No description available.

No description available.

Call number: LD2668 .T4 1986 O77 / Master of Science / Biological and Agricultural Engineering

[Abstract]: Sugarcane farmers in Bundaberg have had limited access to irrigation water over the last ten years. The district has the potential of growing 3.8 million tonnes of sugarcane. However, a series of dry seasons saw this reduce to 2.1 million tonnes in 2002. Compounding the effects of both dry seasons and limited water supplies has been a 30% reduction in the sugar price over this period. The irrigation requirement of sugarcane in the Bundaberg area is 8 ML/ha. The original allocated volume for sugarcane production in this area was 4.5 ML/ha (based on 1970 production areas). However, as the area under production has increased and announced allocations in each year has reduced, this allocation is now equivalent to an application volume of about 2 ML/ha A change from the traditional practice of full irrigation is required as water supplies become depleted. As there were no clear guidelines on how growers could respond to diminishing water supplies, this research investigated opportunities to fine tune irrigation practices and the performance of irrigation systems (ie. low cost solutions) that would assist growers to maximise sugarcane yield. A grower survey was initially conducted to identify current practice and opportunities for change. Field investigations focused on the performance of water winch and furrow irrigation systems, which make up 91% of the irrigated area in the district. As most of these application systems have insufficient capacity to meet crop demands opportunities to schedule irrigations were limited to start up after rain. Improvements in irrigation system performance were found to provide the greatest potential to increase sugarcane yield under conditions of limited water. Investigations identified that irrigation performance could be significantly improved through relatively minor adjustment. Field trials found that wind speed and direction significantly influenced the performance of travelling gun irrigators. Although growers were generally aware of the effects of wind, meteorological data suggested that the opportunity to operate water winches in low wind conditions is limited. Changing to a taper nozzle under moderate to high wind conditions will reduce the effect of wind on performance. This practice was found to improve the uniformity (measured by Christiansen’s Uniformity Coefficient, CU) by 16%. The grower survey indicated that there was no preference towards the use of taper nozzles in windy conditions. Additional trial work developed a relationship between the variation in water applied to the field through non uniformity and sugarcane yield. An 8% reduction in yield was determined for a 10% reduction in CU. This indicated that changing to a taper nozzle could potentially increase sugarcane yield by 15% in high wind conditions. Other settings, which also influenced uniformity, included lane spacing and gun arc angle Simple changes to the operation of furrow irrigation systems were also found to dramatically improve irrigation performance. Field measurements in combination with simulation modelling of irrigation events using SIRMOD II identified that current irrigation performance ranged in application efficiency from 45 to 99% (mean of 79%) and a distribution uniformity from 71 to 93% (mean of 82%). Both application efficiency and distribution uniformity were increased to greater than 90% and 84% respectively, except on a cracking clay soil. Improvements in application efficiency and distribution uniformity were achieved by adjusting furrow flow rate (cup size), turning the irrigation off at the right time (ie. just as it reached the end of the field) and banking the end of the field. Growers had a good understanding of the correct cut off time and were attentive to reducing run off through either banking ends or tail water return. However, growers had a poor understanding of the significance of furrow flow rate. Other opportunities to improve irrigation performance on high infiltration soils included alternate furrow irrigation and shallow cultivation practices which maintained compaction in the interspace and reduced infiltration. Soil moisture and crop growth measurements indicated that sugarcane yield could be maximised by starting the irrigation rotation earlier after rainfall (ie. at a deficit equal to the irrigation amount). These observations were modelled using the crop simulation model APSIM sugar to assess the strategy over a longer time interval and the influence of seasonal variation. Simulation modelling showed that final sugarcane yields were not sensitive to irrigation start-up strategies. Yields for the start-up strategies modelled varied by less than 5 tc/ha. This minor difference occurred as the crop yield was driven by the total amount of water available to the plant. The limited amount of irrigation water available to the plant (2 to 3 ML/ha) had only a minor effect on the water balance and no significant change to effective rainfall between strategies. The greatest difference in yield occurred between irrigation treatments when water was left over at the end of the season (9.2 tc/ha). Starting irrigation earlier after rainfall events (on a 14 day rotation) provided the greatest opportunity to use all of the available irrigation supply. By comparison, delaying the application of the first irrigation after rainfall resulted in some of the irrigation water not being applied in 30% of years.

