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Item Soil nutrient enrichment in pastoral systems through shelterbelts(Elsevier Ltd, 2025-10-01) Fonseka D; Jha N; Jeyakumar PShelterbelts along pasture boundaries are a natural, cost-effective, and sustainable solution to environmental challenges such as soil degradation and nutrient losses in New Zealand's pastoral systems. However, there's limited information on how shelterbelts affect nutrient dynamics in neighbouring pasture soils. Three field study sites, two dairy farms and one beef and sheep farm, consisting of the same soil type, were selected. Shelterbelts on the sites were composed of Pinus or Macrocarpa, or a mix of Macrocarpa and Willow. Soil samples were collected from each site, both with and without shelterbelts, at three transects for six distances (1 m, 5 m, 10 m, 20 m, 40 m, 80 m) and two soil depths (0–7.5 cm and 7.5–15 cm) in late spring 2023. Shelterbelts on all four farms significantly affected soil nutrient distribution in the adjacent area. Soils within 10 m of shelterbelts had higher total and Olsen phosphorus levels by up to 65 % and 80 %, respectively; the total and nitrate nitrogen levels increased by up to 64 % relative to control (no shelterbelt) soils. Shelterbelts increased soil organic carbon by up to 75 %. The macrocarpa and willow combined shelterbelt deposited around 17 Mg more C in the area tested compared to the control. These findings indicate that the shelterbelt with grazed pastures enhances phosphorus and nitrogen availability within the immediate vicinity. The inclusion of diverse species can contribute to the accumulation of topsoil carbon. Future research should focus on comparing more diverse tree species and improved grazing practices within shelterbelts to enhance the sustainability of the grazing farming system.Item The dominance of Ligularia spp. related to significant changes in soil microenvironment(Elsevier B.V., 2021-09-09) Ade L; Millner JP; Hou FExploring how plants adapt to and change the surrounding environment has become essential to understanding their survival strategies and co-evolution mechanisms. Ligularia virgaurea and Ligularia sagitta are the two most common species in the alpine grazing ecosystems of the eastern Qinghai-Tibetan Plateau (QTP) and becoming increasingly dominant. Studies have suggested that overgrazing has allowed Ligularia to gain a competitive advantage by changing plant community structure, which is often closely related to the soil environment. However, we don't fully understand the soil environment changes during this process, and the underlying mechanisms have not been explored. Therefore, we investigated plant community characteristics, soil fertility and soil microbial diversity in the L. virgaurea and L. sagitta communities on the eastern QTP. Ligularia spp. significantly changed the plant community by reducing biomass, vegetation coverage, abundance, and biodiversity, and the effect of L. sagitta on the plant community was stronger than that of L. virgaurea. In the plant communities dominated by L. virgaurea and L. sagitta, soil nutrients and soil microbial communities changed significantly. Aggregated boosted trees analysis revealed that soil Mg levels had the greatest relative influence on the structure and diversity of the soil microbial community. Our study provides data and a theoretical basis for revealing the survival strategies of L. sagitta and L. virgaurea and, provides a basis for weed management in grazed ecosystems.Item Plant invasion down under: exploring the below-ground impact of invasive plant species on soil properties and invertebrate communities in the Central Plateau of New Zealand(Springer Nature Switzerland AG, 2024-09-15) Pearson BM; Minor MA; Robertson AW; Clavijo McCormick ALThe impacts of invasive plants on arthropod communities are often reported to be negative and have predominantly been explored aboveground, but there is a paucity of information regarding what happens belowground. To address this gap, we compared soil properties and soil fauna communities associated with two native plant species (Leptospermum scoparium—mānuka and Chionochloa rubra—red tussock) and two invasive species (non-N-fixing Calluna vulgaris—European heather and N-fixing Cytisus scoparius—Scotch broom) in the Central Plateau of New Zealand. We expected that (1) at individual plant level soil properties would be different under invasive and native plant species, with higher soil nutrient concentrations under invasive species, especially N-fixing broom; (2) total abundance of soil fauna would be higher under invasive plant species, as generally positive impact of invasive plants on soil invertebrates is indicated in the literature; (3) invasive plants, and especially N-fixing broom, will be associated with greater abundances of soil decomposer groups. We found that soil properties and soil fauna assemblages did not cluster by plant invasive status as initially predicted. At individual plant level, there was similarity in soil conditions between mānuka and broom, and between red tussock and heather. The invasive N-fixer (broom) had positive effects on soil N availability, with higher N pool and lower C/N ratio in soil under this species. There were no consistent differences in total soil fauna abundance between invasive and native plants. Broom and mānuka were associated with higher abundances of Collembola, Oligochaeta and Diplopoda; heather and red tussock had higher abundances of Hymenoptera and Hemiptera. Significantly more Oligochaeta and Collembola under broom matched the prediction of invasive plants (and especially N-fixing invasives) being associated with greater abundances of decomposers. However, another important decomposer group—oribatid mites—did not show the same tendency. These results evidence that simplified generalizations regarding the impacts of invasive plants are unlikely to be justified, since the ecological effects of plant invasions are complex and do not always follow the same pattern. Therefore, we need to take into consideration the ecological context and the traits of individual plant species and target organisms in an unbiased manner to fully understand the impacts of plant invasions.Item Nutrient management plans and their influence on the farm management practices of dairy farmers : a thesis presented in partial fulfilment of the requirements for the degree of Masters of Environmental Management, Massey University, Palmerston North(Massey University, 2013) Neal, GavinNutrient Management Plans (NMPs) are a relatively recent innovation in the New Zealand dairy industry, however due to their growing use in regional council policy, and initiatives such as the Dairying and Clean Streams Accord (2003), it is likely that NMPs will become mandatory for the diary industry in the near future. There is currently limited information on the use and benefits of NMPs in the New Zealand context, and how dairy farm management practices have been influenced by the introduction of NMPs. The main objective of this research was to investigate how the introduction of an NMP has influenced the farm management practices of dairy farmers. This was achieved through the use of two case studies within the Waikato and Otago regions. These regions have contrasting approaches to nutrient management; The Waikato Regional Council has incorporated the use of NMPs in regional policy and has supported a number of community initiatives regarding nutrient management. In comparison, at the time of the research, the Otago Regional Council, while stating that they promoted the adoption of nutrient management practices, had no current policy requiring NMPs. Results indicated that the degree of NMP uptake varied amongst farmers, depending on a variety of influences with regards to the farmer’s own unique goals, circumstances and opinions. It was also found that while the reasons for NMP introduction varied amongst the farmers interviewed, the overall influences of NMPs on farm management practices were similar across both cases. The key influences of NMPs on farm management practices were; the increased precision and efficiency of fertiliser application, an increased appreciation and use of effluent as a nutrient source, and the identification and manipulation of other factors such as the effects of bought in feed and stock movement on nutrient flows on the farm. There was a perceived lack of ongoing support and education for farmers regarding NMPs. This contributed to a general distrust amongst farmers of NMPs, in turn affecting their opinions, and uptake of NMPs. Furthermore NMPs were not being used to their full potential by the majority of farmers who participated in this research. The greater the involvement and support offered by the regional council and industry, the greater the trust and cooperation amongst the particular farmers with the relevant regional council and industry representatives. Overall, while this research has found that NMPs do provide benefits to farmer’s management practices, further support and ongoing education is required to ensure NMPs are accepted and used to their full potential by dairy farmers.Item Duration-controlled grazing of dairy cows : impacts on pasture production and losses of nutrients and faecal microbes to water : 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, 2013) Christensen, Christine LynneMitigation strategies for improved environmental sustainability of the New Zealand dairy industry need to focus on reducing the transport of nitrogen (N) from urine patches and phosphorus (P) and faecal microbes from dung patches to waterways. One strategy is Duration-controlled grazing (DC grazing), a system based upon shorter grazing periods on pasture (4 hours) and removing cows to a stand-off facility for rumination and excretion. The stored effluent is applied to pasture as a slurry at an appropriate time when nutrients are required and soil conditions are suitable. A three year field study was established in the Manawatu to compare key features of DC grazing with a standard grazed (SG) system. This thesis explores the impact of a DC grazing system on the losses of N, P, potassium (K) and faecal microbes to water through drainage and surface