Purpose Forecasting the annual water supply in an arid area by using the water content of snow on watersheds on some particular date, such as April 1, has become a very useful practice. Although these forecasts have given results of great practical value, they have sometimes been considerably in error. Seeking to minimize error, forecasters have incorporated various additional data such as temperature and antecedent rain to improve the relation between snow measurement and measured runoff. Numerous methods have been suggested in the search for a reliable streamflow forecasting equation and various data have been used. Nearly all of the methods made some improvements, but in the attempt to minimize the number of variables, perhaps full use has not been made of all the available data. A successful streamflow forecasting method for Logan River, Cache County, Utah was suggested by Professor Cleve H. Milligan (11) and Dr. Rex L. Hurst. They utilized Fourier Series and Multiple Linear Regression as a mathematical model. In their study, four primary factors were used which are antecedent streamflow, temperature, precipitation, and snow survey data. This method has also been used in the forecasting for the Blacksmith Fork River, south of the Logan River, by Fok (5) with a high degree of accuracy. In his study, temperature and precipitation data were both measured outside the watershed and showed a lower degree of significance in the complete forecasting equation. If these data had been measured in the watershed they might have yielded greater significance in the forecasting equation. Perhaps a better factor than temperature and precipitation would be soil moisture data obtained on the watershed. Objective The major objective of this thesis is to develop a method for use of soil moisture data in an equation for streamflow forecasting for the Logan River in Northern Utah. Several Investigators have recognized the need for soil moisture data and for a method of including it in the forecasting equations (see literature review).

This study investigated the role of exopolysaccharide (EPS) in cheese moisture retention. Analysis of low-fat Mozzarella cheese made with different combinations of EPS-producing (Streptococcus thermophilus MR-1C and Lactobacillus delbrueckii ssp. bulgaricus MR-lR) and non-EPS-producing (S. thermophilus TA061 and L. helveticus LH100) starters showed significantly higher moisture levels in cheese made with S. thermophilus MR-1C. To determine if the S. thermophilus MR-1C EPS was responsible for increased moisture retention, gene replacement was used to inactivate the epsE gene in this bacterium. Low-fat Mozzarella cheese made with L. helveticus LH100 plus the EPS-negative mutant, S. thermophilus DM1O, had significantly lower moisture content than cheese made with LH100 and MR-1C, which confirmed that the MR-1C capsular EPS was responsible for the water-binding properties of this bacterium in cheese. Chemical analysis of the S. thermophilus MR-lC EPS indicated that it had a repeating unit composed of D-galactose, L-rhamnose, and L-fucose in a ratio of 5:2:1. Interestingly, carbohydrate utilization tests showed that DMlO had acquired the ability to ferment galactose.

nitrogen has commonly been a deficient element in the cultivated soils of the world since the beginning of agriculture. The general acceptance of the practice of using manures as a means of increasing plant growth, as shown by the records of ancient civilizations, attest to this fact. Since the time of von Liebig there has been an increasing awareness of the importance of this deficiency in soils. As a result of a better understanding of the problem and the increasing availability of commercial forms of nitrogen, a rapid increase in the use of nitrogen fertilizers has taken place in the last few decades. this increasing use of commercial forms of nitrogen is accompanied by the need for more information concerning the proper use of these materials in order to accomplish the greatest benefit. For example, with the advent of increasing use of ammonium fertilizer to improve soil productivity, there has arisen a possibility of lengthening the period from the date of the fertilizer application to the time of utilization by the crop. this advanced application, especially in the fall of the year, has many advantages and is widely advocated. The following questions need to be answered in connection with efficiency of such a practice: Will the ammonium form of nitrogen remain unoxidized in the soil over the winter months? Could it be only partially oxidized and result in an accumulation of nitrites that may cause toxicity or be lost from the soil in gaseous forms such as nitrous oxide? What are the chance for significant losses by volatilization before it is oxidized? How does the amount of moisture and the prevailing temperature affect these transformations? The study reported here is an endeavor to contribute to more complete answers to some of these questions. Although much research has been conducted relating to the effects of moisture or temperature on nitrogen transformations in the soil, more information is needed covering greater variations in the moisture and temperature levels along with the interactions of these. Accordingly, experiments were conducted under carefully controlled conditions to measure the changes occurring in the inorganic soil nitrogen from an applied ammonium source, at various moisture and temperature levels.

