Heavy metals, such as cadmium, copper, lead, chromium and mercury, are important environmental pollutants, particularly in areas with high anthropogenic pressure. Their presence in the atmosphere, soil and water, even...Heavy metals, such as cadmium, copper, lead, chromium and mercury, are important environmental pollutants, particularly in areas with high anthropogenic pressure. Their presence in the atmosphere, soil and water, even in traces can cause serious problems to all organisms, and heavy metal bioaccumulation in the food chain especially can be highly dangerous to human health. Heavy metals enter the human body mainly through two routes namely: inhalation and ingestion, ingestion being the main route of exposure to these elements in human population. Heavy metals intake by human populations through food chain has been reported in many countries. Soil threshold for heavy metal toxicity is an important factor affecting soil environmental capacity of heavy metal and determines heavy metal cumulative loading limits. For soil-plant system, heavy metal toxicity threshold is the highest permissible content in the soil (total or bioavailable concentration) that does not pose any phytotoxic effects or heavy metals in the edible parts of the crops does not exceed food hygiene standards. Factors affecting the thresholds of dietary toxicity of heavy metal in soil-crop system include: soil type which includes soil pH, organic matter content, clay mineral and other soil chemical and biochemical properties; and crop species or cultivars regulated by genetic basis for heavy metal transport and accumulation in plants. In addition, the interactions of soil-plant root-microbes play important roles in regulating heavy metal movement from soil to the edible parts of crops. Agronomic practices such as fertilizer and water managements as well as crop rotation system can affect bioavailability and crop accumulation of heavy metals, thus influencing the thresholds for assessing dietary toxicity of heavy metals in the food chain. This paper reviews the phytotoxic effects and bioaccumulation of heavy metals in vegetables and food crops and assesses soil heavy metal thresholds for potential dietary toxicity.展开更多
In Uganda, grain amaranth is relatively new and has generally not been considered as an important crop compared to other grain crops and legumes. This study was therefore conducted to determine factors affecting adopt...In Uganda, grain amaranth is relatively new and has generally not been considered as an important crop compared to other grain crops and legumes. This study was therefore conducted to determine factors affecting adoption of grain amaranth growing, factors affecting production, and economic returns on investment of its production. The study was carried out in Kamuli district where a total of 174 grain amaranth farmers and 90 non-grain amaranth farmers were randomly selected and interviewed. Using descriptive statistics, regression analysis (logit model and a Cobb-Douglas type production function) and profitability ratios, it was found that grain amaranth is produced on a small scale and yields are low. Farmer adoption of the crop was favoured by age, gender (female), education of the farmer, and source of income. The output was positively affected by the amount of labour and manure used in production, while a negative relationship existed between output and male farmers. The crop was most viable under small acreages (0.02-0.04 ha) with positive returns to investment of 0.016. Its production should therefore be encouraged because of its income generation potential and since it requires small land.展开更多
African indigenous vegetables (AIVs) play an important role in house hold food and nutrition security among many communities in Uganda. However, there is limited information on the value chain. Yet, the contribution...African indigenous vegetables (AIVs) play an important role in house hold food and nutrition security among many communities in Uganda. However, there is limited information on the value chain. Yet, the contribution of AIVs in terms of food and nutrition security is undisputable. A cross sectional survey targeting 60 respondents including farmers, key informants and extension officers was conducted to assess the systems of production system of the AIVs, profile an inventory and diversity of the cultivated AIVs in Agweng sub-county, Lira district. Semi-structured questionnaires and direct field observation were used to gather the necessary data. The findings revealed that AIVs form a very important part of the diets of the local populace both during the normal and off seasons as well as hard times among others. However, a number of constraints were reported to hinder the AIVs value chain including lack of quality seed, competition from exotic vegetables, low market demand, pests and diseases infestation, among others. The most commonly cultivated and consumed vegetables were cowpeas, hibiscus, pumpkins and crotolaria among others. The reasons for cultivation and consumption included source of food, high nutritive value and short maturity period. Other reasons were medicinal, resistance to pests and diseases, source of cash income and resilient to harsh weather conditions. In contrast, lack of quality seeds, bitterness, low market demand and difficulty in preparation contributed to their neglected use. Therefore, in the wake of climate change and variability there is need for deliberate investment to improve adaptability and acceptance of these vegetables. There is also need for sensitization of farmers on the benefits of AIVs, developing an effective means of improved seed production and distribution to replace the farmer-to farmer seed exchange and conservation of AIVs germplasm as the strategies to improve AIVs production in the study area.展开更多
Runner bean is usually grown in Chile as household plantings, in small surfaces with trellis support. Several studies were made to grow runner beans extensively without trellis support, like common beans are grown. Th...Runner bean is usually grown in Chile as household plantings, in small surfaces with trellis support. Several studies were made to grow runner beans extensively without trellis support, like common beans are grown. Three runner bean ecotypes were evaluated, with and without trellis support. Although the highest yield was obtained with trellis support, significant yields were obtained without trellis. Thus, this specie can be established without support like the common bean, allowing a great economic advantage especially at large scale plantings. The ecotype named "Quilapallar" was selected by its white and large grains and excellent cooking quality. Then, seed rates and dry grain yield were compared with commercial varieties of common bean. There was not statistical difference in yield among row distances, except when this was 25 cm apart. Besides, there was not statistical difference among Quilapallar and Torcaza INIA, although the later is a common bean variety with a high yield potential.展开更多
