Browsing by Author "Kenyon P"

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    A Field Evaluation of the LuciTrap and the Western Australian Trap with Three Different Baits Types for Monitoring Lucilia cuprina and Lucilia sericata in New Zealand.
    (15/09/2021) Brett P; Lawrence K; Kenyon P; Gedye K; Pomroy W
    Flytraps can be used on farms to monitor the populations of primary strike flies (Lucilia cuprina and Lucilia sericata) and, hence, offer a view regarding the incidence of flystrike on sheep. This study aimed to contrast the specificity and effectiveness of the LuciTrap with its combination of three chemical lures (Lucilures) and the Western Australian Trap with three bait types (LuciLure, Sheep liver with 30% sodium sulphide and squid). A mean model and rate model were fitted to the data. The mean model showed no difference (p > 0.05) in the mean weekly catch for L. cuprina between the Western Australian Trap with LuciLures and the Western Australian Trap baited with sheep liver with 30% sodium sulphide (p < 0.05). Whereas, for L. sericata, no difference (p > 0.05) was found between the Western Australian Trap with LuciLures, the Western Australian Trap baited with sheep liver with 30% sodium sulphide and the LuciTrap. The rate model illustrated that the Western Australian Trap with sheep liver with 30% sodium sulphide and LuciTrap did not differ (p > 0.05) for L. cuprina and L. sericata. Combined, these results indicate that New Zealand farmers can use either the LuciTrap or the Western Australian Trap with sheep liver with 30% sodium sulphide to monitor these target species.
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    Drainage, salt-leaching impacts, and the growth of Salicornia bigelovii irrigated with different saline waters
    (Elsevier B.V., 2023-09-14) Al-Tamimi M; Green S; Dahr WA; Al-Muaini A; Lyra D; Ammar K; Dawoud M; Kenyon P; Kemp P; Kennedy L; McLachlan A; Clothier B
    We sought to assess the impact on groundwater of using three types of saline waters to irrigate the halophyte Salicornia bigelovii Torrey in the hyper-arid United Arab Emirates. These were groundwater (GW) at 25 dS m−1, reverse-osmosis brine (RO) from a desalination unit at 40 dS m−1, and the aquabrine (AQ) effluent from land-based aquaculture in tanks filled with RO brine, also at 40 dS m−1. The three waters were applied through bubblers (BUB), pressure-compensated drippers (PCD), or subsurface irrigation tape (SUB). The yields of Salicornia fresh tips, harvest forage, and seed were greatest for AQ applied through BUB, being 650 g m−2. We found 2–2.6 kg m−2 for dry forage yield with AQ through BUB, compared with 1–2.3 kg m−2 for the other waters and emitter devices. The highest water productivities WPI (kg m−3) across all three crop-outputs came from Aquabrine applied by pressure-compensated drippers. We assessed the gross economic water productivity (GEWPI, $ m−3) based solely on gross revenue. The GEWPI was highest for AQ applied through PCD and SUB, namely 5.8–6.2 $ m−3. The value derives primarily from fresh tips. The GEWPl was well above the cost of desalination at $1.5 m−3. We measured drainage and leaching using fluxmeters. The greatest salt load to groundwater came from BUB, being 135–195 kg m−2. For PCD and SUB it was between 14 and 36 kg m−2. Mass-balance calculations of these salt loadings can predict the impact on the saline quality of aquifers. We used an exemplar loading of 75 kg m−2, and results in an annual salinity rise of 2.6 dS m−1 y−1 for an aquifer of saturated depth of 100 m. This significant rate of rise in the salinity of groundwater would represent a continuing deterioration in the utility of groundwater.
