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    Impact of plantain (Plantago lanceolata) based pasture on milk production of dairy cows and nitrate leaching from pastoral systems : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Animal Science at Massey University, Manawatu, New Zealand
    (Massey University, 2023) Nguyen, Truong Thi
    In temperate dairy systems, the traditional perennial ryegrass (Lolium perenne)-white clover (Trifolium repens) (RGWC) pasture often has excessive nitrogen (N) content relative to the N requirement of animals, posing a risk of nitrate (NO₃⁻) leaching into the environment. Recently, incorporating plantain (Plantago lanceolata) with RGWC pasture has been increasingly used to improve economic and environmental benefits for dairy farms. However, the impact of plantain incorporation on farm productivity and NO₃⁻ leaching at the farm level has not been fully understood. The objectives of this thesis were to quantify the effect of incorporating increasing rates of plantain in grazing swards on pasture production, milk yield and composition of dairy cows, and NO₃⁻ leaching from pastoral dairy systems. To address the objectives of the thesis, a grazing trial was implemented at a research dairy farm between September 2019 and December 2021. Pasture treatments were RGWC (perennial ryegrass cv. ONE⁵⁰ and white clover cv. Tribute), RGWC + low plantain (cv. Agritonic) rate (PLL), RGWC + medium plantain rate (PLM), and RGWC + high plantain rate (PLH). Pastures were established with 20 experimental plots and four adaptation areas in April 2019 and were rotationally grazed by dairy cows over 22 grazing events during the experimental period. In each grazing, 60 or 80 cows were assigned to graze for 6 days in their adaptation areas and 1.5–3 days in the experimental plots. The experimental cows were managed under a typical practice, milking twice daily, offering grazing pasture and approximately 25% supplementary dietary feeds. Measurements were conducted to quantify the yield, botanical composition and nutritive value of the pasture, milk yield, milk composition and N excretion of dairy cows, and NO₃⁻ leaching from the pastoral system. The results showed that, over the first two lactation years after sowing, plantain-based pastures have a similar dry matter yield and contain higher water content, non-structural carbohydrates, minerals, and bioactive compounds than the RGWC pasture. The average plantain proportion in the swards over the first two years after sowing was 32% in PLL, 44% in PLM, and 48% in PLH, which increased in the first 15 months and declined to 20% in PLL and 30% in PLM and PLH at day 705 after sowing. Cows grazing the plantain-based pastures had a similar milk yield, composition and yield of solids, protein, fat, and lactose as those grazing the RGWC pasture. Furthermore, when 25% plantain was included in the diet of cows in late lactation, it resulted in a 44% increase in urine volume and a 29% reduction in urine N concentration by 29%. By incorporating an average of 30% and 50% plantain with RGWC pasture, NO₃⁻ leaching was reduced by 32 and 52%, respectively, over two drainage years after establishment, with a greater reduction in the first year than in the second year. Among sowing rates, PLM resulted in the greatest decrease in NO₃⁻ leaching, with 64% in the first year and 41% in the second year. The decreased NO₃⁻ leaching was associated with increased plantain content, enhanced herbage N uptake, reduced UN excretion of dairy cows and a lower N load in urine patches. In conclusion, in a typical practice, as in the present study, incorporating 30–50% plantain with RGWC pasture decreases NO₃⁻ leaching from pastoral systems without adversely impacting farm productivity for at least two years from sowing. However, the reduction of plantain content in the second year suggests further measurements to determine the effectiveness of plantain-based pasture in the longer term. In the conditions and time scale of the present study, the medium plantain rate treatment (PLM) is suggested to achieve a high effectiveness of plantain incorporation in reducing NO₃⁻ leaching.
