ISSN: 2463-2880 (online); 2463-2872 (print) The Journal of New Zealand Grasslands publishes peer-reviewed papers with a focus on temperate grassland research. The scope of the journal includes all aspects of pastoral research including agronomy, soils, animals, agricultural extension and farm-systems research. The Journal is published by the New Zealand Grassland Association (NZGA). Formed in 1931, the NZGA facilitates discussion on grassland farming, and promotes the value of research and its application. Our membership includes a wide range of scientists, consultants, agribusiness and farmers making it truly fuelled by science and tempered by experience. The Journal has been published since 1932 (prior to 2015 as the Proceedings of the NZ Grassland Association) so provides a long-term resource reflecting agricultural research and innovation. Open access: All articles published by the Journal of New Zealand Grasslands are freely and permanently accessible online immediately upon publication.
Copyright This work is licensed under a Creative Commons Attribution-Non Commercial-NoDerivatives 4.0 International License. Rights granted to the New Zealand Grassland Association through this agreement are non-exclusive. You are free to publish the work(s) elsewhere and no ownership is assumed by the NZGA when storing or curating an electronic version of the work(s). The author(s) will receive no monetary return from the Association for the use of material contained in the manuscript. If I am one of several co-authors, I hereby confirm that I am authorized by my co-authors to grant this Licence as their agent on their behalf. For the avoidance of doubt, this includes the rights to supply the article in electronic and online forms and systems.
Using plantain (Plantago lanceolata) with other on-farm strategies to meet N loss reduction targets while maintaining profit in Rotorua Lake catchment
make significant reductions in nitrogen (N) leaching to improve freshwater quality. One option is the inclusion of plantain (Plantago lanceolata L.) in pastures, which has been shown to reduce N leaching without compromising pasture or milk production. From 2022-2025, we worked with five Rotorua partner dairy farmers to develop strategies to establish and maintain plantain in pastures as part of a whole-farm approach to reducing N loss to water while limiting impacts on profitability. Modelling and benchmarking were used to determine the impact on N leaching and profitability at farm and catchment scale. Farms on well-drained pumice or podzol soils achieved up to 20% plantain (%DM) by broadcasting 4-6 kg/ha of coated plantain seed (2-3 kg/ha bare seed) across the whole farm each year, costing $45-$68/ha per year. Plantain content in pasture DM varied from 1-65% depending on establishment method, management, soil type and contour. Including 20% plantain in pastures was estimated to lower N leaching by 8-14% with a 1-2% reduction in profit. Using plantain in a modelled mitigation stack to meet the 2032 N loss reduction targets (27-30% reduction from 2021-22 N loss), resulted in 4.7-7.5% higher profit/ha/year compared to meeting the same targets without plantain. At catchment scale, implementing plantain at 20% DM content of pasture was estimated to reduce N entering Lake Rotorua by 39 t N/year. A case study using benchmarking data demonstrated high profitability with low N loss by maintaining a lowcost structure, strategic use of mitigations including plantain, and tactical management of low N fertiliser inputs.
Copyright (c) 2025 http://creativecommons.org/licenses/by-sa/4.0
Forage yield, botanical composition and soil characteristics of a species diversity by harvest height experiment in Hawke’s Bay
There has been considerable pastoral sector interest in regenerative agriculture practises and the potential impact of diverse forage mixes and grazing to higher residuals on pasture production and soil quality. This small plot study aimed to evaluate the productivity, botanical composition, and soil characteristics of four different forage mixtures under two mowing regimes over two years at a summer-dry site. The mixtures were: ryegrass/clover (4 species), plantain/clover (6 species) and two ‘hyper-diverse’ (31 species sown at 45 or 180 kg/ha). The two mowing heights were 8 cm and 20 cm to replicate lax and very lax grazing management systems. The diverse mixtures produced more feed in the first six months due to the presence of cereals and brassicas. In fact, these vigorous annuals may have reduced the success of other species as only a small number of species in the diverse plots were present after 2 years. The 8 cm cutting height produced a mean of 26 185 kg DM/ha and the 20 cm cutting height produced a mean of 15 951 kg DM/ha across the four forage mixtures. Within the 20 cm mowing height the two diverse mixes produced the most herbage while within the 8 cm mowing height the plantain/clover mix and hyperdiverse mix at a high sowing rate produced the most herbage. There was no effect of forage mix or mowing height on soil carbon, soil nitrogen, water infiltration rates, earthworm abundance or decomposition activity over the two year period.