runoff. It also investigates the effects of such a system on pasture production and intakes of pasture by cows. Pasture accumulation was the same for both treatments in the first year, but there was a 20% and 9% decline on the DC treatment in the subsequent two years. This was due to the way that slurry applications were managed. A large amount of slurry (212 kg N/ha) was applied in the first year, and no slurry was applied in the second year. In the third year slurry was applied four times at a total rate of 115 kg N/ha. The study indicates more frequent application of all nutrients captured in the effluent from standing cows off is required to maintain pasture production. Compared to the SG plots, the reductions in N losses from DC grazed plots were large, with an average 52% reduction in NO3- and 42% reduction in total N leached. Reducing urine deposition during autumn grazings appeared to have the largest impact on reducing NO3- leaching. Runoff losses of N were small and similar between treatments. The losses of P were small through both surface runoff and drainage. There was a large variation in runoff volume, which resulted in highly variable P runoff loads across plots and between treatments. The average 32% reduction in total P load from DC grazed plots was not significantly different from SG plots. Useful predictors of P load lost from all plots were runoff depth and the time cows spent grazing. Faecal microbe losses were also similar between treatments, with the useful predictors of faecal microbe concentration across all plots being the number of days since grazing and the climate after grazing. The amount of K applied in slurry and urine had a large influence on both soil and herbage K. It was determined that in a DC grazing situation, the K-rich liquid component must be included in the applied slurry to maintain soil K levels. The OVERSEER® nutrient budgeting software was able to simulate nutrient cycling in the DC grazing system reasonably well. The total N loss from the system was predicted accurately, although the relative proportion of N in drainage and runoff was not. Several opportunities for further work arise from this research. While DC grazing is a tool that could be implemented to significantly reduce N leaching losses, the management of collected excreta needs to be further developed to ensure pasture production gains are realised, or at least maintained. The combined effects of reducing treading damage and DC grazing should be investigated. Finally, a comprehensive economic analysis of standing cows off should be undertaken.Item Nutrient cycling in Eucalyptus short rotation forests : sustainable production linked with meatworks effluent land treatment : a thesis submitted in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Agricultural Engineering at Massey University Palmerston North, New Zealand(Massey University, 1998) Guo, Lanbin; Guo, LanbinShort rotation forests have the potential to provide a renewable energy source and thus reduce the demand for fossil fuels. They absorb CO2 quickly during their rapid growth, which then is recycled during the energy conversion process. However, short rotation forests are highly nutrient-demanding, and cause great depletion of soil nutrients from the site after frequent harvests. Effluents, such as from meatworks, contain high levels of nutrients which could be irrigated on to land to aid crop productions in land treatment. In many instances, this is more acceptable than disposal to waterways. Application to short rotation forests is an ideal option as it may lead to a sustainable production system. The successful link between short rotation forests and effluent land treatment depends on good management based on knowledge of nutrient cycling in the system. The objective of this study was to investigate the nutrient cycling in Eucalyptus short rotation forests linked with land treatment of meatworks effluent, through monitoring soil change, tree nutrient uptake, nutrient return via litter fall, and nutrient release via litter decomposition. A series of field experiments and one growth cabinet experiment were conducted from 1993 to 1997 at the Richmond Meat Processors & Packers Ltd. processing plant at Oringi, Dannevirke, and at Massey University, Palmerston North, New Zealand. Application of meatworks effluent increased soil nutrient levels and enhanced tree biomass production. Compared with non-irrigated crops, biomass was increased by 17%, 25% and 80%, and nitrogen uptake by 15%, 64% and 77% among the three studied species (E. botryoides, E. globulus and E. ovata). E. globulus showed the best performance of the three species, whether without irrigation or irrigated with effluent. When E. globulus stands were irrigated with effluent, 90 oven dry t/ha of above ground total biomass was produced after 3 year growth with a total of 859 kg nitrogen uptake. The amount of litter fall and nutrient return depended on the degree of biomass production and nutrient uptake in the stands. Up to 13.4 oven dry t/ha/y litter fall with up to 160 kg/ha/y of nitrogen was recorded. During the 3 year period, up to 