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    Manipulating soil bioavailable copper as an innovative nitrate leaching mitigating strategy in New Zealand pastoral soils : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy (PhD) in Soil Science, School of Agriculture and Environment, College of Sciences, Massey University, Palmerston North, New Zealand
    (Massey University, 2023) Matse, Dumsane Themba
    Urine patches are the primary sources of nitrate (NO₃⁻ -N) leaching from pastoral dairy farms. Since NO₃⁻ -N is the product of nitrification, a clear understanding of the nitrification process is a vital step toward the development of effective and efficient mitigation approaches. The first step of ammonia (NH₄⁺) oxidation to hydroxylamine (NH₂OH) is catalyzed by the ammonia monooxygenase enzyme (AMO), and copper (Cu) is a co-factor in the activity of the AMO enzyme. Therefore, manipulating Cu bioavailability through the application of Cu-complexing organic compounds such as calcium lignosulphonate (LS) and co-poly acrylic-maleic acid (PA-MA) to soil could influence AMO activity and consequently limit the nitrification rate in soil. There are no published studies that have examined the effect of bioavailable Cu concentration changes on nitrification rate, ammonia-oxidizing bacteria (AOB) and archaea (AOA), and NO₃⁻ -N leaching. The overall aim of this thesis is to determine the significance of bioavailable Cu in the nitrification process in the context of developing novel Cu-complexing organic compounds to inhibit nitrification rate in pastoral soils. A soil incubation study was conducted to characterize the relationship between changes in soil bioavailable Cu concentration and nitrification rate. This study was conducted using three pastoral soils (Pumice, Pallic, and Recent soils) spiked with five Cu levels (0.1, 0.3, 0.5, 1, and 3 mg kg⁻¹). Treatments of Cu-complexing compounds were separately applied to each Cu level. The treatments were urea applied at 300 mg N kg⁻¹, urea + LS at 120 mg kg⁻¹, and urea + PA-MA at 10 mg kg⁻¹. Results show that increasing the added Cu concentration from 0.1 to 3 mg kg⁻¹ increased nitrification rate by 35, 22, and 33% in the Pumice, Pallic, and Recent soils, respectively. Application of LS and PA-MA significantly (P ˂ 0.05) decreased nitrification rate with the mean reduction being 59 and 56%, 32 and 26%, and 39 and 38% in the Pumice, Pallic, and Recent soils, respectively at Day 8 relative to the urea-only treatment. To further extend knowledge of the relationship between bioavailable Cu and the key nitrifying microorganisms in soils, a greenhouse-based pot trial using three soils (Pumice, Pallic, and Recent soils) planted with ryegrass and treated with synthetic urine applied at 300 kg N ha⁻¹ and three levels of Cu (0, 1, 10, 100 mg added Cu kg⁻¹) was established. Results show that AOB amoA gene abundance increased as a function of increasing added Cu from 1 to 10 mg kg⁻¹ but was inhibited at 100 mg added Cu kg⁻¹ in both Pallic and Recent soils. The effect of bioavailable Cu was not apparent in the Pumice soil. The increase in AOB amoA gene abundance positively correlated with nitrification rate in both the Pallic (r = 0.982, P < 0.01) and Recent soil (r = 0.943, P < 0.01) but not in the Pumice soil. There was no effect of increasing Cu concentration on AOA amoA gene abundance in all three soils. Results from both incubation and greenhouse pot trials provide strong evidence that Cu is an important trace element in the nitrification process and reducing Cu can reduce nitrification in soil. However, in order to definitively quantify this treatment effect, further field studies were necessary. Therefore, a field lysimeter study was conducted using Pumice soil (Manawatu climate) and Pallic soil (Canterbury climate). The following treatments were investigated to reduce NO₃⁻ -N leaching during late-autumn application; urine only at 600 kg N ha⁻¹, urine + PA-MA at 10 kg ha⁻¹, urine + LS at 120 kg ha⁻¹, urine + a split-application of calcium lignosulphonate (2LS at same rate, initial and after a month of first application), and urine + ProGibb SG (GA at 80 g ha⁻¹) + LS (GA + LS). Another set of treatment applications, urine only, urine + GA only, and urine + GA + LS, were applied mid-winter to both soils. The GA was applied to improve the effectiveness of these organic compounds during climatic periods of poor plant growth. Results showed that there was no significant reduction in mineral N leaching associated with the late-autumn application of both PA-MA and LS for the Pumice or Pallic soils. However, the application of 2LS reduced mineral N leaching by 16 and 11% in Pumice and Pallic soils, respectively, relative to urine-only. The late-autumn inclusion of GA increased the effectiveness of LS in both soils. This was confirmed by a significant reduction of mineral N leaching by 35% from both Pumice and Pallic soils. Mid-winter application of GA + LS significantly reduced mineral N leaching only in the Pumice soil (by 20%) but not in the Pallic soil relative to urine-only. In both late-autumn and mid-winter treatments application of the different Cu-complexing treatments did not have negative effects on pasture dry matter yield in either Pumice or Pallic soils. In this lysimeter study, the mechanistic effect of PA-MA and LS on reducing bioavailable, nitrification rate and AOB/AOA amoA gene abundance was not investigated. A second field lysimeter experiment was established using the Recent soil in Manawatu to explore the mechanism of Cu manipulation through the application of LS and PA-MA on nitrification rate, AOB/AOA amoA gene abundance, and mineral N leaching. The effect of combining organic inhibitors with GA on reducing mineral N leaching was also investigated. This study evaluated the same treatments used in the first lysimeter study and applications were again conducted at two different seasonal periods (late-autumn and mid-winter). The results showed that the effect of PA-MA and 2LS on bioavailable Cu corresponded with a reduction in nitrification rate and AOB amoA gene abundance. The effect of PA-MA and 2LS was associated with reduced mineral N leaching by values of 16 and 30%, respectively, relative to urine-only. The reduction in mineral N leaching induced by PA-MA and 2LS increased N uptake by 25 and 7.8% and herbage DM yield by factors of 11 and 8%, respectively, relative to the urine-only. The LS treatment did not induce a significant change of either bioavailable Cu or nitrification rate which corresponded to no significant effect on mineral N leaching. The late-autumn combination of GA + LS reduced mineral N leaching by 19% relative to urine-only, but there was no significant difference in mineral N leaching observed for the mid-winter application relative to urine-only. The overall results of this research show that bioavailable Cu is a vital trace element in the nitrification process and for AOB functioning in soil. Therefore, reduction in bioavailable Cu through the application of Cu-complexing compounds can inhibit nitrification. In this doctoral study, the application of Cu-complexing compounds (LS and PA-MA) showed potential to inhibit nitrification rate and subsequently reduce mineral N leaching in pastoral systems, but their efficacy depends on soil characteristics. Future work is recommended to investigate the effect of LS and PA-MA application on nitrous oxide emissions. Further research is recommended to investigate the short and long terms effects of these treatments on non-target soil microbiota.
