D. J. Houlbrooke

Land-use intensification in New Zealand: effects on soil properties and pasture production

Land-use intensification requires more farm inputs to sustain or increase farm product outputs. However, a common concern for land-use intensification is the potential deterioration of soil. The North Otago Rolling Downlands (NORD) region of New Zealand is drought prone, and although traditionally limited to extensive sheep farming, there are large-scale conversions to intensive cattle grazing operations such as dairy farming resulting from an irrigation scheme commissioned in 2006. Pallic soils (Aeric Fragiaqualf in US Soil Taxonomy) such as those in the NORD region are prone to soil compaction because of their ‘high’ structural vulnerability under intensive management. To address these concerns, a field trial was established on a common NORD Pallic soil (Timaru silt loam) to determine how land-use intensification affects indicators of soil quality (macroporosity, bulk density, structural condition score, total and mineralizable carbon and nitrogen and earthworms) and pasture production. The treatments compare irrigated v . dryland pasture and sheep v . cattle grazing on 16 plots. The findings show that soil physical quality responds more quickly to changes in land-use pressure than do biochemical and organic indicators. Both irrigation and cattle grazing, particularly in combination, increased soil compaction; macroporosity on irrigated plots grazed by cattle ranged from 9·1 to 13·3% v/v at a depth of 0–50 mm, compared to dryland plots with sheep grazing (18·9–23·0% v/v). Soil compaction/damage has implications for pasture production, soil hydrology and nutrient movement. Land management practices for intensive cattle grazing of irrigated soil prone to treading damage therefore need to implement high compaction risk strategies to avoid or ameliorate potential changes to soil quality.

Land application of farm dairy effluent to a mole and pipe drained soil: implications for nutrient enrichment of winter-spring drainage

Spray irrigation of farm dairy effluent (FDE) to artificially drained land in accordance with deferred irrigation criteria causes minimal direct drainage of partially treated FDE at the time of irrigation. The influence of deferred irrigation of FDE on the subsequent nutrient enrichment of winter–spring drainage from mole and pipe systems is unknown. Research was conducted in the Manawatu region, New Zealand, to investigate the influence of deferred irrigation of FDE on the quality of water in artificial drainage. The experimental site was established on a Pallic soil (Tokomaru silt loam) at the No. 4 dairy farm at Massey University, Palmerston North. There were 6 plots (each 40 m by 40 m), each with an isolated mole and pipe drainage network. Four of the plots received fertiliser according to the farm’s fertiliser program (non-effluent plots), while the other 2 plots received applications of FDE according to the deferred irrigation scheduling criteria (effluent plots). All of the plots were subject to the farm’s standard grazing management. The average concentrations of N and P in the 2003 winter drainage (average 236 mm) from both the non-effluent and FDE irrigated plots were well above the threshold concentrations that stimulate aquatic weed growth in fresh water bodies. Annual nutrient losses of 31.4 kg N ha/year and 0.65 kg P ha/year in drainage were recorded for non-effluent plots. Deferred irrigation of FDE in the summer period did not increase the loss of N in winter–spring drainage (N loss from effluent plots was 31.1 kg N ha/year) but did cause a significant increase (P < 0.001) in total P in drainage (an additional 1.03 kg P/ha, c. 160% of losses from non-effluent plots, a loss of 3.3% of applied P). Furthermore, an irrigation of FDE to near-saturated soil in mid September resulted in the direct drainage of partially treated effluent, and hence, N and P concentrations in drainage were 6–10-fold greater than those that would normally be expected from drainage events induced by winter–spring rainfall. This illustrates the importance of scheduling FDE irrigation in accordance with deferred irrigation principles.

Trends in water quality of five dairy farming streams in response to adoption of best practice and benefits of long-term monitoring at the catchment scale

Five streams in catchments with pastoral dairy farming as the dominant land use were monitored for periods of 7–16 years to detect changes in response to adoption of best management practices (BMPs). Stream water quality was degraded at the start with respect to N, P, suspended solids (SS) and E. coli concentrations, and was typical of catchments with intensive pastoral agriculture land use. Trend analysis showed a decrease in SS concentration for all streams, generally increasing water clarity, and lower E. coli concentrations in three of the streams. These are attributed to improved stream fencing (cattle exclusion) and greater use of irrigation for treated effluent disposal with less reliance on pond systems discharging to streams. Linkages between water quality and farm actions based on survey data were used to develop BMPs that were discussed at stakeholder workshops. Generic and specific BMPs were developed for the five catchments. The 3–7 year periodicity of major climate cycles, as well as market forces and a slow rate of farmer adoption of simple BMPs mean that monitoring programs in New Zealand need to be much longer than 10 years to detect changes caused by farmer actions. Long-term monitoring is also needed to detect responses to newly legislated requirements for improved water quality.