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    Effects of alternative forages on nitrate leaching under intensive sheep grazing
    (NZ Society of Animal Production, 2021) Maheswaran S; Cranston LM; Millner J; Horne D; Hanly J; Kenyon P; Kemp P
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    Measurement and heuristic modelling of nitrogen and salt dynamics under Salicornia growing in a hyper-arid region and irrigated with groundwaters of differing nutrient and Salt loadings
    (Springer Nature, 2024-10-03) Al-Tamimi M; Green S; Dahr WA; Al-Muaini A; Lyra D; Ammar K; Dawoud M; Kenyon P; Kemp P; Kennedy L; McLachlan A; Clothier B
    New data highlight the economic value of using nitrogen-rich saline waters, either from groundwater or reject brines from desalination units, to irrigate the halophytic crop Salicornia bigelovii for food, fodder, and fuel in a hyper-arid environment. The greatest benefit was achieved using pressure-compensated drippers. Field measurements of drainage and leaching under the crop showed that all of the salt and nitrogen from the groundwater was returned back to the aquifer as leachate. A simple, heuristic model of groundwater quantity and quality was developed to infer the environmental impacts of irrigating crops with saline and high-nitrate groundwater in a hyper-arid environment. The rise in solute concentration in groundwater is hyperbolic. The parameters needed for this simple model are the fraction of the land that is irrigated, the initial depth of the saturated thickness, the saturated water content, and the annual rate of evapotranspiration. An indicator of the time-rise is the number of years to double the solute concentration. This is ӨAho /2 ETC, where ӨA is the aquifer’s saturated water content, ho is the original thickness of the saturated layer, and ETc is the annual rate of crop evapotranspiration. The general model is simple and straightforward to parameterise to predict the evapoconcentration of groundwater salinity.
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    Reproductive Performance of Triplet-Bearing Ewes on Commercial Farms and Research Priorities Identified by Sheep Producers to Improve the Survival of Triplet-Bearing Ewes and Their Lambs
    (MDPI (Basel, Switzerland), 2023-04-05) Thompson AN; Allington T; Blumer S; Cameron J; Kearney G; Kubeil L; Lockwood A; Trompf J; Winslow E; Kenyon P; Duarte MS; Gionbell MP
    Consultation with sheep producers was used to quantify the mortality of triplet-bearing ewes and their lambs, identify management practices adopted by producers to reduce these losses and prioritise future research needs to improve the survival of triplet-bearing ewes and their lambs. Surveys were completed by 64 producers across Australia who identified and separated triplet-bearing ewes from twin-bearing ewes in 2017 and/or 2018. On average, 5.9% of all ewes mated were identified as carrying triplets (6.6% of non-Merino ewes and 2.9% of Merino ewes). The average mortality of triplet-bearing ewes was 6.4%, and ewe mortality did not differ significantly between ewe breeds. The average survival of triplet-born lambs was 59%, and survival was significantly higher for lambs from non-Merino compared to Merino ewes (60.1 vs. 52.9%, p < 0.05). The key strategies adopted to reduce the mortality of triplet-bearing ewes and their lambs included management of condition score, feed-on-offer, mob size at lambing and use of shelter. There were no differences (p > 0.05) in the average mortality of triplet-bearing ewes or their lambs between producers that prioritised the adoption of certain management practices. However, significant variation existed between producers in their targets at lambing for ewe condition score (2.8 to 3.5), mob size (10 to 150 ewes) and feed-on-offer (800 to 2500 kg dry matter/ha). Overwhelmingly, the highest priorities for further research identified by producers from surveys, workshops and a webinar were ewe condition score, mob size, feed-on-offer at lambing and mineral supplementation. This study informs benchmarks for mortality of triplet-bearing ewes and their lambs under extensive grazing conditions in Australia, and the priorities for future research to reduce these losses.
