• Advanced and conventional methods for vegetative propagation of selected lines of oak and cherry.

      Douglas, Gerry C. (Teagasc, 1999-04-01)
      Oak and wild cherry (Prunus avium) are important broadleaved species. We have identified superior trees and conserved them by grafting. Methods for the large scale propagation of selected trees was evaluated using the technology of micropropagation. For oak we could establish shoot cultures from mature oaks but their propagation rate was too low and difficult for practical application. With wild cherry micropropagation is a feasible option for large scale production of selected material. Genetic fingerprinting technology was developed and applied to oaks. We showed that all material propagated vegetatively from oak was genetically similar to the original donor tree. Furthermore we used genetic fingerprinting to analyse a unique stand of elite oaks in Co. Westmeath and determined that the selected trees were not closely related to each other. The analysis of genetic fingerprints of 16 elite oaks also showed that five of them had an unusual pattern of DNA and one tree was identified as a rare triploid tree.
    • Agronomic performance of acid-based liquid fertilisers on winter wheat.

      Burke, J.I.; O'Reilly, B.; Gallagher, E.G. (Teagasc, 1999-12-01)
      In the early 90’s, a new and novel means (liquid Flex system) of crop fertilisation was launched on the Irish market which was capable of supplying the crop’s total nitrogen, phosphorus, potassium and trace element requirement in liquid form, formulated to meet specific crop requirements. This system included novel chemistry, untested under Irish conditions and with little specific reference in the scientific literature. The chemistry of the liquid Flex system consists of an acid-based material. Stable compounds i.e. urea sulphate, urea phosphate and urea-metal complexes are formed by the reaction of urea with sulphuric acid, phosphoric acid and metal salts, respectively. Interest in these materials has been generated because they possess a number of physical and chemical characteristics, which, in theory, should be beneficial. However, the ability of the Flex system to effectively supply nutrients to the plant has not been researched. A field and greenhouse experimental programme was carried out over the three seasons, 1996-1998 to compare acid-base/urea-metal complexes with conventional fertilisers and to investigate whether this unconventional chemistry could lead to increased biological efficiency. The trial programme evaluated the Flex system, both as individual components and as a complete fertiliser. In field comparisons, formulation of P as urea phosphate gave similar results to conventional granular superphosphate in terms of grain yield, recovery of P by the crop and grain quality, regardless of soil type. This was supported by the results from the greenhouse experiment. In field comparisons of the main soil-applied liquid Flex source of N, i.e. N24 (urea with the addition of a standard level of acid and metal salts) with conventional N formulations, N24 gave poorer performance than CAN and granular urea in warm dry conditions due to insufficient inhibition to substantially reduce ammonia volatilisation. In wet conditions, the slow release of N from inhibited urea may have reduced the potential loss from leaching or denitrification, and led to a better performance than CAN or urea. The additional product of the Flex system, i.e. liquid Flex urea - N18 (urea with the addition of metal salts), applied as a foliar spray, was no more efficient than liquid urea as a late N source. The Flex urea had the disadvantage that it gave higher scorch levels than conventional liquid urea. When flag leaf scorch was excessive, grain yield was affected and quality suffered, with reduced grain and hectolitre weights. Where early application of P may have been critical to obtain maximum response, the N that accompanied the early application of P as urea phosphate was most likely lost through leaching. The application of large quantities of K in any one application with the liquid system was restricted due to solubility problems, which ultimately resulted in delayed application in soils with low K levels. The Flex system does not lead to increased biological efficiency. However, as farms get bigger and greater emphasis is placed on the reduction of water and air pollution, the liquid Flex system may become attractive because of its practical advantages in handling, storage and application and the ability to tailor-make specific formulations for given crop requirements.
    • Ammonium thiosulphate as an environmentally friendly tool for reducing N inputs.