Differences in texture at any particular stage of ripening depend upon differences in the basic structure and the extent to which the basic structure is modified by physical parameters. Thus, very young cheeses of the same variety differ in texture because of variations in pH and in salt, moisture, and fat content. How well a cheese melts and shreds depend on its texture and physical parameters. Streptococcus thermophilus MR1C produces an exopolysaccharide (EPS) that is tightly associated with the bacterial cell wall. Addition of S. thermophilus MR1C to the cheese make will increase the moisture of the cheese 2-3% and thus affect the texture, melt, and shreddability of that cheese. To determine the effect of S. thermophilus MR1C on the texture, melt, and shreddability of cheese, two stirred-curd cheeses with equivalent physical parameters using BPS-producing S. thermophilus MR1C or non-BPS-producing S. thermophilus DM10 adjunct cultures were produced. Because MR1C cheese would increase moisture, the curd size, wash water temperature, and pH at salting had to be altered in order to make the physical parameters the same for both cheeses. The MR1C cheese was harder and had a higher fracture stress than the DM10 cheese. The MRlC cheese was also more adhesive, but only for one of the two trials. Even with adjustments in the method of manufacture, the MR1C cheese still had a slightly higher SM and pH, which may be partly responsible for the differences between the two cheeses. There were no differences between the MRlC cheese and the DM1 0 cheese in shreddability as determined by fines, stickiness, and gumminess. Cheese produced without a streptoccus adjunct culture was more cohesive and had fewer fines than the MRIC or DM10 cheese.

Severe water stress reduced the number of flowers produced by Capsicum annuum var. annuum L. Longum plants, but the timing of flower production was less affected. The use of different plant establishment techniques modified flower production. Bare rooted transplants slowed the rate of flower production in comparison with direct seeded plants or those established from cell tray transplants. Bare rooted transplants delayed the onset of water stress. The capabilities of male and female gametophytes were reduced by water stress, with the female more affected, and the interaction of male and female gametophytes was affected by moderate water stress. Moderate water stress increased the time to fruit set, but affected neither the number nor percentage of fruit set, whereas severe water stress increased the time and reduced the number and percentage. Severe water stress reduced the number and percentage of mature fruit, fruit quality indices and total fruit yield. Moderate water stress reduced the number of seeds per fruit and fruit dry weight, but total fresh weight yield was not significantly affected. The time to fruit set was negatively correlated with the quality indices of mature fruit, whereas the number of seeds was positively correlated with the same. Fertilisation determined the success of seed set, and the rapidity of fruit set. Successful fertilisation can only occur when the pollen tube arrives at a viable ovule. The processes of pollen tube growth and longevity of the ovule are the factors most critically affected by water stress in determining the yield of C. annuum Longum. / Master of Science (Hons)

The vegetation of the Sydney Basin, Australia, is highly flammable and subject to a wide range of fire regimes. Sclerophyllous shrubs and sedges are common and in some vegetation types up to 70 % of fuel consumed during a fire can be live. Research into fire behaviour and fuel dynamics has been minimal. To address this issue this thesis investigated the principal factor affecting the ease of ignition and rate of combustion of individual fuel particles and fuel beds in bushfires: dead fine fuel moisture (FFM). Two common Sydney Basin vegetation types, eucalypt woodland and heathland, each with a history of problematic fire management, were measured in the field for diurnal fluctuations in FFM following rain, under conditions similar to when prescribed burns are conducted. The FFM components of current operational fire behaviour models were found to be inadequate for predictions of FFM and fire behaviour under these conditions. The equilibrium moisture content (EMC) of five fuel types from the field site was investigated in a laboratory study. An existing function describing EMC as a function of temperature and relative humidity was evaluated and found to be very accurate for these fuels. Two FFM predictive models incorporating this function were evaluated on the field data and the laboratory results were shown to be applicable to the estimation of FFM in the field. One model gave very accurate predictions of FFM below fibre saturation point, but its accuracy was reduced when screen level conditions were used instead of those measured at fuel level. A recent process-based model that accounts for rainfall showed promise for predicting when fuel is < 25 % FFM. Systematic problems with the radiation budget of this model reduced the accuracy of predictions and further refinement is required. Live fine fuel moisture content (LFMC) of common heathland shrubs and sedge was investigated over two years and found to be both seasonal and influenced by phenology. LFMC minima occurred in late winter and spring (August to October), and maxima were in summer (December to February) when new growth was recorded. The dominant near-surface fuel in mature heath was sedge. It was found to have little seasonal variation in its??? percentage dead but the percentage dead maxima occured at the same time as the LFMC minima of shrubs and sedge in both years. Simple instantaneous models for duff moisture content in woodland and heathland and LFMC and the percentage dead sedge in heathland were developed. The information gained by this study will form the basis for future development of fuel moisture models for prescribed burning guidelines and fire spread models specific to the vegetation communities of the Sydney Basin.

