Thesis (M.Dev.) --University of Limpopo, 2011 / Agricultural development programs under the former apartheid homeland system which was dissolved in 1994 could not successfully achieve their objectives. The current democratic government reviewed the policies and programs put in place during apartheid era which eventually led to the implementation of the Revitalisation of Smallholder irrigation Schemes (RESIS) in line with the Reconstruction and Development Program (RDP) and Growth, Employment and Redistribution (GEAR) programs. It was anticipated that RESIS would among others improve agricultural productivity, play a role in local economic development, improve food security, provide improved benefits and the livelihoods of the rural communities where the schemes are situated. The aim of the study is to assess whether the RESIS program has had an impact so as to make recommendations for future similar programs. The objective of the study is to assess the impact of RESIS program on the livelihoods of the participants and to shed light on whether such programs can be used for poverty reduction, which is a key objective in the programs of LDA. Tšwelopele irrigation scheme in Greater Tubatse Municipality within Sekhukhune District Municipality was selected as the area at which the study was conducted. A random sample of 50 beneficiaries was selected from a total of 75 RESIS beneficiaries and divided into two strata, namely, full-time farmers (both male and female) and part-time farmers (male and female) farmers. Interviews were conducted through completion of questionnaires responded to by the selected participants and key informants in the scheme. Qualitative and quantitative methods were used to obtain the responses from the scheme participants and the data processed using SPSS. Based on the analysis of respondents‟ perceptions of the farmers, the study concludes that RESIS is perceived to have had a positive impact on the livelihoods of the beneficiaries. Gross margin analysis supports the farmers‟ perceptions.

Orientador: Rogério Teixeira de Faria / Coorientador: Willians César Carrega / Banca: Everton Luis Finoto / Banca: Luiz Fabiano Palaretti / Resumo: O déficit hídrico é considerado um dos principais fatores limitantes na produção de amendoim, com perdas elevadas na região centro-sul do Brasil, principalmente na safra da seca, entre janeiro e junho. A irrigação pode contribuir para aumentar e estabilizar produtividade, além de afetar a fitossanidade da cultura, porém o recurso hídrico disponível é escasso nas regiões de cultivo. Dessa forma, a determinação da demanda hídrica do cultivo é essencial para se obter alta produtividade com maior eficiência de uso de água. O objetivo do trabalho foi avaliar os efeitos de níveis de irrigação plena e deficitária sobre a produtividade e incidência de Cercosporidium personatum em amendoinzeiro semeado na época da seca. O experimento foi conduzido em delineamento de blocos casualizados em esquema fatorial 5 x 2, sendo 5 níveis de irrigação (L1= 8%; L2= 27%; L3= 63%; L4= 94% e L5= 100% da evapotranspiração da cultura) e semeados em 2 épocas, com quatro repetições. Os resultados mostraram que é mais vantajoso o cultivo com irrigação plena em E2, devido aos incrementos de produtividade em até 30% em relação a E1. A irrigação deficitária reduziu altura de plantas, massa de sementes e produtividade de vagens, enquanto que a irrigação plena (L5) proporcionou produtividades de 4.141 a 5.102kg ha-1 em E1 e E2, respectivamente, com incrementos em cerca de três vezes às produtividades obtidas no menor nível de irrigação (L1). O déficit hídrico promoveu maior severidade de danos de C. personatum... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Crop water deficit is considered one of the main constraint in the peanut production, with high losses in the central-eastern Brazil, mainly during the dry season, between January and June. Irrigation can contribute to increase and stabilize productivity, as well as affect crop sanity, but the available water resources are scarce in the growing regions. Thus, the determination of the crop water demand is essential to obtain high yield with greater efficiency of water use. The objective of this work was to evaluate the effects of full and deficit irrigation levels on the yield and also the incidence of Cercosporidium personatum in peanut sown in the dry season. The experiment was conducted in a randomized block design in a 5 x 2 factorial scheme, with 5 irrigation levels (L1 = 8%, L2 = 27%, L3 = 63%, L4 = 94% and L5 = 100% of crop evapotranspiration) and sown in 2 planting dates, with four replications. The results showed more advantage for treatment with full irrigation in E2, due to yield increases of up to 30% as compared to E1. Deficit irrigation reduced plant height, seed mass, and pod yield, while full irrigation (L5) provided yields of 4,141 to 5,102 kg ha-1 in E1 and E2, respectively, with increments of about three times the yields obtained at the lowest irrigation level (L1). The water deficit promoted greater severity of C. personatum and there was a lower incidence of the disease in E2. Under ideal water conditions and regardless of sowing time, the cultivar IAC 505... (Complete abstract click electronic access below) / Mestre