The effect of furrow spacing on infiltration should be determined in order to properly design an irrigation system. The blocked furrow infiltrometer (BFI) and the flowing furrow infiltrometer (FFI) methods were investigated for this purpose in two areas upon a precision field furrow. Three irrigations were performed in each method. The initial and final soil moisture contents (before and after irrigation), the furrow cross-section (before and after irrigation), the inflow volume and the furrow water surface elevations (during irrigation) were measured in each test furrow. Cumulative infiltration and infiltration rates were determined for each irrigation. The results indicate that the FFI test furrows infiltrated more water than did the BFI test furrows for the same infiltration time. The infiltration rates were higher in the FFI test furrows than in the BFI test furrows until they approach the basic intake rate. The infiltration rates were also higher during the 0.90 m spacing tests than during the 1.80 m spacing tests. The 0.90 m spacing test furrows infiltrated more water than did the 1.80 m spacing test furrows.

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.

Thesis (Ph.D.). / Written for the Dept. of Bioresource Engineering. Title from title page of PDF (viewed 2008/02/12). Includes bibliographical references.

Lygus bug (Lygus Hahn) and predator (Chrysopa carnea Stephens, Geocoris, and Nabis) abundance and spatial distribution in production-managed, drop and furrow-irrigated cotton (Gossypium hirsutum L.) in central Arizona were compared during the early seasons of 1980-1983. Sweep net and drop cloth samples revealed lygus bug populations were established and reached pest status in drip-irrigated cotton 2-3 weeks prior to those in furrow. Several factors combined to make drip cotton more favorable than furrow for Lygus: more dense plant populations, taller plants, lower vapor pressure deficits within the plant canopy, and earlier availability of squares. Within furrow-irrigated cotton, lygus bugs and the percent Lygus-damaged squares were greater in areas of tall, dense plantings, primarily in areas distant from the water source. In drip, damage was significantly greater than in furrow, and comparable in all field ares. Predator populations were not consistently greater under either irrigation system. Under furrow, Geocoris and Nabis populations were greatest in areas of Lygus abundance. Morisita's index and Taylor's power law indicated a higher degree of aggregation in the spatial patterns of Lygus and predator populations in furrow-irrigated cotton than in drip. The two indices agreed in magnitude and trend across the insects studied, but Morisita's index was more frequently significant for contagion. Sweep net samples revealed a higher degree of aggregation than drop cloth. Taylor's coefficients were used to determine optimum sweep net and drop cloth sample sizes to evaluate Lygus populations for pest management. The sweep net requires a greater sample size than the drop cloth to ensure a given level of precision, and more samples are required in furrow-irrigated cotton than in drip. Based on percent damage and the relative variability of damage estimates, the number of squares examined for lygus bug damage should be comparable in all drip field areas, but twice as many should be examined in the furrow head-water as in the middle and tailwater. Extrafloral nectar volumes are greatest in leaves of the middle and top plant regions, and in the blossom and young boll stages of fruiting bodies. Irrigation timing and method affect nectar production. The effects of extrafloral nectar production phenology on insect distribution are discussed.

A cross-section averaged Advection-Dispersion equation (ADE) model was developed to simulate the transport of fertilizer in furrow irrigation. The advection and dispersion processes were solved separately by implementing the method of the characteristics with cubic spline interpolation (and natural boundary condition) and weighted finite difference scheme respectively. A zero-flux boundary condition during advance and an advective gradient at the downstream end of an open furrow were established. Local pseudo-steady state was assumed in order to apply Fischer's longitudinal dispersion equation under non-uniform and unsteady furrow flow conditions. Also, several parameters were used to evaluate the ADE model and fertigation performance.A field tracer experiment in two types of downstream-end furrow and two treatments was conducted and described. Infiltration and roughness parameters were calibrated by implementing a volume balance approach. The calibrated parameters were used as input data to run the surface irrigation model (SRFR). The roughness coefficient was 0.045 for wheel and 0.055 for non-wheel furrow treatment for bare soil. The root mean square error (RMSE) comparing the computed and observed infiltrated volume was in the range of 0.09-0.38 m3. The close match between simulated and observed data indicates an acceptable calibration. Pulses of fertilizer injected at the head end of four furrows each having unique management characteristics were simulated satisfactorily during the entire duration of the irrigation event. The constant value of the longitudinal dispersion coefficient was 1 m2 min-1 and yielded an acceptable space-time evolution of the pulses of tracer injected. Similar results for the dispersion coefficient were obtained with Fischer's equation in non-uniform and unsteady stream flow conditions in the furrow. An evaluation of several fertigation strategies for furrow systems indicated that fertigation by pulses could help reduce leaching and runoff losses in surface irrigation systems.

