In the scope of future population support, agricultural productivity, in particular in sub-Saharan Africa, has to increase drastically to meet the UN’s millennium development goals of eradicating extreme poverty and hunger by 2015. Water availability in the root-zone limits crop production in large parts of the developing world. As competition for fresh water increases, water of lower quality, for example saline or polluted water, is often used for irrigation. Low-cost drip systems are suitable for saline water irrigation because they effectuate a minimisation of salt accumulation, leaf burn and peaks in salt concentration. Nonetheless, all types of saline water irrigation contain the risk for causing soil salinisation. Thus, in order to achieve long-term sustainability of these systems, appropriate management strategies are needed. The choice of management practices may be influenced by local conditions such as climate, soil and irrigation water salinity. A litera-ture review showed that there is a potential for saline water irrigation in sub-Saharan Africa in water scarce areas. Low-cost drip irrigation with saline water (6 dS m-1) was successfully used to irrigate two consecutive crops of tomato in semi-arid South Africa. An integrated ecosystems model was developed to simulate long-term yield and salt accumulation in a drip-irrigated agricultural system for a range of salinities, climates and management techniques. Crop, salt and water balance data from two field experiments conducted in Israel and South Africa, respectively, were used to parameterise and test the model. Emphasis was placed on testing the usability of the model as a tool for evaluating the importance of certain plausible management options of low-cost, drip-irrigation systems. Therefore, particular focus was directed towards correctly describing soil salinity stress on plant growth and soil evaporation from a distributed (wetted and dry) surface. In addition, the model was developed to function for different climates without having to change any other parameters or variables except for the actual climatic data. Simulations were subsequently run over a 30-year period to study long-term yield and salt accumulation in the soil profile for two sites in South Africa, demonstrating the applicability of the model. Model simulations showed that high soil salinities reduced crop growth and thus increased both drainage and soil evaporation. Further, covering the soil with a plastic sheet led to a reduction of soil evaporation and a subsequent increase in both transpiration and drainage. Rainfall was crucial for the leaching of salts from the soil, and thus in regions with low levels of rainfall, a higher leaching fraction of supplied saline irrigation water has to compensate for the lack of rain. However, a high leaching fraction also causes large amounts of salt leaching, which could potentially pollute underlying groundwater and downstream ecosystems. This risk can be mitigated using mulching, which minimises non-productive water losses, thereby lowering irrigation water needs. The choice of irrigation water salinity, frequency of irrigation and soil coverage may differ between the farmer and the regional water manager due to different preferences. Furthermore, the study highlighted how environmental variables such as water use efficiency and radiation use efficiency can be used as indicators of system performance. Whereas the latter is first and foremost a general stress indicator, water use efficiency more precisely describes specific factors such as plant size, allocation patterns and evaporative demand, which will affect the exchange of carbon dioxide and water through the stomata. / QC 20101102

Precision management of cotton production can increase profitability by decreasing inputs. The overall objective of this project is to improve cotton production by minimizing seeding rates while still maximizing yields and lint quality in water-limited soils. The research for this study was conducted at the Texas AgriLife Research IMPACT Center located in the Brazos River floodplain. In 2008 and 2009, 27 measurement locations were selected in production-sized center-pivot irrigated fields and planted in cotton variety Deltapine 164 roundup ready flex / bollgard II. Sites were selected based on soil apparent electrical conductivity (ECa) values, in a low, medium, and high ECa zones. Three seeding rates (74,100; 98,800; and 123,500 seeds ha-1) were established in each of the three ECa zones with three replications. In 2009, an additional seeding rate was added at 49,400 seeds ha-1. At each measurement location, soil texture, soil moisture (weekly), lint quantity and quality (High Volume Instrument) were measured. An additional replication for each ECa zone and seeding rate was selected for lint quantity and quality (HVI) measurements. Results indicated that cotton lint yield increased as ECa values, clay content, and water holding capacity of the soil increased. The seeding rates did not consistently affect cotton lint yield or quality. Seeding rates of 74,100 and 49,400 seeds ha-1 in a low and medium ECa zone for IMPACT-08 and -09 yielded more lint (300 kg ha-1), respectively. HVI lint quality parameters, such as, micronaire, fiber length, strength, uniformity, and elongation were significantly better in ECa zone 3. While the seeding rates did not affect the amount of soil water used throughout the season, lint yield variations between ECa zones can be explained by the rate at which soil water was used. Lower rates at which soil water was used within ECa zone 3 resulted in higher lint yields when compared to ECa zones 1 and 2, which used soil water faster and at greater depths. The findings suggest that irrigation applied to the low ECa zone was not sufficient to meet the plants demand, while in a high ECa zone, irrigation could have been reduced, resulting in cost savings through reduced inputs.