基金Project supported by the Science and Technology Ministry of China (No. 2002CB410804) and the Education Ministry of China (No. IRT0536)
文摘Heavy metals, such as cadmium, copper, lead, chromium and mercury, are important environmental pollutants, particularly in areas with high anthropogenic pressure. Their presence in the atmosphere, soil and water, even in traces can cause serious problems to all organisms, and heavy metal bioaccumulation in the food chain especially can be highly dangerous to human health. Heavy metals enter the human body mainly through two routes namely: inhalation and ingestion, ingestion being the main route of exposure to these elements in human population. Heavy metals intake by human populations through food chain has been reported in many countries. Soil threshold for heavy metal toxicity is an important factor affecting soil environmental capacity of heavy metal and determines heavy metal cumulative loading limits. For soil-plant system, heavy metal toxicity threshold is the highest permissible content in the soil (total or bioavailable concentration) that does not pose any phytotoxic effects or heavy metals in the edible parts of the crops does not exceed food hygiene standards. Factors affecting the thresholds of dietary toxicity of heavy metal in soil-crop system include: soil type which includes soil pH, organic matter content, clay mineral and other soil chemical and biochemical properties; and crop species or cultivars regulated by genetic basis for heavy metal transport and accumulation in plants. In addition, the interactions of soil-plant root-microbes play important roles in regulating heavy metal movement from soil to the edible parts of crops. Agronomic practices such as fertilizer and water managements as well as crop rotation system can affect bioavailability and crop accumulation of heavy metals, thus influencing the thresholds for assessing dietary toxicity of heavy metals in the food chain. This paper reviews the phytotoxic effects and bioaccumulation of heavy metals in vegetables and food crops and assesses soil heavy metal thresholds for potential dietary toxicity.
文摘In Uganda, grain amaranth is relatively new and has generally not been considered as an important crop compared to other grain crops and legumes. This study was therefore conducted to determine factors affecting adoption of grain amaranth growing, factors affecting production, and economic returns on investment of its production. The study was carried out in Kamuli district where a total of 174 grain amaranth farmers and 90 non-grain amaranth farmers were randomly selected and interviewed. Using descriptive statistics, regression analysis (logit model and a Cobb-Douglas type production function) and profitability ratios, it was found that grain amaranth is produced on a small scale and yields are low. Farmer adoption of the crop was favoured by age, gender (female), education of the farmer, and source of income. The output was positively affected by the amount of labour and manure used in production, while a negative relationship existed between output and male farmers. The crop was most viable under small acreages (0.02-0.04 ha) with positive returns to investment of 0.016. Its production should therefore be encouraged because of its income generation potential and since it requires small land.
文摘African indigenous vegetables (AIVs) play an important role in house hold food and nutrition security among many communities in Uganda. However, there is limited information on the value chain. Yet, the contribution of AIVs in terms of food and nutrition security is undisputable. A cross sectional survey targeting 60 respondents including farmers, key informants and extension officers was conducted to assess the systems of production system of the AIVs, profile an inventory and diversity of the cultivated AIVs in Agweng sub-county, Lira district. Semi-structured questionnaires and direct field observation were used to gather the necessary data. The findings revealed that AIVs form a very important part of the diets of the local populace both during the normal and off seasons as well as hard times among others. However, a number of constraints were reported to hinder the AIVs value chain including lack of quality seed, competition from exotic vegetables, low market demand, pests and diseases infestation, among others. The most commonly cultivated and consumed vegetables were cowpeas, hibiscus, pumpkins and crotolaria among others. The reasons for cultivation and consumption included source of food, high nutritive value and short maturity period. Other reasons were medicinal, resistance to pests and diseases, source of cash income and resilient to harsh weather conditions. In contrast, lack of quality seeds, bitterness, low market demand and difficulty in preparation contributed to their neglected use. Therefore, in the wake of climate change and variability there is need for deliberate investment to improve adaptability and acceptance of these vegetables. There is also need for sensitization of farmers on the benefits of AIVs, developing an effective means of improved seed production and distribution to replace the farmer-to farmer seed exchange and conservation of AIVs germplasm as the strategies to improve AIVs production in the study area.
文摘Runner bean is usually grown in Chile as household plantings, in small surfaces with trellis support. Several studies were made to grow runner beans extensively without trellis support, like common beans are grown. Three runner bean ecotypes were evaluated, with and without trellis support. Although the highest yield was obtained with trellis support, significant yields were obtained without trellis. Thus, this specie can be established without support like the common bean, allowing a great economic advantage especially at large scale plantings. The ecotype named "Quilapallar" was selected by its white and large grains and excellent cooking quality. Then, seed rates and dry grain yield were compared with commercial varieties of common bean. There was not statistical difference in yield among row distances, except when this was 25 cm apart. Besides, there was not statistical difference among Quilapallar and Torcaza INIA, although the later is a common bean variety with a high yield potential.