There is a regulatory tension within wastewater treatment, between the requirement to meet tightening consents and the need to reduce the carbon footprint of treatment processes. With 75% of wastewater treatment works serving populations of less than 2,000, low-energy tertiary treatment options suitable to small rural works need to be developed. One option that lends itself particularly well to small works is land-based wastewater treatment (LBWWT). The aim of this research was to evaluate the role of LBWWT in the UK water industry and investigate the impact ridge-and-furrow enhanced microtopography (MT) may have upon a particular type of LBWWT - slow-rate (SR) infiltration. This was achieved through meeting three objectives. Firstly, the use of LBWWT was reviewed and assessed. Secondly, the impact of ridge-and-furrow enhanced MT upon the vegetation diversity and nutrient removal of a SR- LBWWT was established by means of a three year field trial. Finally, the cost- effectiveness of SR-LBWWT and the impact of ridging and furrow irrigation upon cost-effectiveness were evaluated using Cost-Effectiveness Analysis (CEA). The first objective comprised of a review of the historical and current use of LBWWT, a review of the relevant changing legislation to identify what may be required of LBWWT and an assessment of LBWWT’s potential to meet these requirements. The result of the evaluation found that, based upon the literature, SR-LBWWT is ‘fit-for-purpose’ as tertiary treatment for small treatment works. To meet the second objective, a SR-LBWWT system trial was established at a small wastewater treatment works in Knowle, Hampshire. The trial consisted of three clay-loam grass plots irrigated with secondary treated effluent. There were two configurations of trial plot - flat and ridge-and-furrowed. Effluent (sub- surface soil water) nutrient concentrations were monitored as was vegetation diversity. In addition a number of physical, hydrological and biogeochemical parameters were monitored and hydrological modelling carried out. Mean nutrient removal performances of 90% for ammonia, 72% for nitrate, and 91% for phosphate were observed with the ridge-and-furrowed plot. Ridging and furrow irrigation was found to not have a significantly detrimental effect upon the trial plots’ removal performance for ammonia, nitrate or phosphate. Extrapolation modelling suggested, however, that this would not be the case for LBWWT systems on predominantly clay or sand soils. Ridging and furrow irrigation was found to have a statistically significant positive effect upon the vegetation diversity of the LBWWT trial plots; with mean final year Shannon-Wiener values of 0.96 and 0.69, for the ridge-and-furrowed and non-ridged plots, respectively. For the final objective, analysis found that SR-LBWWT are cost-effective when compared to horizontal sub-surface flow constructed wetlands (HSSFCW), an established low-energy treatment option. Mean cost-effectiveness ratio values of £208.5 and £262.7 per % effectiveness were observed for LBWWT and HSSFCW, respectively. Following the field trial CEA was extended to include ridge-and-furrowed SR-LBWWT systems. This found that ridging and furrow irrigation improves the cost-effectiveness of SR-LBWWT serving small populations, reducing the mid cost-effectiveness ratio to £193 per % effectiveness. This is a result of the cost-reducing effect of ridge-and-furrowing over laser-level grading; and based upon the findings of the trial that ridging and furrow irrigation can be achieved (in clay-loam soil slow-rate systems) without significant detriment to the water treatment effectiveness of LBWWT. The main conclusions of this thesis are: that SR-LBWWT has a role to play in the UK water industry, as tertiary treatment for small wastewater treatment works. That SR-LBWWT is cost-effective in relation to HSSFCW. That ridging and furrow irrigation increases that cost-effectiveness by reducing the construction and operational costs. That ridging and furrow irrigation can be employed without significant detriment to a SR-LBWWT system’s water treatment performance. And finally, that ridging and furrow irrigation can have a positive impact upon the establishment vegetation diversity of a SR-LBWWT system.