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    Meta-analysis of New Zealand's nitrous oxide emission factors for ruminant excreta supports disaggregation based on excreta form, livestock type and slope class.
    (Elsevier B.V., 2020-08-25) van der Weerden TJ; Noble AN; Luo J; de Klein CAM; Saggar S; Giltrap D; Gibbs J; Rys G; Jenerette D
    Globally, animal excreta (dung and urine) deposition onto grazed pastures represents more than half of anthropogenic nitrous oxide (N2O) emissions. To account for these emissions, New Zealand currently employs urine and dung emission factor (EF3) values of 1.0% and 0.25%, respectively, for all livestock. These values are primarily based on field studies conducted on fertile, flatland pastures predominantly used for dairy cattle production but do not consider emissions from hill land pastures primarily used for sheep, deer and non-dairy cattle. The objective of this study was to determine the most suitable urine and dung EF3 values for dairy cattle, non-dairy cattle, and sheep grazing pastures on different slopes based on a meta-analysis of New Zealand EF3 studies. As none of the studies included deer excreta, deer EF3 values were estimated from cattle and sheep values. The analysis revealed that a single dung EF3 value should be maintained, although the value should be reduced from 0.25% to 0.12%. Furthermore, urine EF3 should be disaggregated by livestock type (cattle > sheep) and topography (flatland and low sloping hill country > medium and steep sloping hill country), with EF3 values ranging from 0.08% (sheep urine on medium and steep slopes) to 0.98% (dairy cattle on flatland and low slopes). While the mechanism(s) causing differences in urine EF3 values for sheep and cattle are unknown, the 'slope effect' on urine EF3 is partly due to differences in soil chemical and physical characteristics, which influence soil microbial processes on the different slope classes. The revised EF3 values were used in an updated New Zealand inventory approach, resulting in 30% lower national N2O emissions for 2017 compared to using the current EF3 values. We recommend using the revised EF3 values in New Zealand's national greenhouse gas inventory to more accurately capture N2O emissions from livestock grazing.
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    Estimating hill country rainfall without full data sets for the Manawatu River catchment : a thesis presented in partial fulfillment of the requirements for the degree of Master of Resource and Environmental Planning at Massey University, Turitea, New Zealand
    (Massey University, 2014) Sijbertsma, Jorn Arjan
    Nowadays, people anticipate floods using flood warning systems, and building stop banks and flood ways in place that use flood models generated with hydrological information in their design. Nevertheless, various regions in the world are still hit by floods with catastrophic effects to urban areas, because of a lack of local hydrological knowledge, especially of upstream areas in their catchments. This lack of hydrological knowledge is a result of difficult accessible highly elevated upstream areas, which makes monitoring of hydrological variables difficult or impossible. This thesis examines models for determining montane rainfall using spatial estimation methods and data sets. The distribution and quantity of montane rainfall were assessed by applying five appropriated spatial estimation methods, data of historical and current rain gauges, and a performance measurement. The methodology applied to gain more knowledge about montane rainfall was established with the results of a literature analysis of 40 articles about montane rainfall. This literature analysis revealed that ordinary kriging is the most frequently applied spatial estimation method for montane rainfall, with regression and regression kriging completing the top three of the most applied methods. Also, two other spatial estimation methods, empirical Bayesian kriging and geostatistical simulation, performed well with rainfall data. The same literature analysis disclosed that the root mean square error was predominantly used as a performance measure of spatial estimation methods. The literature analysis revealed a number of data gap-filling techniques, with the inverse distance weighting method and the coefficient of correlation weighting method as the two most suitable techniques. These techniques were applied to complete historical rainfall data sets and their performance was compared within this research. The result showed that the coefficient of correlation weighting method outperformed the inverse distance weighting method in 74% of all data gap estimations, and the coefficient of correlation weighting method was 22% more accurate (based on the overall performance) than the inverse distance weighting method. The most accurate data gap-filling technique, the coefficient of correlation weighting method, was used to complete the historical rain gauges data. The overall ranking of the spatial estimation methods revealed that Gaussian geostatistical simulation performed the best. Regression kriging was the second best spatial estimation method, but there was no significant difference with Gaussian geostatistical simulation. At the same time, the results showed that the best performance of the spatial estimations was accomplished without the maximum number of rain gauges. However, better visual representation of the distinct pattern of rainfall was generated with the historical rain gauges in the second and third experiment of the spatial estimations. Finally, this research discussed the factors that can impact the performance of the spatial estimations. Two of these factors were the removal of ?bad data? and the the strategic placing of rain gauges. The results of this research clearly defined that the removal of ?bad data? increased the accuracy of estimation, while a more even and strategic distribution of rain gauges was suggested to increase the accuracy of the spatial estimation of rainfall.