Tucson, Arizona is often said to have a water problem. The water table is falling, giving rise to concern on the part of the public and conflicts between water users in the Basin. Many see the problem as a shortage of water to be solved by bringing more water to Tucson by means of the Central Arizona Project. This dissertation examines the occurrence and use of water in the region in order to determine the real nature of Tucson's water problem. First, the institutions governing the use of water in the Basin are described and the disputes between the local water users are discussed. Next, an account is given of the use of water by businesses and residences in Tucson, by the copper mines to the south of Tucson, and by the farms in the Basin. The effect of changes in the cost and availability of water on each of these classes of water user is investigated and the effect that changes in water use could have on the region's economy is discussed. Next, an account is given of the water available for use in the Basin. The occurrence of groundwater in the region is described and the merits of the proposed Central Arizona Project are investigated. The information on the use of water in the Basin and the information on the sources of water available for use in the Basin are then combined to forecast the depletions of groundwater that will take place under various circumstances. Various ways of balancing the region's water budget are described and an assessment is made of the effect that curtailing the use of water in the region would have upon the local water users and the region's economy. The principal conclusions of this study are as follows. First, there is no danger of the supply of water in the Basin becoming exhausted in the near future. The economic and physical effects of the continuing fall in the level of the water table are unlikely to be serious. The second main conclusion is that the region's water budget could be balanced very economically by retiring all agriculture in the region and making modest reductions in the amount of water consumed by urban water users and the copper mines. Given suitable institutional arrangements, curtailing the use of water in the Basin would be a much more economical way of balancing the region's water budget than building the Central Arizona Project. The final conclusion is that the real water problem is an institutional problem. The threat of the Indians' claims to the groundwater of the Tucson Basin, together with the difficulty of resolving the continual disputes between the mines, the farms, and the City of Tucson over water puts all of the local water-using interests in a position where they see the provision of more supplies of water as the only cure to their woes. The remedy to the region's water problem is not the provision of more supplies of water, but a settlement of the Indians' claims and a reform of Arizona's groundwater law to enable a resolution of the conflicts between the water users in the Tucson Basin.

Ozonation has been utilized for water treatment for over 100 years. During that time, the range of applications has grown considerably, and includes the remediation of nursery and greenhouse irrigation water. Ozone is dissolved into irrigation water to kill pathogens and degrade chemical contaminants. By convention, growers remove ozone from solutions, prior to distribution to the crop, to avoid phytotoxic effects. The available literature regarding aqueous ozone (O3(aq)) phytotoxicity is limited, making this a sagacious practice, although the removal does preclude any ancillary benefits beyond the point of treatment. The effects of applying O3(aq) under two irrigation systems are examined. Initial studies suggested O3(aq) concentrations as high as 20 mg⋅L-1 could be applied directly to mineral wool substrate in a limited (one time) fashion without a negative response. To be effective as a remediation tool, however, ozone would need to be applied more frequently (e.g. daily). The effects of daily O3(aq) application, via drip irrigation in mineral wool hydroponic tomato culture, was examined. In the first of two studies, daily applications of 3.0 mg⋅L-1 O3(aq) elicited an overall positive growth response. In a follow-up study, 6.0 mg L-1 elicited a negative response. Nursery operators often utilize overhead irrigation. A study was conducted to determine if overhead irrigation utilizing O3(aq) was compatible with select woody perennial nursery species. The amount of ozone lost from solution during application was examined, as well as crop response to the ozone environment generated. It was shown that 60 to 70% of the ozone was unaccounted for at canopy level, while phytotoxic effects were elicited at emitter concentrations above 1.5 mg L-1. Marchantia polymorpha is a significant weed species in greenhouse and nursery production; a species with few control options. Anatomical features of M. polymorpha suggested sensitivity to O3(aq). Studies were performed to examine contact time (CT) and exposure frequencies required for M. polymorpha suppression. A CT of 0.84 mg⋅L-1⋅min at an application frequency of 3-times/week achieved measurable suppression. / Natural Science and Engineering Research Council (NSEARC); Ontario Ministry of Agriculture Food and Rural Affairs (OMAFRA); Ontario Centres of Excellence (OCE); Purification Research Technologies INC (PRTI); Flowers Canada (Ontario).

No description available.