The increasing demand worldwide for Australian wine has driven the recent expansion in vineyard plantings which in turn, has increased the requirement for irrigation water in grape growing regions. Large areas of Australia's national vineyard are already irrigated with relatively poor quality water and many districts have a limited supply of water available for irrigation. Therefore, improving the efficiency of vineyard irrigation is essential for the long term sustainability of the Australian wine industry. Reducing the volume of irrigation applied to vineyards can improve water use efficiency (WUE) and reduce vine vigour. However, it can be difficult to accurately apply the required degree of water stress and this may result in a yield reduction. An irrigation technique known as partial rootzone drying (PRD) involves applying a continuous water deficit to alternate sides of the root system while ensuring the other half is well watered. This has been found to increase WUE, reduce vine vigour, improve fruit quality but not affect vine yield. Where the soil volume available for root growth is limited, so too is the resultant vine growth and yield, as access to water and nutrients is restricted. Shallow soil profiles present a major limitation to root development and grapevine vigour. In shallow soils, mounding topsoil from the vineyard mid row to form raised beds in the vine row has been found to improve vine growth and productivity. Soil mounds tend to have a higher moisture holding capacity than flat soil but the greater surface area of the mound can increase surface evaporation. Applying mulch to the mound surface has been shown to reduce evaporative soil moisture loss and conserve irrigation water. The general hypothesis tested in this experiment was that: 'Combining soil mounding, straw mulch and partial rootzone drying (PRD) irrigation will improve grapevine growth and production and reduce levels of sodium and chloride in the vine.' The experiment was established on Vitis vinifera cv. Shiraz in a mature vineyard at Padthaway, South Australia, where the soil profile consisted of a shallow loam over clay and limestone. Soils of the experimental site were classified as moderately saline because their electrical conductivity (ECse) was greater than 4 dS/m. Three main factors, irrigation method (standard or PRD), soil mounding (flat or mounded) and surface cover (bare or straw mulch) were combined into a 2X2X2 factorial experiment such that the randomised block experiment comprised three replicates of eight treatments. The irrigation treatments were control (the application of water to both sides of the vines) and PRD (the application of water to one side of the vines only at any time). In the PRD treatment the frequency of alternating the 'wet' and 'dry' sides was determined according to soil moisture measurements and was typically every 5-7 days. It was very difficult to accurately schedule the irrigation at this site to avoid applying a moisture deficit to the PRD treatment. The shallow soil profile dried very quickly following irrigation and there were problems with the accuracy of the soil moisture sensing equipment for the duration of the experiment. As a result, PRD vines experienced repeated, excessive soil moisture deficits such that vine growth and production were significantly reduced each season. Shoot length was measured weekly during the growing season, while photosynthetically- active radiation (PAR), leaf area and canopy volume were measured at full canopy. Shoot number and pruning weight were measured during dormancy. All measures of vegetative growth (with the exception of PAR) were reduced in response to PRD. The decrease in lateral shoot growth for PRD resulted in greater bunch exposure and PAR. As a direct result of the severe soil moisture deficits experienced by the PRD treatment, all components of yield were significantly reduced compared to the control treatment each season. In particular, bunch weight and berry weight were significantly lower in the PRD treatment compared to the control, which suggests a period(s) of severe soil moisture deficit was experienced. Despite the yield loss sustained by the PRD treatment, WUE was improved compared to the control treatment in the first two years of this experiment. Berry anthocyanin levels were higher for the PRD treatment than the control but this may be due to the reduction in berry size. Weekly volumetric soil moisture monitoring showed that mounded soil was wetter than flat soil each year at similar horizons. In addition, the larger soil volume of the mounded treatment enhanced vine root development. Vegetative growth was greater in the mounded treatment than the flat treatment. Mounded vines grew more shoots than non-mounded vines, although there was no effect of mounding treatment on