20% of total above ground biomass produced fell as litter and up to 24% of total nitrogen uptake was returned to soil surface via litter. Litter decomposition and subsequent nutrient release from the litter were significantly influenced by internal factors (species, litter source, and the initial contents of cellulose, lignin and magnesium) and external factors (planting density, plantation age, effluent irrigation, water irrigation, temperature and light condition). The concept of growing short rotation forest linked with effluent land treatment has good potential to provide both a sustainable renewable energy source and a sustainable effluent treatment system. If they are designed and managed rationally according to the nutrient cycling within the system, the environment will be protected. The system design and management include: species selection (on the basis of biomass production, nutrient uptake, litter characteristics), tree planting density, effluent irrigation, rotation length, time of harvest, and litter management.Item Investigations into the influence of fertiliser history and climate regime on the soil fertility, soil quality, and pasture production of Wairarapa hill soils :|ba thesis submitted in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Soil Science at Massey University(Massey University, 1994) Moir, James LaingThe effects of long-term application of single superphosphate (SSP) on soil plant-available nutrient supply and indicators of soil biological quality was investigated on Wairarapa hill soils ranging widely in previous fertiliser history (from 0 to 250 kg SSP ha-1 yr-1) and climate regime (annual and seasonal rainfall distribution). At 12 field sites spring pasture response to strategic N fertiliser application was measured, while the plant-available nutrient (P, N and S) supplying capacity of the soils was assessed in glasshouse studies. Based on the pasture growth patterns in field and glasshouse studies, a new climate-driven, soil fertility dependent pasture growth model was developed and tested. In addition, the suitability of the Biolog™ GN microtitre plating system was assessed as an indicator of soil 'quality', using these Wairarapa hill country soils. Results of soil analyses indicated that small increases in mineralisable N, in the order of 280 kg mineralisable Nha-1, with increased rates of fertiliser (P and S) may represent inefficient use of P and S fertiliser. Soil mineralisable N increased by approximately 8.6 kg mineralisable Nha-1 for every 1 unit increase in Olsen P. The ratio of accumulated plant-available N:P:S of these soils, resulting from long-term SSP applications, is approximately 17:2:1. Olsen P status was shown to be strongly correlated with measures of plant-available N and S. Pasture growth response in the field to strategic N fertiliser (30 kgNha-1) applied in spring was highly variable across sites, and within the range of 0:1 to 31:1 kgDM kgN-1. Simple single factors representing soil fertility indices, or climatic regime, could not explain the variation in site-to-site pasture growth response to applied N. Factors constraining N response are discussed. In glasshouse studies, on samples of the same soils, ryegrass and white clover showed large yield differences (clover, 0.27-2.29 gDM pot-1; ryegrass, 0.22-2.25 gDM pot-1) on low P status and high P status soils respectively. Glasshouse DM yields did not correlate with those measured in the field, confirming that at field sites yield responses to nutrient availability are strongly modified by (site-specific) climate. The relationship between Olsen P and clover yield in the glasshouse (curvilinear, R2 = 0.80) was similar to that previously seen in (spring) field conditions. The S:P and N:P ratios of clover in the glasshouse trials confirm that P availability in these soils is the major growth-limiting factor, probably followed by S or N, which becomes limiting when P availability is adequate to high. A modified Stanford and DeMent bioassay technique was used to estimate the amount of plant available N, P and S in each soil. Using an exhaustive cropping regime, these soils exhibited a large variation (range) in ryegrass yields when soils were the sole source of P and N. Yields for each soil were strongly correlated with various soil tests for N, S and P availability. S availability to plants was less variable across soils, but the smaller variation in S limited yield was still strongly correlated with the variation in a newly developed soil hydrogen peroxide-extractable S test. Results from both glasshouse experiments provide strong evidence that the Olsen P soil test is a valuable soil fertility indicator of plant-available P, N and S on legume-based pasture soils with a history of superphosphate use. The amount of dry matter production, when considered with the quantity of soil used for each treatment (-N, 100g; -P, 50g; -S, 25g), suggest that these soils have large pools of plant-available or mineralisable P and S, and, relative to plant demand, small pools of soil mineralisable N. A four-fold increase in field DM production resulted from a 3-fold increase