title: Evaluating the mineral nutrient status of fresh pasture herbage using laser-induced breakdown spectroscopy

authors: Seelye, M.

abstract: Comprehensive determination of the mineral nutrient status of pasture or horticultural crops currently requires leaf or herbage samples to be harvested and taken to a laboratory for analysis, which is both labour-intensive and time-consuming. This study examined the potential of laser-induced breakdown spectroscopy (LIBS) to provide immediate, in-field assessment of the mineral nutrient status of standing plants. Success would offer the prospects of spatially and temporally improved knowledge of plant status and of real-time remediation of nutrient deficiency. The mineral nutrient status of fresh pasture herbage has been evaluated using an Applied Photonics Ltd？ LIBS-6 system, comprising a Qswitched Nd:YAG laser, a SpectroModule-6 spectrometer (covering wavelengths in the range ~185 – 1064 nm) and an ICE 450 water-cooled Laser power supply. LIBS spectra obtained from the fresh pasture samples were collected with the aim of determining the nutrient status of the herbage. An enclosed Modular Sample Chamber housed the Qswitched Nd:YAG laser, generating energy in the near infrared region at λ = 1064nm. The laser power was set to 100mW per pulse. Samples of approximately 50g of fresh ryegrass and ryegrass/clover mixed pasture were loaded into a sample holder which allowed a flat ‗carpet‘ of individual leaves to be presented at a relatively uniform distance from the laser. The optimum vertical distance between sample and laser was determined by maximising spectra amplitudes. Automated control of the translation stage supporting the sample holder was used to ensure each shot of the laser was acquired from a fresh location. Spectrum sets comprising both 100 individual spectra and 100 shot accumulated spectra were obtained from each sample under both air and under the inert gas, argon. Following the spectral analysis of the fresh pasture, each sample was sent to a commercial laboratory for standard nutrient analysis, providing elementary composition on the most common plant elements (N, P, K, S, Ca, Mg, Na, Fe, Mn, Zn, Cu and B). Once standard nutrient analysis was completed a second set of spectra was taken from tablets formed from compressed dried ground powder remaining after laboratory analysis. To date, initial results from simple chemometric analysis have shown limited success in predicting the nutrient content of fresh pasture with slightly improved results in estimating tablet composition. While initial analyses have concentrated on trends and correlations between actual spectra and laboratory analysis, known emission spectra, have for the meantime, been ignored. Further in-depth analysis using more robust chemometric analysis, utilizing known emission spectra and adjusting for variations in plasma intensity are currently underway and are expected to improve the accuracy of composition measurement.

text: Evaluating the mineral nutrient status of fresh pasture herbage using laser-induced breakdown spectroscopy Comprehensive determination of the mineral nutrient status of pasture or horticultural crops currently requires leaf or herbage samples to be harvested and taken to a laboratory for analysis, which is both labour-intensive and time-consuming. This study examined the potential of laser-induced breakdown spectroscopy (LIBS) to provide immediate, in-field assessment of the mineral nutrient status of standing plants. Success would offer the prospects of spatially and temporally improved knowledge of plant status and of real-time remediation of nutrient deficiency. The mineral nutrient status of fresh pasture herbage has been evaluated using an Applied Photonics Ltd？ LIBS-6 system, comprising a Qswitched Nd:YAG laser, a SpectroModule-6 spectrometer (covering wavelengths in the range ~185 – 1064 nm) and an ICE 450 water-cooled Laser power supply. LIBS spectra obtained from the fresh pasture samples were collected with the aim of determining the nutrient status of the herbage. An enclosed Modular Sample Chamber housed the Qswitched Nd:YAG laser, generating energy in the near infrared region at λ = 1064nm. The laser power was set to 100mW per pulse. Samples of approximately 50g of fresh ryegrass and ryegrass/clover mixed pasture were loaded into a sample holder which allowed a flat ‗carpet‘ of individual leaves to be presented at a relatively uniform distance from the laser. The optimum vertical distance between sample and laser was determined by maximising spectra amplitudes. Automated control of the translation stage supporting the sample holder was used to ensure each shot of the laser was acquired from a fresh location. Spectrum sets comprising both 100 individual spectra and 100 shot accumulated spectra were obtained from each sample under both air and under the inert gas, argon. Following the spectral analysis of the fresh pasture, each sample was sent to a commercial laboratory for standard nutrient analysis, providing elementary composition on the most common plant elements (N, P, K, S, Ca, Mg, Na, Fe, Mn, Zn, Cu and B). Once standard nutrient analysis was completed a second set of spectra was taken from tablets formed from compressed dried ground powder remaining after laboratory analysis. To date, initial results from simple chemometric analysis have shown limited success in predicting the nutrient content of fresh pasture with slightly improved results in estimating tablet composition. While initial analyses have concentrated on trends and correlations between actual spectra and laboratory analysis, known emission spectra, have for the meantime, been ignored. Further in-depth analysis using more robust chemometric analysis, utilizing known emission spectra and adjusting for variations in plasma intensity are currently underway and are expected to improve the accuracy of composition measurement.