shoot length. The difference in shoot number was significant only in year 2, possibly due to the time required for vine roots to establish in the mounds. Pruning weight and mean shoot weight were higher for the mounded treatment each year and mounded vines grew more shoots than non-mounded vines in years 1 and 2. The increase in shoot weight of mounded vines, relative to non-mounded, was most likely due to the increase in lateral shoot growth which is supported by the lower PAR values of the mounded treatment compared to the flat treatment. Each year soil mounding resulted in higher vine yields than in flat soil beds as a direct result of the increased vine capacity of mounded vines. The mounded treatment had more shoots per vine than the non-mounded treatment and thus more bunches per vine. In addition, bunch weights were higher in the mounded treatment each year, due mainly to improved fruit set and more berries per bunch. Despite the mounded treatment resulting in a denser canopy than the non-mounded treatment this did not affect fruit composition in years 1 and 2. WUE was higher for the mound treatment in years 2 and 3 only, due to the volume of irrigation water applied being reduced, yet mounded vines continued to produce higher yields than non-mounded vines. In year 3, berries from vines grown in mounded soil had significantly higher pH than berries from vines grown in flat soil beds. Mounding treatment did not consistently affect berry anthocyanin or phenolic levels. Soil moisture levels were higher in the mulch treatment than the bare treatment in all seasons. In contrast to the mounding treatment, wetter soil did not consistently lead to improved vine growth or yield. Mulched vines developed fewer roots than non-mulched vines which is likely to have limited vine access to water and nutrients. As a result, shoot growth was similar for both treatments each season. The only significant difference between treatments for pruning weight was found in year 3 and was due entirely to shoot weight. The mulched treatment had lower PAR than the bare treatment in year 3, probably the result of increased lateral shoot growth and thus increased shoot weight, although this was not significant. PAR was significantly higher for the mulch treatment, compared to the bare treatment, in year 1 only but this was not supported by significant increases in vegetative growth. The mulch treatment resulted in higher vine yield than the non-mulch treatment in years 1 and 3. This difference was significant in year 3 only when both bunch number and bunch weight were significantly higher for mulched vines. In year 1 only bunch weight was significantly higher for mulched vines. Differences between treatments occurred in year 2 for fruit composition, specifically juice TA and anthocyanin levels. The mulch treatment had significantly higher TA and a significantly lower anthocyanin concentration in berries than the non-mulch treatment in year 2. There was no evidence of increased shading in the mulched treatment relative to the bare treatment that year but the difference in anthocyanin concentration may be explained by the significantly smaller berries of the bare treatment. Analysis of samples taken regularly from the soil profile and vine rootzone showed that there was no treatment effect on soil salinity but that soil ECse increased with soil depth and time each year. Petiole samples were collected at flowering, veraison and pre-harvest and levels were deemed toxic by pre-harvest each year. The PRD treatment received approximately 60% of the salt applied to the control treatment. This did not reduce ECse but did result in lower measures of sodium and chloride in petioles and juice at harvest. Vines grown in soil mounds had access to a greater volume of soil water than the non-mounded vines. The mounded treatment had higher levels of pre-harvest petiole chloride in years 1 and 3 but this was significant only in year 3. There was no consistent trend in levels of sodium and chloride in the juice from either mound treatment, although in year 3 berry extract chloride levels were found to be significantly higher in the mounded treatment than the flat treatment. Similarly, a consistent trend in sodium and chloride levels of petioles and juice was not evident for the mulch treatment. Although, in year 3 petioles of vines grown in bare soil were found to contain significantly more petiole chloride than those which had straw mulch applied. The hypothesis that combining soil mounding, straw mulch and partial rootzone drying (PRD) irrigation will improve grapevine growth and production and reduce levels of sodium and chloride in the vine is rejected as there was not a consistent, cumulative effect of the three factors in this experiment. / Thesis (M.Ag.Sc.)--School of Agriculture and Wine, 2005.

