The agricultural industry in New Zealand, especially intensified dairy farming, faces pressures from environmental regulations and market dynamics, prompting a shift toward more sustainable practices like horticultural land use. Existing literature on land use change has primarily focused on geographical factors, leaving a gap in understanding farm-level influences on farmers' land use decisions. This study addresses this gap by analysing farm-level land use change patterns in New Zealand and identifying how farmer and farm characteristics, values, and demographics influence these decisions, using machine learning methods to enhance analytical capability. Our results indicate that younger farmers and those in horticulture/crop and sheep and beef industries are more likely to engage in land use changes, driven by environmental values and risk attitudes. The findings provide insights into drivers of rural landscape transformation among different farming sectors, emphasising the need for tailored policy and support mechanisms to manage land use transitions effectively.

Climate change will affect New Zealand's diverse range of climatic systems in different ways. The impacts on agriculture are expected to vary with geographical location and the specific biophysical requirements of different crops and agricultural systems. To improve our understanding of these impacts, key biophysical vulnerabilities for the main farming systems in New Zealand were identified and modelled using the daily projected climate scenario data. Results show high spatial variability but a general pattern of suitability ranges for crops moving south, and animal health issues intensifying and also moving south. Sediment loads are projected to increase, particularly in soft-rock hill country areas in the North Island. The modelling approach offers opportunities for analysing the temporal significance of projected changes, such as the timing and duration of drought, the effect on timing of phenological stages, the timing of pasture growth and the effect on animal farm systems.

This study explores the potential benefits of transitioning from livestock farming to high-value alternative crops as a strategy for mitigating agricultural greenhouse gas (GHG) emissions in New Zealand. The government has set ambitious targets for reducing methane (CH4) emissions. However, since animal product exports play a crucial role in New Zealand’s economy, any shift in land use will have significant impacts on both the regional and national economy. We developed a GIS framework that integrated (i) growing requirements, (ii) GHG emissions and (iii) profitability for crops. Analysis of export market opportunities identified twelve high-value “alternative crops”. Availability of suitable land for crop expansion was not a limiting factor. Working with the Ministry for Primary Industries, we explored how land use change scenarios contributed to Government 2050 biogenic CH4 emission reduction targets. Doubling the area of alternative crops (a 195,000-ha increase) by reallocating land from livestock farming resulted in reducing biogenic CH4 emissions by 1.2 to 5.4

To determine the impact of potential reductions of terrain-targeted nitrogen (N) fertilisation rates on N losses a simulation study was carried out using the Agricultural Production Systems Simulator (APSIM). To simulate N runoff a simple approach was used, in which runoff is based on the N concentration in the soil solution and an extraction coefficient. Firstly, APSIM parameters that have the largest effect on runoff of water and N were determined for terrains with different slopes for a poorly drained silt loam. A sensitivity analysis was then conducted to assess the effect of soil hydraulic properties and soil organic carbon content on runoff losses. Finally, APSIM was set up to simulate pasture production and water and N dynamics (including pasture N uptake, leaching and N runoff) for a farm on rolling hills in South Canterbury, New Zealand. Two different fertilisation approaches were used, either scheduled or based on the aboveground N concentration of the pasture. For the poorly drained silt loam, the rainfall intensity and the surface conductance had the highest effect on the amount of water lost by runoff. Soil hydraulic conductivity at saturation and field capacity, as well as plant available water content also controlled runoff of water and N, while the organic carbon content of the topsoil had less effect on N runoff. Both the extraction coefficient and the depth considered to exchange N with the runoff water affected the amount of N lost via runoff. Using the aboveground pasture N concentration prior to fertilisation had positive effects on pasture yield and reduced N runoff losses.