      Murphy, Matthew D. (Teagasc, 1998-09-01)
      The overall objective of the EU funded project was to evaluate the ability of ammonium thiosulphate (ATS) to act as an inhibitor of urease and nitrification processes and as a source of plant nutrient S when added to solid and liquid fertilisers and to slurries. These initial experiments have shown the need for further research on (a) applying ATS directly to the soil rather than to the herbage surface, and (b) adding ATS to the slurry in the storage tank simultaneously with slurry excretion.
    • The Application of Harvester -Mounted Forage Yield Sensing Devices.

      Forristal, P.D.; Keppel, D. (Teagasc, 2001-07-01)
      The development and application of precision agriculture technology to forage crops offers scope for improved management practices and targeting of inputs. In particular, the ability to measure forage throughput on a harvester would form the basis for improved management decisions and the ability to exploit precision agriculture technology, including accurate application of forage additives. The aim of this project was to develop a forage throughput sensor and to use that sensor to record yield variability and to accurately control additive application. Following preliminary trials, a force sensing plate placed in a forage harvester chute was developed and assessed. A very good relationship between sensed throughput and measured throughput was achieved, with regression coefficients of between 0.88 and 0.96 recorded in a series of trials. The relationship was established on a fresh-weight basis. Calibration could present difficulties in practice. The forage throughput sensor was linked to a GPS positioning system and a modified yield monitor/recording system to facilitate the measurement of yield variability in the field. Considerable difficulties were encountered with compatibility of the various components, including the analysis software. While a forage yield map was created and illustrated the levels of yield variability within a field, the need for simultaneous on-harvester dry matter sensing was apparent. A throughput-based additive application control system was designed, developed and tested. The unit performed satisfactorily, resulting in less variation in the quantity of additive applied to harvested grass compared to conventional application systems. In conclusion, there is scope for the application of precision agriculture technology, based on forage yield sensing, on grassland farms. However, there are many differences between the adoption of this technology on grassland farms compared to arable farms. In particular, yield-sensing accuracy is unlikely to be as good, and the need for simultaneous DM sensing is critical. Forage yield sensors will be commercialised soon. There will then be a need to evaluate these systems and the application of precision agriculture technology to grassland systems.
    • Aspects of slurry management on pig farms.

      O'Connell-Motherway, S.; Lynch, P.B.; Carton, Owen T.; O'Toole, P. (Teagasc, 1998-09-01)
      The objectives of manure or slurry management on intensive pig farms are the provision of adequate slurry storage capacity and the efficient recycling of the slurry nutrients for crop production. However, recent surveys of pig slurry dry matter suggest there is excessive dilution of raw pig slurry with water. This has two important implications for management. The first is greater storage capacity will be required due to the increased volume of slurry generated. Slurry storage is expensive. For example, a 350 sow unit adding 10 weeks storage needs to invest £50,000. Secondly, evidence from the literature indicates an improved slurry nitrogen efficiency with the more dilute manure. The results of field trials showed that higher dry matter pig slurries reduced the relative efficiency of pig slurry nitrogen for second cut silage production. This is probably linked to reduced ammonia volatilisation losses, consequent to the less viscous nature of dilute slurry which permits a more rapid infiltration of the ammonium nitrogen into the soil. The use of a band spreader or shallow injection rather than the conventional splash plate were shown to increase the efficiency of pig slurry nitrogen for grass silage production. Therefore, the potential for the higher pig slurry dry matter, required for cost effective storage/ handling costs, to reduce the efficiency of its nitrogen for grass silage production can be partially offset by using band spreaders or shallow injection spreading systems. These have the added advantage of reducing odour emissions from the land spreading operation.
    • Assessing populations of the major cereal pathogens for reduced sensitivity to MBC, DMI and Strobilurin fungicides