There is a need in the dairy industry for instrumentation capable of providing on-line information about the moisture content of cheese during manufacture. Present measurement techniques are usually performed off-line and can be susceptible to human error. It is demonstrated that microwave-based moisture sensing techniques offer a number of potential advantages over conventional methods due to the strong interaction of microwaves with water. The permittivity of cream cheese curd and low-fat cheddar cheese curd has been measured over a range of frequencies and moisture contents in order to establish the relationship between these variables. A vector reflection coefficient measurement engine based on a six-port reflectometer has been built and tested. A suitable sensing head has been fabricated from a short length of microstrip transmission line. Two sensor characterisation models have been developed and compared with measured data. A novel algorithm has been developed to resolve the ambiguity inherent in many permittivity measurement techniques. It has been discovered that surface waves can propagate on a grounded dielectric slab covered by a material with a higher dielectric constant, provided the loss factor of the covering medium is greater than zero. It has also been found that the dominant mode of microstrip can radiate when the line is covered by a high-permittivity material, although this can be suppressed if the covering material is sufficiently lossy. There are three principal conclusions to draw from the investigation in this thesis. Firstly, changes in the moisture content of cheese curd during manufacture produce measurable variations in permittivity. Secondly, these changes can be measured accurately and cheaply using off-the-shelf microwave hardware. Finally, considerable attention must be paid to the characterisation of the sensing head if the instrument is to achieve its full potential. Promising results have been obtained in this area, however certain issues pertaining to the propagation of multiple dominant modes and higher order modes have not been fully resolved and would repay further theoretical analysis.

Growth, productivity and fruit quality of grapevines are closely linked to soil water availability. Withholding of water for any length of time results in slowed growth. If drought continues yield may be lost. Vines can be manipulated to stimulate early defence mechanisms by decreasing soil water availability. By using an irrigation technique, which allows for separate zones with different soil moisture status, it is possible to stimulate response mechanisms of the root system which are normally related to water stress. The difficulty of separating 'wet' and 'dry' zones was initially overcome by using split-root plants with root systems divided between two containers. Such experiments on split-root model plants resulted in the development of an irrigation technique termed partial rootzone drying (PRD). Results from irrigation experiments using PRD have shown that changes in stomatal conductance and shoot growth are some of the major components affected (Dry et al., 1996). The idea of using irrigation as a tool to manipulate stress responses in this way had its origin in the concept that root- derived abscisic acid (ABA) was important in determining stomatal conductance (Loveys, 1984). Later experiments on split-root plants have demonstrated that many effects of water stress can be explained in terms of transport of chemical signals from roots to shoots without changes in plant water status (Gowing et al., 1990). The necessary chemical signals are provided by the dry roots, and the wet roots prevent the development of deleterious water deficits. The general hypothesis tested during this study was that partial drying of the root system gives rise to a change in the supply of root-derived chemical signals which determine changes in grapevine physiology, thereby affecting fruit quality. Experiments were conducted on split-root vines (Vitis vinifera L. cvs. Cabernet Sauvignon and Chardonnay) grown in pots of different sizes, on field-grown vines which had either their root system divided by a plastic membrane (Vitis vinifera L. cv. Cabernet Sauvignon on own roots or grafted on Ramsey rootstocks) or conventional vines with a non-divided root system (Vitis vinifera L. cv. Cabernet Sauvignon, Shiraz and Riesling) with a commercial PRD irrigation design. The irrigation treatments were vines receiving water on both sides (control) and PRD-treated vines, which only received water on one side at any time. The frequency of alternation of 'wet' and 'dry' sides was determined according to soil moisture and other influences such as rainfall and temperature. In most of the experiments the irrigation was alternated from one side to the other every 10 to 15 days. Chemical signals from roots: the role of ABA and cytokinins Studies on chemical signals have