in soil mineralisable N at these sites. This suggests that the rate of N cycling probably also increases with yield increase, and that the size of the soil mineralisable N pool is not directly related to pasture N supply. A new climate-driven, soil fertility dependent pasture production model has been developed and tested using actual DM yields from the field trial sites. The model assumes that pasture growth is proportional to evapotranspiration, and that the proportionality constant (k) depends on soil fertility Pasture growth per mm of evapotranspiration was strongly related to soil available P status at these sites. From results of the glasshouse study, it was concluded that Olsen P was a strong indicator of 'general' (plant-available P, N and S) across these sites, and therefore suitable for use as the soil fertility proportionality constant in the pasture production model. Soil-limited evapotranspiration is calculated from a simple daily soil water balance model. Values for k varied from 11 to 19 kg DM ha-1 mm-1 of evaporation. With the exception of growth after severe drought conditions, the model shows potential to closely predict actual pasture yield. It is hoped that discrepancies between the modelled and measured production may lead to useful speculation and further research on the interacting effects of weather and fertility on pasture growth. The Biolog™ GN microtitre plate system, for comparing substrate use patterns of 95 single C compounds was assessed as an indicator of soil microbial functional diversity across the 12 test hill soils. Preliminary studies showed that saline extracts of different fertility status pasture soils used for Biolog™ microtitre plate assay inoculation contain significant amounts of readily available C. It was concluded that in order to interpret the substrate use patterns correctly, this effect must be corrected for. The Biolog™ microtitre plate system, for use as an indicator of soil quality and health, was shown to have limited application to this range of pasture soils with differing pasture histories. Adaptive factors, such as constitutive and inducible enzyme activities, were shown to complicate the interpretation of microbial growth on the C substrates. Substrate use patterns also changed when soils were rewetted and incubated. Possible 'indicator' substrates were identified, but it was concluded that these were low-energy decomposition products, and as such, are not useful as indicators of microbial functional diversity across these soils. Further research would be required to establish how stable the substrate use patterns are, or the relevance of these indicators to field soil processes. However, as a research tool, the Biolog™ assay showed potential to separate these soils on the basis of microbial functional diversity. The direction of future research, and limitations of current techniques used in this field are discussed.Item Transformation and plant availability of copper in pasture soils : a thesis presented in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Soil Science at Massey University, Palmerston North, New Zealand(Massey University, 2001) Khan, Md. Afiqur RahmanThe response of pasture to copper (Cu) fertilisers in most soils is very short-lived necessitating frequent applications of Cu fertilisers. The short-term response to Cu by plants is attributed to the ready adsorption of Cu by organic matter and other soil components. Cu distribution among these different fractions and the relative availability of these fractions for plant uptake, are fundamental to an understanding of the transformation of Cu in soil. As Cu has not been routinely analysed in the past, there is no standard soil test extractant in New Zealand. The use of single chemical extractions in routine soil analysis is a fast and simple way to evaluate the availability of soil nutrients to plants. Farmers require accurate information on the length of time that Cu applications remain fully effective in order to supply the Cu required for the grazing animal. Pasture provides the main source of Cu for grazing animals. There is a need to define the rates of change in the effectiveness of Cu fertiliser over the range of soil and climatic conditions encountered in New Zealand. The specific objectives of the study were: (i) to investigate the effect of soil components on the sorption and desorption of added and native Cu in soils; (ii) to examine the soil and fertiliser properties that influence the effectiveness of Cu topdressing in terms of increasing Cu uptake by pastures; (iii) to determine the transformation of Cu added through fertiliser applied to soils; (iv) to quantify the forms of Cu in soils using a sequential fractionation procedure; (v) to identify the forms of Cu in various soil test extractants and to assess the efficiency of these soil test extractants in predicting Cu uptake; (vi) to estimate the effects of N and P fertilisers on the uptake of native Cu by ryegrass; (vii) to examine at the residual effectiveness of two Cu source fertilisers as influenced by N fertiliser, lime and EDTA additions; and (viii) to evaluate