Please read the abstract in the section 00front of this document / Dissertation (MSc Agric (Horticulture))--University of Pretoria, 2006. / Plant Production and Soil Science / unrestricted

8 pp. / az1329: Measuring Water Flow in Surface Irrigation Ditches and Gated Pipe Martin, E.C. 2000. Determining the Amount of Water Applied to a Field. Cooperative Extension Pub. No. AZ1157, Arizona Water Series No. 29. University of Arizona, Tucson, AZ. Martin, E.C. 1999. Measuring Water Flow and Rate on the Farm. Cooperative Extension Pub. No. AZ1130, Arizona Water Series No. 24. University of Arizona, Tucson, AZ. / Measuring water is a critical part of any irrigation management system. This informational bulletin gives some simplistic methods of measuring flow rate in an open ditch and in gated pipe. Using the float method, dye tracers and velocity head meters, growers can get a quick estimate of the flow in their farm ditch. From this, an estimate of water applied or a set time can be determined. The bulletin also explains how a propeller meter works for gated pipe. Gated pipe is widely used through the state and in the West.

Magister Philosophiae (Land and Agrarian Studies) - MPhil(LAS) / This study explored the production and livelihoods of smallholder farmers in irrigation schemes in South Africa. The particular focus has been on the farming styles of smallholder farmers, the impact of irrigation scheme production on their income and livelihoods, and the issue of smallholder social differentiation. The New Forest irrigation scheme located in Bushbuckridge Local Municipality was used as a case study. The research methodology utilized a combination of extensive and intensive research designs. The farming style approach was compared with the livelihood strategies approach to determine the relationship between the farmers’ approach to farming and their livelihood development trajectory. The underlying assumption is that small-scale irrigation has the potential to make a positive contribution to the livelihoods of farmers. New Forest irrigation farmers face a number of challenges at the irrigation scheme such as neglect by government, inadequate irrigation water, and access to affordable crops inputs. The farmers were not organised to be able to purchase inputs, engage in co-operative marketing, and manage the irrigation scheme. The notion of investing in smallholder irrigation schemes in order to convert smallholders into commercial farmers is unrealistic. Those that were classified as ‘food farmers’, benefit from irrigation development and participation through meeting their household consumption needs. Those classified as ‘employers’, obtained negative gross margins per plot and hired most farm labour. Diversification by employers into other less risky livelihood activities on-farm and off-farm is an option. The ‘profit makers’, make high returns from crop production, and obtained the highest gross margins per plot. This thesis argues that support to farmers in smallholder irrigation schemes should be provided in the context of their farming objectives, and livelihood aspirations which are not only varied but evolve across time and individual circumstances.

Det förändrade klimatet innebär fler och längre perioder av torka och därmed minskad vattentillgång. En del dricksvatten används för bevattning av växter, trots att regnvatten duger lika bra. Det finns många regnvattentunnor och liknande produkter som samlar in och tillgängliggör regnvatten för bevattning. Dessa produkter är lämpliga för villaägare men är för småskaliga för större verksamheter. Avsikten för detta arbete är att få verksamheter att minska sin dricksvattenförbrukning. Detta sker genom att utveckla en produkt som möjliggör insamling och bevattning av regnvatten. Initiativet till detta arbete kommer från kommunalförbundet VA SYD som dels vill minska belastningen på ledningsnäten men även få verksamheter att minska sin dricksvattenkonsumtion. Arbetet omfattar metoder som berör produktutveckling, hållfasthetsberäkningar och materialval. Produktutvecklingen innefattar marknadsanalyser, studiebesök, konceptgenerering och -utvärdering. Hållfasthetsberäkningarna inkluderar beräkningar av spänning i konsolbalk, knäckning och kompression samt momentjämvikt och vindlastberäkning. Sex olika koncept framtas i konceptgenereringen som skissas och beskrivs innan ett konceptval görs i konceptutvärderingen. Därefter utvecklas det valda konceptet på detaljnivå. Resultatet är en produkt som samlar in vatten och bevattnar små växter. Vatten sparas framförallt genom att det recirkuleras i produkten. Konceptet visualiseras med hjälp av 3D-modellering. Genom att använda denna produkt minskar verksamheter sin dricksvattenkonsumtion och sparar dessutom arbetstid som annars skulle ägnats åt bevattning. The changing climate means more and longer periods of drought and thus reduced water supply. Some drinking water is used for irrigating plants, although rainwater is just as good. There are many rainwater barrels and similar products that collect and make rainwater available for irrigation. These products are suitable for homeowners but they are too small-scale for larger businesses. The purpose of this project is to get businesses to reduce their drinking water consumption. This is done by developing a product that enables collection of and irrigation of rainwater. The initiative for this project comes from the municipal association VA SYD, which wants to reduce the load on the pipe networks but also make businesses reduce their drinking water consumption. The project includes methods that concern product development, calculations of strength and material selection. Product development includes market analyzes, study visits, concept generation and evaluation. The calculations of strength include calculations of stress in a console beam, buckling and compression as well as moment equilibrium and wind load. Six different concepts are developed in the concept generation which are sketched and described before a concept choice is made in the concept evaluation. The selected concept is developed in detail. The result is a product that collects water and irrigates small plants. Water is saved primarily by recycling it in the product. The concept is visualized using 3D-modelling. By using this product, businesses reduce their drinking water consumption and also save working time that would otherwise be used for manual irrigation.