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    Phosphorus cycling in grazed, steep hill country : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Soil Science at Massey University
    (Massey University, 1978) Gillingham, Allan Gilbert
    Measurements of P uptake by pasture and P return in posture litter and dung were made on two intensively grazed, north- and south-facing paddocks in steep hill country with soils of moderate to high P status. Both P uptake and more particularly the return of P in dung by grazing sheep, was high on the relatively level campsite areas but decreased sharply as ground surface slope increased. A high grazing pressure ensured that P return via litter was low relative to plant uptake. A net P balance derived for differing paddock strata showed a large net annual gain of P on campsites (50.1 and 119.8 kg ha-1 on north and south aspects, respectively) but a considerable net P loss from both 25° slopes (19.5 and 10.0 kg ha-1 on north and south aspects, respectively) and 45° slopes (15.3 and 13.8 kg ha-1 on north and south aspects, respectively). Differences between aspects in the net P balance could be explained by the overall difference in the topography of the two paddocks as it affected relative camping and grazing pressure on each stratum. Subsequent simulation studies were conducted using a mathematical model based on field data from the north-aspect paddock and validated against results from the south-aspect paddock. Results obtained from the model indicated that the quantity of P transfer from slopes increased at a greater than directly proportionate rate as stocking rate increased and was also directly related to pasture P content. Determination of relative root activity using 32P showed that approximately 90% of P uptake by pasture in spring occurred from within 7cm of the soil surface. The greater proportion of this occurred within the 0-3cm soil depth. No significant P uptake occurred from depths greater than 30cm. Although the extent of P uptake front 0-3cm depth soil was similar both upslope and downslope from a P source, the direction of predominant root activity at greater depths was affected by the steepness of slope, tending to be at an angle between vertical and that normal to the soil surface. A technique was developed to characterize short term plant-available P, using both 32P and 33P. Results indicated that the 32P/33P ratio of the water-extractable P fraction more closely resembled that in the plant than was the case for the Olsen P extract. Both ryegrass (Lolium perenne) and white clover (Trifolium repens) apparently utilized P from the same soil pool, the measured higher P content of ryegrass in this study being due only to a more extensive and rapidly developing root system than that of clover. The addition to soil of P extracted by water from litter, dung, and superphosphate sources showed that all forms had similar effects in increasing the water-extractable and Olsen P levels in the soil. Thus it could be expected that P from these three sources would have a similar availability to plants. The results of these and also P desorption experiments were qualitatively similar to those derived from a simple Langmuir model, suggesting that sorption and desorption of P in the soil from the field area occurred at sites on the solid phase with predominantly uniform sorption characteristics. Marked and largely unexplained variations in several soil parameters monitored over a year obscured the effects of P addition as a maintenance fertilizer application and also the net P transfer by grazing animals. In this and related situations, soil P analysis may not provide a sensitive measure of P status, except in the longer term. A more detailed examination is required to assess the usefulness of routine soil P analysis of hill soils for advisory purposes. The significant net P transfer from slopes by grazing animals suggests that the complementary roles of grazing management and fertilizer requirements in hill country should also be examined further.
