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Item Assessing diverse swards and regenerative management for mitigating nitrous oxide emissions from urine patches : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Animal Science at Massey University, Manawatū, New Zealand. EMBARGOED until 31st March 2027(Massey University, 2025) Qiao, XiaonanNitrous oxide (N₂O) is a potent greenhouse gas and is a significant driver of climate change. Grazing systems are geographically extensive and a major contributor to rising N₂O levels, due to their reliance on synthetic nitrogen (N) fertilisers to meet production goals. Increasing regulation and public scrutiny are currently driving a re-evaluation of N use in agricultural systems. The adoption of regenerative farming practices for livestock production, represents a potential management strategy for the reduction of N₂O emissions from grazing systems. Regenerative grazing systems are typically characterised by reduced N inputs, use of diverse pastures (i.e., grasses, legumes, and herbs), longer grazing rotations, and higher post-grazing residuals, which are expected to impact plant growth and soil function/health, potentially increase N use efficiency and biodiversity, and thus affect N₂O emissions. This study site was located at Massey University's Dairy No.1 Farm in Palmerston North, New Zealand (40°22'35"S, 175°36'49"E). Three adjacent paddocks were selected at this site, with similar soil type, classified as sandy loam soil. A total of 60 static chambers were used to measure N₂O emissions from 3 different pastures: i) perennial ryegrass (Lolium perenne L.) and white clover (Trifolium repens L.) under contemporary management (Std-Con); ii) hyper-diverse pasture under regenerative management (Div-Reg); and iii) hyper-diverse pasture under contemporary management (Div-Con). Three months before the study commenced, grazing cows (Jerseys, Friesians and Crossbreds) were excluded from accessing the pastures. Static flux chambers (250 mm diameter × 200 mm height) were inserted 100 mm into the soil 2 weeks prior to the initial sampling. Soil samples (~10 cm) were taken adjacent to the chambers to assess nutrient content. Each pasture system had 24 dairy cows which only grazed that system. On day 0, fresh urine was collected opportunistically from each group of cows and was uniformly applied inside half of the chambers within each respective pasture at a rate of 10 L/m². Day 0 N₂O flux measurements were collected 4 hours after urine application, with measurement repeated at 1, 2, 3, 6, 10, 13, 16, 20, 23, 28, 30, 38, 44, 55, 56, and 70 days. Data were analysed as repeated measurements and the area under the curve was computed by trapezoidal rule representing the cumulative emissions. The N concentration of applied urine was 0.3% in the Std-Con and Div-Reg, and 0.2% in the Div-Con. Nitrous oxide emissions in urine patch from the Std-Con and Div-Con pastures were both significantly (P<0.01) greater (55%), compared to Div-Reg pasture system. When urine was applied, cumulative N₂O emissions throughout the study period were 3.57, 3.44, and 1.56 kg N₂O-N/ha for Div-Con, Std-Con, and Div-Reg, respectively. These findings suggest a potential role for regenerative practices to mitigate N₂O emissions.Item Effect of increasing cow urine patch area on nitrogen losses from grazed pastures : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy (PhD) in Soil Science at Massey University, Palmerston North, New Zealand(Massey University, 2024) Hedges, May TanaThe expansion and intensification of dairy farming in New Zealand (NZ) over the last few decades has made a major contribution to the country’s greenhouse gas emissions, and to the nitrogen (N) enrichment of its surface and ground waters. The environmental concerns associated with dairy farming have led researchers to investigate potential mitigations to reduce N losses from cow urine patches, which are the main source of N losses. However, there has been little research conducted on the effect of increasing the spread area of urine patches as a mitigation for N losses. The development of a prototype urine spreading device, intended to be worn by cows during summer and autumn, has made such a mitigation possible. The primary aim of this device is to provide a method to reduce nitrate (NO₃⁻) leaching, by directly reducing the N application rate in the urine patch. The impact of increasing the size of the urine patch on N emissions to the atmosphere is also an important consideration. Research was required to quantify the effects of increasing urine spread on N losses from urine patches. This research quantified the effect of increasing the urine patch spread area on ammonia (NH₃) and nitrous oxide (N₂O) emissions, and on NO₃⁻ leaching losses. The first field experiment was conducted in early autumn on Dairy Farm 1, Massey University, near Palmerston North, New Zealand. The soil at the site is a Manawatu silt loam. Three urine application depth treatments of 10 mm, 5 mm and 2.5 mm were applied to an area (0.018 m²) inside