Oversowing arrowleaf clover on North Island East Coast dryland hill country – results from two farm case studies
Low clover content of grass-based pastures is often a challenge on summer-dry hill country. This study measured the performance of oversowing arrowleaf clover (Trifolium versiculosum) on two East Coast properties (Wairakaia in Gisborne and Tourere in Central Hawke’s Bay) following a herbicide/oversowing programme on steep uncultivatable hill country. Arrowleaf clover is a hard-seeded aerial flowering plant and the intention was for light grazing in Year 1 to achieve maximum seed set and develop a long-term seed bank to increase pasture clover content. In Year 1, dry matter production was 11.7 tonnes/ha at Wairakaia and 10.5 tonnes/ha at Tourere. Seed set was 425 and 1380 kg/ha, respectively. Because arrowleaf is hard seeded, little germination was expected in Year 2 and both paddocks were oversown in a cover crop of plantain (Plantago lanceolata) at Wairakaia and arrowleaf at Tourere. Over 3 years, the areas which had been oversown produced substantially more dry matter than adjacent resident pastures, with significantly higher herbage accumulation rates in the first two years. However, the high residual cover (‘trash’) that resulted from seed set was difficult to clean up. Moreover, subsequent germinations suffered from heavy slug infestations. Whilst oversowing with arrowleaf clover was successful in the first year, the challenges in managing arrowleaf clover in subsequent years means that arrowleaf clover is unlikely to have a role in improving clover content under a permanent pasture situation.
Future Northland Pastures: 3. Potential woody forages for Northland
Woody vegetation can provide numerous benefits onfarm, such as shade and shelter for livestock, erosion control, livestock forage, vista enhancement and fodder for honeybees and other pollinators. Research on woody species for forage has occurred in the South Island and in the central and lower North Island for exotic species such as tagasaste, saltbush, poplar and willow. We located no information on woody forages for Northland. This review identifies woody forage species with potential for use in Northland’s pastoral systems, drawing on New Zealand and international literature. Ten candidate species were selected, including leucaena, tagasaste, saltbush, and others, based on drought tolerance, nutritional traits, and adaptability. Although not woody, bananas were also included due to their potential as a forage crop, particularly on effluent treatment areas. The findings highlight the need for regional trials to evaluate establishment, management, and livestock responses.
Is soil fertility a factor limiting pasture production and persistence in New Zealand?
Clover-based pastures are an important foundation on which New Zealand’s $38b pastoral sector is based. However, clover has a higher requirement for all nutrients than the associated companion grasses and does not persist when the soil fertility is less than optimal. This paper summarises data on the nutrient status of pastoral soils in New Zealand collected in the last 20 odd years. It is found that most New Zealand pastoral soils are sub-optimal in respect to optimal clover growth. It is suggested that this is a factor limiting the production and persistence of clover-based pastures in New Zealand. The data suggest that many New Zealand pastures are operating at about 60%-80% of potential pasture production.
Sheep liveweight and dry matter production from Year 3 of the Regenerative Agriculture Dryland Experiment
Sheep liveweight and dry matter (DM) production from Regenerative and Conventional dryland systems under two levels of soil fertility (Olsen P 20-25 and 10 mg/kg) were measured in Year 3 (July 2023-June 2024) of an on-going experiment at Lincoln University. The Regenerative system comprised multispecies pastures and winter forage crops, and short-duration, high-density rotational stocking at 12.9 ewes/ha. The Conventional system had lucerne and cocksfoot/sub clover pastures, annual ryegrass as the winter forage crop, and longerduration, lower-density rotational stocking at the same stocking rate. There were no effects of soil fertility. Sheep liveweight production was 131 kg/ha (23%) less for Regenerative than Conventional (496 vs. 627 kg/ha), but DM production was 1,550 kg/ha (22%) greater (8,490 vs. 6,940 kg/ha) with lower crude protein (13% vs. 19%), lower metabolisable energy (9.5 vs. 10.0 MJ/kg DM) and higher neutral detergent fibre (51% vs. 40%). This contributed to lower liveweight gains of priority lambs compared ith the legume dominant Conventional system.
