Silica optical fibres were used to measure colour (mg anthocyanin/g fresh berry weight) in samples of red wine grape homogenates via optical Fibre Evanescent Field Absorbance (FEFA). Colour measurements from 126 samples of grape homogenate were compared against the standard industry spectrophotometric reference method that involves chemical extraction and subsequent optical absorption measurements of clarified samples at 520 nm. FEFA absorbance on homogenates at 520 nm (FEFA520h) was correlated with the industry reference method measurements of colour (R² = 0.46, n = 126). Using a simple regression equation colour could be predicted with a standard error of cross-validation (SECV) of 0.21 mg/g, with a range of 0.6 to 2.2 mg anthocyanin/g and a standard deviation of 0.33 mg/g. With a Ratio of Performance Deviation (RPD) of 1.6, the technique when utilizing only a single detection wavelength, is not robust enough to apply in a diagnostic sense, however the results do demonstrate the potential of the FEFA method as a fast and low-cost assay of colour in homogenized samples.

The EM38 has a widely accepted role in precision agriculture for the efficient mapping of sub-surface apparent electrical conductivity at data densities of the order of 10 m. The resultant high-resolution maps of apparent conductivity enable agriculturists to infer soil properties such as soil moisture and salinity which aid localized crop management decisions. However, when applied to viticulture, previously published research has confirmed that the use of electromagnetic induction instruments, such as the EM38, has been flawed by the interference from the conducting wire and steel-post loops of the grapevine trellising. This has raised questions about the reliability of interpretations made from potentially flawed maps of apparent conductivity in vineyards. In this research, a combination of component and whole trellis assembly trials confirmed that this interference was separable into two significant components: the steel trellis loops and the trellis-earth system. Furthermore, while these two effects theoretically interact, the contributions from each were found to be conceptually separable in terms of both the EM38 response and possible mitigation or data correction strategies.

Active optical sensors that contain their own modulated light sources are becoming popular for 'sensing' photosynthetically-active biomass in crops and pastures. These sensors detect optical reflectance to derive spectral vegetation indices, such as the normalised difference vegetation index (NDVI), and are subsequently calibrated to measure plant parameters e.g. biomass. However, research has demonstrated the accuracy of the derived measurements can often be improved by including both a spectral index and a corresponding measure of plant height. This paper describes an active, optical sensor that integrates modulated reflectance sensing with the ability to measure (range) the distance between the source and a target surface. Two ranging techniques are evaluated; one based on the inverse square law (ISL) of reflected radiation and another based on a position-sensitive detector (PSD). Both ranging methods proved capable of reliably delineating target distances out to 4.0 m from the source. Over this range, the PSD detector exhibited a distance-invariant RMSE of ± 2.6 cm whilst the ISL method exhibited an almost linear increase in error of ± 25 % of the measured distance to a spectralon target. Application to a vegetative target (Kikuyu grass), demonstrated the ISL ranging method to yield an average RMSE of ± 3.0 cm in the range of 0.60-1.40 m, while the average RMSE of the PSD over a range of 0.50-1.10 m was observed to be ± 10.0 cm. Despite superior accuracy, target reflectance variations may prove problematic in the use of a PSD ranging sensor and requires further investigation.

Mono-molecular layers, or monolayers, on the surface of water can reduce evaporation by up to 40% on small storages. Effective reduction requires the maintenance of coverage by dispensers, which must be informed by sensors capable of detecting the presence/absence of the monolayer. However, no system has yet been developed that can reliably automatically detect the presence of monolayer. Numerous detection techniques for potential field deployment, including optical and infrared reflectance, measurement of surface tension and wave damping methods were investigated. A wind assisted surface probe (WASP), based on the temperature differential between the sub-surface and volume of a small sample of periodically-entrapped water was subsequently developed. In small scale testing it has shown to be a reliable indicator of monolayer in all but very high humidities.

