There are many vegetable fruits recognized in Nigeria, but tomato, a vegetable fruit is a major food component, an ingredient utilized by every house hold and constitutes the national food security programme. The record confirmed that Nigeria produces approximately 1.8 million metric tons of fresh fruits for domestic consumption, with national demand of about 2-3 million tons per annum with a demand gap of about 500,000 metric tons. Tomato production is an important source of income to farmers unfortunately diseases such as Alternaria alternata greatly increase food losses by an approximately 20-30% and methods of using synthetic chemical compounds can be costly and dangerous if applied by an unskilled operator and are often not available at the time when required. As a result this study focused on the effect of hot water dipping as a non-chemical method to control the black mould disease caused by Alternaria alternata on red tomatoes. Hot water dip at 50ᴼC for 5 or 10 min was carried out on Alternaria alternata spore suspension (in-vitro), the results showed a significant (P≤0.05) reduction in germination of spores after 48 h. The in-vivo hot water treatment was carried out in three groups, viz-a-viz; first group consists of 30 and 50⁰C and tomato fruits were heated in hot water for 30 and 60 min respectively. The second group was 30, 40 and 50⁰C and fruits were dipped in hot water for 20 min. In the third group the temp was at 40, 45 and 500C and fruit were dipped in hot water at these temperatures respectively for 10 min. Furthermore, the hot water temp was increased to 50 and 55⁰C and inoculated fruits were immersed for 5 min in separate hot water bath. In this trial the result showed that dipping artificially inoculated fruit at 50 or 55⁰C for 5 min significantly reduced (P≤0.05) decay development caused by A. alternata. Conidia germination was more sensitive than mycelia growth to 50⁰C, but inhibition of both processes increased with the duration of time of treatment. The in-vitro hot water treatment of Alternaria alternata spores at 50⁰C i for 30 min significantly reduced the spore germination and mycelia elongation of the fungal pathogen in 48 h. The in-vitro result obtained was attributed to the direct effect of heat on the spore germination as well as mycelia growth resulting in the reduction of the growth of the fungus on the inoculated red fruit. Splitting was observed on the pericarp (skin) at the point of inoculation of fruits before hot water treatment at 55°C for 5 min. The hot water treatment of the tomatoes had the following effects on the attributes of quality: the Brix degrees measurement showed a negligible difference in 40 °C or 50°C compared with the control for 30 min heat treatment after 24 h storage. Also there was no effect of heat on the total soluble solid likewise, the firmness measurement on flesh of tomato showed no significant difference when compared with the control. In this study the change in colour after heat treatment was not statistically significant. Similarly, in the taste test there appears no real difference recorded in the attributes of juiciness, flavour and overall acceptance except that the skin of the tomato was recorded “softer” by some of the taste panellists. This study has shown that prestorage hot water treatment may be a useful non-chemical method of controlling A. alternata postharvest disease pathogen without adverse consequence on the fruit quality.

To meet the rapid growth of the global population and the expected demand for food, significant enhancements in yields are needed, together with optimised N fertilisation and environmental issues, particularly in the production of major grain crops, such as wheat and rice. Improving photosynthesis, together with NUE, has been considered an unexploited opportunity in the research on improving crop yields. Therefore, transgenic wheat plants with increased SBPase activity showed an improved photosynthetic leaf rate and total biomass production. The Rubisco protein is a major N investment in crops, but it has also been exhibited that under some environmental conditions, there may be an excess of Rubisco greater than that needed to maintain photosynthesis. This raises the question of whether a small reduction in the amount of the Rubisco enzyme can be used to improve NUE without any negative effects on plant yield. To address the question, wheat plants with decreased Rubisco were produced. Physiological studies were performed on five independent transgenic lines with different levels of Rubisco, and the photosynthetic rates, biomass and grain yields were determined. Rubisco RNAi lines with reductions in the Rubisco protein of more than 40% showed a significant decrease in photosynthesis, growth and grain yield. Interestingly, the plants with the lowest level of Rubisco activity had significantly higher levels of leaf and seed N when compared to WT plants. In contrast, small reductions in the Rubisco protein of between about 10% and 25% did not have an adverse effect on photosynthesis, growth or grain yield in two independent transgenic wheat lines. Furthermore, to search for new promoters to drive good transgene expressions specialised to wheat leaves, two Brachypodium promoters, SBPase and FBPA, were cloned upstream of the GUS fusion gene and transformed into wheat leaves. Consequently, both promoters resulted in detectable GUS expression in wheat leaves at different growth stages and did not show expressions in the roots.