Soil hydraulic properties (SHPs), including available water content and near-saturated hydraulic conductivity (K-ns), affect hydrological and biochemical processes. The SHPs information is crucial to agricultural water management. The objective of this study using paired sites was to investigate the effects of land use on SHPs in two contrasting soil orders. Soil water retention curves and Kns at three soil depths (0-10, 10-20 and 20-30 cm) were measured under two land uses (pasture, consisting of a rye grass [Lolium perenne L.] and white clover [Trifolium repens L.] mix, and maize [Zea mays L.] cropping > 10 years) in Waikato, New Zealand. For each land use, two soil orders with contrasting soil structural vulnerability were selected: less vulnerable Allophanic soil and more vulnerable Gley soil. Compared with pasture, maize cropping reduced macroporosity, readily available water capacity and K-ns of 0-30 cm, and the effect was greater in the deep layer (20-30 cm). This indicated that maize cropping practices result in greater structural degradation to soils compared with pasture, which include the potential for greater subsoil compaction. There was no land use by soil order interaction effect on SHPs, suggesting that the relative SHP degradation under maize cropping compared with pasture grazing was not associated with soil structural vulnerability. Our study emphasised that long-term continuous cropping with maize on the more vulnerable soil (i.e. Gley soil) resulted in the poorest soil physical health.

ABSTRACT Agencies are increasingly developing evidence-based policies to manage natural resources. However, the influence of science in policy is not straightforward nor guaranteed. Critiques based on literature meta-analyses or policy-maker interviews suggest deficiencies in science production and delivery with some studies highlighting the importance of human dimensions. In interviews with decision-makers in freshwater policy in New Zealand and California, we investigated barriers to using science in complex and contested policy contexts. Findings highlighted the importance of the science, scientist, decision-maker, and the decision maker’s relationship with the scientist, for improving the influence of science on policy decisions. The influence depended more on the scientist delivering the information and the audience receiving it, than on the nature of the science itself. Frameworks like CRELE (credibility, relevance, legitimacy) and ACTA (applicability, comprehensiveness, timing, accessibility) are essential but outweighed by the human dimensions of policy development. With greater public, industry and NGO oversight of policy debates related to highly contested resources like water, the volume and quality of science for policy has greatly improved, meaning CRELE and ACTA factors have less prevalence. We give three categories of recommendations for improving the use of science in decision-making – science communication, science production and policy processes.

Soil hydraulic properties (SHP) control water movement and storage and thus affect a wide range of biogeo-chemical processes and ecosystem services. The objectives of this study were to identify the interactions between long-term land use and soil type on SHP (e.g., available water content [AWC], hydraulic conductivity [K]), and the effects of soil organic carbon (SOC) content on these properties. Soil water release curves and (near) saturated hydraulic conductivity at three soil depths (0-7.5, 7.5-15, and 15-30 cm) were measured under three long-term (>20 years) land uses (irrigated pasture [IP], dryland pasture [DP], and irrigated cropping [IC]) in Canterbury, New Zealand. For each land use, three soil types with contrasting drainage characteristics were selected: well-drained Lismore (LIS) stony silt loam, moderately well-drained Templeton (TEM) silt loam, and poorlydrained Waterton/Temuka (WAT) clay loam. Compared to DP, the IP and IC soils had lower AWC and K. Significant interactions between land use and soil type were found for AWC but not for K. Bulk density, SOC, and clay content could explain half the variation in AWC but had limited influence on K. More variance in AWC (6-13%) and K (5-27%) could be explained by including categorical variables (i.e., land use, soil type, and soil depth) and their interactions with continuous variables, indicating the potential benefit of including these categorical variables when developing pedotransfer functions for AWC and K. This study suggests that many macropores (>30 mu m) were poorly connected and contributed more to water storage than to conducting water. The commonly used soil matric potential of -10 kPa was suitable for defining field capacity in DP and IC soils but a lower matric potential (-33 kPa) was more appropriate for IP soil affected by livestock treading during grazing. Soil organic carbon mainly increased AWC by affecting water retention at soil matric potentials of between -40 and -1500 kPa (equivalent to pore size 0.2-7.5 mu m). Therefore, soil carbon sequestration may be important to alleviating water stress in dry environments. Our study also suggests that the effects of land use and its interaction with soil type, soil matric potential at field capacity, and soil organic carbon on SHP need to be considered during soil parameterization of hydrological models.

