Browsing by Author "Hedley M"

Now showing 1 - 4 of 4
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    Dry matter yield, nutritive value and tiller density of tall fescue and perennial ryegrass swards under grazing
    (New Zealand Grassland Association, 31/12/2016) Hendricks S; Donaghy D; Matthew C; Bretherton M; Sneddon N; Cosgrove G; Christensen C; Kaufononga S; Howes J; Osborne M; Taylor P; Hedley M
    Alternative pasture species with the potential to supply quality forage during summer feed shortages, such as tall fescue (TF), are of interest to dairy farmers. A paddock scale study was undertaken to compare performance of TF managed on a shorter rotation similar to perennial ryegrass (RG) (TF-RG) with TF managed on a longer rotation more consistent with its morphology of 4 live leaves/tiller (TF-TF), and with RG (RG-RG). Accumulated dry matter (DM) yields were similar for the three treatments. Patch grazing was observed during the first spring, with more long patches in TFTF than in either TF-RG or RG-RG. Sown-species leaf area index (LAI) was greater in TF-TF compared with TF-RG and RG-RG (2.25, 1.56 and 0.90, respectively; P<0.05). The proportions of grass weeds were higher in the TF-RG (P<0.05) compared with TF-TF and RG-RG treatments (302, 207 and 164 g/kg DM, respectively). A soil fertility gradient with distance along the paddock away from the farm race was recorded, with Olsen P declining at 0.130 mg/kg/m with distance from the farm race. Tiller density, LAI and yield of sown species and total yield sampled were all positively correlated with Olsen P. Overall, this study highlights the importance of managing TF pastures according to its specific growth habits. However, attaining longer grazing rotations under field conditions whilst trying to maintain cow intakes, is likely to continue to prove elusive.
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    Influence of Soil Moisture Status on Soil Cadmium Phytoavailability and Accumulation in Plantain (Plantar lanceolata)
    (MDPI (Basel, Switzerland), 2018-03) Stafford A; Jeyakumar P; Hedley M; Anderson C
    The effect of fluctuating soil moisture cycles on soil cadmium (Cd) phytoavailability was investigated in a pot trial with two contrasting soils (Kereone (Allophanic), total Cd 0.79 mg kg−1; and Topehaehae (Gley), total Cd 0.61 mg kg−1) that were either sown with plantain (Plantago lanceolata) or left unseeded. Varying soil moisture contents were established using contrasting irrigation regimes: “flooded” (3 days flooded and then 11 days drained); or “non-flooded” (irrigation to 70% of potted field capacity every 7 days). Overall, there was no significant difference in mean 0.05 M CaCl2 soil extractable Cd concentrations or plant tissue Cd concentrations between flooded and non-flooded irrigation. However, there was a consistent trend for an increase in soil extractable Cd concentrations following irrigation, regardless of the irrigation regime. Mean soil extractable Cd and plant tissue Cd concentrations were significantly greater (approximately 325% and 183%, respectively) for the Topehaehae soil than the Kereone soil, despite the lower soil total Cd concentration of the Topehaehae soil. These results indicate that Cd solubility is sensitive to increases in soil moisture following periods of soil drainage, but insensitive to short-term periods of soil saturation. Plant tissue Cd concentrations in Cd-sensitive forage crops such as plantain are likely to be greater following large rainfall events over summer and autumn. This has the potential to increase animal dietary Cd exposure and rate of liver/kidney Cd accumulation.
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    Nitrogen Excretion by Dairy Cows Grazing Plantain (Plantago lanceolata) Based Pastures during the Lactating Season
    (MDPI (Basel, Switzerland), 2022-02-14) Navarrete S; Rodriguez M; Horne D; Hanly J; Hedley M; Kemp P
    The use of plantain pasture in dairy systems can potentially reduce nitrogen (N) leaching losses via the lower N concentration in the urine (UNc) of cows. Reducing the urinary N load while cows graze pastures can reduce the risk of N leaching losses from urine patches. Research needs to demonstrate that these environmental benefits are not at the expense of milk production and farm profit. Three groups of 20 cows grazed in the following three pasture treatments: (i) plantain, (ii) plantain-clover mix (plantain, red [Trifolium pratense] and white clover), or (iii) ryegrass-white clover (wc) pastures, from spring to autumn for two years. Each year, pasture intake, diet quality, milk production and animal N (milk and urine) excretion were evaluated in spring, summer, and autumn. The cows grazing the plantain and plantain-clover mix pastures produced similar milk solids as cows grazing ryegrass-wc pasture but reduced their UNc during summer and autumn, when compared to those grazing the plantain-clover mix and ryegrass-wc pastures. Plantain reduced urinary N loads onto pastures by a greater number of urine patches with lower urinary N loading rates. The results demonstrate that plantain pastures do not diminish milk solids production from cows, and the lower UNc from summer to autumn could reduce N being lost to the environment.
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    Quantification of denitrification rate in shallow groundwater using the single-well, push-pull test technique
    (Elsevier BV, Amsterdam, 2025-02) Rivas A; Singh R; Horne D; Roygard J; Matthews A; Hedley M
    Denitrification has been identified as a significant nitrate attenuation process in groundwater systems. Hence, accurate quantification of denitrification rates is consequently important for the better understanding and assessment of nitrate contamination of groundwater systems. There are, however, few studies that have investigated quantification of shallow groundwater denitrification rates using different analytical approaches or assuming different kinetic reaction models. In this study, we assessed different analytical approaches (reactant versus product) and kinetic reaction (zero-order and first-order) models analysing observations from a single-well, push-pull tests to quantify denitrification rates in shallow groundwater at two sites in the Manawatū River catchment, Lower North Island of New Zealand. Shallow groundwater denitrification rates analysed using the measurements of denitrification reactant (nitrate reduction) and zero-order kinetic models were quantified at 0.42-1.07 mg N L-1 h-1 and 0.05-0.12 mg N L-1 h-1 at the Palmerston North (PNR) and Woodville (WDV) sites, respectively. However, using first-order kinetic models, the denitrification rates were quantified at 0.03-0.09 h-1 and 0.002-0.012 h-1 at the PNR and WDV sites, respectively. These denitrification rates based on the measurements of denitrification reactant (nitrate reduction) were quantified significantly higher (6 to 60 times) than the rates estimated using the measurements of denitrification product (nitrous oxide production). However, the denitrification rate quantified based on the nitrate reduction may provide representative value of denitrification characteristics of shallow groundwater systems. This is more so when lacking practical methods to quantify all nitrogen species (i.e., total N, organic N, nitrite, nitrate, ammoniacal N, nitrous oxide, nitric oxide, and nitrogen gas) in a push-pull test. While estimates of denitrification rates also differed depending on the kinetic model used, both a zero-order and a first-order model appear to be valid to analyse and estimate denitrification rate from push-pull tests. However, a discrepancy in estimates of denitrification rates using either reactant or product and using zero- or first-order kinetics models may have implications in assessment of nitrate transport and transformation in groundwater systems. This necessitates further research and analysis for appropriate measurements and representation of spatial and temporal variability in denitrification characteristics of the shallow groundwater system.