[Abstract]: There is currently a shortage of irrigation water available for cotton production in Australia due to recent climatic and legislative conditions. Some growers have responded to this water shortage by changing from traditional furrow irrigation to alternative irrigation systems such as centre pivots and lateral move irrigations(collectively known as large mobile irrigation machines – LMIMs). Improved efficiency of irrigation application, as well as labour savings, have been the main reasons for the increased adoption of LMIMs. The use of LMIMs also enables a higher level of control in water application in terms of irrigation volume, timing and placement. As a result, growers now have much greater control over soil moistureconditions which enables the implementation of improved irrigation management strategies that have the potential for improved crop water use productivity (yield/ML).Two irrigation strategies which have been demonstrated to achieve benefits in terms of crop water use are partial rootzone drying (PRD) and deficit irrigation (DI). PRDand DI involve manipulating the placement of irrigation water and the moisture deficit maintained in the root zone, respectively. Neither PRD nor DI is able to beapplied easily under furrow irrigation. However, both PRD and DI may be able to be implemented under LMIMs within the Australian cotton industry. Deficit irrigation has been shown to be effective at improving water use productivity in cotton, although it is not widely used within the Australian cotton industry.Similarly, there has been little research conducted to identify whether cotton responds to partial rootzone drying and there is currently little understanding of theway in which DI and PRD strategies could be implemented commercially using LMIMs.This research carried out from 2002 to 2005 investigated the response of cotton to a range of PRD and deficit irrigation strategies for use under LMIMs. Assessment ofthe biochemical and physiological response of cotton to PRD and regulated deficit irrigation strategies was conducted under glasshouse conditions in Toowoomba, Qld.Field trials conducted under a commercial centre pivot and lateral move situated on the Darling Downs assessed the crop response, soil moisture movement, yield andgross production water use associated with the implementation of a range of PRD and deficit treatments. Modelling of rainfall probability and soil moisture movement were also undertaken to quantify constraints to the successful commercial implementation of irrigation management strategies such as PRD within theAustralian cotton industry.PRD applied to cotton grown in split-pot containers under glasshouse conditions was found to produce a biochemical response in the form of a four fold increase in xylemAbscisic Acid concentration. The application of alternated PRD strategies was generally found to reduce both vegetative (i.e. height, leaf area) and reproductive(i.e. fruiting sites) plant growth compared to Control treatments irrigated on both sides of the plant. Increasing the period between PRD alternations from 5 to 15days when the soil moisture potential in the wet root zone was maintained between 30 and 60 kPa also reduced the plant height and the number of fruiting sites.However, where the soil moisture in the wetted root zone was maintained at <3 kPa and alternation was based on the dry root zone moisture levels 16% (~350 kPa) and10% (>1500 kPa) there was no difference in the major plant growth indicators (i.e. height, fruiting branches, fruiting sites, leaf area) between the various alternatedPRD treatments. This suggests that the level of moisture availability in the wet root zone area is a key factor influencing water uptake and crop stress under alternatedPRD conditions.No significant difference in crop growth or yield was found as a result of the PRD treatments implemented under commercial field conditions. However, this may havebeen attributed to the inability to apply and maintain a sufficient soil moisture gradient across the root zone to successfully induce biochemical signalling from PRD. Practical limitations in the successful application of PRD in cotton production are attributed to the soil hydraulic properties, current irrigation practices (i.e. volumeand frequency of water applied) and the occurrence of in-season rainfall events. Rainfall probability and soil moisture modelling were used to evaluate the practical application of PRD within the Australian cotton industry. This work suggested thatthe creation of a soil moisture gradient across the plant root zone large enough to trigger a PRD response is most likely to be achieved on light textured soils located insemi-arid regions which experience minimal in-season rainfall events. However, the conditions are only met for a relatively small proportion of the current Australiancotton industry. Hence, it would seem that further research into the benefits of implementing PRD in cotton under LMIMs is not warranted.Regulated deficit irrigation applied under glasshouse conditions was found to have a controlling influence over partitioning between vegetative and reproductive growth.Improved physiological and gross production to water use benefits were measured as a result of deficit irrigation under field conditions and regulated deficit irrigationunder glasshouse conditions. Deficit irrigation (79% of predicted ET) under field conditions produced a 31.5% improvement in gross production water use index(GPWUI = Yield / Total water applied (rainfall, irrigation and stored soil moisture)) over commercial practice (i.e. applying 100% of predicted ET). However, thelargest benefits derived from deficit irrigation were associated with the management of crop agronomics (i.e. vegetative growth, retention rate and crop earliness) and the increased ability for capture of in-crop rainfall. Hence, deficit irrigation may provide substantial benefits for the cotton industry in terms of productivity of irrigation water applied as well as total water applied (irrigation, rainfall and soil moisture reserves).The ability to implement a suitable deficit irrigation strategy is regionally and seasonally dependent as the uncertainty over the timing of rainfall events andirrigation allocation both within and between seasons makes the optimal use of water resources difficult. Hence, future research should aim to enhance current cropproduction models to predict crop growth and response to a range of deficit irrigation treatments. Greater knowledge and adoption in the use of climatic predictors (suchas SOI) are required to improve the volume and timing of deficit irrigations applied. An economics framework should be developed which encompasses resource costs and constraints on a farm basis to enable the identification of optimal management practices based on the risk profiles of the various deficit irrigation strategies.Irrigation scheduling under LMIMs is also currently limited by the use of point scale soil moisture measurements (especially under low energy precision applicator LEPA) socks) and this may be improved by the use of plant based sensors.