Subsoil physical characteristics are often limiting to root growth, one of the major reasons being high density soil. However, deeper and more efficient root systems could help to explore a larger soil volume and reduce the input of nitrogen fertilisers if roots make more use of the nitrogen at depth. The first target was to develop a screening method which allowed barley root extension rates to be quantified after four days of growth in loose and compacted soils. Firstly, seed quality (loss of germination ability caused by poor conditions in storage and long storage time) was identified as a potential source of variation for root extension rate in seedlings. The screening showed that roots growing in compacted soil had a slower extension rate than roots growing in loose soil. In addition, there was an interaction between soil conditions and cultivars meaning that not all of them showed the same ability to overcome high soil density. Root architecture was characterized at days eight and 12 after planting for four selected divergent cultivars. Measurements were made using X-ray micro-computed tomography (µCT)-scanning. The differences between the four genotypes in root architecture (number of primary roots, root extension rate, root length, root area, root volume, convex hull, centre of mass, lateral density, lateral length) were significant at eight days after planting but disappeared at 12 days after planting for most of the traits measured (i.e. growth rate of primary roots). Soil density influenced the root system architecture at both two-time points, roots elongated less and explored less soil in the high compaction treatment. A third experiment was conducted to test the hypothesis that the differences in root architecture observed between the genotypes in response to the soil bulk density in the µCT-scanning would lead to different patterns of nutrient uptake from topsoil and subsoil. Layered soil columns of topsoil and subsoil were constructed with different subsoil physical parameters (loose, compacted and compacted with macropores) and a nitrogen tracer to measure nitrogen capture from the subsoil. Root length density and other traits determining root architecture differed between two barley cultivars and oat, but increased root length density in the subsoil did not improve nitrogen uptake from the subsoil. Hence showing that nitrogen uptake from the subsoil was not directly related with a greater presence of roots in the experiment.

Sandy soils are one of the most widely distributed soils in the world. However, crop production on these soils can be problematic especially in terms of water and nutrient retention. In the face of climate change and a projected reduction in water availability, food production is likely to be particularly affected. The aim of this research is to examine if amending soils with clay and organic matter can improve their water and nutrient retention. The research approach employed laboratory column leaching experiments, rainfall simulation, Computed Tomography (CT) scanning and field trials to investigate the potential of two types of clay, Kaolin (K) and Bentonite (B), and peat (Pt), as well different combinations of clay and peat, to act as effective soil amendments. The influence of amendment materials was assessed by examining water retention, nutrient retention, soil organic carbon and changes in soil properties. Laboratory analysis was supported by field trials to examine the productivity of spring wheat. The results showed that the amendment materials increased soil water retention and availability, reduced water infiltration, increased nutrient uptake, increased spring wheat growth and yield, and improved soil carbon storage compared to an unamended control. The findings provide a further understanding of how the addition of clay and OM can affect ecological function of sandy soils and elucidate the mechanisms involved in controlling water retention and availability, as well as nutrient retention in the amended soils.