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For intensive production systems like the Blue Ridge Aquaculture (BRA), based in Martinsville, VA, there are significant economic incentives to reuse the waste by diverting it into a cropping system that would increase the total productivity and total resource-reuse efficiency, and decrease the environmental, ecological, and financial costs of aquacultural waste disposal. In order to facilitate the reuse of effluent from the tilapia production at the BRA, a green house was developed. On this site, sludge waste from recirculating aquaculture was separated and composted using a vermicomposting technique and the resulting compost was utilized as an amendment to conventional greenhouse potting mixes. These aquacultural waste products were compared to conventional greenhouse culture of a common ornamental annual plant. It was hypothesized that (1) vermicomposted aquaculture sludge would increase the growth of plants over conventional greenhouse potting mixes, and (2) recycled aquacultural wastewater can serve as a quality source of irrigation water, and plant response would differ with irrigation method. Plant growth and 11 out of 12 plant tissue nutrients were greater when compost was increased in the substrate. Plant root growth and 3 out of 12 tissue nutrients were increased when irrigated with wastewater. Plant shoot mass and total mass was greater when irrigated by ebb and flow irrigation compared to overhead mist irrigation, and 4 out of 12 tissue nutrients were greater when irrigated with mist irrigation. Overall plant performance was greatest with 15% vermicomposted sludge in the substrate and watered with wastewater by ebb and flow irrigation. / Master of Science

Integrating water-saving technologies with optimized nutrient management strategies provides opportunities for sustainable agriculture in the Mississippi Delta. Three studies were conducted to determine the effects of irrigation systems, row patterns, and nutrient management strategies on corn and soybeans. The first study determined the effects of irrigation, row pattern, and nitrogen (N) placement methods on corn (Zea mays L.) productivity and N use efficiency. The effects of N placement methods were only evident in 2021 when the rainfall events were more pronounced than in 2020. Regardless of the row pattern, placing N with one knife increased corn grain yield and the agronomic N use efficiency by 14.1% and 16.8%, respectively, when compared to the surface dribble method. The second study investigated the effects of irrigation systems and row patterns on grain yield, grain quality parameters, and irrigation water use efficiency (IWUE) on soybeans (Glycine max L.) grown on Sharkey clay. When irrigation was triggered at -80 kPa, furrow-irrigated soybeans produced 3.9% more grain yield compared to sprinkler-irrigated soybeans. The total amount of water applied by the sprinkler irrigation system represented 19-52% of the total amount applied by the furrow system. Narrow-row patterns achieved greater IWUE than single-row patterns. In the third study, we evaluated the effects of N and irrigation levels on grain quantity, quality, and plant growth on corn grown across different soil electrical conductivity (EC) levels and its implications for variable rate technology. Corn grain yields increased with the increase of N and irrigation levels but decreased as soil EC decreased. Overall, maintaining a sprinkler irrigation threshold between -40 and -70 kPa optimized corn yield. In addition, these results did not provide enough evidence to use variable rate irrigation or variable rate N application in the Mississippi Delta.

A procedure was developed to estimate optimum irrigation requirements for lowland rice cultivation in Southeast Asia. The procedure uses a water balance equation of semi-stochastic nature to maintain minimum desired water depths in paddy fields at the end of each irrigation period. The procedure estimates weekly pan evaporation (EV) and rainfall (RF) at different probability levels, which is then used to determine weekly irrigation requirements at different probability levels. To illustrate the use of the method, the Kalawewa irrigation scheme in Sri Lanka was selected for demonstration purposes. Different transformations were applied to Rf and EV data in an attempt to normalize these variates and to obtain a unique distribution to describe their variations. Statistical analysis of weekly EV arid RF showed that the power transformation was best able to transform the weekly RF and EV data to normality. Comparison of the use of the model and current system practices showed that a significant amount of water could be saved even when the system was operated at high probability levels (90% reliability). The irrigation water required when the system was operated at the 72% probability level was about 21% less than the amount required when the system was operated at 90% probability level during some weeks. The EXTRAN flow routing model was used to simulate water flow in the upper reaches of the main canal system for varying discharges at the head gate each day. The simulated water depths were used to determine the gate settings required at the turnout structures to divert the desired amount of irrigation water into the turnout areas. The flow simulation for the demonstration area, showed that it was not possible to regulate irrigation water from the main reservoir to meet daily demands at all the turnouts. This was due to the large distances between the regulating reservoir and turnouts that caused appreciable time lag for the flow to reach the turnouts farthest from the regulating reservoir. / Ph. D.

Au Canada, 84 % de la production de laitue provient du Québec et s'effectue essentiellement sur des sols organiques. Toutefois, elle possède des risques importants de stress hydrique (brûlure de la pointe) lors de périodes à forte demande d'évapotranspiration qui peuvent être accentuées par une variabilité spatiale importante des propriétés physiques du sol. Une étude visant à évaluer la performance (consommation en eau et en énergie, lessivage et rendements) de deux échelles de gestion de l'irrigation de la laitue et à étudier les mécanismes de transport de l'eau dans le sol et leurs implications dans l'apparition de symptômes de brûlure de la pointe a été réalisée. Les résultats ont démontré la pertinence d'une gestion fine de l'irrigation, se soldant par un gain de rendement de l'ordre de 17 % lorsque le potentiel matriciel de départ de l'irrigation est maintenu à - 15 kPa lors de période à forte demande d'évapotranspiration.

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