      O’Sullivan, Eugene (Teagasc, 2009-08-01)
      Studies of eyespot populations in winter wheat crops in the period 2001 to 2003 showed that the R type (Tapesia acuformis) is the dominant strain comprising 77% of isolates. Over 90% of isolates were resistant to MBC fungicides, 53% showed reduced sensitivity to prochloraz and 22% reduced sensitivity to cyprodinil. A study of winter wheat crops in February and March 2003 showed that resistance to strobilurin fungicides was widespread in Mycosphaerella graminicola (Septoria tritici) populations. Resistance was found in all but one of 21 crops sampled, at levels ranging from 9% to 84% with an average of 48%. Subsequent studies of 27 crops over the summer of 2003 showed that strobilunin resistance increased from an average of 31% before the application of the second (T2) spray to an average of 73%, three to four weeks after the application of the final (T3) spray. Strobilurin resistance in M. graminicola remained high in 2004, ranging from 50% to 100% with an average of 83% in populations in winter wheat crops sampled in March. The effect of different fungicide programmes on resistance was studied during summer 2003 at two experimental sites. Levels of strobilurin resistance in M. graminicola populations increased during the summer, in unsprayed plots and plots treated with triazole fungicides as well as in those treated with strobiurin fungicides at both sites. M. graminicola populations in winter wheat crops sampled in 2003 and 2004 were predominantly resistant to MBC-generating fungicides and sensitive to the triazole-based fungicides. Studies of the barley leaf blotch pathogen Rhynchosporium secalis showed that resistance to MBC fungicides occurred in 20% of isolates collected from crops from 2001 to 2003, but all isolates were sensitive to triazole and strobilurin fungicides.
    • Assessment of field sattelite-based positioning systems for reduced, more precise use of crop inputs.

      Rice, B.; Colfer, S. (Teagasc, 2000-11-01)
      The mapping of within-field crop yield variations offers a basis for the adjustment of input application rates to match yield potential. The aim of this project was to examine available yield mapping components and systems, and to assess the benefits that could accrue from yield mapping. The work also included site investigations of possible causes of yield reduction, and an evaluation of the potential increase in profitability from variable-rate N application. Yield mapping requires the continuous measurement of harvester position and grain yield. Accurate positioning was achieved with systems which received a remote correction signal via communications satellite. A grain flow meter in the clean grain elevator gave low errors in conditions where the deflector plate could be kept clean. The production of useful yield maps was sometimes limited by rainy weather leading to wet crops, lodging, and big variations in harvest conditions within the field. Difficulties are also presented by small, irregularly-shaped fields. The level of within-field variation in cereal yields (25% of the field area at least 21% below the mean) suggests that there is scope for identifying low-yielding areas and either taking corrective action or applying reduced inputs. An analysis of the results of N fertiliser trials suggests a potential gain from about £20/ha in sugar beet to less than £10/ha in spring barley if N application rate could be varied to apply the optimum amount to each area within a field. All the costs of application map development and variable-rate application would need to fall below these gains to justify the use of the technology. To allow further use to be made of yield maps, it is desirable that the factors responsible for yield reduction be identified, in particular those which recur each year. In the present study, soil chemical analysis and compaction affected yield in only a small proportion of cases. Differences between maps from successive years have been small. It is concluded that the immediate financial benefits from the use of this technology will be small. However, in a future where the recording, justification and minimisation of inputs such as pesticides and fertiliser will grow in significance, and where the cost of the equipment and software will continue to fall, yield mapping and variable-rate input application will find a useful role.
    • An assessment of the long-term effects of three phosphorus fertiliser regimes on soil phosphorus and sward condition.