a series of 20 chambers (5 replicates). These treatments represented the depths that would result from applying 2.5 L of urine to three different patch areas: 0.25 m² (i.e. typical patch size), 0.5 m² and 1 m², respectively. A control treatment with no urine applied was also included. The concentration of total N in applied urine was 4.53 g N L⁻¹. Ammonia measurements were conducted over a period of 20 days using the Dynamic Chamber method. Soil samples were also collected periodically from adjacent treatment plots to measure mineral-N (nitrate and ammonium), soil moisture and pH. The results showed that increasing the urine patch area from 0.25 to 1 m² has increased total NH₃ emissions from 25 to 36% of the total urine-N applied and, consequently the emission factor also increased. This NH₃ increase also increases indirect N₂O emissions, which can have an influence on annual emissions. However, the loss of NH₃ from the urine patch also reduces the amount of urinary N that is available for subsequent direct N₂O emissions and NO₃⁻ leaching. The second and third field experiments were carried out on Dairy Farm 4, Massey University. The soil type at both sites is the Tokomaru silt loam soil. One of the field experiments involved urine application in early-autumn and the other in early-winter. Urine collected from lactating dairy cows was applied to small, mowed plots at application depths of 10 mm (applied to 0.25 m²), 5 mm (applied to 0.5 m²) and 2.5 mm (applied to 0.5 m² and results were extrapolated to a notional patch area of 1 m²). A control treatment with no urine applied was also included. All treatments were replicated five times. Gas sampling was conducted in the field using the static chamber method (chamber area of 0.50 m²). The results of these studies showed that increasing the size of the urine patches from 0.25 to 1 m² with the same volume of urine-N in early-winter did not significantly increase N₂O emissions and emission factors (EF₃). Although increasing the urine patch area increased N₂O emission by 39%, this difference was not large enough to be statistically significant (P>0.05). However, for the first 14 days of total N₂O emissions, the 1 m² urine patch treatment was statistically different (P<0.05) from the 0.25 m² urine patch treatment. In contrast, increasing the size of the urine patches from 0.25 to 1 m² in early-autumn decreased N₂O emissions and EF₃ by 56% (P<0.05). The different effect of increasing the urine patch area in these two different seasons, is likely to be attributed to the differences in soil moisture conditions at the time of urine application and the weeks that followed. To determine the overall effect on N₂O emissions, the reduction in N₂O emissions in autumn was compared with the increase in NH₃ emissions at this time using the N₂O inventory emission value of 0.1 for indirect emissions. These indirect N₂O emissions was estimated to be about 3.6 times higher than the reduction in direct N₂O emissions. Therefore, the use of a urine spreading device to increase the spread area of cow urine in autumn is expected to result in greater overall accumulation of N₂O in the atmosphere. The fourth experiment was conducted on Dairy Farm 4, Massey University. The experimental paddock consisted of twelve pasture plots measuring 800 m² per plot, with separate mole and pipe drainage systems. There were two treatments and six replicates of each treatment. The treatments were cows wearing urine-spreading devices (‘Device’ treatment) and without the device (‘Control’ treatment). The devices were used on four grazing events over the late summer and autumn period. Drainage water from the plots was monitored and analysed for total N and NO₃⁻-N, and pasture accumulation measurements were also conducted. Overall N leaching losses were low, and the differences in total N and NO₃⁻ leaching between the two treatments were small and not statistically significant (P>0.05). There were also no differences in pasture accumulation over a 9-month period. Further improvements to the device are required to consistently increase the spread area of urine patches and the uniformity of the spread. The improved device should then be evaluated over a number of years to assess its potential to reduce leaching of N and its impact on N gaseous emissions to the atmosphere.Item Methane emissions of grazing dairy cows fed graded levels of concentrates : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Agricultural science at Massey University, Manawatū, New Zealand(Massey University, 2024) Bosher, Troy JamesThe GHG inventory of New Zealand currently assumes that all dairy cattle emit 21.6 grams of methane (CH4) for every kilogram of dry matter (kg DM) of pasture eaten. However, supplement feeding has increased in New Zealand pastoral systems in recent decades to comprise ̴18% of the total feed offered to New Zealand’s dairy herd. Previous studies have shown different diets can alter the CH4 emissions of dairy cattle and therefore the objective of this study was to determine the effect of increasing