Journal Articles
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Item Modelling and mapping of subsurface nitrate-attenuation index in agricultural landscapes(Elsevier Ltd, 2025-06) Collins SB; Singh R; Mead SR; Horne DJ; Zhang LEnvironmental management of nutrient losses from agricultural lands is required to reduce their potential impacts on the quality of groundwater and eutrophication of surface waters in agricultural landscapes. However, accurate accounting and management of nitrogen losses relies on a robust modelling of nitrogen leaching and its potential attenuation – specifically, the reduction of nitrate to gaseous forms of nitrogen – in subsurface flow pathways. Subsurface denitrification is a key process in potential nitrate attenuation, but the spatial and temporal dynamics of where and when it occurs remain poorly understood, especially at catchment-scale. In this paper, a novel Landscape Subsurface Nitrate-Attenuation Index (LSNAI) is developed to map spatially variable subsurface nitrate attenuation potential of diverse landscape units across the Manawatū-Whanganui region of New Zealand. A large data set of groundwater quality across New Zealand was collated and analysed to assess spatial and temporal variability of groundwater redox status (based on dissolved oxygen, nitrate and dissolved manganese) across different hydrogeological settings. The Extreme Gradient Boosting algorithm was used to predict landscape unit subsurface redox status by integrating the nationwide groundwater redox status data set with various landscape characteristics. Applying the hierarchical clustering analysis and unsupervised classification techniques, the LSNAI was then developed to identify and map five landscape subsurface nitrate attenuation classes, varying from very low to very high potential, based on the predicted groundwater redox status probabilities and identified soil drainage and rock type as key influencing landscape characteristics. Accuracy of the LSNAI mapping was further investigated and validated using a set of independent observations of groundwater quality and redox assessments in shallow groundwaters in the study area. This highlights the potential for further research in up-scaling mapping and modelling of landscape subsurface nitrate attenuation index to accurately account for spatial variability in subsurface nitrate attenuation potential in modelling and assessment of water quality management measures at catchment-scale in agricultural landscapes.Item Make African grasslands climate-change resilient(Springer Nature Limited, 2025-02-14) Akpensuen TT; Cartmill AD; Pérez-Márquez S; Sheridan H; Lee MRF; Rivero MJClimate change has negatively impacted grassland productivity in Africa. Climate-smart technologies such as forage grass, legume, and herb mixtures could enhance grassland productivity and resilience, offering a sustainable solution for African pasture-based livestock systems.Item 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 MDenitrification 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.Item Review and update of a Nutrient Transfer model used for estimating nitrous oxide emissions from complex grazed landscapes, and implications for nationwide accounting(John Wiley and Sons Inc on behalf of American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, 2022-09-30) Vibart R; Giltrap D; Saggar S; Mackay A; Betteridge K; Costall D; Rollo M; Draganova I; Zhu-Barker. XIn New Zealand, nitrous oxide emissions from grazed hill pastures are estimated using different emission factors for urine and dung deposited on different slope classes. Allocation of urine and dung to each slope class needs to consider the distribution of slope classes within a landscape and animal behavior. The Nutrient Transfer (NT) model has recently been incorporated into the New Zealand Agricultural GHG Inventory Model to account for the allocation of excretal nitrogen (N) to each slope class. In this study, the predictive ability of the transfer function within the NT model was explored using urine deposition datasets collected with urine sensor and GPS tracker technology. Data were collected from three paddocks that had areas in low (<12°), medium (12-24°), and high slopes (>24°). The NT model showed a good overall predictive ability for two of the three datasets. However, if the urine emission factors (% of urine N emitted as N2 O-N) were to be further disaggregated to assess emissions from all three slope classes or slope gradients, more precise data would be required to accurately represent the range of landscapes found on farms. We have identified the need for more geospatial data on urine deposition and animal location for farms that are topographically out of the range used to develop the model. These new datasets would provide livestock urine deposition on a more continuous basis across slopes (as opposed to broad ranges), a unique opportunity to improve the performance of the NT model.Item Characterization and management of human-wildlife conflicts in mid-hills outside protected areas of Gandaki province, Nepal(PLOS, 2021-11-19) Baral K; Sharma HP; Rimal B; Thapa-Magar K; Bhattarai R; Kunwar RM; Aryal A; Ji W; Sharma LKWith the intent to better management human wildlife conflict (HWC) and wildlife conservation in mid-hills outside protected areas of Gandaki province, Nepal, we analyzed the patterns and drivers of HWC. Using data collected from literature, government records and questionnaire survey, we investigated temporal, seasonal and spatial distribution of human casualties caused by wildlife attacks. We also appraised the perception of local people towards wildlife conservation. We have recorded 77 cases (69 human injuries and 8 mortalities) during the period of nine year between 2011 and 2019. The number of wildlife attacks increased over this period. Wildlife attacks were more frequent in winter with 50% (42) of attacks occurred between September and December. Common leopard (Panthera pardus) and Himalayan black bear (Ursus thibetanus laniger) were