      Culleton, Noel; Murphy, W.E.; Carton, Owen T.; Cuddihy, A. (Teagasc, 1999-04-01)
      A grazing trial using beef animals (mean weight 260 kg) was used to determine optimum soil phosphorus levels for dry stock farming. · The trial commenced in 1968. There were three fertiliser P treatments, 0, 15 and 30 kg P/ha applied annually. There were two stocking rates, 3300 and 2400 kg liveweight at turn out, respectively. Animals were rotationally grazed around six paddocks per treatment and stocking rates were reduced in June and September to match feed supply. The trial continued until 1998. ¸ Nitrogen was applied at a rate of 220 kg/ha per year to all treatments. ¹ Liveweight gains/ha/year were monitored annually. Soil P levels were monitored by sampling to 10 cm depth. º The distribution of phosphorus in the soil was recorded by analysing P levels at various depths from 0-2 mm to 100 cm. Botanical composition was recorded at the commencement of the trial and again in 1997. Phosphorus levels in herbage were also recorded. » An analysis of the liveweight gain data showed that for optimum output a Soil Index of 3 (Morgans P between 6.1 and 10.0 mg/l) is the target Soil P Index. ¼ Phosphorus recovery (as expressed by percentage of P fertiliser recovered in product) in the P30 treatments was low and was better in the P15 treatments. ½ The vast bulk of P accumulated near the surface of the soil, but there was some evidence of movement down the profile in the P30 treatment over a 30 year period. The soil P status influenced both the botanical composition of the sward and the P content in the herbage. The perennial ryegrass content declined on the zero P treatment, while there were no significant differences between the P15 and P30 treatments. The P concentration in the herbage in the zero P treatments were not sufficient for healthy growth of plants or animals.
    • Beef production from feedstuffs conserved using new technologies to reduce negative environmental impacts

      O'Kiely, Padraig; Crosson, Paul; Hamilton, William J.; Little, Enda; Stacey, Pamela; Walsh, Karl; Black, Alistair D.; Crowley, James C.; Drennan, Michael J; Forristal, Dermot P.; Hackett, Richard; McGee, Mark; Moloney, Aidan P; O'Brien, Martin; O'Riordan, Edward G.; Rice, B.; Schulte, Rogier P. O. (Teagasc, 2007-12-01)
      The three separate components with parallel objectives to this programme were to: 1. Develop technologies for conserving and optimally feeding alternative/complimentary feedstuffs to grass silage. 2. Quantify the use and re-use of plastic sheeting or film used to seal ensiled feedstuffs or mulch maize, and evaluate some new options. 3. Develop computer programs that will facilitate investigating prototype models of forage-based beef production systems.
    • Better management and economy of the N resource in Ireland.

      Ryan, M. (Teagasc, 1998-09-01)
      The project, which was carried out at Johnstown Castle, was concerned with measuring denitrification at depth in grazed grass plots receiving 362 kg fertiliser N per ha. Reports in the scientific literature had indicated that such was likely, given the conditions necessary for the denitrifying microbial reactions to take place. In one experiment, denitrification was detected in measurable amounts to 90cm soil depth in spring-summer, using the acetylene block technique. A second more extensive experiment carried out under similar conditions within one year from March to August and from October to March looked at denitrification in greater detail to 50 cm deep. Results showed the importance of soil water and soil ammonium (NH4) to rate of denitrification. The rate was much greater in the 0-10 cm layer than in the lower layers in both time periods. Of the total denitrification occurring in the 0-50 cm layers in the year, which was 16.6 kg N per ha, 80% occurred at 0-10 cm with 62% occurring in the second time period, October to March.
    • Bi-cropping of winter wheat and white clover.

      Burke, J.I.; Thomas, T.M.; Finnan, John. (Teagasc, 1998-09-01)
      Growing cereals in a leguminous living mulch (bi-cropping) could potentially reduce the need for synthetic inputs to cereal production while preventing losses of nutrients and increasing soil biological activity. The objective of this project was to investigate how bi-cropping (a low input production system for cereals) would compare with conventional winter wheat production systems in terms of total biomass, grain yield and biological diversity. This study has resulted in valuable information on bi-cropping being generated as well as identifying the potential benefits that can be expected under Irish conditions. While the results indicate that winter wheat can be successfully established in an understorey of white clover if sown early in good conditions, competition from grass weed species represents a serious impediment to successful bi-cropping in the longer term. Consequently further research is needed before such a system can be presented to the agricultural community.
    • Biodiesel production from camelina oil, waste cooking and tallow.