Since the establishment of a democratic South Africa in 1994, a number of rural water supply schemes have been implemented. A specific aim of these schemes is to improve the health of the population. The underlying assumption is that a supply of reticulated water will improve the quality of water used by the community, reduce the exposure of the community to contaminated water supplies, and reduce water related diseases, in particular diarrhoea. This research thesis focuses on two rural water supply schemes in KwaZulu-Natal: Mpolweni and Vulindlela, both being developed by Umgeni Water, the regional water utility. These communities depended variously on rivers, rain harvesting, and springs for their water supply. For sanitation, the majority of people used unimproved pit latrines. This research thesis is based on information gathered from the communities prior to the installation of the water supply schemes. It focuses on the linkage between water supply and health by examining diarrhoeal morbidity as a measurable disease outcome and by identifying possible pathways to the prevalence of diarrhoea. Questionnaire and observational surveys were undertaken of 181 households in Mpolweni and 100 households in Vulindlela. From these surveys, the prevalence of diarrhoea in Vulindlela households was found to be 40.4% and in Mpolweni to be 49%. Children under the age of five years old are the most vulnerable, with 20.1% of children in Mpolweni and 21 .3% of children in Vulindlela reported as having had diarrhoea in the recall period prior to the surveys. The Mpolweni study considered eighty exposure variables, finding an association between diarrhoeal disease and sixteen of these variables (p value < 0.05). The Vulindlela study considered fifty-five exposure variables, of which eight were considered significant (p value < 0.05). In regard to water and diarrhoea: • no association was found between the prevalence of diarrhoea and the source of water in either Mpolweni or Vulindlela. • using water to wash nappies was associated with diarrhoeal disease in Vulindlela. However, it is postulated that it is the faecal contamination in the nappy, rather than the water, that is problematic. No association between water use and diarrhoea was established in Mpolweni. • poor disinfection of stored water supplies was associated with diarrhoeal disease in both Mpolweni and Vulindlela. In addition, the use of plastic storage containers to store water at the household provided additional risk in Mpolweni. However, once the reticulated system is installed, the communities are likely to continue to store water due to a distrust of the reliability of water supply. The above surveys form the baseline for additional studies currently being undertaken by Umgeni Water that are intended to measure the effectiveness of the water supply schemes on community health. However, from this thesis, it is concluded that many of the risk factors associated with diarrhoeal disease in both Vulindlela and Mpolweni will not directly be addressed by the introduction of the water supply schemes. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2000.

Master of Science in Veterinary Science / A investigation into soil nutrient and the change soil physical properties was carried out for three pasture systems for dairy cows; the complementary forage rotation (CFR) which comprised of brassica (Brassica napus )/clover (Trifolium resupinatum ) and maize (Zea mays) capable of achieving more than 40 t/ha, the typical intensive pasture (PI) with kikuyu grass (Penisetum clandestinum) over-sown with ryegrass ( Lolium multiflorum ) and the extensive system (PE); on two soil types (brown chromosol and black vertisol) . The study demonstrated that the CFR system was capable of doubling its yield by using similar fertilizers (N, P and K) and water inputs compared to these of the PI system resulting of greater nutrients (N and K) and water use efficiencies. Overall, the nutrient lost through runoff water was very limited for two intensive systems and nearly nil for PE system. Also similar trends were observed for soil physical properties in the intensive systems except for the topsoil (0-10 cm) where light acidification (P= 0.04) was recorded in the CFR probably due to the soil works before the maize sowing.

Master of Science in Veterinary Science / A investigation into soil nutrient and the change soil physical properties was carried out for three pasture systems for dairy cows; the complementary forage rotation (CFR) which comprised of brassica (Brassica napus )/clover (Trifolium resupinatum ) and maize (Zea mays) capable of achieving more than 40 t/ha, the typical intensive pasture (PI) with kikuyu grass (Penisetum clandestinum) over-sown with ryegrass ( Lolium multiflorum ) and the extensive system (PE); on two soil types (brown chromosol and black vertisol) . The study demonstrated that the CFR system was capable of doubling its yield by using similar fertilizers (N, P and K) and water inputs compared to these of the PI system resulting of greater nutrients (N and K) and water use efficiencies. Overall, the nutrient lost through runoff water was very limited for two intensive systems and nearly nil for PE system. Also similar trends were observed for soil physical properties in the intensive systems except for the topsoil (0-10 cm) where light acidification (P= 0.04) was recorded in the CFR probably due to the soil works before the maize sowing.

Master of Science in Veterinary Science / A investigation into soil nutrient and the change soil physical properties was carried out for three pasture systems for dairy cows; the complementary forage rotation (CFR) which comprised of brassica (Brassica napus )/clover (Trifolium resupinatum ) and maize (Zea mays) capable of achieving more than 40 t/ha, the typical intensive pasture (PI) with kikuyu grass (Penisetum clandestinum) over-sown with ryegrass ( Lolium multiflorum ) and the extensive system (PE); on two soil types (brown chromosol and black vertisol) . The study demonstrated that the CFR system was capable of doubling its yield by using similar fertilizers (N, P and K) and water inputs compared to these of the PI system resulting of greater nutrients (N and K) and water use efficiencies. Overall, the nutrient lost through runoff water was very limited for two intensive systems and nearly nil for PE system. Also similar trends were observed for soil physical properties in the intensive systems except for the topsoil (0-10 cm) where light acidification (P= 0.04) was recorded in the CFR probably due to the soil works before the maize sowing.

Diss. (sammanfattning). Umeå : Sveriges lantbruksuniv. / Härtill 5 uppsatser.