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    Nutrient leaching under intensive sheep grazing : a dissertation presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Animal Science at Massey University, Manawatu, New Zealand
    (Massey University, 2023) Maheswaran, Sarmini
    The use of some alternative forages may help sheep farmers to reduce nitrogen (N) leaching while increasing production. This thesis explores the effects of four forages (perennial ryegrass/white clover: RGWC; Italian ryegrass/white clover: IRWC; plantain/white clover: PWC; and a winter brassica) on sheep performance, urinary N excretion and N loss in drainage over two and a half years (Year 1: July to December 2019; Year 2: January to December 2020; Year 3: January to December 2021). This study was conducted on an artificially drained, fine textured Tokomaru silt loam soil at Massey University’s Keeble farm, near Palmerston North, Manawatu, New Zealand. The study design included four self-contained farmlets (each approximately 3.3 ha): three farmlets had 0.8 ha (24% of their grazing area) sown to include one of three alternative forages (IRWC or PWC or brassica), and the remaining 2.5 ha was sown in a perennial ryegrass/white clover sward. The entire area (100% of grazing area) of the fourth farmlet was sown in RGWC. Approximately 0.4 ha of each farmlet was located in a paddock where a series of 20 drainage plots (each 40 m by 20 m) were established to measure N leaching. Each of the alternative forages, and the RGWC, were sown on five of the drainage plots i.e., five replicates (combined area of 0.4 ha), which composed about one-half of the area of each alternative forage on each farmlet. The amount of N leached through a mole-pipe network on each drainage plot was also measured. Breeding ewe productivity including liveweight, condition score and lambing performance, as well as N excretion was also measured. In addition, forage growth and DM production were monitored along with chemical and botanical composition. The inclusion of alternative forages into the RGWC system did not affect animal performance. This was due, in part, to animal management. The N leached under various forages was, therefore, able to be compared without the confounding effects of differences in animal performance. The daily urinary N excretion per animal by sheep grazing PWC or brassica was lower (18 to 70%) than the daily urinary N excretion by sheep grazing RGWC or IRWC. It is likely that the diuretic effect of plantain and a lower N concentration in the brassica caused lower N concentrations in urine. Nitrate (NO₃⁻) leaching losses under RGWC, IRWC and PWC were very small in Years 1 and 2 (ranging from 0.4 to 0.8 kg N/ha). The poor persistence of IRWC and PWC at this site and the need to re-establish these forages on the plots resulted in greater NO₃⁻ leaching under these forages in Year 3, negating some of the advantages associated with these forages in Years 1 and 2. In contrast, NO₃⁻ leaching losses were greater under brassica forages (ranging from 0.4 to 6.4 kg N/ha) than under RGWC (ranging from 0.5 to 1.5 kg N/ha). Although sheep grazing brassica forages excreted less urinary N (on an individual animal basis), leaching losses under the brassica treatments were higher. In addition to the effect of cultivation, this increased leaching was likely because brassica plots were grazed for a more extended period during winter than other forages, and there was no crop (forage) cover until the spring resowing; therefore, the urinary N accumulated during winter grazing was displaced by subsequent drainage. With the assumption that the cropped area occupies a relatively small portion of the farm, grazing brassica is likely to result in a relatively small increase in whole farm NO₃⁻ leaching. Overall, NO₃⁻ leaching losses under sheep grazing forages were lower (ranging from 0.5 to 9.5 kg N/ha) than those reported under dairy cattle grazing forages, which suggests that sheep production may offer an alternative land use option for dairying areas where it is difficult to achieve the large reductions in NO₃⁻ leaching required to meet water quality objectives.