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    Salt dynamics, leaching requirements, and leaching fractions during irrigation of a halophyte with different saline waters
    (CSIRO Publishing, 2023-12-18) Al-Tamimi M; Green S; Dahr WA; Al-Muaini A; Lyra D; Ammar K; Dawoud M; Kenyon P; Kemp P; Kennedy L; Clothier B; McGrath G
    Context More than 830 million ha of soils are salt affected, representing around 9% of the world’s land surface. Groundwater high in salt already covers some 16% of the land area. Saline water can be used effectively for irrigation by salt leaching to despatch the accumulated salts, but this can pose a risk of salinisation of groundwater. It is important that the efficacy of salt leaching is confirmed, and the impacts of salt loading below the rootzone can be assessed. Aims We examine the efficiency and impact of salt leaching to remove salt from the rootzone. Methods Our soil, a Typic Torripsamment, is the dominant soil across the Arabian Peninsula. We carried out detailed laboratory experiments of salt leaching dynamics via salt breakthrough curves, analytical modelling, and through the field monitoring of impacts. Key results Analytical solutions well predicted the salt breakthrough curves from repacked soil columns in the laboratory and we were able to confirm that all of the soil’s water was actively involved in transport, and that salt behaved as an inert tracer. The breakthrough curves were well predicted using a small solute dispersivity, so piston displacement was found to be a good assumption. Salt was easily flushed from the columns. To back this up in the field, soil sampling was carried out down to 1 m across 36 profiles after the harvest of a halophytic crop irrigated with saline water. Salt storage was only 1.8 kg m−2, even though 80 kg m−2 had been applied. This is a positive result for managing irrigation. Conclusions Salt leaching can maintain equable salinity in the rootzone. However, this leaching carried salt back to groundwater at 2–3 times the concentration of the applied water. We confirmed that the amount of salt leaching back to groundwater can be significant. Implications This salt dilemma will require careful management to achieve crop yields and protect the environment.
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    The Behaviour of Sheep around a Natural Waterway and Impact on Water Quality during Winter in New Zealand
    (MDPI (Basel, Switzerland), 2023-04-25) Bunyaga A; Corner-Thomas R; Draganova I; Kenyon P; Burkitt L; Giuseppe P
    Access of livestock, such as cattle, to waterways has been shown to be a cause of poor water quality due to pugging damage and excretion entering the water. In New Zealand, regulations require that cattle, deer, and pigs are excluded from accessing waterways, but there are no such requirements for sheep. The current study utilised 24 h video cameras, global positioning system units, and triaxial accelerometers to observe the interaction of Romney ewes (n = 40) with a natural waterway. Ewes were either restricted (week 1) or given access to a reticulated water trough (week 2). Proximity data showed that ewes spent more time within 3 m of the waterway when the trough was unrestricted than when restricted (14.1 ± 5.7 and 10.8 ± 5.1 min/ewe/day, respectively; p < 0.05). Ewes travelled shorter distances on the steeper areas of paddock than flatter areas. Similarly, ewes showed a spatial preference for the flat and low sloped areas of the paddock. Concentrations of suspended sediment and total phosphorus were higher during access to a reticulated water trough which coincided with the week with more rainy days. Phosphorus and E. coli concentrations in the stream water samples were the above recommended Australian and New Zealand Environment and Conservation Council water quality guidelines, especially after rainy days, but did not appear to be directly related to sheep activity. Overall, the results suggest that during winter, ewes interacted very little with the waterway and were thus unlikely to influence the levels of nutrient and pathogens in the waterway.
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    The Effect of Age of Dam and Birth Rank on the Reproductive Performance of Ewes as One- and Two-Year-Olds.
    (10/03/2021) Pettigrew E; Hickson R; Morris S; Kenyon P; Corner-Thomas R; Haslin E; Blair H
    Currently, 30-43% of New Zealand sheep farmers breed their ewe lambs, but few retain the offspring as replacements for their flock. No difference in lamb production as a yearling among singletons and twins born to ewe lambs and twins born to mature ewes has been reported, provided the ewe lambs had reached the 60-65% of their likely mature weight prior to breeding at seven to eight months of age. The aim of this experiment was to determine the lamb production from singletons and twins born to ewe lambs and twins born to mature ewes during their first two years of lambing. The experiment included 8-month-old ewes born as twins to mature ewes (M2, n = 135), singletons born to ewe lambs (L1, n = 135), and twins born to ewe lambs (L2, n = 88), bred during the same period to the same rams, over two years. The efficiency of lamb production (total litter weight at weaning divided by the pre-breeding weight of the ewe, for all ewes presented for breeding) after two years of production was not significantly different (p > 0.05) among the groups (0.40 ± 0.02, 0.39 ± 0.02, and 0.39 ± 0.03, for M2, L1, and L2, respectively).
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    The effect of defoliation frequency and height on plantain and chicory-based swards
    (2021) Cranston L; Kenyon P; Morris S; Lopez-Villalobos N; Kemp P