the major species involved in these conflicts. Common leopard was the most feared species that causes highest number of human mortalities (87%, n = 67); the most severe type of HWC outcome. Forty-eight percent (n = 37) attacks were reported at human settlement areas followed by 27% attacks in agriculture land (n = 21) and 24% (n = 19) in forest. Generalized linear model analysis on spatial variables showed that the probability of human attacks increases with decreasing elevation (β = -0.0021, Z = -1.762, p = 0.078) and distance from the forest (β = -0.608, Z = -0.789, p = 0.429). We recommend to decrease habitat degradation / fragmentation, carry out habitat management program within forest to increase prey availability to decrease the wildlife invasion into human settlement area, and decrease dependency of people on forest resources by providing alternative livelihood opportunities. Simplified relief fund distribution mechanism at local level also helps alleviate the impact of HWC. The knowledge obtained by this study and management measures are important for better human-wildlife co-existence.Item Agriculture and forestry impact assessment for tephra fall hazard: fragility function development and New Zealand scenario application(Volcanica, 2021-12-31) Craig HM; Wilson TM; Magill C; Stewart C; Wild AJDeveloping approaches to assess the impact of tephra fall on agricultural and forestry systems is essential for informing effective disaster risk management strategies. Fragility functions are commonly used as the vulnerability model within a loss assessment framework and represent the relationship between a given hazard intensity measure (HIM; e.g. tephra thickness) and the probability of impacts occurring. Impacts are represented using an impact state (IS), which categorises qualitative and quantitative statements into a numeric scale. This study presents IS schemes for pastoral, horticultural, and forestry systems, and a suite of fragility functions estimating the probability of each IS occurring for 13 sub-sectors. Temporal vulnerability is accounted for by a ‘temporality/seasonality coefficient,’ and a ‘fluoride toxicity coefficient’ is included to incorporate the increased vulnerability of pastoral farms when tephra is high in leachable fluoride. The fragility functions are then used to demonstrate a deterministic impact assessment with current New Zealand exposure.Item Cancer incidence in agricultural workers: Findings from an international consortium of agricultural cohort studies (AGRICOH).(Elsevier Ltd, 2021-12) Togawa K; Leon ME; Lebailly P; Beane Freeman LE; Nordby K-C; Baldi I; MacFarlane E; Shin A; Park S; Greenlee RT; Sigsgaard T; Basinas I; Hofmann JN; Kjaerheim K; Douwes J; Denholm R; Ferro G; Sim MR; Kromhout H; Schüz JBACKGROUND: Agricultural work can expose workers to potentially hazardous agents including known and suspected carcinogens. This study aimed to evaluate cancer incidence in male and female agricultural workers in an international consortium, AGRICOH, relative to their respective general populations. METHODS: The analysis included eight cohorts that were linked to their respective cancer registries: France (AGRICAN: n = 128,101), the US (AHS: n = 51,165, MESA: n = 2,177), Norway (CNAP: n = 43,834), Australia (2 cohorts combined, Australian Pesticide Exposed Workers: n = 12,215 and Victorian Grain Farmers: n = 919), Republic of Korea (KMCC: n = 8,432), and Denmark (SUS: n = 1,899). For various cancer sites and all cancers combined, standardized incidence ratios (SIR) and 95% confidence intervals (CIs) were calculated for each cohort using national or regional rates as reference rates and were combined by random-effects meta-analysis. RESULTS: During nearly 2,800,000 person-years, a total of 23,188 cancers were observed. Elevated risks were observed for melanoma of the skin (number of cohorts = 3, meta-SIR = 1.18, CI: 1.01-1.38) and multiple myeloma (n = 4, meta-SIR = 1.27, CI: 1.04-1.54) in women and prostate cancer (n = 6, meta-SIR = 1.06, CI: 1.01-1.12), compared to the general population. In contrast, a deficit was observed for the incidence of several cancers, including cancers of the bladder, breast (female), colorectum, esophagus, larynx, lung, and pancreas and all cancers combined (n = 7, meta-SIR for all cancers combined = 0.83, 95% CI: 0.77-0.90). The direction of risk was largely consistent across cohorts although we observed large between-cohort variations in SIR for cancers of the liver and lung in men and women, and stomach, colorectum, and skin in men. CONCLUSION: The results suggest that agricultural workers have a lower risk of various cancers and an elevated risk of prostate cancer, multiple myeloma (female), and melanoma of skin (female) compared to the general population. Those differences and the between-cohort variations may be due to underlying differences in risk factors and warrant further investigation of agricultural exposures.Item Ballistic modeling and pattern testing to prevent separation of New Zealand fertilizer products(American Society of Agricultural and Biological Engineers, 18/06/2015) Grafton MCE; Yule IJ; Robertson BG; Chok SM; Manning MJIn recent years twin disc centrifugal spreaders have become larger with some manufacturers claiming to be able to spread fertilizer products as far as 60 m. To achieve wider spread widths, the fertilizer particle exit velocity off the disc has increased, as a result the ballistic qualities of the product becomes more critical. This case study uses data-mined information from Ravensdown Fertiliser Co-op Ltd, a major fertilizer supplier. This article examines and researches products used by arable and grassland farmers and studies the effect of changes in product characteristics on spread bout width from these newer spreaders. Ballistic modeling, based on particle density, size, and shape was used to test the distance fertilizer particles travel at various velocities. Fertilizer particle velocities were measured by high speed photometry using both common fertilizers and common