Active optical sensors that contain their own modulated light sources are becoming popular for 'sensing' photosynthetically-active biomass in crops. Primarily confined to on-ground deployment, these sensors rely on detecting optical reflectance in two or more wavebands (for example red and near infrared). The derived spectral vegetation indices, such as the widely-used normalised difference vegetation index (NDVI) are subsequently calibrated to a measure of biomass, tiller number, leaf area index or the like. However research has demonstrated the accuracy of the conversion process can often be improved by including both spectral index and a corresponding measure of plant geometry such as height. This paper describes an active, optical sensor that integrates the modulated reflectance sensing with the ability to measure (range) the distance between the source and a target surface. Two ranging techniques are evaluated; one based on the inverse square law (ISQ) of reflected radiation from a target and another based on position-sensitive detector (PSD). Both ranging methods proved capable of reliably delineating target distances out to 4.0m from the source. Over this range, the PSD detector exhibited a distance-invariant uncertainty of ±2.6cm whilst the ISQ method exhibited an almost linear increase in error of ±25% of the measured distance.

On large water storage surfaces, the evaporation reducing ability of monolayers depends on the coverage which can be maintained. Automatic monolayer dispensing systems are cost effective; however require an automatic detection system to advise on the condition of coverage so that appropriate dosing can be used. In this work, existing monolayer detection methods and novel techniques were tested for reliability, robustness and potential for automation when applied on water storages. The main existing techniques; oil indicator, and wave damping, proved to be fairly limited in the range of conditions for which they can be successfully used. Surface tension, wave damping, absorption and radiation of electromagnetic radiation, contact temperature measurements at a depth, remote surface IR temperature measurements and the effects of wind were explored to determine a reliable indicator of monolayer coverage. In this work measurement of temperature, either with shallow depth thermocouples or surface IR thermometer has shown to be the most reliable indication of the difference in evaporation rate which occurs with monolayer coverage. Additionally, these temperature changes are augmented by the application of artificial wind, and with measurements taking place in a confined, small volume of water. Using these findings, a floating wind assisted surface probe (WASP) was developed which can test the condition of coverage of the surface. Small scale tests indicate that by measuring the temperature changes, using a either contact or IR sensors the presence or absence of coverage can be deduced for a range of humidity conditions. The characteristics of monolayers on large surfaces, are also investigated, with explanations of other effects monolayers have on storages, such as changes to local wind structure, viscous impairment of convection currents and alterations to wind induced drift velocity. Understanding how monolayers behave on a storage surface may improve coverage with correct positioning of dispensers and detectors, exploiting the spreading behaviour of wind while ameliorating the destructive effects.

Retardation of evaporation by monomolecular films by a 'barrier model' does not explain the effect of air velocity on relative evaporation rates in the presence and absence of such films. An alternative mechanism for retardation of evaporation attributes reduced evaporation to a reduction of surface roughness, which in turn increases the effective vapour pressure of water above the surface. Evaporation suppression effectiveness under field conditions should be predictable from measurements of the surface dilational modulus of mono layers and research directed to optimising this mechanism should be more fruitful than research aimed at optimising a monolayer to provide an impermeable barrier.

Actual evapotranspiration (ETc) is one of the important parameters that determines the daily and seasonal water requirement by the crop community. It varies with numerous factors including weather, soil moisture availability and other crop related factors such as growing stage, fraction of field coverage and crop vigour. In this study we investigated the relationship between normalized difference vegetation index (NDVI) that is closely related to photosynthetically-active biomass (PAB) and the evapotranspiration of pasture at different soil moisture condition. A portable enclosed chamber was used to measure ETc of a target pasture canopy and consequently the NDVI with a hand held active optical sensor. The portable chamber was calibrated in the laboratory and produced a calibration factor of C=1.02. Field experiments were conducted on the UNE SMART Farm in Tall Fescue pastures (Festuca arundinacea var. Dovey). Under limiting soil moisture condition the relationship between NDVI and ETc showed a negative correlation (R2=0.73) whereas a strong and positive correlation (R2=0.82) were observed in a non-limiting soil moisture condition.