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    Comparison of maize silage and traditional forage crops in New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Plant Science at Massey University, Manawatū Campus, New Zealand
    (Massey University, 2022) Thant, Aung Myo
    Cattle wintering systems using crops including grazing kale, swede, and fodder beet crops in situ have resulted in soil and water quality deterioration. Nitrate leaching is the most common problem due to the high deposition of urine N driven by excess N intake. Alternative cropping systems offer a potential solution to reduce these environmental problems while maintaining or maximising productivity. We proposed maize silage as an alternative crop because it has high yield potential, flexible feeding requirements, compliments the nutritive value of pasture, and is potentially suitable for more regions in New Zealand in the future due to climate change. However, research needs to determine whether maize silage yield, feed quality and potential nitrate losses during production and utilisation means it is a viable alternative to in situ grazed forage crops in these areas. Field experiments were conducted at Massey University, Tokoroa and Kiwitea to determine forage yield and feed quality, management effects and site differences in 2018/19 and 2019/20. Crop yields and forage N content were utilised to simulate urine N loads from the feeding of these forage crops. The excreted N loads were analysed in APSIM (Agricultural Production Systems sIMulator) to predict nitrate leaching losses. Maize produced significantly higher yields compared with the winter forage crops at all Massey University trials while producing competitive yields at Tokoroa and Kiwitea. Yields ranged from 10,940 to 30,417 kg DM/ha for maize whilst wide and lower yield ranges were observed for the winter forage crops (4,579 to 22,928 kg DM/ha). Irrigation increased yields of forage crops by 29-63%. Similarly, nitrogen fertiliser increased yield by 30%, on average. The faster canopy development of maize has the advantage of intercepting more radiation in summer and suppressing weeds, contributing to greater growth and yield despite a shorter crop season. All forage crops produced forage with good metabolisable energy content (MJ/kg DM); higher values in swede (10.1-14.5) and fodder beet (10.8-14.9) whereas intermediate values in kale (8.9-12.7) and maize (9.9-12.2). However, maize was the highest energy-yielding crop, ranging from about 200-316 GJ/ha while other crops varied from 34 to 217 GJ/ha. Protein content in kale (7.5-16.6% DM) and swede (11.4-18.2% DM) were adequate for non-lactating cows whereas maize (5.4-9.2% DM) and fodder beet (7.6-11.2% DM) were lower than recommended protein levels for dairy cows but offering an opportunity to reduce urinary N excretion. Maize also had recommended fibre content. With higher sugar contents, swede and fodder beet were poor in fibre sources, potentially prone to rumen acidosis unless considered mixed diet with high fibre feed. APSIM modelling indicated that maize would produce the lowest urine N output while swede the highest in simulated feeding. Accordingly, N loads/ha was higher for winter forage crops especially when good yields were produced. When common feeding practices were considered, i.e., off-paddock maize feeding (no urine N deposition) and on-paddock grazing of winter forage crops (high urine N deposition), simulated nitrate losses from maize cropping systems were the lowest. Predicted nitrate losses were 21 and 32 kg N/ha for maize under irrigated and non-irrigated conditions. A ryegrass cover crop further reduced simulated nitrate losses by 20-30%. Predicted nitrate losses for fodder beet, kale, and swede crops were 126, 162, 154 kg N/ha under irrigated conditions and 72, 201, 199 kg N/ha under non-irrigated conditions, respectively in grazing systems.
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    Targeted duration controlled grazing - the effects of timing of grazing on nitrate leaching and treading damage : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Soil Science at Massey University, Palmerston North, New Zealand
    (Massey University, 2019) Howes, Jay
    Duration controlled (DC) grazing is successfully employed for two main reasons: to reduce N leaching and to protect pastures and soils from treading damage in wet conditions. These two objectives are currently very important for the New Zealand (NZ) dairy industry and this will only continue to increase with changing environmental expectations and legislation. However, while there have been a number of studies showing the benefits of DC grazing, there has not been any detailed research into the means to modify or improve the management of DC grazing systems. Therefore, the overall objectives of this research were to further the understanding of the advantages of targeted cow standoff from pastures during the late-summer to early-winter period and its effect on nitrate (NO3-) leaching, and to identify the relationship between soil water deficit (SWD), grazing duration and treading damage (related to standoff in winter to early spring). Two experiments were conducted on a fine textured Tokomaru silt loam soil at Massey University’s Dairy 4 Farm near Palmerston North, Manawatu, New Zealand. One experiment was conducted to investigate the interaction of grazing duration and SWD on soil damage and pasture production, while the other experiment compared NO3- leaching under a standard dairy grazing system and a grazing system that used targeted DC grazing (i.e. during late-summer to early-winter). Irrespective of drainage season and grazing treatment, the greatest NO3- concentrations in drainage occurred in the first seven to eight drainage events, which equated to the initial 50 to 100 mm of drainage. The majority of N losses following this were in the form of total organic nitrogen (TON). The average reductions in NO3- and TN leaching following targeted DC grazing in the summer to early winter periods of 2015 and 2016 were 28% and 20% respectively. The uniform return of slurry contributed to the DC treatment maintaining similar pasture production to the standard grazing treatment. Compared with year-round DC grazing, targeted DC grazing could be relatively inexpensive and so is likely to be a good mitigation option for N leaching in many cases, particularly on free draining soils where treading damage is uncommon. Treading damage can be easy to observe; however, it can be time consuming to measure and even more difficult to quantify in a spatially aware manner. Therefore, two new and contrasting methods of assessing treading damage were developed, namely, the visual scoring