Grazing strategies to protect soil physical properties and maximise pasture yield on a Southland dairy farm.

Abstract intensive dairy cattle grazing on wet soil can have a detrimental effect on soil physical quality and consequently on pasture production. Soil physical properties (porosity, bulk density, saturated hydraulic conductivity) of a Pallic soil (Pukemutu silt loam) and pasture production were assessed on a dairy farm in Southland, New Zealand, under a number of different cattle grazing strategies: (i) normal grazing management on undrained land, (ii) normal grazing practice on drained land, (iii) restricted autumn grazing, (iv) restricted grazing when soil conditions were wet, (v) never pugged, and (vi) never grazed. a hand‐pushed cone penetrometer determined treatments (iv) and (v). Soil macroporos‐ity was significantly greater (P < 0.05) on the never grazed plot than all other treatments at post‐spring sampling each year. There were no significant differences in any soil physical properties measured on cattle grazed treatments. Spring pasture yield from the never grazed treatment was greater (P < 0.05) than the drained and undrained standard practice grazing treatments for one of the three seasons. The lack of treatment differences in soil physical properties and pasture yield from grazing treatments suggests that the never pugged grazing strategy failed to prevent soil compaction by dairy cows. To some extent this is expected as soil compaction occurs at soil water contents lower than the thresholds for pugging damage. However, the large number of grazing events when soil conditions were considered safe according to the never pugged treatment protocol, but when soil water content was greater than the plastic limit, probably contributed to both soil treading damage and compaction during the traditionally wet early spring period.

Soil quality and plant yield under dryland and irrigated winter forage crops grazed by sheep or cattle.

In New Zealand, the winter grazing of standing forage crops combines high animal stocking densities with soil water and climatic conditions conducive to soil compaction and pugging deformation. The extent of soil damage under winter forage cropping practices and impact of management factors such as stock type and irrigation on soil quality is relatively unknown. A research trial was established, on a Pallic soil type (Aeric Fragiaquept) in the North Otago Rolling Downlands of New Zealand, to compare cattle v. sheep and dryland v. irrigation management. Kale, Swedes, and triticale were direct-drilled in 3 consecutive years and soil physical (macroporosity, bulk density, structural condition score), chemical (total C, total N, C : N ratio), and biological (mineralisable N, mineralisable C, and earth worm mass and numbers) properties were assessed annually post grazing in midwinter. Increased soil compaction was evident following grazing of winter forage crops, with lower macroporosity (P < 0.01) measured at 0–50 mm under cattle grazing compared with sheep grazing for 2 of 3 years and greater bulk density (P < 0.05) measured under cattle grazing for all years. However, there was no affect of stock type on crop yield for all 3 forage crops as a result of the measured differences in soil compaction. There were few differences between treatments or through time in soil chemical or biological properties following 3 years of continuous winter forage cropping as pools of C and N are slow to change under a no-tillage cropping regime and not necessarily measurable over a relatively short time frame.

The use of low-rate sprinkler application systems for applying farm dairy effluent to land to reduce contaminant transfers

Abstract Runoff of farm dairy effluent (FDE) is a major concern in New Zealand water management. To improve handling and applying FDE, this work evaluated the performance of a low-rate (K-line) sprinkler application system compared with that of a travelling irrigator. The volumes of FDE discharged in either mole-pipe drainage or overland flow were monitored at two sites, as were nutrient concentrations and loads (and Escherichia coli (E. coli) at one site). The low-rate sprinkler decreased overland flow losses of applied FDE compared to the travelling irrigator. The relative concentrations of E. coli, total P and ammonium-N (presented as C/C o, the measured concentration in drain flow divided by the concentration in applied effluent) in overland flow at South Otago and mole-pipe drainage at West Otago were also consistently less for the low-rate sprinkler. There were significant and positive correlations between drainage C/C o values and effluent application rate for E. coli, total P and turbidity. Modelling predicted potentially large contamination with E. coli, total P and ammonium-N in mole-pipe drainage with no pond storage when using a travelling irrigator. Modelled loads were considerably less for FDE application to mole-pipe drained land using a low-rate sprinkler. Practical implications are that: (i) effluent pond storage is important for decreasing FDE losses in overland flow and mole-pipe drainage when soils are wet; (ii) a low-rate sprinkler application system requires less pond storage; (iii) a low-rate low-depth management system can decrease mole-pipe drainage discharges of pollutants when soils are wet.