Catchment level modelling of dairy farm adaptation to meet nitrogen loss targets and the value of including plantain as a mitigation
Regulations addressing nutrient losses to ground and surface water bodies are increasingly applied at the catchment level, necessitating catchment-level analysis of implementing environmental mitigations. We conducted catchment-scale modelling to predict the production and economic impacts for dairy farms to achieve N (nitrogen) loss targets, using the Dairy Sector was used as a case study. The DSP model simulated a population of dairy farms within the catchment based on real farm data, applying ‘stacked’ mitigation steps over time to meet N leaching targets. The targets required reductions in N leaching per hectare of 31% on average. The study focused on forage plantain as a key low-cost mitigation. When plantain was included, the impacts of farms achieving the final N loss targets were predicted to be substantial, including: 1,100 fewer cows farmed, 790,000 kg fewer milksolids produced annually, and $3.3 million lower annual operating profit across the 26 dairy farms in the catchment. However, without plantain, the economic impacts were even greater, with operating profit reduced by $3.8 million. Adoption of N loss mitigations for significant mandated reductions were predicted to have a large impact on the dairy farming community. Relatively low-cost mitigations such as plantain were demonstrated as valuable for softening these impacts.
The challenges of monitoring insect sleeper pests: the example of Spodoptera litura in Aotearoa New Zealand
Farmers will face a different suite of insect pests under climate change. Monitoring their population dynamics over time is important for risk assessment and mitigation, but it can be expensive and time-consuming. After appropriate quality checks and analyses, data from two online citizen science platforms, iNaturalist and the Global Biodiversity Information Facility (GBIF), indicated higher numbers and an extended geographical range of the representative sleeper pest in Aotearoa New Zealand, Spodoptera litura, in 2018 and 2022-23. This example suggests that these platforms could be a useful tool for future pest monitoring.
Laboratory measurements of Aporrectodea caliginosa earthworm counts using qPCR in agricultural soils
Traditionally, the abundance of earthworms in soil is perceived as a good biological indicator of soil health. While the direct relationship between earthworms and soil health is perhaps uncertain, it is well known that earthworms do provide benefits to the soil. The conventional method of determining the abundance of earthworms is a physical count within a spade square of sampled soil, which is a manual and timeconsuming process, and where speciation is desired, requires technical expertise. Earthworm abundances vary spatially and hence the values derived will be dependent on the sites selected for measurement. Hill Labs in conjunction with AgResearch have developed a quantitative PCR (qPCR) test to determine the concentration of environmental DNA (eDNA) of the earthworm Aporrectodea caliginosa. A. caliginosa, is the most abundant earthworm in agricultural New Zealand. The eDNA contained within routine (7.5 cm transect cores, 38°C dried and < 2 mm ground) agronomic soil samples, was correlated to abundance. The field calibration was highly correlated with a log equation having an R2 of 0.68, and the remaining variation largely explainable by the precision of the measurements. While eDNA appears to degrade in the field-moist samples post collection, the eDNA is stable once the soil samples are dried and ground within the lab. The analysis is run in triplicate to account for inherent variation and potential for ‘spikes’ of genomic DNA within the subsampling process. While there is evidence that a single result is as precise as the fieldsampling technique, we believe testing in triplicate and using the average value (excluding outliers), provides a result that is more reflective of the earthworm population. We believe this method is overall fit-forpurpose for determining the state of earthworms in New Zealand.
Performance across 60 years of the Dairy Economic Survey
For the last 60 years DairyNZ and its predecessors (the New Zealand Dairy Board and Dexcel) have been publishing the Economic Survey under various names. These publications summarise the financial performance of New Zealand dairy farms for each financial year (season). By combining the results of each publication, we create a dataset that describes the financial position and performance of the average New Zealand dairy farm including the following observations: The intensification and expansion of the sector A negative trend in the percentage total return on assets Fluctuations in the Debt to Asset Ratio of dairy farms Dairy farmers are spending more on feed in real terms.