concentrated on ABA and cytokinins (CK). An improved stable isotope dilution protocol, which enables analysis of ABA and CK from the same tissue sample, was developed. Analysis of cytokinins focused on zeatin (Z), zeatin riboside (ZR), zeatin glucoside (ZG) and iso pentenyl adenine (iP). Roots are relatively inaccessible, particularly in field situations. To enable easier access to roots of field-grown vines, split-root vines were planted in a trench which was refilled with a sandy soil. This created a homogenous soil substrate and did not restrict root growth while still allowing access to roots under field conditions. Analyses of root samples of field-grown vines have shown that cytokinins and ABA may originate in roots and their concentrations can be substantially altered during an irrigation cycle. Alternating soil water conditions showed that [ABA] in roots on the 'dry' side was significantly higher compared with the 'wet' side. Due to a reduction in CK on the 'dry' side of PRD-treated vines, the ratio between ABA and CK was substantially changed during an irrigation cycle. The ABA levels in root tissue and in petiole xylem sap were negatively related to stomatal conductance. This further suggests that ABA, mostly synthesized on the 'dry' side of the root system, might be responsible for a decline in stomatal conductance. Furthermore, a higher pH of petiole xylem sap was observed in PRD-treated vines which may also contribute to the regulation of stomatal conductance. Studies on stomatal patchiness showed that non-uniform stomatal aperture occurred in field-grown vines under natural environmental conditions and was more abundant under PRD conditions. The degree of stomatal opening, determined by using a water infiltration technique, correlated with measurement of stomatal conductance. Exogenous application of a synthetic cytokinin (benzyl adenine) can override the possible ABA-mediated stomatal closure resulting from PRD treatment, providing further evidence for the in vivo role of these growth regulators in the control of stomatal conductance. The effect of benzyl adenine was transient, however, requiring repeated applications to sustain the reversal. In addition, CKs may also be important in influencing grapevine growth. Following several weeks of repeated spray applications with benzyl adenine, it was found that the development of lateral shoots in PRD-treated vines was enhanced compared to PRD-treated vines sprayed with water only. This supports the idea that the reduction in lateral shoot development seen in PRD-treated vines is due to a reduced production of CKs (Dry et al., 2000a). By measuring shoot growth rate it was found that one common feature of PRD-treated vines, which were not sprayed with CK, was a reduction of lateral shoot growth. It can therefore be speculated that the reduction in lateral growth is related to a reduced delivery of cytokinins from the roots. Zeatin and zeatin riboside concentration in shoot tips and prompt buds/young lateral shoots were reduced by the PRD treatment providing further evidence in support of this hypothesis. Water movement from 'wet' to 'dry' roots Roots, being a primary sensor of soil drying, play an important role in long- and short-term responses to PRD. Using stable isotopes of water and heat-pulse sap flow sensors water movement was traced from wet to dry roots in response to PRD. The redistribution of water from roots grown in a soil of high water potential to roots growing in a soil of low water potential may be of significance with regard to the movement of chemical signals and the control of water balance of roots. Measurements of the relative water content (RWC) have shown a slower decline of RWC of the 'dry' roots of PRD vines relative to roots of vines which received no water, despite similar water content in soil surrounding those roots. The redistribution of water may help to sustain the response to PRD for longer periods possibly releasing chemical signals and to support the activity of fine roots in drying soil. Field vines, irrigated with PRD over several growing seasons, altered their root distribution relative to the control vines. PRD caused a greater concentration of fine roots to grow in deeper soil layers and this may contribute to a better water stress avoidance. The effect on root growth may be augmented by the water movement and by the large difference in ABA to cytokinin ratio, which are also known to alter root growth. PRD makes more efficient use of available water In experiments where both control and PRD-treated vines received the same amount of water many differences between the vines were demonstrated. Under conditions where water supply was adequate for both treatments, the stomatal conductance and growth of the PRD-treated vines was restricted as has been observed in many previous experiments. As total water input was reduced, however, the stomatal conductance of PRD-treated