concentrate intakes on pastoral dairy cows’ CH4 emissions and milk production. Early lactation dairy cows (n = 72) were allocated (n = 18 per treatment group) to receive 0, 2, 4 or 6 kg DM of concentrates per day while grazing pasture ad-libitum over 63 days. Methane emissions were measured in the field for individual animals using the ‘GreenFeed’ automated emissions monitoring system. Changes to liveweight and body condition score, daily milk production and weekly milk composition were recorded and used to estimate individual animals’ dry matter intakes. Liveweight change, milk production and estimated dry matter intakes were not found to significantly change with increased concentrate feeding rates. Methane production (g CH4 / day) was not affected by concentrate feeding and was similar across all treatment groups, however CH4 yield (g CH4 / kg DM) and CH4 intensity (g CH4 / kg fat and protein corrected milk) linearly decreased with increasing concentrate inclusion in the diet (P = 0.041; P = 0.022, respectively). This was also confirmed by a significant and linear decrease of the methane to carbon dioxide ratio (CO2 : CH4) emitted by animals with increased concentrate feeding (P = 0.011). These results have demonstrated that CH4 yields change when feeding increasing levels of concentrate feed to pasture-based dairy cattle in New Zealand, which differs from the current assumption for calculating the national GHG inventory. Responses in CH4 emissions and milk production parameters were however relatively small in this study however, which was likely due to generous pasture offers that resulted in a large substitution of pasture as concentrate feeding rates increased.Item Nutrient leaching under intensive sheep and beef grazing : Master of Philosophy in Animal Science, School of Agriculture and Environment, Massey University, New Zealand(Massey University, 2024) Algharibeh, FirasThe sheep and beef industry plays a vital role in the New Zealand economy, but there is growing concern about water quality in the pastoral farming systems. To address this issue, regional councils are implementing restrictions on nitrate leaching rates to improve water quality. Nitrate leaching is influenced by factors such as plant uptake rate, rainfall, soil type, and texture, as well as the stocking rate of grazing animals. However, there is a lack of information on nitrate leaching from sheep and beef farms, particularly in the context of winter cropping options like kale (Brassica oleracea) and Turnips (Brassica rapa subsp. rapa). Additionally, the potential of planting Italian ryegrass as a cover crop mixed with brassica to reduce nitrate leaching has not been thoroughly explored. This study aims to compare nitrate leaching under sheep and beef cattle which are grazing perennial ryegrass/white clover, as well as investigate whether mixing Italian ryegrass with brassica can mitigate nitrate leaching. Furthermore, the study will compare the measured rates of nitrate leaching with predicted values using Overseer and a model that simulates N dynamics in urine patches. An experiment has been established in twenty hydrologically isolated plots at Massey University’s Keeble farm for the year 2022. Each plot contains an isolated mole and pipe drainage system to monitor drainage water and assess nitrate leaching. There were five replicates of four treatments: sheep grazing perennial ryegrass/white clover, sheep grazing turnips/Italian ryegrass, sheep grazing kale, and cattle grazing perennial ryegrass/white clover. Measured leaching losses under all treatments were small and there was no significant difference between the nitrate leaching flux of any of the treatments. While Overseer estimates of nitrate leaching were greater than the observed values, they also suggested that there should be no significant difference in leaching rates from the plots Overseer was used to explore likely leaching rates at greater stocking rates. These results suggested that under more intensive farm systems (18 SU/ha), leaching rates under cattle are likely to be greater than under sheep. This difference can be explained by reference to the distribution pattern of urine-N of sheep verse cattle: sheep spread the urine-N load over a greater area. The findings of this study are evidence of the advantages of dry stock farming, particularly sheep, to water quality.Item Evaluation of methodologies to quantify dry matter intake in grazing New Zealand dairy cattle : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Agricultural Science at Massey University, Manawatū, New Zealand(Massey University, 2023) Stubbs, Ellen AmyDry matter intake (DMI) is a key driver of enteric methane emissions in cattle, therefore the accurate measurement of DMI in grazing dairy cattle is necessary for research in methane emission reduction. A gap in methodologies currently available in New Zealand (NZ) to accurately predict individual grazing cow DMI for use in greenhouse gas (GHG) emission research has been identified. Therefore, the objective of this thesis is to quantify the