Brix was not a good indicator of pasture quality
Measuring pasture quality by drying, grinding and laboratory analysis is expensive and time consuming. Some commentators have suggested using Brix (a measurement of soluble sugars used in wine and fruit industries) to estimate the feed value of fresh forages. However, there is little data on how useful Brix measurements are in determining pasture quality. This study compared Brix measurements to standard laboratory measurements of pasture quality for five pasture treatments: ryegrass/clover and a multi-species mixture, each harvested to 8 and 20 cm, and plantain/clover harvested to 20 cm, across three sampling dates between October 2021 and January 2022. Plant species and their physiological state varied across pasture treatment and date and resulted in variation in Brix and laboratory measures of quality. Metabolisable energy (ME) declined but Brix values increased between October and January as pasture changed from a vegetative to a reproductive state with seedheads. There was a positive relationship between Brix and dry matter percentage (Brix = 1.49 + 0.40 × DM%, R2 = 72.1%). There was no consistent relationship between Brix and ME, neutral detergent fibre, acid detergent fibre and water-soluble carbohydrate contents. This severely limited the use of Brix in determining pasture quality.
An overview of the cost-effectiveness of nitrogen leaching mitigation strategies based on marginal abatement cost for eighteen dairy farms in Hauraki and Horizons regions
Nitrogen (N) management is crucial for reducing environmental impacts in New Zealand’s dairy farming sector, particularly in minimising N leaching into freshwater systems. This study employs Marginal Abatement Cost (MAC) analysis to assess the costeffectiveness of various N leaching mitigation strategies across 18 dairy farms in the Hauraki and Horizons regions. These farms represent a range of systems, soil types, and management practices. The results show that the MAC varies significantly due to differences in farm characteristics, biophysical conditions, and economic factors. Farms with high purchased N surplus (imported N via fertiliser and supplementary feeds minus exported N in products) generally have lower MAC for early-stage mitigations, such as optimising N inputs and nutrient recycling (optimal use of effluent and manure on crop or pasture). In contrast, farms with low purchased N surplus and already efficient management practices face higher MAC, as further reductions require costly interventions like infrastructure upgrades or stocking rate reductions. Additionally, soil type, climate, existing infrastructure and how the mitigations complement the existing system play key roles in the effectiveness and cost of mitigation strategies. Despite considerable variation in the MAC among farms, overall trends revealed that the most cost-effective strategies often involve nutrient recycling, improved N use efficiency, and the use of plantain. In contrast, de-intensification and off-paddock structures were among the most expensive mitigation options. However, off-paddock structures can become cost-effective when they complement the existing farm system. These findings emphasize the need for farm specific mitigation strategies to balance environmental sustainability with economic viability.
Vulnerability and resilience of farm systems in the Gisborne-Tairawhiti Region in the aftermath of Cyclone Gabrielle
This exploratory study aims to understand the vulnerability and resilience of farm systems in the Gisborne-Tairawhiti Region as perceived by the farmers in the aftermath of Cyclone Gabrielle. Results highlighted the complex nature of farm systems in the region and the need to strengthen their adaptive capacity in the face of climate change and associated severe weather events. Farmers need to allow sufficient buffer within their farm systems and adopt long-term, adaptive management strategies to reduce vulnerability and promote resilience. More coordinated approaches across government agencies, rural professionals and the farming communities are needed for future recovery efforts.
A comparison of two pasture growth models with observed data from Central Waikato from 2000 to 2020
Pasture is essential to New Zealand farming, but its seasonal and annual variability complicates feed budgeting, farm management, and research predictions. This study evaluated the AgPasture and McCall-Romera pasture models for predicting monthly growth ates and annual herbage accumulation using observed data from Scott Farm, Newstead, New Zealand, from 2000 to 2020. Both models overestimated annual pasture yield, with AgPasture showing a slightly higher bias (Mean Bias Error (MBE) = 1256 vs. 1155 kg DM/ha/year). However, the difference was not statistically or practically significant. Adjusting for differences in annual nitrogen use between the observed and modelled data improved accuracy. McCall-Romera performed slightly better (MBE = 692 vs. 793 kg DM/ha/year), but again, not statistically significant. Both models showed seasonal biases underestimating pasture growth in late autumn and winter and overestimating it in late spring and summer. In May, the MBE was -11 kg DM/ha/day for AgPasture and -6 kg DM/ha/day for McCall-Romera, whereas in December, the MBE was 46 kg DM/ha/day and 23 kg DM/ha/day, respectively. Despite increased variability over two decades (coefficient of variation for AgPasture increased from 67% to 74%; McCall-Romera 46% to 58%), prediction accuracy remained stable, demonstrating robustness under changing climate conditions. While both models are suitable for predicting pasture growth, further calibration is recommended to improve seasonal accuracy and enhance research reliability.