Predicting soil water, tile drainage, and runoff in a mole-tile drained soil

Abstract There has been considerable intensification of agriculture on mole‐tile drained soils in New Zealand. Management techniques and tools are needed for predicting and understanding water and nutrient transport. While simple water balance models have been effective in estimating soil water deficit, such models cannot differentiate between the different water loss mechanisms. More complex water‐transport models include the ability to predict the flow of water and nutrients through mole‐tile drainage systems but none have yet been applied, or tested, under New Zealand conditions. Here we test such a model against existing data. The simulation model APSIM was used to estimate soil water extraction by pasture, slow drainage through the fragipan, mole‐tile drainage, surface runoff, and evaporation from the soil surface of the Tokomaru silt loam. Soil hydraulic properties were derived from the literature. Comparison was made against previously published data on soil water deficit, tile drainage, and surface runoff. APSIMs predictions of soil water deficit compared well against much of the available data. The exception to this was during a period of exceptionally dry soil conditions when the model predicted a lower soil water deficit than indicated by the data. There was excellent agreement between the simulated and measured drainage, as well as reasonable agreement of measured and modelled surface runoff on a cumulative basis, although there was some deviation when considered on an event basis.

Effect of application of dairy manure, effluent and inorganic fertilizer on nitrogen leaching in clayey fluvo-aquic soil: A lysimeter study

Dairy farm manure and effluent are applied to cropland in China to provide a source of plant nutrients, but there are concerns over its effect on nitrogen (N) leaching loss and groundwater quality. To investigate the effects of land application of dairy manure and effluent on potential N leaching loss, two lysimeter trials were set up in clayey fluvo-aquic soil in a winter wheat-summer maize rotation cropping system on the North China Plain. The solid dairy manure trial included control without N fertilization (CK), inorganic N fertilizer (SNPK), and fresh (RAW) and composted (COM) dairy manure. The liquid dairy effluent trial consisted of control without N fertilization (CF), inorganic N fertilizer (ENPK), and fresh (FDE) and stored (SDE) dairy effluent. The N application rate was 225kgNha-1 for inorganic N fertilizer, dairy manure, and effluent treatments in both seasons. Annual N leaching loss (ANLL) was highest in SNPK (53.02 and 16.21kgNha-1 in 2013/2014 and 2014/2015, respectively), which were 1.65- and 2.04-fold that of COM, and 1.59- and 1.26-fold that of RAW. In the effluent trial (2014/2015), ANLL for ENPK and SDE (16.22 and 16.86kgNha-1, respectively) were significantly higher than CF and FDE (6.3 and 13.21kgNha-1, respectively). NO3- contributed the most (34-92%) to total N leaching loss among all treatments, followed by dissolved organic N (14-57%). COM showed the lowest N leaching loss due to a reduction in NO3- loss. Yield-scaled N leaching in COM (0.35kgNMg-1 silage) was significantly (P<0.05) lower than that in the other fertilization treatments. Therefore, the use of composted dairy manure should be increased and that of inorganic fertilizer decreased to reduce N leaching loss while ensuring high crop yield in the North China Plain.

Nitrogen gaseous emissions from farm effluent application to pastures and mitigation measures to reduce the emissions: a review

Potential losses of nitrogen (N) from land application of effluents include ammonia (NH3) and nitrous oxide (N2O) emissions. In this review paper, the extent of the NH3 and N2O losses resulting from application of effluents to pastoral soils is assessed. Nitrogen losses, as NH3 and N2O, from applied effluent to pastoral soil ranged from 1%–66% and <0.1%–6% of the applied N, respectively. The potential mitigation methods include: reducing livestock numbers; lowering N content of the effluent; using N process inhibitors; optimising timing of effluent application; and applying effluent at rates that match plant uptake. It is important to remember that some of these options can result in ‘pollution swapping’ and some of them are in the early stages of development. Future research needs to focus on the overall impact of mitigation options on the whole suite of gaseous emissions and the practicality of those options.

Assessing the production and economic benefits from preventing cows grazing on wet soils in New Zealand.

BACKGROUND Intensive grazing by cattle on wet pasture can have a negative effect on soil physical quality and future pasture production. On a North Otago dairy farm in New Zealand, experimental plots were monitored for four years to assess whether preventing cow grazing of wet pastures during the milking season would improve soil structure and pasture production compared with unrestricted access to pastures. The DairyNZ Whole Farm Model was used to scale up results to a farm system level and ascertain the cost benefit of deferred grazing management. RESULTS Soils under deferred grazing management had significantly higher total porosity, yet no significant improvement in macroporosity (values ranging between 0.112 and 0.146 m(3)  m(-3) ). Annual pasture production did not differ between the control and deferred grazing treatments, averaging 17.0 ± 3.8 and 17.9 ± 4.1 t DM ha(-1) year(-1) respectively (P > 0.05). Furthermore, whole farm modelling indicated that farm operating profit was reduced by NZ