method and the pugometer. The advantage of the pugometer is that it can automatically capture spatial variability rapidly, which no current method is able to do. Only minimal treading damage and no reduction in pasture production was associated with cows grazing pasture at SWD > 2 mm, and this SWD appears to be a critical value, which farmers on fine textured soils, like the Tokomaru silt loam, could use to schedule grazing to protect soils and pastures from pugging damage. However, due to the need to maintain pasture quality there will be numerous occasions when the pasture on farms practising DC grazing will need to be grazed at a SWD < 2 mm. A modelling exercise revealed that up to 60% of a farm with standoff facilities could be damaged in an average season. While the damage inflicted on pastures may look unsightly, this may have little influence on overall accumulated (annual) pasture production. However, when the SWD was less than 2 mm, there were short-term losses in pasture production of approximately 500 to 1000 kg DM/ha under the grazing regimes studied here (i.e. 4- or 8-hour grazing duration and single and repeat damage events). If there is a need to graze in wet conditions (at or near saturation), then short durations (up to 4 hours) are recommended. Targeted DC grazing management provides the opportunity to achieve improved environmental outcomes, and the effectiveness of targeted DC grazing as a multi-purpose tool is not undermined by the need to graze in wet conditions.
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    Glyphosate displacement from New Zealand soils and its effect on non-target organisms : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Agricultural Science at Massey University, Palmerston North, New Zealand
    (Massey University, 2019) Jimenez Torres, Jesus Adalberto
    Glyphosate (GlyP) is the most commonly used herbicide worldwide; it is retained in the soil and is decomposed by soil microorganisms. The main degradation product of GlyP is Aminomethyl-phosphonic acid (AMPA). Phosphorus and GlyP are antagonistic anions that compete for the soil’s reaction sites; P accumulation in the soil can increase GlyP translocation through the environment and increase its bioavailability. Residual GlyP and AMPA accumulation in the soil has generated concerns about their potential toxicity to non-target organisms such as crops and soil microorganisms. GlyP in situ remediation has therefore emerged as an option to reduce the residence time of the herbicide in soil. Laboratory experiments were carried out in order to elucidate the effect of the interaction between soil chemical and physical properties, and phosphorus addition on GlyP sorption to soil surfaces. The results of the GlyP-AMPA batch adsorption- desorption experiment demostrated that the Kd and fixation of GlyP and AMPA in the soil was proportional to the Al-Fe oxy-hydroxides content of the soil, in the following order Allophanic>Brown>Pallic. In another experiment, phosphorus addition to soil reduced GlyP adsorption, which demonstrated that phosphate will occupy the same soil reaction sites as GlyP. These results suggest that due to the stability of the bond formed between Al oxy-hydroxides and P, Al oxy-hydroxides will fix GlyP; while the higher reactivity of Fe oxy-hydroxides will facilitate the exchange of phosphate by GlyP. A column leaching experiment demonstrated that the interaction between the physical and chemical characteristics of the soil will influence water infiltration and solubilisation of GlyP. Phosphorus addition to the columns enhanced GlyP’s vertical displacement through the soil and AMPA detection in the leachate. The Pallic soil with a poor physical structure had reduced GlyP vertical displacement. In contrast, the free- drained Brown soil had higher AMPA percolation regardless of the P addition. The Allophanic soil had the lowest GlyP percolation risks, despite the fact that P addition increased AMPA detection at the bottom of the column. However, AMPA was undetected in the Allophanic soil’s leachate. A soil induced respiration (SIR) experiment demonstrated that GlyP (variable doses) did not affect soil microorganism respiration, while Agave amendments were used as an exogenous source of carbon and triggered soil respiration (Agave applied had 0.382 mg TC/g soil and control C applied was 1.25 mg C/g soil). The SIR ratio values observed in the soils were as follows Allophanic>Pallic>Brown, and were inversely proportional to the total dissolved carbon concentration in soil extracts. These results demonstrate that the greater Al- Fe oxy-hydroxide content of the Allophanic soil protected organic matter from mineralisation enabling greater microbial activity over the GlyP molecule. The P adsorption-desorption experiment using Agave powder demonstrated that Agave constituents desorbed phosphorus from soil surfaces, which might help in the desaturation of P from soil, while increasing its bioavailability. Glasshouse experiments using Roundup doses and Agave amendment applied to the soil of white clover potted plants were carried out in order to elucidate the potential for GlyP degradation in soil and the biochemical responses of white clover plants. The results demonstrated that Agave amendment attenuated the translocation of GlyP to white clover shoots for a Roundup dose of 90 kg a.i./ha. The chemical constituents of Agave, 12 hrs after GlyP application to the soil, enhanced GlyP degradation to AMPA in soil at the 15 kg GlyP treatment. A similar improved GlyP degradation was observed during three days of evaluation at the 7.5 kg dose. The biochemical responses of white clover shoots demonstrated an increase of gallic acid and tartaric acid accumulation proportional to the increasing Roundup doses. This suggested that Roundup alone, and in combination with Agave amendments, exerted oxidative stress on the plants. Alternatively, the herbicide could have affected the EPSPS enzyme disrupting the carbon cycle. These results demonstrate that the white clover metabolic disruption caused by the Roundup treatments of 7.5 and 15 kg/ha, expressed through tartaric acid and gallic acid, was alleviated at the third day of evaluation. The results of this thesis can support decision-making for the implementation of strategies which could mitigate glyphosate and AMPA displacement from New Zealand farmland; as example, it may encourage the prevention of phosphorus accumulation in the farmland. In addition, these results can encourage the development of further research related to the potential use of Agave amendments for glyphosate remediation, and help in the understanding of the effects of the herbicide on the metabolism of non-target organisms.