Case studies of alternative wintering practices in sheep, beef and deer farming in Southern New Zealand
Practical uptake of alternative winter-feeding practices can be aided by providing examples of the processes farmer have used, and their experiences when implementing non-traditional approaches. Six farmers in Otago and Southland used a range of forage options over a 3-year period. Crop yield and crop nutrient concentration data were collected by the research team in winter and spring. Information on management practices, grazing days, and in some cases animal performance was recorded by the farmer. Winter yields were quite varied, ranging from approximately 6 to 10 t DM ha-1. After grazing during winter, forage regrowth contributed between 1,900 and 3,800 kg DM ha-1 to spring feed requirements. Benefits came both from the management methods and the actual wintering practices. Reducing mud was identified as a key aspect of all practices. Wintering of heavy cattle still compromised soil strength in very wet soil conditions. The replacement of traditional winter crops with alternative wintering options increased complexity and the need for precision, while offering some opportunities in autumn and spring, such as increasing spring feed supply in sheep, beef and deer systems.
Implementing deferred grazing on New Zealand sheep, beef and dairy farms
Deferred grazing is the practice of excluding livestock from a pasture between late spring and mid- to late summer to allow reseeding of desirable pasture species. It can be used as a pasture rejuvenation tool, and to control feed supply and pasture quality at farm scale. In this perspectives paper, we i) review the scientific literature on the impacts of deferred grazing on pasture and livestock performance; (ii) discuss key decision criteria involved in implementing deferred grazing for dairy, and beef and sheep farm systems; and (iii) present a decision tree for farmers to assist them in implementing deferred grazing.
Looking at the past to prepare ahead: adapting Red Clover for future New Zealand climates
Developing adaptive, resilient pastural cultivars is crucial for maintaining New Zealand’s (NZ) highly productive farming sector. With growing challenges from climate change, including heat and extreme rainfall, identifying genetic material that provides resilience is vital. Wild populations, shaped by their local environmental pressures and isolation, hold unique gene makeups that can help develop climateadaptive cultivars. In this study, we examined the genetic response of 92 internationally geographically diverse red clover populations to their source bioclimatic environments using partial redundancy analysis. The aim was to identify bioclimatic variables driving environmental adaptation and the resulting DNA variants (outlier single nucleotide polymorphisms (SNPs)) associated with adaptation. Calculation of adaptive indices and genomic offset values enabled us to predict the suitability of these populations to future NZ environments. We found that Annual mean diurnal range, Isothermality (variance in daily temperature relative to annual variation), Mean temperature of the wettest quarter, and Precipitation seasonality underpinned adaptive genetic variation. Forty-two outlier SNPs strongly associated with key bioclimatic variables show potential as markers for climateresilient breeding. Mapping adaptive indices and genomic offset values to NZ’s current and predicted future climates showed the genetic diversity captured in these germplasm populations could help develop future-proofed adaptive cultivars.
On-farm prediction of red clover yields.
Red clover (Trifolium pratense L.) grown at Taihape, New Zealand, was analysed to validate coefficients to predict biomass yield. The mean annual production of red clover over three years was 12,830±472 kg DM/ha/year, with the maximum mean growth rate of 112±7.21 kg DM/ha/day (spring). In non-limiting soil moisture conditions, red clover grew 7.44±0.31 kg DM/ha/°Cd up until the 11th of January and then at 2.67±0.47 kg DM/ha/°Cd. This pattern of production confirms previously results that show a reduction in growth rate for the mid-January-July period. This probably reflects increased partitioning of assimilate to red clover roots in response to a decreasing photoperiod. These coefficients are easily transferable to estimate red clover yield under non-limiting conditions for other locations. These could be integrated into feed budgeting software to assist on-farm decision-making. For years with a significant period of water deficit, a soil water budget is required coupled with the temperature-based coefficients to estimate yield and the potential loss of yield from summer dry conditions.