Improved process understanding of temporal change in soil hydraulic, water retention, and soil physical properties is required to improve modelling of soil-water dynamics. This study reports on temporal trends in soil physical properties for intensive till and no till irrigated wheat, from autumn sowing to summer harvest. There were significant temporal trends for bulk density, readily available water capacity, and unsaturated hydraulic conductivity (at three matric potentials). Using a simple two-parameter exponential model for unsaturated hydraulic conductivity, the model coefficients appeared to increase over the first 10 weeks, followed by a decrease and later increase, but the temporal effect when using this model was not significant given the parameter uncertainty. Daily rainfall, irrigation, and evapotranspiration were evaluated as possible explanatory variables, but these were not generally significant in explaining temporal trends of soil properties. An implication is the need to provide temporal data to parameterise hydrological models for more accurate modelling, including irrigation scheduling.

Irrigation is likely to increase water losses from hillslopes, particularly on loess-derived soils with impeded drainage. This is important as irrigation of these soils in New Zealand is increasing. A field site was established to measure runoff from a pasture hillslope irrigated by a centre-pivot in South Canterbury. Between November and March, 161 and 199 mm of irrigation was applied, with 23% more at the bottom of the slope. Runoff varied with position in the hillslope, with 3.5 times from the bottom plot (52 mm) compared to the top. Over the length of the slope (40 m) this represents a potential loss of 9% of precipitation, or 21% of the irrigation. Evidence for saturation excess and infiltration excess runoff was observed, with antecedent soil moisture conditions being a key factor. Pasture production and water use efficiency (WUE) also varied with slope, the least (4.6 t DM/ha or 12 kg DM/ha/mm) observed at middle and most at the top of the slope (10.1 t DM/ha or 23 kg DM/ha/mm). This was likely due to a combination of differences in radiation and soil conditions. There was indication that pasture growth was limited by water availability at the top and potentially excess at the bottom of the slope. Our results indicate potential for improving irrigation practices.

Terrestrial ecosystems, both natural ecosystems and agroecosystems, generate greenhouse gases (GHGs). The chamber method is the most common method to quantify GHG fluxes from soil-plant systems and to better understand factors affecting their generation and mitigation. The objective of this study was to review and synthesize literature on chamber designs (non-flow-through, non-steady-state chamber) and associated factors that affect GHG nitrous oxide (N2 O) flux measurement when using chamber methods. Chamber design requires consideration of many facets that include materials, insulation, sealing, venting, depth of placement, and the need to maintain plant growth and activity. Final designs should be tailored, and bench tested, in order to meet the nuances of the experimental objectives and the ecosystem under study while reducing potential artifacts. Good insulation, to prevent temperature fluctuations and pressure changes, and a high-quality seal between base and chamber are essential. Elimination of pressure differentials between headspace and atmosphere through venting should be performed, and designs now exist to eliminate Venturi effects of earlier tube-type vent designs. The use of fans within the chamber headspace increases measurement precision but may alter the flux. To establish best practice recommendations when using fans, further data are required, particularly in systems containing tall plants, to systematically evaluate the effects that fan speed, position, and mixing rate have on soil gas flux.