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    Effects of increasing cow urine deposition area on soil mineral nitrogen movement and pasture growth on a recent soil in the Manawatu region, New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Master of Environmental Management at Massey University, Manawatū, Palmerston North, New Zealand
    (Massey University, 2017) Romero Ramírez, Stefanía Yanina
    The cow urine patch is a major source of nitrate (NO₃⁻) leaching from grazed dairy pasture farms. Increasing the urine deposition area is a direct way of reducing the potential risk of this cause N leaching losses. Research is required to quantity the effectiveness of this mitigation across a range of different soil and climatic conditions. The objective of this study was to determine the effect of increasing the cow urine deposition area on NO₃⁻ leaching risk and short-term pasture accumulation on Recent soil in the Manawatu Region, New Zealand. A field trial was conducted, which consisted of three treatments evaluated on pasture plots: Urine (1 m2), Urine (0.2 m2) and No-urine. The two urine treatments received the same volume of 2.1 L urine/patch. Urine treatments were applied on the 6th of March 2017, and soil inorganic N was measured on three occasions; 15, 36 and 53 days after urine application (DAUA). At the third soil sampling time, which was 24 days after the drainage season was estimated to have commenced, the net inorganic N (inorganic N in the urine treatment minus the value for the No-urine treatment) in the 45-120 cm soil depth was 1.08 g net inorganic N/patch for the Urine (1 m2) treatment compared to 2.97 g net inorganic N/patch for the Urine (0.2 m2) treatment. Therefore, the Urine (1 m2) treatment resulted in a 63.6% reduction in the quantity of net inorganic N that was highly susceptible to leaching, compared to the more typical urine patch area of 0.2 m2. At a paddock scale, when net inorganic N from the urine treatments is multiplied by an estimate of the quantity of urine patches per hectare in a single grazing, this equates to a reduction of 2.53 kg N/ha from a single autumn grazing. It is expected that increasing urine deposition area at multiple grazings would result in greater reductions in the annual NO₃⁻ leaching risk. Over the two pasture harvests conducted in the trial, the pasture DM accumulation for the No-urine treatment produced an average of 3220 kg DM/ha. The two urine patch treatments achieved a similar level of pasture DM accumulation to that of the No-urine treatment. The lack of a pasture growth response from the added urine could have been influenced by the high clover content (35.9%) of the pasture, and in addition, there may have been adequate background soil mineral N levels, which together could have contributed to N not being growth limiting during the trial. This research has demonstrated that increasing cow urine deposition area in autumn has potential to be an effective mitigation for decreasing N leaching losses from grazed dairy pastures. Further research is required to investigate the effects of increasing cow urine deposition area at multiple grazings, in order to determine the effect of this mitigation option on annual NO₃⁻ leaching and pasture production.