[Abstract]: The performance of surface irrigation is a function of the field design, infiltration characteristic of the soil, and the irrigation management practice. However, the complexity of the interactions makes it difficult for irrigators to identify optimaldesign or management practices. The infiltration characteristic of the soil is the most crucial of all the factors affecting the performance of surface irrigation and both spatial and temporal variations in the infiltration characteristic are a major physicalconstraint to achieving higher irrigation application efficiencies. Real-time optimisation and control has the potential to overcome these spatial and temporalvariations and return highly significant improvements in performance. Calculation of the infiltration parameters from irrigation advance data is now the preferred method.If the process is to be included in a real time control system it must be done accurately, reliably and rapidly, and with a minimum of field data. Substantial workhas been directed towards developing methods to estimate the infiltration characteristics of soil from irrigation advance data. However, none of the existing methods are entirely suitable for use in real time control. The greatest limitation is that they are data intensive and or unreliable and provide soil infiltration propertiesafter an irrigation event.A simple real-time control system for furrow irrigation is proposed that: predicts the infiltration characteristics of the soil in real-time using data measured during anirrigation event, simulates the irrigation, and determines the optimum time to cut-off for that irrigation. The basis of the system is a new method for the Real-timeEstimation of the Infiltration Parameters (REIP) under furrow irrigation, developed during this research study, and that uses a model infiltration curve, and a scalingprocess to predict the infiltration characteristics for each furrow and each irrigation event. The underlying hypothesis for the method is that the shape of the infiltration characteristic for a particular field or soil is relatively constant (across the field andwith time), despite variations in the magnitude of the infiltration rate or amount. A typical furrow in the field is selected for evaluation (known as the model furrow)and its infiltration parameters (a, k, fo) in the Kostiakov–Lewis equation are determined by a model such as INFILT or IPARM using inflow, advance and runoffdata. Subsequently the infiltration parameters for this model furrow can be scaled to give the cumulative infiltration curves for the whole field. In this process a scaling factor (F) is formulated from rearrangement of the volume balance equation and is calculated for each furrow/event using the model infiltration parameters and the single advance point. The performance of each furrow can then be simulated and optimised using an appropriate simulation model to determine the preferred time tocut-off.Using this new method, infiltration parameters were calculated for two different fields T & C. The SIRMOD simulation model was then used to simulate irrigationperformance (application efficiency, requirement efficiency and uniformity) under different model strategies. These strategies were framed to assess the feasibility of and demonstrate the gains from the real-time control strategy. The infiltration evaluation results revealed that the infiltration curves produced by the proposed method were of similar shape and hence gave a distribution of cumulative depths of infiltration for the whole field that was statistically equivalent to that given using the complete set of advance data for each furrow. The advance trajectories produced bythe proposed method also matched favourably to the measured advances.The simulation results showed firstly that the scaled infiltration gave predictions of the irrigation performance similar to the actual performance. They also indicated that by adopting the simple real time control system, irrigation application efficiencies forthe two fields could be improved from 76% for field T and 39% for field C (under usual farm management) to 83% and 70% for the fields T & C, respectively. Savingsof 1239 m3 in the total volume of water applied per irrigation over the area of 7.1 ha of both fields were indicated, which can be used beneficially to grow more crop. The proposed real-time control system is shown to be feasible. It requires few data for itsoperation and provides the infiltration characteristics for each furrow without significant loss of accuracy. The irrigation performance is improved greatly from thatachieved under current farmer management and a substantial reduction in the volume of water applied per irrigation is achievable.