Pathways to climate resilience: Adaptation of dairy farm systems in response to climate changes
Changes in climate across New Zealand (NZ) require ongoing adaptation strategies for pasture-based dairy farmers to remain productive, resilient and economically viable. In this study we explored strategies that NZ dairy farmers are using to adapt their systems to changes in regional climate. This research used a qualitative semistructured interviews to conduct case study research on seven dairy farms throughout NZ. The case study farmers noted more variable regional climate with changes such as warmer winters with less frosts, more frequent and serious flooding events, longer dry periods interspersed with more intense rainfall events, heat in summer, and increased wind intensity during storms. They used a range of adaptation strategies in response to regional climate changes. These strategies can be classified as a) enhancing system robustness through lowering stocking rates to increase feed buffers, b) increased adaptability through greater responsiveness to significant events such as floods, or c) transformative change such as moving to whole season once-a-day milking or investing in housing infrastructure. The case studies highlight that farmers already need support from agricultural research, extension and policy to increase their adaptive capacity to more variable and extreme weather; this is now a current, rather than future, issue.
Spring growth of lucerne (Medicago sativa L.) after different winter grazing regimes
This experiment determined if the removal of basal buds by grazing in autumn/winter affected the spring growth or development of lucerne. Established at Iversen Field Lincoln University, New Zealand and the experiment ran from the 1st of June 2024 to 1st of October 2024 (122 d). Four grazing dates (1st of June, 3rd of July, 17th of July, and the 1st of August) were were applied by mob stocking mixed age Coopworth ewes to simulate a “clean-up” winter graze. The start of rapid stem extension in spring occurred at a photoperiod of 10.8 (± 0.2) hours for all treatments. However, shoot biomass differed at each harvest until the 3rd of September. Taproot yield was highest in crops grazed on the 1st of June (3300±124 kg DM/ha) and lowest (1100±124) kg DM/ha) in the latest (1st of August) grazing date at the final harvest on the 1st of October. Results suggested that spring shoot biomass production was unaffected by winter grazing date. However, the ~1000 kg DM/ha lower root yield for lucerne grazed on 1st August meant the crop would require a longer period of autumn recovery to recharge reserves to maintain stand persistence.
Future Northland Pastures 4. Northland arthropod pests and ‘sleeper pests’ that will increase in response to climate change
The distribution and abundance of some of the exotic invertebrates established in New Zealand will be altered by direct and indirect effects of climate change. Some of the invertebrates will become more active and subsequently their impact on pastoral systems will increase. A literature review focused on arthropod ‘sleeper pests’ in pastures in New Zealand was conducted. The results show that there are currently 12 arthropod pests that are likely to increase in numbers and/or distribution in Northland, becoming more damaging under future climate and habitat composition. Little is known about the current occurrence and abundance of these arthropods and their associated natural enemies in Northland. A monitoring programme for both the arthropod pests and the abundance of natural enemies throughout the year is needed. There is a need to develop a farmer-research partnership that allows for proactive creation of practical control solutions before serious outbreaks occur.
Reflections on the past and links to the future
My presidential address is not going to follow the traditional format of the last decade or so where the president reflects on where in the world New Zealand agriculture sits, or how we can transform New Zealand agriculture. Rather I am going to reflect upon my own research career which spans 50 years of mainly field studies and how I see some of the early research being relevant even in today’s very different environment. When I look back and reflect on my 50 years as a researcher, both field technician and scientist, one thing stands out. The first 25 years was mainly spent researching production increases via increased and more efficient fertiliser usage. The second 25 years were spent investigating and mitigating the environmental impacts of this increased production. In doing this I can see several themes that have re-occurred, some for the better and some not. There have been incidences of research appearing to repeat some 20 + years after the first study. I will give an example of this and why I feel that in the right situation this is not always a bad idea. I have also been involved with farmers doing on farm research as well as working on research stations. Both have their place.
Will wide-spaced silvo-pastoral plantings maintain soil carbon stocks?