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    Modelling and analysis of leaching of copper from volcanic ash soil : a thesis presented in partial fulfilment of the requirments [i.e. requirements] for the degree of Master of Technology in Environmental Engineering
    (Massey University, 1999) He, Dali
    Soil contaminated by heavy metal ions has become a global problem. Besides legislation to restrict the input of heavy metals, remediation of contaminated soil is also essential. The most common means of remediation is leaching. There have been many studies published in this field, some of which relate to development of mathematical models. Volcanic ash soil is common in New Zealand. Developing a model to predict the process of leaching heavy metal from volcanic ash soil is important for New Zealand. No model was found for predicting the process of leaching heavy metal from volcanic ash soil. Heavy metal soil contamination can not be remedied by microorganisms, so the heavy metals will inevitably accumulate in soils over time. Once heavy metals have accumulated in soil to exceed a threshold, they will be released and then be taken up by plants, entering the food chain or moving into the groundwater system. Therefore, it is necessary to leach the heavy metals from the contaminated soil. The batch stirred process is a fast and convenient method, and it is easily used in the field. The main purpose of this study is to develop a model that can predict the bulk liquid concentration of heavy metal in the stirred vessel. In the present study, the internal model is pore diffusion model. The explicit method is used to translate a partial differential equation to a finite difference equation. The results from thermodynamic and kinetic experiments agree with the model. With the exception of the equilibrium parameters for Freundlich isotherm derived by experiment, all other parameters were obtained from literature on volcanic ash soil. Therefore, the model can be used for leaching of other heavy metals from volcanic soil under similar conditions. The leaching of heavy metals from volcanic soil is shown to be an internal diffusion controlled process, so increasing the agitating speed in a stirred reactor is of no use for improving the mass transfer. Decreasing the size of volcanic soil aggregates by breaking them clearly increases the rate of the leaching process. The equilibrium relationships of the adsorption process and the desorption process are different for the system, and there is a hysteresis.
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    Experimental simulations of the weathering of volcanic ash : a case study to better understand short- and long-term impacts of ash-leachable elements on the environment : a thesis presented in the partial fulfilment of the requirements for a degree of Master of Science in Earth Science at Massey University, Palmerston North, New Zealand
    (Massey University, 2017) Greig, Alexander Robert
    The aim of this project is the development and testing of a new methodology for the investigation of the short- to long-term leaching behaviour of volcanic ash. Previous research has demonstrated that volcanic eruptions can have strong impacts on the environment, which result from elements that have been leached from volcanic ash. To date, there is relatively little understanding of the minor and trace element composition of ash-leached brines, and how this varies over time. These gaps in knowledge currently preclude an estimate of both the detrimental and the beneficial impacts of volcanic ash fall due to leaching on the environment, agriculture, as well as on human and animal health. An adaption of a soxhlet reactor was found to be an adequate experimental technique for the constant flushing of volcanic ash samples with deionised water. This was designed to accelerate the weathering of a volcanic material in a laboratory setting. A number of shortcomings in the experimental method could be identified through the course of this research and should be considered in future investigations. In this experiment nine volcanic ash samples from four different and highly active volcanoes have been tested. These volcanoes are Mt. Ruapehu and White Island in New Zealand, Mt. Kelut in Indonesia and Mt. Sakurajima in Japan. All volcanic ash samples were found to release elements into brine over the experimental time in a strongly non-linear fashion. Based on the current data set of nine ash samples, three main classes of time-variant element release behaviour are here suggested and defined, whose characteristics are primarily controlled by the element, rather than volcanic source or ash characteristics. A preliminary interpretation of these different element release pattern is that their temporal changes are most likely restrained by the strength of chemical and mechanical bond of elements to the surface of juvenile and non-juvenile ash material. Moreover, significant controls on the long-term leaching concentrations of elements were found to be by the style of eruption as well as the nature of the volcano plumbing system, confirming results of earlier batch leaching experiments. The 1995-96 Mt. Ruapehu eruption sequence in particular illustrated some significant variability in leaching behaviour as a result of specific eruption parameters. Volcanic ash samples that have been derived from a phreatomagmatic style eruption have been found to have a higher short-to long-term impact than those volcanic ash samples derived from dry magmatic eruptions. A simple method was developed to estimate the real–world equivalent weathering time corresponding to the duration of a soxhlet reactor leaching experiment. The method, which is primarily based on the total volume of water percolating through an ash sample, and to relate this to local annual rain fall data, was found to estimate real-world weathering times in the natural environment fairly accurately. Based on these natural time constraints, detrimental short-term impacts (months to years) are concluded for lead and fluoride, and beneficial short-term impacts for calcium and manganese. Long-term beneficial effects (up to 20 years) are seen for zinc, copper and iron, while long-term detrimental impacts are concluded for the cases of lead and fluoride. The strong dependence of the leaching rate on the effective ash surface area precludes that future forecasts of short- and long-term impacts should be made by considering local soil permeability and ash grain-size characteristics. In that way future modelling approaches via reactive and non-reactive porous media flow of ash-leached brines into soil and groundwater may form an interesting avenue for future developments of this pilot study. This approach may hold potential to give quantitative advice to regional councils, the agricultural industry and governmental agencies on detrimental and beneficial short- to long-term impacts of volcanic ash.