variation between individual intake of “grazing” dairy cattle in NZ predicted from five methodologies; two indigestible markers techniques being n-alkanes and titanium dioxide paired with indigestible neutral detergent fibre (iNDF) and three standard energetics back calculation equations, all compared to actual intake measured by the Calan gate disappearance method. To test the marker techniques, an experiment was designed to provide data on actual individual cow DMI to compare intake predicted by the n-alkane, titanium dioxide and iNDF methodologies. The experiment occurred from 26 October to 4 November 2022, using two 5- day measurement periods, within the DairyNZ Calan gate facility, so that actual individual cow intakes were measured and alternative methodologies could be compared against each other. Using 40-multiparous early-lactation Holstein Friesian cattle, in two treatment groups - Control (pasture only diet) or Supplement (pasture and supplement diet), with treatment groups balanced for age, days in milk, liveweight and milk production. The cattle were previously adapted to diet, treatment and indigestible markers used, over a 3-week period prior to the measurement period beginning. All the cattle were dosed with n-alkane C32 (377.6 mg) and titanium dioxide (5 g) twice a day, following faecal collection. Supplement, pasture and faecal samples were bulked by measurement period for each individual cow, alongside samples of n alkane and titanium dioxide dosed, then analysed for n-alkanes C27 to C35, titanium dioxide and iNDF. The n-alkanes C29, C31, C33 and C35 were each paired with C32 to predict DMI, as was the pair titanium dioxide and iNDF. The n-alkane pair C32:C33 provided the most accurate prediction of pasture intake in relation to actual pasture intake, although there was an underestimation on average of 35 to 40%. Titanium dioxide and iNDF did not accurately predict total intake, with both over and underestimations of actual intake occurring. The back calculation methodologies included three energetic back calculation equations commonly used in NZ (NRC, MPI GHG Inventory and Nicol and Brookes). The ability of these methodologies to predict actual individual dairy cow DMI was tested across six datasets: five previous DairyNZ trials were used along with data from the experiment discussed above, all of which have DMI measured from the Calan gate system. Liveweight change is a variable included in the Nicol and Brookes equation and within these analyses added large variation to the energetic requirements and calculated daily DMI for individual cows. Based on this, the equation from Nicol and Brookes was not included in the full analysis, consequently as the other two equations that were analysed in full were not suitable for use in non-lactating cattle, a trial was excluded due to the use of non-lactating cattle. At an individual cow level, a single equation did not consistently provide predictions within the same range of accuracy across the trials. The data indicated that of the equations analysed, the NRC equation provided the best DMI predictions for individual lactating dairy cows in terms of accuracy and ease of use. At the herd level, DMI predictions were in a range of accuracy for all equations, with the NRC equation providing the most consistent results.Item The behaviour of sheep around a hill country stream and impacts on freshwater quality : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Animal Science, School of Agriculture and Environment, Massey University, Palmerston North(Massey University, 2021) Barnes, CharlieRecent amendments by the New Zealand Government to the Resource Management Act (RMA) regulations proposed that fencing and a 3m setback were required for streams more than 1 m wide and the exclusion of farmed cattle, deer and pigs from these waterways (Ministry for the Environment, 2020). Currently, sheep are not required to be excluded from waterways. Furthermore, there is no literature on the behaviour of sheep in New Zealand around hill country streams or their impacts on water quality. During the Summer of 2021 (February), a crossover design trial was conducted with forty mixed aged ewes in a hill country paddock transected by a fifth order stream on Massey University’s Tuapaka farm. During the study, ewes had access to a trough for the first week and did not have access to the trough on the second week. Ewes were monitored using motion activated cameras, accelerometers attached to a halter, and GPS units attached to a collar. Water sampling was conducted for two days of each week during each treatment and analysed for suspended sediment, total phosphorus, dissolved phosphorus, total nitrogen, ammonia, nitrate, and E. Coli. The results from the summer trial showed that the behaviour of sheep around the stream was not influenced by the availability of a drinking trough. When sheep had no access to the trough, however, they spent more time within areas of the stream that were easy to access and were observed to drink from the stream. Total phosphorus