The primary aims of this project were to: i) provide a survey of selenium and iodine concentrations in the terrestrial environment and locally grown crops of Iraqi-Kurdistan; ii) gain greater understanding of the factors controlling bioavailability of these elements in the calcareous soils of the region; iii) investigate the feasibility of biofortification of selenium and iodine and test the use of isotopically enriched tracers for this purpose; iv) assess iodine and selenium dietary intake and nutritional status of the local population using dietary questionnaires and a survey of a human biomarker. A survey was conducted covering locally grown crops, matched soil samples and irrigation water including 300 plant, 100 soil and 20 water samples. The potential availability of Se and I for plant uptake was examined by quantifying the soluble and adsorbed fractions of both micronutrients and their species. The influences of soil factors on plant Se and I uptake were examined. Results indicated that total soil Se (SeTot = 309 μg kg-1) was lower than the global average (400 μg kg-1). Approximately 2.5% of soil Se was present in the soluble and adsorbed fractions with an equal proportion of selenate and selenite in the soluble fraction and mainly selenite in the adsorbed fraction. The organically-bound Se extractability ranged from 20-89% of SeTot, depending on soil pH. Plant Se content was variable between crop species and different areas within Kurdistan with mean concentration of 113,112, 69 and 49 μg kg-1dw for leafy vegetables, tubers, fruit vegetables and wheat grain respectively. Higher plant Se concentrations were observed in plants grown in soils with pH > 8. The mean concentration of total soil iodine was 4140 μg kg-1. Almost 10% of this value was present in the soluble and adsorbed fractions. Mean plant iodine concentrations were 439, 368, 140, and 12 μg kg-1dw for leafy vegetables, fruit vegetables, tubers and grains respectively. The combined concentrations of soluble and adsorbed iodine were correlated with plant iodine content. The mean concentrations of irrigation water Se and I were 0.495 and 11.9 μg L-1 respectively. The amount (%) of soil CaCO3 was strongly correlated with iodine concentration in groundwater used for irrigation and irrigation water iodine concentration was again strongly correlated with plant iodine concentrations. The feasibility of Se biofortification in calcareous soils using local vegetable genotypes from Kurdistan was examined using 10 g ha-1 77Se as a biofortification treatment (and isotopic tracer). Five commonly used vegetables, including celery, chard, lettuce, radish and spring-onion were planted in soils spiked with the 77Se application and grown for 8 weeks under controlled growth room conditions. Results indicated that, at the end of the growth period approximately 35% of applied 77Se had been transferred to a recalcitrant form in the soil which resisted extraction with 10% TMAH. Only 5% of 77Se was present within the soluble and adsorbed soil fractions combined, at harvest. The amount of 77Se taken up by plant biomass varied according to crop species; 25% for radish and 7-8% for other vegetables from the total 77Se applied. Plant 77Se concentrations varied despite growing in identical soils and, unexpectedly, plants contained more Se originating from the soil rather than the fertilizer. The ratio of Sesoil/Sefertilizer also varied between varieties reflecting different growth patterns and uptake rates against a backdrop of decreasing fertilizer Se availability during the growing season. Biofortification of iodine using a range of vegetable crops grown in calcareous soil was investigated, using soil and vegetable genotypes from Kurdistan, and employing 129I as a tracer. Vegetables were irrigated daily with water containing 5.56 and 6.89 μg L-1 129IO3- and 129I- respectively for 8 weeks. Total and fractionated iodine (127I and 129I) was conducted on moist soil (c. field capacity) and air dried soil at the end of the growing season. Plant analysis was also undertaken for 127I and 129I, using ICP-MS. Results showed that plant iodine concentrations originating from native soil iodine were variable even when grown in identical soils. Generally, iodine concentrations in roots was greater than in shoots for both 127I and 129I. Vegetables irrigated with 129I- (iodide) had considerably lower iodine concentrations (6.2-12 μg kg-1dw) than those irrigated with 129IO3- (iodate) (53.3-479 μg kg-1dw). The majority of plant iodine originated from soil iodine rather than fertilizer iodine and varied depending on 129I species applied (iodate or iodide) and the vegetable plant type grown. For vegetable shoots treated with 129I- (iodide) only 3% of the iodine of the three test plants originated from the 129I treatment. By contrast, for 129IO3- (iodate) applications 11, 22 and 58% of iodine in the shoots of celery, lettuce and chard were from the 129I additions respectively. The recovery rate of 129I from soil extracted with 10% TMAH ranged from 63-95% of total iodine applied and varied depending on vegetable variety. The 129I recoveries from pots irrigated by 129IO3- were less than from 129I- irrigated soils suggesting greater loss of iodine from the iodate irrigated system. To assess the Se and I status of the population in a region of