The global demand to increase food production from underperforming, water and nutrient limited soils is increasing, which has resulted in an increased dependency on water for irrigation. As fresh water is a finite resource, the increase in irrigation use has resulted in competition between water used for municipal purposes and that used for food and fibre production for an increasing global population. An opportunity exists to improve the efficiency of both urban and agricultural systems by taking green waste compost generated in urban centres and incorporating it into agricultural soils with poor water retention, thereby increasing the ability of these soils to efficiently retain irrigation water for plant use and also to capture a greater volume of water from rainfall. Addition of amendments to soil changes the pore space. The magnitude and cause for this change depends on amendment type, application rate, soil type and climatic conditions. The aim of this research was to determine if the incorporation of municipal compost (MC) can increase the quantity (total volume) and concentration (total volume per unit volume) of soil pores that hold readily available water (defined as macro-mesopores of 30–3 μm diameter) and plant available water (defined as mesopores of 30–0.3 μm diameter). We hypothesised that increases in total porosity would be positively correlated with MC application rate and increases in water holding porosity (macro-mesoporosity and mesoporosity) would be positively correlated with decreasing MC particle size due to the creation of inter-particle pore spaces < 30 μm in diameter. The MC was screened to three different maximum particle sizes – MC4 (<4 mm), MC2 (<2 mm) and MC0.25 (<0.25 mm) – and incorporated into repacked soil cores at five different rates: 0, 5, 25, 50 and 80% wt/wt. Incorporation of MC0.25 increased the concentration and quantity of macro-mesopores and mesopores at significantly lower application rates than MC4 and MC2. The finding that modification of MC particle size can produce targeted changes in inter-particle porosity suggests that this practice has potential to remediate hydraulic limitations of soils.

Grazed pasture constitutes a major source of agriculturally derived nitrous oxide (N 2 O), which is a potent greenhouse gas. Soil texture and structure, soil moisture, and soil-gas diffusivity are considered to be major soil physical drivers controlling pastoral N 2 O emissions. Research gaps exist regarding their combined roles on N 2 O emissions dynamics. This study used 2-mm-sieved and repacked soil samples, retrieved at three depths (0, 10, and 15 cm) from three grazed pasture sites in New Zealand, to investigate the combined effects of soil-water characteristic (SWC) and soil-gas diffusivity on N 2 O emissions. The existing and modified parametric functions were used to numerically characterize and parameterize measured particle size distribution (PSD), SWC, and soil-gas diffusivity. We observed distinct PSDs within the three soils with little variation across depths. Distinct fingerprints were observed for SWC and gas diffusivity in the three pasture soils, suggesting clear effects of soil type on diffusion-controlled gas emissions. The soil moisture retention above approximately −10 kPa decreased with increasing depth and showed clear soil type effects. Soil-gas diffusivity, on the other hand, showed pronounced depth-wise variation below approximately −1000 kPa. Pore tortuosity was found to be nonlinearly correlated to air-filled pore space as well as the PSD. The measured N 2 O fluxes peaked around a diffusivity window of 0.005 to 0.01 for all soil types, and the corresponding water-filled pore space ranged from 0.80 to 0.95. The results provide guidance for managing pasture soils to reduce high N 2 O fluxes through reductions in compaction and excess irrigation such that the critical diffusivity window, where peak N 2 O emissions occur, is avoided.

Grazed pastures and cultivated fields are significant sources of greenhouse gas (GHG) emissions, in particular N2O emissions derived from fertilizer deposition and animal excreta. Net surface emissions rely on subsurface gas transfer controlled mainly by diffusion, expressed as the soil-gas diffusivity (D-p/D-o). The value of D-p/D-o is a function of soil air-filled porosity (epsilon) and gaseous phase tortuosity (T), both of which vary with soil physical properties including soil texture and structure. Agricultural soils are often structurally aggregated and characterized by two distinct regions (inter- and intra-aggregated pores), however, such soils are subjected to frequent compaction and tillage resulting in alteration to structural arrangement. In this study, a comparative analysis between the Currie (1960) and Taylor (1949) methods was performed to provide a computational insight into selecting an appropriate method for calculating D-p/D-o in agricultural soils. Currie's (1960) method was chosen for further analysis of the soils in this study. Results show that the D-p/D-o in aggregated soil cannot be expressed using a simple linear, power law or combined linear and power law functions due to the presence of two-region characteristics. A new "Two-Region model" was developed to parameterize the D-p/D-o of aggregated soils, and tested against repacked samples from two Sri Lankan agricultural soils. This Two-Region model clearly distinguished tortuosity effects on gas movement with respect to density and textural variations within and between aggregates and outperformed previous models. The fitting parameters (alpha (1), alpha (2), beta (1) and beta (2)) varied correspondingly with soil density, and the weighting factor (w) clearly distinguished the boundary between the two regions (inter- and intra-aggregates) of structured soils. The model developed will be of interest to those seeking to model the diffusion of GHG emissions and gas exchange between the atmosphere and soils.