Several methods of infering plant water stress for irrigation scheduling are based upon measurements of the environment in which the plants grow. These measurements include parameters such as soil water content, air temperature, pan evaporation and incident radiation. It is hypothesized that improved estimates of plant water deficit can be obtained by direct measurements made on the plants. The main objective of this study was to test the performance of measurements of canopy temperature and leaf water potential for irrigation scheduling. This study seeks to establish whether a correlation exists between these monitoring methods and measurements of soil moisture content, leaf area, and evapotranspiration. The experiments were conducted in first-year peppermint irrigated at five different rates. Canopy and air temperatures were measured with a hand-held infrared thermometer. Leaf water potential was measured with a pressure bomb. A non-stressed baseline for the difference between canopy temperature and air temperature using data from well-watered plants was used together with the vapor pressure deficit to determine the crop water stress index (CWSI). The results of this study show that the CWSI is well correlated to evapotranspiration deficit and is useful for irrigation scheduling. The relationship between leaf area yield and CWSI in peppermint was described by a quadratic function. Leaf water potential varied during the day in such a way that it was not possible to establish a relationship with water stress, differences in soil moisture content, or different irrigation levels. Leaf water potential was influenced by the daily weather conditions and represented the current demand more than the cumulative demand. The results of this study indicate that mid-day pressure bomb measurements cannot be used in irrigation scheduling. Predawn measurements of leaf water potential were stable, were well correlated with the different irrigation levels and soil moisture content, and therefore may be useful in irrigation scheduling. / Graduation date: 1993

Implementation of a small-scale irrigation project in southern Mauritania is analyzed in this report. The main objective is to demonstrate that small-scale irrigation farming is the best suited solution for Mauritania's agriculture. To reach this objective different steps are taken in this study. The first step highlights the different aspects affecting the development of agriculture in the Senegal River basin such as climatic, environmental, and socio-economic constraints. The next step is the design of a small-scale irrigation system for a small region in the middle valley of the Senegal River called the Dirol plain. Finally, analysis and discussion of the design is made. This discussion centers on the problems faced during the design and the different assumptions made to implement it. The conclusion section addresses the feasibility of the design and gives recommendations that will help improve the design process for future work in the Senegal River basin. / Graduation date: 1996