      waste cooking oil; Rice, Bernard; Frohlich, A.; Leonard, A. (Teagasc, 1998-09-01)
      The high cost and lack of availability of raw materials is limiting the expansion of bio-diesel production. The aim of this project was to examine the potential of alternative vegetable oils, oil wastes or animal fats as bio-diesel feedstocks, and the performance of road vehicles using bio-diesel blends made from these materials. Three feedstock materials were considered: waste cooking oil from the catering industry, Camelina oil, and beef tallow. Thirty-four 300-litre pilot-scale batches of these materials were esterified, and yields and bio-diesel properties were measured. Five growers produced about 6 ha of camelina sativa on their set-aside land. Vehicle performance trials were carried out with five fuel blends involving bio-diesel and mineral fuel. A plant to produce approx 3000 tonnes per annum of bio-diesel was specified and costed. The work has concluded that waste cooking oil is the most promising raw material for the immediate start-up of bio-diesel production. A proportion of camelina oil could also be used. Further work is required to overcome technical problems with tallow. The cost of bio-diesel production in a 3000 t/yr plant from these raw materials was estimated at from 27 to 32 pence per litre of fuel. Reduction of excise on biodiesel to the level applied to heating and agricultural fuels would make its final price competitive with mineral diesel for road use. The excise remission could be justified by a reduction of global warming and harmful vehicle exhaust emissions, and the provision of a safe disposal system for otherwise waste materials.
    • Blockage reduction to increase the efficiency of slurry application.

      Ryan, D.; Brett, P. (Teagasc, 1999-12-01)
      Discussions with farmers using band and injection slurry spreaders suggested that the rate of breakdown due to blockages, in these machines, was approximately one per day. This report shows how the use of an intake filter and a modified distributor on a band spreader can reduce this problem. A set of obstacles was assembled on the basis of information from farmers and from literature. Ten classes of obstacles were selected, at random, and between size limits. Two prototype filters, a commercial filter and an open pipe were tested while drawing slurry from an open tank to a tanker. During each test, obstacles were thrown into the slurry stream. Obstacles retained by the filter were counted afterwards. A second filter trial was organised to test the tendency of filters to clog. Obstacle tests with 3 prototype distributors and a control were conducted in a similar manner to the first filter trial but, in this case, preliminary tests were conducted in water and final tests in slurry. The initial tests identified the best prototype. This was then compared to the control distributor using slurry. The open pipe allowed 80% of obstacles to pass while the filters allowed only 4 – 19% through. The new filters offered no improvement over the commercial unit. Filters required 16 hours agitation but the open pipe required 4 hours or less. The best prototype had the same diameter as the control but had an obstacle trap attached at the side. In a test using obstacles and slurry, the control was obstructed by 56% of the obstacles while the prototype allowed only 21% to cause a blockage. Flow through the prototype was initially too large. Slowing down the rotor in the distributor and restricting the outlet from the obstacle trap with a single long pipe, connected to two nozzles, controlled the flow. The results of the filter and distributor trials were combined. Of the seventy obstacles dropped above the filter, six passed through. Four of these caused blockages in the control distributor, but only one became stuck in the prototype. The blockage rate in the distributor and nozzles was significantly reduced compared to the original unit.
    • Breeding Improved Varieties of Perennial Ryegrass.

      Connolly, V. (Teagasc, 2001-05-01)
      The background, methodology and objectives of the current ryegrass breeding programme are outlined. Six varieties have been released and are currently on Recommended Lists in Ireland and elsewhere. The varieties have shown improvement in yield and yield distribution: these traits are important in the context of improving the productive potential of Irish grasslands. In parallel with the breeding programme, research on projects which is related to future selection strategy was undertaken. The results of this research on hybrid breeding system and quality objectives are summarised.
    • Breeding Improved Varieties Of White Clover.