Grazed pastures rich in nitrogen (N) from ruminant urine and fertilizer inputs are significant sources of nitrous oxide (N2O), a highly potent greenhouse gas. Diffusion-controlled emission of N2O from pasture systems can be described by soil-gas diffusivity (D-p/D-o), and its dependency on soil physical properties and soil moisture dynamics. But studies linking soil aggregation, soil moisture variation, D-p/D-o and N2O emissions are lacking. Using coarse (2-4 mm) and fine ( < 0.2 mm) aggregates, and seven different combinations thereof, the effect of soil aggregate size distribution on soil-water characteristic (SWC), D-p/D-o and N2O fluxes in a pastoral soil were investigated. Sieved-repacked samples, with varying fine aggregate fractions (F = 0, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, and 1.0) were saturated with KNO3 (1800 mu g(-1)) solution and systematically drained to nine different matric potentials (-1 kPa to -10 kPa), followed by an air-dry step (- 30 kPa). At each potential, D-p/D-o and N2O fluxes were measured. The measured SWC and SWC-derived pore-size distributions showed clear bimodal pore structures in all combinations. The highest and lowest total porosities were observed with F = 0 and 0.7, respectively. The lowest N2O peak flux was observed with F = 0.7 which also had the lowest D-p/D-o, while the highest flux among all combinations was observed in F = 1.0 at D-p/D-o = 0.002. Peak N2O flux varied with D-p/D-o dynamics that were in turn a function of inter-aggregate pore drainage. Initially increasing the fine fraction is speculated to have enhanced nitrifier-denitrification while further increases in the fine fraction, which lowered N2O peak emissions, were likely due to a shift from nitrifier-denitrification to denitrification and associated N2O consumption or entrapment.

While the benefits of irrigation for agricultural production are well established, the effects of irrigation management on production and environmental consequences are not well quantified. We used the APSIM (Agricultural Production Systems sIMulator) model to simulate the effect of six different irrigation management scenarios on pasture production and nitrogen (N) losses from both urine patches and non-urine affected areas using New Zealand farming systems as a test case. Nitrogen losses included nitrate (NO3) leaching, and gaseous emissions via ammonia (NH3) volatilisation and denitrification (nitrous oxide (N2O) and dinitrogen (N-2) emissions). The effects of different climate and rainfall regimes were simulated for three different soil types - deep, poorly drained (Otokia), deep, well drained (Templeton) and shallow, well drained (Eyre) soils, using 20 years of data from two climate stations with mean annual rainfall amounts of 600 and 800 mm. In the shallow soil with the least plant available water, more frequent irrigation with higher total annual amounts resulted in a significant increase in predicted pasture production compared with less frequent irrigation due to less plant water stress. However, predicted N losses through leaching, denitrification and N2O emissions also increased. In the deep soils pasture growth was not affected by the frequency of irrigation, whereas denitrification increased with higher frequency irrigation, especially in the poorly drained soil, leading to increased N2O emissions. Based on these modelling results, N losses can be reduced with little effect on production by irrigating less frequently and maintaining soil water deficits.