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    Improving soluble chemical oxygen demand yields for anaerobic digester feedstock using leaching : a thesis presented in partial fulfilment of the requirements for the degree of Master of Engineering in Environmental Engineering, School of Advanced Technology and Engineering, College of Sciences, Massey University, Palmerston North, New Zealand
    (Massey University, 2012) Ralphs, John Leonard
    Waste biomass is often a liability to many municipalities. Technologies exist that can turn this biomass into energy which can then be sold. Anaerobic digestion is one of the important technologies that utilises this biomass to turn it into biogas. One of the factors that affects the rate that biogas can be produced is the speed that suitable organic compounds can be delivered to methanogenic microorganisms. These organic compounds such as sugars and amino acids are released from plant material at different rates depending on their availability. A portion of the compounds are readily soluble in water and are immediately available, some of the compounds are locked up inside the plant cells and some of the compounds such as cellulose are not soluble and need to be hydrolysed into sugars before they can be converted into methane. Hydrolysis is usually the rate limiting step in anaerobic digestion. Leaching of green waste was investigated as a form of pre-treatment to externalise the initial stages in anaerobic digestion that makes soluble organic compounds available for the consecutive mthanogenic stages of anaerobic digestion. The added benefit of leaching is it removes the complexity of solids handling from inside anaerobic digester. Many various forms of leaching technologies that are coupled to anaerobic digesters have been trialled with grass and silage, little research was found on leaching green waste and few trials had used the simplified unheated flooded tank system as tested here. Pilot and laboratory leaching trials were conducted on shredded green waste as well as grass clippings to establish the efficiency of leaching by measuring the COD yields in the leachate. Additionally, rumen contents from cattle rumen were added to grass clippings in order to investigate if the leaching efficiency from the grass could be improved. Leaching was tested at a pilot scale in an open to the air reactor tank in ambient temperature in a temperate climate. Hydraulic retention times ranging from 4 hours to 7 days were tested to establish the most effective leaching strategy. The laboratory trials were conducted with the temperature controlled at 25°C to simulate ambient environmental conditions in a temperate climate. The effect of storing feedstock was tested to see how changes in handling times affected the process. Gas production from the leachate was tested using 2 L CSTR (Continuously Stirred Tank Reactor) anaerobic digesters to confirm the usability of the leachate as a feedstock in an anaerobic digester. Pilot scale trials of shredded green waste and grass clippings gave maximum COD concentrations of 5.4 ± 0.5 and 47±4 g COD / L of leachate respectively. Pilot trials of shredded green waste and grass leachate reached a maximum total COD yields of 53 ± 2 and 410 ± 20 kg COD / tonne VS respectively. Laboratory scale trials of shredded green waste and grass clippings gave maximum COD concentrations of 7.0 ± 0.1 and 49 ± 2 g COD / L of leachate respectively. Laboratory trials of shredded green waste and grass leachate reached a maximum total COD yields of 132 ± 8 and 410 ± 20 kg COD / tonne VS respectively. Laboratory trials are indicative of how pilot trials will behave and differences are likely to be due to an increased bulk density in solids in pilot trials. Shredded green waste and grass leachate gave maximum 3.7 and 7.8 g BOD / L respectively. Nutrients in the leachate were tested: nitrogen levels in shredded green waste and grass leachate reached maximum levels of 51 and 460 mg / L respectively; DRP (Dissolved Reactive Phosphorus) levels in the shredded green waste and grass leachate reached maximum levels of 6 and 85 mg / L respectively. The leaching tanks produced gas while leaching was taking place; a sample of this gas was captured and the levels of CH4, CO2 and H2 were measured as 0%, 25.5% and 5.0% respectively. Gas production from anaerobic digestion of shredded green waste and grass in a CSTR at 35°C produced 0.23 ± 0.01 and 0.534 ± 0.005 m3 biogas / kg COD respectively. Use of grass that is fresh gives much higher yields of dissolved organic compounds in the leachate than when the grass is stored in covered area for 30 days. Leaching grass with an HRT (Hydraulic Retention Time) of 1 day gave optimal results in terms of concentration and yields of dissolved organic compounds in the leachate compared to leaching trials with an HRT of 4 hours or 7 days. Green waste gave much lower concentration and yields of COD than grass and an HRT of 7 days was the most suitable for gaining the best concentration and yield of dissolved organic compounds compared to a 4 hour or 1 day HRT. The overall mass transfer of organic compounds when leaching freshly shredded green waste is most likely limited by a combination of hydrolysis and the rate that soluble compounds are released from within plant cells as the cell membranes degrade. In trials of fresh and stored grass and stored shredded green waste, shortening the HRT increases the total yield of dissolved organic compounds leached into the leachate; however, this is at the expense of increased concentrations of dissolved organic compounds within the leachate. The lower leachate concentrations with the shorter HRTs means that the leachate is less suitable to uses as a feedstock for an anaerobic digester. Anaerobic digestion of grass leachate produced much more biogas / kg COD than anaerobic digestion of shredded green waste leachate, this may be a result of an inhibiting compounds such as tannins, additionally to this the material that the shredded green waste is composed of will have higher levels of lignocellulose materials that are not readily soluble. The leachate was found not to degrade when stored at 25°C in an open top container, this maybe a result of low pH inhibiting degrading micro-organisms, this has significant benefit as the leaching process can be separated from the anaerobic digestion process without degrading the quality of the leachate while it is being stored.