to otheryears and climatically different regions arediscussed.