year: 2014

title: Analysis of the SoftKinetic DepthSense for Range Imaging

authors: Cree, Michael J.

subjects: range imaging

abstract: We analyse the SoftKinetic DepthSense 325 range imaging camera for precision and accuracy in ranging out to 3 m. Flat planar targets (one a grey board, the other made from retroreflective material) are imaged at a variety of distances. Straight-forward image processing is used to identify the target and calculate the range and the root mean square variation in ranging to the target. It is found that inaccuracies in ranging of up to 2 cm occur to the grey board when imaging over 0 m to 1.5 m and the precision in ranging degrades from just below 1 cm at 0 m to almost 10 cm at 1.5 m. Similar inaccuracies occur with the retroreflective target but the precision is always under 1 cm even out to 3 m due to the strong signal return received from the target.

text: Analysis of the SoftKinetic DepthSense for Range Imaging We analyse the SoftKinetic DepthSense 325 range imaging camera for precision and accuracy in ranging out to 3 m. Flat planar targets (one a grey board, the other made from retroreflective material) are imaged at a variety of distances. Straight-forward image processing is used to identify the target and calculate the range and the root mean square variation in ranging to the target. It is found that inaccuracies in ranging of up to 2 cm occur to the grey board when imaging over 0 m to 1.5 m and the precision in ranging degrades from just below 1 cm at 0 m to almost 10 cm at 1.5 m. Similar inaccuracies occur with the retroreflective target but the precision is always under 1 cm even out to 3 m due to the strong signal return received from the target.

year: 2013

title: Dual cultural identity and tangihanga: Conflict, resolution and unexpected outcomes

authors: Edge, Kiri

subjects: bereavement

abstract: New Zealand has a significant number of dual-cultural whānau (families) which incorporate the identities of both Pākehā (New Zealander of European descent) and Māori (indigenous peoples of New Zealand). Little attention has been paid to the bereavement processes that will inevitably impact upon the lives of these whānau/families. As part of the Tangihanga Research Programme based at The University of Waikato, a directed study was conducted with a participant whose family/whānau included two life ways: Māori and Pākehā. An open-ended narrative approach was used to explore the participant’s bereavement after the death of his beloved wife. Two central themes emerged within the narrative, which related to conflict and eventual resolution. Decision-making processes and language played significant roles in the conflict experienced by the participant. Communication and compromise helped to resolve these conflicts. Unexpected outcomes included new understandings and strengthened connections between the participant and his wife’s marae.

text: Dual cultural identity and tangihanga: Conflict, resolution and unexpected outcomes New Zealand has a significant number of dual-cultural whānau (families) which incorporate the identities of both Pākehā (New Zealander of European descent) and Māori (indigenous peoples of New Zealand). Little attention has been paid to the bereavement processes that will inevitably impact upon the lives of these whānau/families. As part of the Tangihanga Research Programme based at The University of Waikato, a directed study was conducted with a participant whose family/whānau included two life ways: Māori and Pākehā. An open-ended narrative approach was used to explore the participant’s bereavement after the death of his beloved wife. Two central themes emerged within the narrative, which related to conflict and eventual resolution. Decision-making processes and language played significant roles in the conflict experienced by the participant. Communication and compromise helped to resolve these conflicts. Unexpected outcomes included new understandings and strengthened connections between the participant and his wife’s marae.

year: 2010