Silvo-pastoral systems are common globally but not so in New Zealand, where there are limited examples within pastoral landscapes. Pastoral soils in New Zealand have relatively high soil organic carbon (SOC) stocks by global standards, and tree planting may reduce these. This study aimed to investigate whether wide-spaced tree planting into pasture would maintain SOC stocks after 25-27 years, extending the data previously reported at 14-16 years after planting on two North Island pasture sites. Two deciduous tree species were planted in the late 1990s in part-Nelder experimental designs – poplars (Populus deltoides × P. nigra) at a summer-moist site, and alders (Alnus cordata) at a summer-dry site. Soil OC stocks to 600 mm depth were re-measured in 2023, under open pasture and two tree stem densities at each site, along with pasture herbage accumulation and micro-climate variables. Soil OC stocks had continued to decline under the poplars but were relatively stable under the alders. Pasture production was c. 60% of open pasture under the poplars but not reduced under wide-spaced alders (120 stems/ha). The nitrogen-fixing capability of the alders may be an important function in this silvopastoral context, offering nitrogen input for additional biomass C sequestration without compromising pasture productivity and SOC stocks.
Long-term impacts of land use change at Whatawhata: the story continues
The Whatawhata Integrated Catchment Management project is New Zealand’s longest-running beforeafter-control-impact catchment farm system study. The economic and environmental impacts of land use changes have been monitored in the 260-hectare Mangaotama Block over 30 years, before and after land use changes implemented in 2001. Those changes included extensive pine plantation (140 ha), indigenous vegetation restoration (12 ha), poplar planting, livestock exclusion from streams, and shifts in livestock enterprises from breeding to finishing systems. This paper updates earlier presentations of the impacts of these changes. Longer-term monitoring has assessed the impacts on water quality, indigenous biodiversity, and greenhouse gas (GHG) emissions. Results indicate mixed water quality outcomes. Visual clarity improved and stream temperature declined, in contrast with rising nitrate and total nitrogen concentrations, partially due to reduced stream flow. Catchment annual average sediment loads have decreased while annual average nitrate loads have increased. Biodiversity monitoring shows increased tree regeneration and forest structure improvement in fenced and planted areas. The land use changes also significantly reduced GHG emissions, primarily through afforestation and lower livestock numbers, converting the catchment farm from a net emitter to a net sink. Soil carbon stocks overall appear to be in decline, though data are limited. These findings provide insights for hill country farmers and policy developers seeking to understand realistic time frames for meeting environmental management goals in the long-term.
Future Northland Pastures: 2. C4 grasses and subtropical legumes for a future Northland
Northland’s subtropical climate presents both challenges and opportunities for pasture systems under future climate scenarios. This study aimed to identify C4 grasses and subtropical legumes with potential to improve resilience, productivity, and sustainability of Northland pastures. Candidate species were compiled from historical Northland trials and the Tropical Forages database, resulting in an initial pool of 60 grass and over 90 legume taxa. Each species was assessed for agronomic potential, availability of seed or cultivars, and regulatory status under the MPI Plant Biosecurity Index. Nomenclature was standardised using authoritative taxonomic databases. Species were classified into three categories—Green, Orange, and Red—based on priority for evaluation. Green list species are both agronomically promising and permitted by MPI, while Orange list species have limitations requiring further consideration. Red list species are either restricted, unrecorded, or deemed agronomically unsuitable. Cultivar availability and breeding activity were highly variable, with legume options especially constrained. A staged approach to evaluation is recommended, including initial use of nitrogen fertiliser in legume trials to defer rhizobium-specific work. This review highlights the need for renewed trialling of selected subtropical species and supports a pathway toward diversifying pasture systems in warmer regions of New Zealand.
Changes in soil fertility, biology and organic carbon under contrasting phosphorus fertiliser and sheep grazing management
The phosphorus (P) fertiliser and sheep grazing experiment established at Ballantrae in 1975 has become an invaluable field laboratory. In-depth experimental studies have explored the long-term link between P fertiliser inputs and pasture and animal production, including the impact of withholding P fertiliser. In this paper we report on changes in soil nutrient fertility, organic matter, biology and physical status of soil across three farmlets that are receiving different rates of P fertiliser. Since 2020, soil pH has dropped by 0.5 units. Prior to 2020 pH values showed very little change, averaging 5.3 over the previous 45 years, despite very limited use of lime. There has been a trend of declining exchangeable magnesium and potassium levels, with differences seen across slopes, while exchangeable calcium has been sustained in the two farmlets receiving P fertiliser. The measured declines in total nitrogen in soil and earthworm abundance are consistent with the decline in pasture production and sheep stocking rates. If we are to fully understand the implications of variable inputs and management for permanent pasture systems within a changing climate, we must continue monitoring and measuring such longterm field experiments.