spreaders found in New Zealand. Spreading equipment was pattern tested using the New Zealand Spreadmark method. Ballistic modeling of particles proved appropriate in ideal conditions. Fertilizer manufacturers believe that spreader operators often fail to take account of physical characteristics of products being spread and target the widest bout width possible. This can lead to an in-field Coefficient of Variation (CV) which is much greater than 15% and leads to sub-optimal utilization of fertilizer, where variations in particle size distribution occur. Similar situations have been experienced when spreading fertilizer blends; where blends previously spread successfully, at narrower bout widths now separate. Ballistic models could provide bout width recommendations for products and blends, for a range of applicators and reduce crop striping.Item Estimating direct N2O emissions from sheep, beef, and deer grazed pastures in New Zealand hill country: accounting for the effect of land slope on N2O emission factors from urine and dung(Elsevier, 2015-03) Saggar SK; Giltrap DL; Davison R; Gibson R; de Klein CAM; Rollo M; Ettema P; Rys GNearly one-half of New Zealand's ruminant livestock graze on hill country pastures where spatial differences in soil conditions are highly variable and excretal deposition is influenced by pasture production, animal grazing and resting behaviour that impact the nitrous oxide (N2O) emission factor from excreta (EF3). New Zealand currently uses country-specific EF3 values for urine and dung of 0.01 and 0.0025, respectively, to estimate direct N2O emissions from excreta. These values have largely been developed from trials on flat pastoral land. The use of the same EF3 for hill pasture with medium and steep slopes has been recognised as a possible source of overestimation of N2O emissions in New Zealand. The objectives of this study were to develop and describe an approach that takes into account the effects of slope in estimating hill country N2O emissions from the dung and urine of ruminant animals (sheep, beef cattle, and deer) across different slope classes, and then compare these estimates with current New Zealand inventory estimates. We use New Zealand as a case study to determine the direct N2O emissions between 1990 and 2012 from sheep, beef cattle and deer excreta using updated estimates of EF3 for sloping land, the area of land in different slope classes by region and farm type, and a nutrient transfer model to allocate excretal-N to the different slope classes, and compare the changes between these hill pastures-specific and current inventory estimates. Our findings are significant - the proposed new methodology using New Zealand specific EFs calculated from a national series of hill country experiments resulted in 52% lower N2O estimates relative to using current inventory emission factors, for the period between 1990 and 2012 and reduces New Zealand's total national agricultural N2O greenhouse inventory estimates by 16%. The improved methodology is transparent, and complete, and has improved accuracy of emission estimates. On this basis, the improved methodology of estimating N2O emission is recommended for adoption where hill land grasslands are grazed by sheep, beef cattle and deer.Item A New Zealand regional work‑related sprains and strains surveillance, management and prevention programme: study protocol(BioMed Central Ltd, 31/12/2022) Laird I; McIntyre J; Borman B; Adank R; Ashby LBackground: The impact and costs associated with work-related sprains and strains in New Zealand and globally are substantial and a major occupational and public health burden. In New Zealand around one-third of all sprains and strains workers compensation (ACC) claims (2019) are for back injuries, but shoulder and arm injuries are increasing at a faster rate than other sprain and strain injuries (ACC, 2020). A need exists for a change to current approaches to sprains and strains prevention, to more effectively manage this significant and persistent problem in workplaces. Designing out hazards is one of the most effective means of preventing occupational injuries and illnesses. This paper outlines the study protocol of the surveillance, management and prevention programme and describes the utilisation of prevention through design principles in the prevention of work-related sprains and strains in agriculture/horticulture/ food production in the Hawkes Bay region of New Zealand. Methods: This is a prospective mixed methods study incorporating the collection of quantitative data to describe the epidemiology of work related sprains and strains injuries presenting to the regional health centre (Hastings Health Centre) over a period of 24 months and qualitative data from participants presenting at the health centre to identify high risk industry sectors/ occupations/ workplaces and tasks and design, develop and apply prevention through design principles/ solutions/ interventions to critical features of the work and work environment and undertake an outcome evaluation during the last 6 months of the project. Discussion: The purpose of this project is to establish an epidemiological surveillance programme to assess the incidence and prevalence of work-related sprains and strains according to age, sex, industry sector and occupation to target efforts to prevent work-related sprains and strains, by applying prevention through design (PtD) principles in selected workplaces in agriculture. The collection of more detailed case, occupational and work history data from a sample of patients presenting at the HHC clinic will identify high risk industry sectors/occupations/ workplaces and tasks. Assessment techniques will include comprehensive design, design thinking and human factors/ergonomics methodologies through co-design and participatory ergonomics techniques. The PtD solutions/ interventions implemented will be evaluated using a quasi-experimental design consisting of a pre-test/ post-test with-in subjects design with control groups that do not receive the intervention.