concentration was lower in the first week (unrestricted access to the trough, p = 0.020) were as suspended sediment, total nitrogen, and E. Coli loads (p = 0.0002, 0.0374 and 0.029 respectively) were higher compared to the second week (restricted access to the trough). There were no recorded instances were sheep defecated into the stream and two occurrences of urination near the stream. This study suggests that sheep had a minimal influence on water quality and any effects were likely due to rainfall events. A follow-up trial following the same methodology was conducted in Autumn (April) within the same paddock and with the same sheep. The behaviour of sheep around the stream during Autumn was not influenced by the availability of a drinking trough. Access to the trough had an inconsequential impact on the behaviour of the ewes within the stream zone. It is probable that the moisture content of the pasture was sufficient to satisfy the water requirements of the sheep during the trial and negated the need to drink from the stream. Indicators of water quality were elevated during and immediately after rainfall events and highlights the sediment loss that can occur from a grazed pasture during a rainfall event. There was no association between sheep activity and a decline in water quality. Suspended sediment loads were greater when during the first week (restricted trough access, p = 0.002) whereas total nitrogen, total phosphorus and E. Coli loads did not differ between treatments (p = 0.629, 0.989 and 0.528 respectively) There were no recorded instances were sheep defecated into the stream. These experiments showed that sheep interaction with a natural waterway during summer and autumn on a Manawatu Hill country farm had an insignificant influence on the water quality metrics measured. Therefore, it is unlikely that excluding sheep from accessing natural waterways would result in improvements to water quality.Item Impact of plantain (Plantago lanceolata) based pasture on milk production of dairy cows and nitrate leaching from pastoral systems : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Animal Science at Massey University, Manawatu, New Zealand(Massey University, 2023) Nguyen, Truong ThiIn temperate dairy systems, the traditional perennial ryegrass (Lolium perenne)-white clover (Trifolium repens) (RGWC) pasture often has excessive nitrogen (N) content relative to the N requirement of animals, posing a risk of nitrate (NO₃⁻) leaching into the environment. Recently, incorporating plantain (Plantago lanceolata) with RGWC pasture has been increasingly used to improve economic and environmental benefits for dairy farms. However, the impact of plantain incorporation on farm productivity and NO₃⁻ leaching at the farm level has not been fully understood. The objectives of this thesis were to quantify the effect of incorporating increasing rates of plantain in grazing swards on pasture production, milk yield and composition of dairy cows, and NO₃⁻ leaching from pastoral dairy systems. To address the objectives of the thesis, a grazing trial was implemented at a research dairy farm between September 2019 and December 2021. Pasture treatments were RGWC (perennial ryegrass cv. ONE⁵⁰ and white clover cv. Tribute), RGWC + low plantain (cv. Agritonic) rate (PLL), RGWC + medium plantain rate (PLM), and RGWC + high plantain rate (PLH). Pastures were established with 20 experimental plots and four adaptation areas in April 2019 and were rotationally grazed by dairy cows over 22 grazing events during the experimental period. In each grazing, 60 or 80 cows were assigned to graze for 6 days in their adaptation areas and 1.5–3 days in the experimental plots. The experimental cows were managed under a typical practice, milking twice daily, offering grazing pasture and approximately 25% supplementary dietary feeds. Measurements were conducted to quantify the yield, botanical composition and nutritive value of the pasture, milk yield, milk composition and N excretion of dairy cows, and NO₃⁻ leaching from the pastoral system. The results showed that, over the first two lactation years after sowing, plantain-based pastures have a similar dry matter yield and contain higher water content, non-structural carbohydrates, minerals, and bioactive compounds than the RGWC pasture. The average plantain proportion in the swards over the first two years after sowing was 32% in PLL, 44% in PLM, and 48% in PLH, which increased in the first 15 months and declined to 20% in PLL and 30% in PLM and PLH at day 705 after sowing. Cows grazing the plantain-based pastures had a similar milk yield, composition and yield of solids, protein, fat, and lactose as those grazing the RGWC pasture. Furthermore, when 25% plantain was included in the diet of cows in late lactation, it resulted in a 44% increase in urine volume and a 29% reduction in urine N concentration by 29%. By incorporating an average of 30% and 50% plantain with RGWC pasture, NO₃⁻ leaching was reduced by 32 and 52%, respectively, over two drainage years after establishment, with a