Nutrient and contaminant profiles of soil, herbage and dung from sheep grazed pastures with varying phosphorus fertiliser histories
country pastures improves productivity and increases the risk of contaminants, particularly cadmium (Cd), that accumulate in soil. This study explores the macronutrient and Cd profiles of soil, herbage, and sheep dung as influenced by contrasting P fertiliser histories: no fertiliser (NF), low fertiliser (LF), and high fertiliser (HF) input. Soil samples from HF showed higher Olsen P, total P, sulphate-S and total Cd compared with NF and LF. Herbage from HF contained higher concentrations of P, K, S, and Cd, with a shift in botanical composition favouring perennial ryegrass. Compared with NF, dung samples from HF had higher concentrations of N (2.4 vs 2.2%), P (0.97 vs 0.54%), indicating greater cycling of nutrients and contaminants through the animal. These findings highlight the legacy effects of P fertiliser use on nutrient and contaminant cycling in hill country systems and support efforts to model their long-term agroecological impact.
Lucerne (Medicago sativa L.) yields were unaffected by phosphorus fertility level under grazing in a dryland farmlet experiment
Phosphorus (P) is a key nutrient recommended for optimal nitrogen fixation by legumes in New Zealand pastoral systems. However, few field studies have examined the response of legume monocultures to soil P levels. This experiment measured lucerne yield under grazing in the field when grown under two P fertiliser regimes for the first three years of the dryland farmlet experiment at Lincoln University. The ‘High’ phosphorus treatment aimed for an Olsen P of ~20 compared with ~10 for the ‘Low’ treatment. Lucerne shoot biomass showed no effect of treatment at any time. This was consistent with no differences observed for lucerne mean daily growth rates and canopy light interception. Additionally linear regression analysis showed no relationship (R2 = 0.01) between soil Olsen P and any of the measured variables. These results suggest that the critical Olsen P may be <10 for dryland lucerne monocultures measured to a soil depth of 75 mm, which is consistent with previous recommendations.
Does wintering on diverse pastures or kale crop affect N loss risk? Findings from a case study of a commercial dairy farm in Methven
This case study describes farmer-led research comparing the practicalities and nitrogen (N) leaching risks from dairy winter grazing on kale or diverse pasture. Two herds of dairy cows grazed either a kale (n=360) or diverse pasture (n=60) paddock on a commercial dairy farm in Methven during June and July 2023. A perennial pasture mix was sown in August following winter grazing on kale. Soil cores were sampled to 15, 30, 60 and 90 cm depth increments in July and November 2023. Herbage yield and N content were measured in November. Following winter grazing in July, soil inorganic N in the 0-90 cm depth under the kale crop areas was two times greater than under pasture (138 vs 67 kg N/ha), and five times greater in November following re-growth of pastures (152 vs 29 kg N/ha). The lower soil inorganic N under pasture could be attributed, at least in part, to a lower stocking density and increased herbage N uptake (98 and 35 kg N/ha under respective pasture and kale paddocks). Pasture wintering demonstrated practical and environmental benefits over kale wintering, but furthe
Challenges in using on-farm animal data for pasture dry matter intake calculations
An accurate dry matter intake (DMI) estimation is crucial for on-farm feed management and research, including calculating methane emissions. Since direct measurement of DMI is labour-intensive (e.g., using n-alkanes), researchers and industry organisations have developed predictive energy equations to backcalculate DMI from theoretical energy demand. However, these equations rely on accurate input data for variables such as animal liveweight, milk production, and supplements fed, which can be challenging to obtain. This study explored an alternative methodology for back-calculating the DMI of lactating dairy cows using farm data from a research farm setting and compared the results with observations of on-farm pasture disappearance using a rising plate meter. While analysis of the alternative approach is ongoing, this paper focuses on the data handling, processing, and quality considerations necessary for applying predictive intake equations in on-farm contexts. Accurately back-calculating DMI remains challenging without high-quality data inputs. Still, the potential of technology in aiding data collection, such as the use of automated processes, holds promise for DMI estimation.