Kurdistan, the food composition data and dietary intake of Se and I was determined for 410 volunteers using a semi- quantitative food questionnaire, including commonly used food items. To directly investigate level of nutritional status of Se and I, urine samples were also collected from each participants as a biomarker. Daily dietary intake and source apportionment of Se and I from each food item was determined using questionnaire survey. The daily intake of I from food excluding salt was 119 μg d-1. Vegetables and fruits supplied 48%, protein sources 25%, cereal and grains 9%, dairy products 8% and water 2% of daily I intake. The majority (>90%) of salt samples collected were iodised with a mean I concentration of 40 mg kg-1 and daily intake of salt was estimated as 13.5g d-1. Accounting for salt intake, average daily iodine intakes increased to 668 μg d-1, with salt supplying 82% of daily I intake. The median urinary iodine (corrected for creatinine) was 379 μg g-1CRT and 424 μg L-1 osmolality corrected. More than 90% of school age children and over 55% all participants had excessive I intake according to WHO classification. The salt I concentration consumed by each family was highly correlated with mean urinary iodine of family members. Urinary Na and I were also correlated. The iodine intake estimated according to salt intake (calculated based on urinary Na) was strongly correlated with iodine intake calculated according to urinary iodine. The daily salt intake estimated by urinary Na was 15.3 g d-1 considerably higher than WHO recommended. Mean total daily intake of Se according to the questionnaire responses was 72.9 μg d-1 with 21% of participants having a daily intake lower than recommended RDA. The mean urinary Se fell in the range of 21.2-24.8 μg L-1 depending on justification methods. The predicted Se intake from urinary Se gave a values of 59 and 42 μg d-1 according to the method used which may imply Se deficiency. To conclude, Kurdistan soils Se content was found insufficient. Despite that, Due to high pH effect in some areas plant Se content seems to be having considerably higher Se content rather than areas with lower pH. Later studies revealed that daily Se intake may not enough to address the Se requirement of population. Biofortification of Se possible but to prevent decreasing availability would be recommend to apply in med season or foliar application. Typically soil and plant of Kurdistan found in a minimum of normal range of iodine and comparable with other areas. Irrigation water was found as a main source of plant iodine uptake. The daily iodine intake from food excluding salt is not enough to meet the recommended iodine level but considering high consumption of iodized salt in that region it can be classified as an excessive iodine intake which could cause high intake iodine consumption disorders such as hyperthyroidism and in turn health issues caused by elevated Na intake such as cardiovascular disease. In current iodine nutritional status of the region plant biofortification would not be recommended.

The aim of this work was to investigate the interactions of anionic radionuclides 129I, 77Se (as a proxy for 79Se) and 99Tc with soil geocolloids under a range of conditions. These anionic fission products are of specific concern to policy makers regarding human and environmental risk assessments. Previous research has demonstrated strong links between soil organic matter (SOM) content and reduced mobility of these radionuclides. Negatively charged humic substances (HS), such as humic acid (HA) and fulvic acid (FA), may constitute 80% of organic matter and the mechanisms that allow anionic radionuclide to interaction with these HSs are not well understood. In the case of all three radionuclides, speciation plays a significant role in controlling their environmental mobility, therefore HPLC and SEC coupled to ICP-MS was used to monitor the speciation changes as the isotopes were progressively incorporated into HA. X-ray absorption spectroscopy was also employed in order to establish the solid phase speciation of Se after reaction with soil geocolloids. Surface charge development of the HA significantly affected reaction with iodate (129IO3-) and iodide (129I-). Iodide added to HA systems demonstrated slow oxidation and formation of organically bound iodine (Org-129I) predominantly at higher pH (pH 6). Conversely IO3-, was rapidly transformed to form both I- and Org-I. As pH decreased, the rate of this reduction reaction increased. Increasing HA concentration also increased the rate of IO3- reduction and formation of Org-I. Previous research has suggested that the most likely mechanism is IO3- reduction to I2 or HOI which then binds with phenolic groups on OM forming Org-I species. However, IO3- was observed to rapidly bind to HA forming Org-I species with no initial evidence of I- formation; I- concentration then increased over time as Org-I decreased. Where Fe2+/Fe3+ was present increased reduction of IO3- to I- was observed, mediated by association with HA, resulting in less Org-I formation overall. Instantaneous reaction of I- with HA was observed in the presence of Fe2+/Fe3+, with bonding via cation bridging. Some I- was subsequently re-released as I- likely due to ongoing Fe hydrolysis. Modelling of the systems alone was successful