greater reduction in the first year than in the second year. Among sowing rates, PLM resulted in the greatest decrease in NO₃⁻ leaching, with 64% in the first year and 41% in the second year. The decreased NO₃⁻ leaching was associated with increased plantain content, enhanced herbage N uptake, reduced UN excretion of dairy cows and a lower N load in urine patches. In conclusion, in a typical practice, as in the present study, incorporating 30–50% plantain with RGWC pasture decreases NO₃⁻ leaching from pastoral systems without adversely impacting farm productivity for at least two years from sowing. However, the reduction of plantain content in the second year suggests further measurements to determine the effectiveness of plantain-based pasture in the longer term. In the conditions and time scale of the present study, the medium plantain rate treatment (PLM) is suggested to achieve a high effectiveness of plantain incorporation in reducing NO₃⁻ leaching.Item Nutrient leaching under intensive sheep grazing : a dissertation presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Animal Science at Massey University, Manawatu, New Zealand(Massey University, 2023) Maheswaran, SarminiThe use of some alternative forages may help sheep farmers to reduce nitrogen (N) leaching while increasing production. This thesis explores the effects of four forages (perennial ryegrass/white clover: RGWC; Italian ryegrass/white clover: IRWC; plantain/white clover: PWC; and a winter brassica) on sheep performance, urinary N excretion and N loss in drainage over two and a half years (Year 1: July to December 2019; Year 2: January to December 2020; Year 3: January to December 2021). This study was conducted on an artificially drained, fine textured Tokomaru silt loam soil at Massey University’s Keeble farm, near Palmerston North, Manawatu, New Zealand. The study design included four self-contained farmlets (each approximately 3.3 ha): three farmlets had 0.8 ha (24% of their grazing area) sown to include one of three alternative forages (IRWC or PWC or brassica), and the remaining 2.5 ha was sown in a perennial ryegrass/white clover sward. The entire area (100% of grazing area) of the fourth farmlet was sown in RGWC. Approximately 0.4 ha of each farmlet was located in a paddock where a series of 20 drainage plots (each 40 m by 20 m) were established to measure N leaching. Each of the alternative forages, and the RGWC, were sown on five of the drainage plots i.e., five replicates (combined area of 0.4 ha), which composed about one-half of the area of each alternative forage on each farmlet. The amount of N leached through a mole-pipe network on each drainage plot was also measured. Breeding ewe productivity including liveweight, condition score and lambing performance, as well as N excretion was also measured. In addition, forage growth and DM production were monitored along with chemical and botanical composition. The inclusion of alternative forages into the RGWC system did not affect animal performance. This was due, in part, to animal management. The N leached under various forages was, therefore, able to be compared without the confounding effects of differences in animal performance. The daily urinary N excretion per animal by sheep grazing PWC or brassica was lower (18 to 70%) than the daily urinary N excretion by sheep grazing RGWC or IRWC. It is likely that the diuretic effect of plantain and a lower N concentration in the brassica caused lower N concentrations in urine. Nitrate (NO₃⁻) leaching losses under RGWC, IRWC and PWC were very small in Years 1 and 2 (ranging from 0.4 to 0.8 kg N/ha). The poor persistence of IRWC and PWC at this site and the need to re-establish these forages on the plots resulted in greater NO₃⁻ leaching under these forages in Year 3, negating some of the advantages associated with these forages in Years 1 and 2. In contrast, NO₃⁻ leaching losses were greater under brassica forages (ranging from 0.4 to 6.4 kg N/ha) than under RGWC (ranging from 0.5 to 1.5 kg N/ha). Although sheep grazing brassica forages excreted less urinary N (on an individual animal basis), leaching losses under the brassica treatments were higher. In addition to the effect of cultivation, this increased leaching was likely because brassica plots were grazed for a more extended period during winter than other forages, and there was no crop (forage) cover until the spring resowing; therefore, the urinary N accumulated during winter grazing was displaced by subsequent drainage. With the assumption that the cropped area occupies a relatively small portion of the farm, grazing brassica is likely to result in a relatively small increase in whole farm NO₃⁻ leaching. Overall, NO₃⁻ leaching losses under sheep grazing forages were lower (ranging from 0.5 to 9.5 kg N/ha) than those reported under dairy cattle grazing forages, which suggests that sheep production may offer an alternative land use option for dairying areas where it is difficult to achieve the large reductions in NO₃⁻ leaching required to meet water quality objectives.