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    Phosphate cycling in grazed hill-country pasture : a thesis presented in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Soil Science at Massey University
    (Massey University, 1987) Rowarth, Jacqueline Sara
    A detailed study of the "above-" and "below-ground" components of the phosphorus (P) cycle was carried out in the North Island hill country of New Zealand. The effect of P fertiliser rate and degree of land-slope on pasture P uptake, faecal P return and changes in soil P fractions was examined over a three year period. Plant P uptake was found to decrease with increasing slope and increase with increasing rate of P fertiliser. The changes in plant P uptake were a function of changes in both dry matter yield and pasture P concentration. Pasture on campsites which initially had a high Olsen P status (>30) showed an unexpected apparent P response in both dry matter yield and plant P uptake. This response results from an artefact of the trial design whereby P fertiliser was applied to whole paddocks. The resulting improved nitrogen status of slopes at high rates of P fertiliser created abnormally high soil nitrogen levels on campsites, leading to very high levels of production. These findings are of significance in relation to soil fertility field trials conducted on individual slopes in hill country. Over the three year period of the trial seasonal plant P uptake followed the order: spring ≥ summer > autumn > winter, irrespective of slope category, fertiliser rate or grazing regime. The distribution of faecal material was found to be markedly affected by slope and approximately 60% of the material deposited in each paddock was returned to campsites. In the remainder of the paddock, faecal P return decreased by at least 50% with each 10° increase in slope. Paddock faecal P concentration (FP%) was predicted from the pre-grazed pasture P concentration (PP%) (calculated on a paddock basis) using the relationship: FP% = 3.19 PP% - 0.09 (r = 0.94). Net P balance calculations for various slope group categories showed that deficits between plant P uptake and faecal P return increased with increasing slope but were little affected by increasing P fertiliser rate and consequent increase in stocking rate. This finding verifies the use of a single animal loss factor for a given topography, irrespective of sheep stocking rate, in the Ministry of Agriculture's (MAF's) Computerised Fertiliser Advisory Scheme (CFAS) for P. Measurements of faecal distribution in this trial suggested the use of a lower animal loss factor (0.5 kg su-1 of P) for "Easy" hill country than that used currently (0.7 kg su-1 of P) in the CFAS model. Independent studies on the rate of P cycling from faeces were conducted. The study investigating breakdown of faecal material revealed that physical disintegration of faecal material is likely to occur before chemical decomposition. In winter conditions faecal material disintegrated within a month; in summer conditions disintegration took approximately three months. In both seasons material on campsites disintegrated more rapidly than that on steeper slopes. A further study using radioisotopes in the field found that the shortterm plant availability of inorganic faecal P was approximately half that of monocalcium phosphate fertiliser over a two month period in the spring. In a study on the "below-ground" components of the P cycle total soil P was found to increase with increasing rate of P fertiliser. The magnitude of these increases decreased with increasing slope and depth. Increases in organic P were found to be higher on campsites than steeper slopes. On campsites, the extent of increase in organic P decreased with increasing rate of P fertiliser. Inorganic P increased with increasing rate of P fertiliser on all slopes; the magnitude of the increase decreased with increasing slope. At low rates of P fertiliser a decrease in inorganic P was measured on steep-slopes over time indicating that P inputs were not balancing P outputs. A change in the non-occluded P fraction accounted for the greatest proportion of the change in inorganic P on most slopes. The fact that calcium-bound P accumulated on all slopes, and that large increases were evident at high rates of P fertiliser suggested that this fraction was not playing an active part in the P cycle but was accumulating as an insoluble residue from superphosphate. The plant availability of soil P fractions was investigated in a glasshouse study. Total plant P uptake was found to be highly correlated with initial levels of total P (r = 0.92),non-occluded P (r = 0.82), inorganic P (r = 0.91), Olsen P (r = 0.93) and water-extractable P (r = 0.97). Levels of organic P, occluded P and calcium-bound P were found to be essentially unchanged by plant growth over the eleven month trial period. Changes in the size of the cycling soil P pool were examined by combining results from the field trial with those from the glasshouse study. At low rates of P fertiliser (10 kg ha-1), increases in occluded P and calcium-bound P (i.e., unavailable inorganic P) in the 0-15 cm depth were occurring at the expense of available P. At a high rate of P fertiliser (100 kg ha-1) approximately two thirds of the P applied remained in the available form. On an annual basis, Olsen P increased with an increasing rate of P fertiliser and decreased with increasing soil depth and slope. Over the period of the trial Olsen P decreased significantly at the lowest rate of P fertiliser (10 kg ha-1) and increased significantly at the highest rate (100 kg ha-1) on the two slope groups studied. This indicated that these areas were not at "equilibrium" as defined by a stable Olsen P. At moderate rates of P fertiliser (20 and 30 kg ha-1) it was not possible to determine whether or not equilibrium conditions existed as the annual variability in Olsen P was too high. An attempt was made to determine soil P losses (as defined by the CFAS model) at the trial site. Despite intensive and careful soil sampling Olsen P could not be used to determine "equilibrium" conditions which are a pre-requisite for measurement of soil P loss. This finding prevented validation of soil loss factors on this hill-country site. Data generated from the large field trial for "above-" and "below-ground" components of the P cycle enabled recommendations to be made on the location of suitable soil sampling sites and also on the location of priority areas for application of P fertiliser in grazed hill country.