Denitrification is sensitive to changes in soil physical properties that affect solute transport, air content and gas diffusion. Using lysimeters, containing intact soil from intensively tilled (IT) and no-tilled (NT) soil used to grow forage crops, we examined how simulated animal treading at different moisture contents (above and below field capacity; >FC and FC greatly increased denitrification, especially from IT soil and produced the greatest amount of N2 (64kg N ha–1), N2O (8.2kg N ha–1), as well as the lowest N2O to N2O+N2 ratio (0.08) and NO3 leaching (136kg N ha–1 below 30cm). In both the uncompacted or compacted soils FC. Treading at

Sequestration of soil organic carbon (SOC) has been recognized as an opportunity to off‐set global carbon dioxide (CO 2 ) emissions. Flipping (full inversion to 1–3 m) is a practice used on New Zealand's South Island West Coast to eliminate water‐logging in highly podzolized sandy soils. Flipping results in burial of SOC formed in surface soil horizons into the subsoil and the transfer of subsoil material low in SOC to the “new” topsoil. The aims of this study were to quantify changes in the storage and stability of SOC over a 20‐year period following flipping of high‐productive pasture grassland. Topsoils (0–30 cm) from sites representing a chronosequence of flipping (3–20 years old) were sampled (2005/07) and re‐sampled (2017) to assess changes in topsoil carbon stocks. Deeper samples (30–150 cm) were also collected (2017) to evaluate the changes in stocks of SOC previously buried by flipping. Density fractionation was used to determine SOC stability in recent and buried topsoils. Total SOC stocks (0–150 cm) increased significantly by 69 ± 15% (179 ± 40 Mg SOC ha ‐1 ) over 20 years following flipping. Topsoil burial caused a one‐time sequestration of 160 ± 14 Mg SOC ha ‐1 (30–150 cm). The top 0–30 cm accumulated 3.6 Mg SOC ha ‐1 year ‐1 . The chronosequence and re‐sampling revealed SOC accumulation rates of 1.2–1.8 Mg SOC ha ‐1 year ‐1 in the new surface soil (0–15 cm) and a SOC deficit of 36 ± 5% after 20 years. Flipped subsoils contained up to 32% labile SOC (compared to <1% in un‐flipped subsoils) thus buried SOC was preserved. This study confirms that burial of SOC and the exposure of SOC depleted subsoil results in an overall increase of SOC stocks of the whole soil profile and long‐term SOC preservation.

Grazed pastures are recognized as a dominant source of nitrous oxide (N2O), a highly potent greenhouse gas. Studies have examined soil physical controls on N2O emissions, including soil moisture status. Limited attempts to link N2O emissions with soil‐diffusivity (Dp/Do), using repacked soil cores, have shown peak N2O emissions to align with a relatively narrow window ofDp/Do, despite a relatively wide range in water‐filled pore space (WFPS), across a range of soil bulk densities. Such detailed studies have not been performed withintactsoil cores. We investigated the effects of soil‐water characteristic (SWC) andDp/Doon N2O emissions from intact soil samples, retrieved at three depths (0–5, 5–10, 10–15 cm) from three perennial pasture sites that received a KNO3solution (1800 mg, N mL−1). We observed distinct fingerprints of SWC andDp/Do, which showed clear effects of soil structure on diffusion‐controlled gas emissions. Depth‐wise variation in soil moisture diminished as the soil was subjected to higher matric potential (> ∼ ‐100 kPa). Variation inDp/Do, was more pronounced in the dry soil (> ∼ ‐1000 kPa), being largely constrained by soil moisture in wet soil (∼ ‐100 kPa) with little depth‐wise variation. Measured N2O fluxes peaked within narrow ranges of WFPS andDp/Do, 0.90–0.95 and 0.005–0.01, respectively. The value ofDp/Docan be determined using parametric models and presents a pasture management (e.g., irrigation, soil physical disturbance such as pasture renovation and animal treading)) tool to minimize N2O emissions: soilDp/Doshould be maintained above a range of 0.005–0.01 to minimize N2O emissions.Core IdeasPeak N2O fluxes fromintactsoil cores occurred when diffusivity ranged from 0.005–0.01This peak N2O flux diffusivity range was 0.005–0.01 regardless of soil or depth (0–15 cm)The diffusivity range for peak N2O flux equalled that observed inrepackedsoil coresDiffusivity values are readily determined and add to the suite of soil management tools