and will assist the improvement of whole soil assemblage models. Selenite (Se(IV)) reaction with HA was most rapid at low pH, with minimal/no reduction occurring at > pH 6. Reduction of selenate (Se(VI)) also occurred but this was less than for Se(IV), at low pH. No formation of Se(VI) from Se(IV) was observed, suggesting no oxidation took place, however some formation of Se(IV) from Se(VI ) was observed, also the formation of an unknown Se species suspected to be organic in nature. Humic acid concentration had no significant effect on the rate of Se(IV) or Se(VI) reduction, suggesting that HA itself was not responsible for the reduction. X-ray absorption spectroscopy (XAS) demonstrated the potential for significant reduction to Se(0) at pH 4 and bonding through a Se-O-C chain. The role of microbial communities on Se(IV) and Se(VI) reduction in the HA systems was demonstrated through the use of soil inoculum and glucose additions in sterile and non-sterile systems. No reduction of Se(IV) or Se(VI) and bonding to HA was observed in filter and -irradiation systems. Additions of inoculum and glucose increased the rate of reduction. Additions of Fe2+ did not increase reduction of Se(IV) or Se(VI) when compared to non-sterile HA systems, however XAS analysis demonstrated formation of HA-Fe cation bridges. No reaction of pertechnetate (99Tc(VII)) with HA was observed in these aerobic systems. An unknown Tc species was occasionally observed (< 0.005 μ L-1) and it is possible that this is an organic-Tc species. Significant incorporation of Tc into the solid phase was observed in aerobic soils, with most Tc(VII) being retained in soils with high OM contents and low pH. The mechanisms considered here build upon the basic processes considered in current biosphere models for I and Se. Assemblage models must be used in order to reliably model the interactions of elements within soils due to the complexity of the systems. In order to understand the long-term radiological risks associated with geological repositories, the fine-scale mechanisms must be understood geochemically across a range of different soil types and conditions. The effect of I and Se speciation on bioavailability in soils determines both the potential transfer of radioactive isotopes to the food chain from GDF’s and from aerial sources of contamination. Alongside this, the work also has significant implications for advising on cost-effect fertiliser application methods for both I and Se, in order to tackle nutrient deficiencies worldwide.

Conservation Agriculture (CA) has potential benefits to the soil, crop yield, and the environment including reducing runoff, enhancing water retention and preventing soil erosion, in addition to increasing soil carbon sequestration and reducing greenhouse gas (GHG) emissions. Although CA is widely adopted in some areas of the world, it is still not widely adopted by UK farmers. The first overall aim of this project was to investigate the effects of tillage practice and residue retention, on soil physical properties, crop yield and GHG emissions. For this purpose, a split-plot field experiment was established on the University of Nottingham farm between September 2014 and August 2016. The main plot treatment was residue retention while cultivation practices were applied to the sub-plots and included three different tillage systems: no-tillage, minimum-tillage and deep ploughing. We used a novel analytical tool, X-ray Computed Tomography, to characterise the 3-D soil pore network in conjunction with a number of other soil physical properties such as bulk density, penetration resistance and shear strength. A range of portable chambers were used to detect the GHG emissions from soil and from soil-plant systems as influenced by the tillage and residue treatments. Winter wheat yield was not affected by the tillage treatments or residue retention in the first year, but, in the second year, no-tillage caused a 10% reduction in triticale yield compared to minimum-tillage and traditional ploughing. Multiple regression analysis showed that the lower triticale yield was partially explained by higher soil strength in the no-tillage plots, together with lower soil moisture content in summer. Our results show that while there is potential for climate change mitigation from no-tillage when the Net Ecosystem Exchange is considered, this effect could not be observed from soil emissions only. The second aim of this project was to assess the current level of reduced tillage (RT) uptake by UK farmers and the constraints for further adoption. A postal questionnaire was conducted in January 2016. This questionnaire found that only 7.0% of the arable land in England is under no-tillage and 47.6% is under minimum-tillage. The adoption of RT increased with an increase in farm size as it was the most adopted on farms >400 ha. Moreover, RT was adopted most on combinable crop farms. Weed management and slugs were identified as main challenges for RT adopters. Increasing uptake of CA from current levels will probably require policy intervention including financial incentives for growers during the early stages of the transition from ploughing to CA. This will encourage farmers to buy RT equipment and may help them to cover any potential yield reduction, if occurred, before the CA system stabilisation.