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    A systems approach to research planning for North Island hill country : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy
    (Massey University, 1984) McCall, David Graeme
    The achievement of increased production from North Island Hill Country (NIHC), through an increased research input, is currently receiving considerable attention in New Zealand. The task of planning future research and setting priorities for this work requires an evaluation of the current state of knowledge relating to hill country grazing systems, and an assessment of future research needs. A number of references have been made to the potential usefulness of systems modelling in research and research planning. The objectives for this study were to apply modelling to the development of research priorities on NIHC, and to evaluate modelling in this role. A simulation model was constructed to assemble the available information on soil, pasture and sheep components of NIHC grazing systems. Evaluation of the state of knowledge on components of hill country systems was based on problems (data and conceptual) confronted during model construction. The model simulated pasture growth, senescence and decay from climate data. The sheep component was based on an energy balance using the metaholisable energy system. Parameters in major components of the model were calibrated against data set aside at the start of the study. This was done in order to obtain the 'most valid' model because there were a range of values reported in the literature for many of the parameters. Statistical goodness-of-fit tests were used as an aid to decide on the structural acceptability of the calibrated model, and some issues facing the choice of appropriate statistical lack-of-fit test for models, were discussed in detail. Model validity was established by subjective judgement. The need for subjectivity arose mainly because of uncertainty about settings of some, or all, important exogenous variables in the data available for validation. Experiments were carried out with the model where stocking rate, lambing day, length of flushing, winter and spring rotations, and the number of paddocks retired from grazing in early summer, were varied. The results were used to define decisions giving 'optimal' levels of production. Climate data from Ballantrae Hill Country Research Station were used. Five representative years were constructed to account for major variations in climate experienced at the site. Early lambing and winter and spring grazing strategies which maximised spring feed supply were clearly shown as the most important decisions in maximising system profitability. The 'optimal' system was used as a base from which to investigate possible benefits from adding feed in spring through the use of nitrogen fertiliser, and increasing ovulation rate by artificial means. Both the above were shown to be profitable, given some adjustments to management strategies. Finally, changes were made to a range of parameters influencing potential pasture and animal performance. Effecting some of these changes by physical, chemical or genetic means would be profitable, particularly where wool production was concerned. Difficulties were confronted in conceiving a means of setting objective research priorities using the model. A number of information deficiencies were noted, but the reasonableness of using sensitivity analysis to rank the importance of each deficiency in an 'invalid' model was questioned. Further the problem of choosing between obtaining information to further improve the model, and developing improved systems suggested by the model, was noted. Subjective priorities were determined based on the need to demonstrate superior systems identified by modelling, and the apparent need for a greater understanding of particular components to enable improved systems to be devised. Advantages were apparent in using modelling as an aid to making these subjective judgements. It was concluded that the process of developing a pre-research model to evaluate research needs had been valuable. The learning aspect of modelling was emphasised, though problems with validation occur where modelling is conducted in isolation from field research. The view was submitted that the modelling should be extended to become an integral part of a research programme.