vines became greater than control vines, suggesting that the latter were experiencing a degree of water stress, whereas the PRD-treated vines were not. This may have been due to the greater depth of water penetration in the case of the PRD-treated vines, where water was applied to a smaller soil surface area. This distinction between PRD-treated and control vines, at very low water application rates, was also reflected in pruning weights and crop yields which were actually greater in PRD-treated vines. It was concluded that at low water application rates, the PRD-treated vines were more tolerant of water stress and made more efficient use of available water. Reduction in vigor opens the canopy. The initial aim of the research which led to the development of PRD was to achieve better control of undesirable, excessive shoot and foliage growth which, from a viticultural point of view, has many disadvantages. Grapevine shoot growth rate responds very sensitively to drying soil conditions. The irrigation strategy used in the PRD experiments maintained a reduction of both main shoot and lateral shoot growth. In response to PRD a decrease in shoot growth rate and leaf area was observed. Much of the reduction in canopy biomass was due to a reduced leaf area associated with lateral shoots, thus influencing the canopy structure. This was one major factor improving the light penetration inside the canopy. Control of vegetative vigour results in a better exposure of the bunch zone to light and, as a consequence, in improved grape quality. It is likely that changes in canopy density, as a result of PRD, is causing changes in fruit quality components. Anthocyanin pigments such as derivatives of delphinidin, cyanidin, petunidin and peonidin were more abundant in berries from PRD vines; by comparison the concentration of the major anthocyanin, malvidin, was reduced. When leaves were deliberately removed from more vigorous control vines, which improved bunch exposure, the differences in fruit composition were much reduced. This further supports the idea that a more open canopy, in response to PRD, improves fruit quality by affecting the canopy structure. Fruit quality consequently determines the quality, style and value of the finished wine. Wines from this study have been produced and data on wine quality from commercial wineries are also available. Sensory evaluations have demonstrated that high wine quality from PRD-treated vineyards can be achieved without any yield-depressing effects. This study has provided evidence to support the original hypothesis. The major findings were: a) Chemical signals, altered under PRD and mostly originating from roots, play an important role in the root to shoot communication in grapevines. b) The movement of water from 'wet' to 'dry' soil layers may help to sustain chemical signals as a response of grapevines to PRD and to support the activity of fine roots in drying soil. c) A reduction in vegetative growth, in particular of lateral shoots, was sustained using PRD and affected the canopy structure which in turn, due to a better light penetration into the canopy, improved the fruit quality. d) The reduction in irrigation water applied did not have a detrimental effect on grape yield and thus the efficiency of water use was improved. e) Application of relatively low irrigation rates showed that PRD-treated vines were more tolerant of water stress and made more efficient use of available water. / Thesis (Ph.D.)--Department of Horticulture, Viticulture and Oenology, 2000.

<p>Transport of chemical substances through a catchment depend to a large extent on the water content of the soil through which they are transported. When the groundwater level rise and fall, redox conditions change in the soil and the transport of substances is affected. </p><p>The aim of this study is to develop a hydrological model which is able to simulate soil water content at different depths and groundwater level in a soil profile. A new type of conceptual model is developed, which uses a continous represenation of the soil and soil water from the soil surface down to the bedrock. The model is intended to be applied on small catchments at a later stage. </p><p>The results show that the simulation of groundwater levels was greatly improved compared to previous results. Simulation of soil water content at selected depths is not yet satisfactory. The runoff simulation was accurate at one of the sites but did not work as well at the other. At one of the sites it was also possible to combine good simulations of runoff and groundwater levels but at the other it was only possible to obtain acceptable simulations of either runoff or groundwater. </p><p>It is suggested that model performance could be improved by letting the porosity decrease and the soil water content increase non-linearly with depth. Calculations of evaporation from soil and runoff also need to be modified.</p>