Plants have developed elaborate defence mechanisms to protect themselves against pathogens. Recently, the ubiquitin-proteasome pathway has been proven to play important roles in regulating plant disease resistance. Previously, the tobacco (Nicotiana tabacum) ACRE276 and its Arabidopsis homolog AtPUB17 have been identified as E3 ligases that are positive regulators of the Cf-9/Avr9- and N/p50-elicited hypersensitive response (HR) in tobacco. In addition, AtPUB17 is required for the RPM1- and RPS4-mediated resistance responses in Arabidopsis. The identification of AtPUB17 signalling partners would allow us to understand the mode of action of AtPUB17 during plant defence. AtPOB1, a BTB/POZ-domain protein was isolated as an AtPUB17 interactor in a yeast-two-hybrid screen. The aim of this study was to confirm this interaction and to investigate the potential involvement of AtPOB1 in mediating disease resistance responses. The analysis of the Atpob1 knock out plants revealed a novel BTB/POZ protein implicated in plant defence. Atpob1 plants rapidly accumulated reactive oxygen species (ROS), induced the expression of pathogenesis related (PR) genes and developed spontaneous necrotic lesions upon infection with a virulent pathogen. AtPOB1 transcript and protein levels were induced by virulent Pseudomonas syringae. And transient overexpression of AtPOB1 in Cf-9 tobacco compromised the Avr9-triggered HR. In addition, Atpob1 plants showed signs of premature senescence. These results indicate that AtPOB1 is a negative regulator of plant defence- and senescence-associated pathways. The Nicotiana benthamiana AtPOB1 homolog was also identified and its cDNA sequence was used to investigate the role of NbPOB1 and its close relative NtPOB1 in disease resistance signalling. Transient overexpression of NbPOB1 and RNA interference (RNAi)-based silencing of NtPOB1 in Cf-9 tobacco compromised and accelerated the Avr9-triggered HR, respectively. Moreover, virus induced gene silencing (VIGS) of NbPOB1 accelerated the dark-induced senescence in N. benthamiana leaves. These observations identify NbPOB1 and NtPOB1 as the orthologs of AtPOB1. The subcellular localization of AtPOB1 and NbPOB1 was analyzed by transiently overexpressing GFP-AtPOB1 and GFP-NbPOB1 fusion proteins in tobacco leaf tissue. Analysis by confocal microscopy revealed that GFP fluorescence was localized in the nucleus of leaf tissue tested. The overexpression of AtPOB1 fused with a nuclear export signal (NES) failed to compromise the Avr9-triggered HR in Cf-9 tobacco, indicating the nuclear localization of AtPOB1 is crucial for its function. The BTB/POZ domain is a highly conserved protein-protein interaction interface that mediates homo- and/or hetero-dimerization of BTB/POZ proteins. The D146A and D141A mutation in the BTB/POZ domain of AtPOB1 and NbPOB1, respectively reduces their dimerization efficiency. These mutants fail to negatively regulate the Cf-9/Avr9-mediated HR, supporting the importance of an intact BTB/POZ interface for the function of AtPOB1 and NbPOB1. Finally, yeast-two-hybrid and immunoprecipitation assays indicate that AtPOB1 interacts with AtCUL3A, a component of E3 ligase complexes, in which AtPOB1 would confer substrate-specificity. We propose that AtPOB1 (and Nicotiana POB1) negatively regulate cell death and senescence possibly through ubiquitin-mediated pathways.

The comunidades agricolas of Chile's Norte Chico are unique entities/systems of indivisible communal land, inherited land use rights, democratic decision-making, and diverse economic strategies that are closely linked to changing environmental conditions. Families reproduce their livelihood in this semi-arid region where drought is chronic and poverty is widespread through a combination of pastoralism, dry land farming, and temporary labor migration. Because this research is based on fieldwork that spanned three years of extreme climate change, the reader is presented with an opportunity to observe a full range of flexible risk management strategies and co-operative mutual assistance that these people make use of at both the family and community level. One particular family's story is given as illustration of the extraordinary resiliency that these communities have shown despite the harsh ecological and, at times, social and political environment in which they are situated. Although government attention to the problems that the comunidades, face has increased during Chile's transition to democracy over the past decade, one of the goals of this dissertation is to bring to light the specifics of their cultural livelihood so that economic development programs that limit their options and conflict with community ideals and practices can be avoided. The material presented here will also address questions concerning the persistence of peasant culture in Latin America in general.

The purpose of this study was to identify the specific tasks performed and not performed by extension workers in the district of Amman, Jordan in 1990, to determine the frequency with which these tasks were performed, to gather perceptions of tasks and task groups and to identify the frequency of the obstacles encountered. Analysis of task performance revealed the majority of tasks performed on a frequent basis were implementation tasks. Extension workers also ranked the implementation group as the most important group of tasks. Extension workers spent the least amount of time on tasks in the areas of planning and results. The most frequently occurring obstacles identified by extension workers were the lack of appropriate technology, lack of transportation and lack of teaching and communication equipment. Study results indicated a need for emphasis on teaching media and for broader participation of extension workers on planning and evaluation of results. Pre- and in-service training programs were recommended, as was the establishment of a media division.