The focus of this study is the economic feasibility of drip irrigation adoption using capital budgeting and quadratic programming techniques. The capital budgeting techniques used in the study are net present value (NPV) and returns above specified costs (RASC). Modified crop enterprise budgets incorporating drip irrigation are developed based on data from Texas AgriLife Extension Service crop enterprise budgets and published literature focusing on costs and returns of drip irrigation. The quadratic programming technique considers risk and incorporates the modified crop enterprise budgets to estimate a cropping pattern that maximizes the net income above specified costs for the region. The RASC per acre for drip-irrigated crops ranged from $56.34 to $1,909.03, while the RASC per acre for flood-irrigated crops ranged from $142.51 to $1,488.12. Flood-irrigated onions, cotton, and sugarcane had higher RASCs per acre, while the RASCs were greater for drip-irrigated grapefruit and oranges. Evaluating the NPV of the crops resulted in similar results; only grapefruit and oranges were economically-feasible drip-irrigated crops. The baseline results identified levels of drip irrigation adoption ranging from 52,000 acres to 64,497 acres as levels of risk were varied. The level of water available at the reservoir suggested minimal impacts on the level of drip-irrigation adoption, but serious implications for the agriculture economy. Several sensitivity scenarios concentrated on the implications of yield response and water savings that result from the adoption of drip irrigation. The greatest amounts of drip-irrigated crops were present when the yield responses were 130% of the flood-irrigated crops with a 20% water savings. As the amount of water available was reduced, the amount of drip-irrigated crops ranged from 46,111 acres to 59,724 acres. Drip irrigation appears to be an economically-viable alternative in the LRGV due to the presence of drip-irrigated crops in the entire myriad of scenarios investigated in this research. If producers are only concerned with the bottom line as provided by the RASC analysis and no other variables such as water availability, risk, and crop rotations affecting the decision making process, only drip-irrigated grapefruit and oranges are economically competitive with conventional irrigation systems.

Mémoire de licence. / En annexes, recueil de documents en latin. Bibliogr. p. 223-233. Index.

No description available.

Automated short furrow irrigation (ASFI) is a prototype irrigation system that has the potential to be robust and relatively low-cost, with highly effective and efficient water use. ASFI has low energy requirements because the pressure at the field edge is relatively low, typically 70 kPa (or 7 m) as compared with approximately 150 kPa for drip and 400 kPa for dragline systems. However, at project onset, the only type of ASFI system tested was Microfurrow which was, among other problems, not robust. The aim of this project was, therefore, to develop, implement and evaluate a suitable ASFI system and to compare the system to a reference sub-surface drip (SSD) irrigation system with sugarcane as the test crop. This process resulted in the development of a boot and piston valve, which was used to automatically control the flow between specific plots. The valve was then implemented, as per design, in the ASFI system at a trial at the University of KwaZulu-Natal’s Ukulinga research farm. Irrigation events were scheduled according to SAsched with the aim of applying equivalent amounts of water to both the ASF and SSD treatments. The testing and evaluation included irrigation uniformity tests and the crop yields. Evaluation of selected furrows in the ASFI treatment showed a low quarter distribution uniformity (DUlq) range between 72 % and 80 %. This is considerably better than approximately 60 % for conventional furrow irrigation. However, the DU for ASFI could be improved to above 90 % if the slope was reduced from 1:40 to approximately 1:250. Both the harvested tons per hectare and sucrose content results were evaluated using a one-way statistical analysis with differences between the results deemed to be insignificant. Therefore, the ASFI performance in terms of harvest data for the Ukulinga trial could be described as “similar to” SSD irrigation. A 10 ha sample ASFI system was designed and compared in economic terms with a respective SSD system. Although further piping options can be explored in order to reduce the capital costs of the ASFI system even further, ASFI was considerably more cost-effective than the SSD system in terms of operating and fixed costs per hectare. The ASFI irrigation system, although having some initial maintenance requirements in insuring all furrows performed properly, required no other maintenance throughout the year in the Ukulinga trial. The drip system, however, required laterals to be flushed and leaks to be repaired. It is therefore believed that the ASFI system meets the required objectives of the project in that it is robust, low-cost (both operating and fixed) and able to supply water efficiently and effectively. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2010.