the seasonal influence on the availability of native and added Cu to pasture. Copper sorption and desorption isotherms were determined for a number of soils (Manawatu, Tokomaru, Ramiha, Ngamoka and Mangamahu) before and after the removal of various soil components. A series of glasshouse and field trials were carried out using three Cu sources, five soils and four Cu levels. The dry matter yields of ryegrass and Cu concentration in the herbage were monitored over a number of harvests. The soil was collected from the glasshouse trial at various intervals and analysed for different fractions (exchangeable, organic, oxide and residual) and were extracted with various soil test extractants. Copper extracted from the soils was correlated with the Cu concentration in the herbage. A second glasshouse trial with two soils, four levels of nitrogen (N) and five levels of phosphate fertiliser was conducted. The dry matter (DM) yield and the Cu concentration in the ryegrass were measured. The effects of N fertiliser, lime and EDTA addition on the availability of residual Cu was investigated in a separate glasshouse trial. A series of field trials were conducted, in the same paddocks, to examine the effect of season on the uptake of Cu from two Cu sources. The differences in the chemical characteristics of the soils resulted in some variation in the sorption and desorption of Cu between the soils. Soil pH, organic carbon, iron and aluminium oxides play a major role in the sorption and desorption of Cu in soils. Organic matter and oxides are important in adsorption reactions, but differences exist in their relative importance. Increasing levels of Cu increased the Cu concentration in plants. Sources of Cu fertiliser have a significant effect on DM yield, and Cu concentration at all harvests. Soil pH, organic matter, CEC and clay content correlated with Cu concentration in plants. Cu uptake in grasses decreased with time after fertiliser application. Organic and oxide bound Cu contributed >80% of total Cu in all the soils. The organically bound Cu fraction was highest in soils with high levels of organic matter. Both the organically bound and the oxide bound fractions of Cu decreased with time after fertiliser application, indicating a possible decrease in the availability of Cu. Soil exchangeable, organic and oxide bound fractions of Cu were correlated with soil organic matter, CEC and clay content. Both the organic and oxide bound Cu were correlated with plant Cu uptake. The major forms of Cu extracted by the soil test reagents include organically bound, followed by oxide bound, residual and exchangeable forms. The ratios of different forms of Cu strongly suggest that Cu is residing mainly in the organic form and increases in this order: exchangeable Mehlich-3 > Mehlich-1 > 0.02M SrCl2 > 0.1M HCl > 1.0M NH4NO3 > 0.01MCaCl2 > 0.1M NaNO3 > 0.01M Ca(NO3)2. Increasing levels of both N and P fertilisers increased both the DM yield and the uptake of native Cu. Increasing levels of N increased both the DM yields and the Cu concentration in soils with residual Cu. The effect on Cu concentration persisted beyond the first cut only at the highest N addition. Increasing levels of lime increased the DM yield of pasture, but decreased the Cu concentration in pasture at the highest level of lime addition. Increasing levels of EDTA increased the Cu concentration in soils and thereby increased the Cu concentration in the pasture. The application of 1000 kg lime ha-1 and 50 kg N ha-1 was very effective in enhancing plant availability of residual Cu in soils, but EDTA increased the plant available Cu to toxic levels. The highest application rate of lime and N fertiliser decreased the exchangeable and free Cu in the Ngamoka soil, but EDTA showed the opposite effect. In the field experiment Cu levels have no significant effect on DM yield during all seasons. The field study shows differences in seasonal response to added Cu. Increasing levels of Cu increased the Cu concentration in pasture. Types of Cu fertiliser have a significant effect on Cu concentration. The differences in pasture growth and Cu concentrations in plants seasonally could be attributed to the differences in air and soil temperature, soil moisture content and solar radiation patterns within the trial period. Adsorption and desorption reactions are likely to be the major factors controlling the availability of Cu to plants. The major forms of Cu that can be extracted by soil test extractants are the organically bound, followed by oxide bound, residual and exchangeable forms. Organic and oxide bound Cu were the main sources of plant available Cu. The uptake of native Cu and residual Cu from soils showed that N and lime at 50 kg N ha-1 and 1000 kg lime ha-1 levels increased the Cu concentration, and EDTA also increased the plant available Cu to toxic levels. The effect of N, lime, and EDTA on the availability of residual Cu in ryegrass needs further investigation. Both the glasshouse and field trials indicate that Cu uptake is internally regulated by the growth of pasture and externally affected by the transformation of Cu in soils.