      Connolly, V. (Teagasc, 2001-08-01)
      White clover is one of the most nutritious species available in grassland/ruminant production systems. In association with grass, this species increases protein, mineral content, intake and nutrient value of the total forage. Because of its nitrogen fixing capacity, white clover has the potential to reduce, or in the case of organic systems, eliminate the need for inorganic nitrogen fertilizer on grazed grassland. Grassland-based animal production is a major part of the Irish agricultural economy, consequently any improvement in this legume has large potential benefit in this sector. The background, methodology, objectives and output of the current Teagasc, Oak Park white clover breeding programme are outlined. Five varieties have been released and are currently on Recommended Lists in Ireland and elsewhere. Aran, first released in 1981, has remained the highest yielding clover variety in UK trials, it is also widely grown in New Zealand, Australia and France as well as Ireland and UK. Avoca has shown very good yield and persistency under a range of managements and is widely used in Ireland and UK. Chieftain, the most recently released variety, has given 25% more clover yield than the control under lax defoliation (simulated grazing) management in UK Recommended List trials. In parallel with the breeding programme, research on nitrogen fixation and development of inbred lines in this species was undertaken. A brief summary of some of the results is included in this report.
    • Breeding, disease resistance screening and seed production of new potatoe varities.

      Keogh, H.W.; Dowley, L.J.; O'Sullivan, E. (Teagasc, 2000-09-01)
      The potato breeding programme at Oak Park was started in the 1960's and has consisted of a number of distinct phases. In the first phase the focus was on the testing of the main domestic and foreign varieties in field trials in the main potato growing areas of the country. This was followed by a breeding programme for the domestic market, with particular emphasis on the production of a blight resistant replacement for Kerr’s Pink. The emphasis then switched to breeding for the export market, with the focus on the UK and Mediterranean markets. Since then the breeding programme has been focused on the domestic, processing and export markets. The process of breeding, testing and multiplying a new potato variety from the making of the initial cross until the new variety can be commercially grown takes about 15 years (see Appendix 2). The objectives of the present Potato Breeding Programme are: 1. Breeding improved varieties for the seed export trade. 2. Developing high yielding early maincrop and maincrop types with resistance to potato cyst eelworm Globodera rostochiensis and or Globodera pallidae with quality suitable for the UK market. 3. Developing a high dry-matter red skinned early maincrop or maincrop variety suitable for the home ware trade with a high level of disease resistance especially to late blight. 4. To select early maincrop or maincrop types suitable for processing into crisps and chips. 5. Breeding 1st and 2nd early varieties suitable for Irish and UK conditions with improved quality and disease resistance.
    • Chemical and biological control of mushroom pests and diseases.

      Staunton, L.; Dunne, R.M.; Cormican, T.; Donovan, M. (Teagasc, 1999-03-01)
      This study set out to determine the occurrence of diseases and pests in Irish mushroom units and their method of control using chemical, biological and other means of control. It also examined the role of a combination of these methods to enable control with minimal pesticide input. It was found that pesticides alone will never give effective disease and pest control and that they should only be considered an adjunct to the implementation of other methods. They include: (1) Exclusion (2) Containment of spread (3) Elimination. A major factor in good disease and pest control was found to be the implementation of a good programme of hygiene which must be followed from the time of filling a tunnel to the time of emptying after cropping. Biological systems offer good potential for control but at present are not as effective as the best chemical control methods.
    • Collection and rejuvenation of rare/scarce plants for the nursey stock industry.

      Murphy, R.F.; Douglas, Gerry C. (Teagasc, 1999-12-01)
      The main objectives of this project were: • Location of scarce/rare or new plants of high garden merit with tolerance to disease and pests • Rejuvenation. • Conservation of rejuvenated plants in the original gardens from which they were collected, at the Kinsealy Research Centre and in other selected locations. • Evaluation of the collection for a variety of uses – foliage, patio etc. over a range of different conditions and locations. • Plant identification. • Commercialisation of these plants by the trade to extend their range of plants.
    • Comparison of Cereals Grown Under High (Conventional) and Low (Reduced) Inputs Systems

      Conroy, M.J.; Hogan, J.J. (Teagasc, 2001-06-01)
      This long-term experiment, which commenced at Oak Park in September 1994, compared the effect of a high inputs system with a low inputs system on the yield and quality of winter wheat and winter barley grown (i) In a non-cereal break-crop rotation with spring barley (ii) In a continuous cereal break-crop rotation with winter oats, and (iii) Continuous cereals. The experimental site at Knockbeg consisted of a medium-heavy textured, freedraining grey-brown podzolic soil (Knockbeg Series). The objective of the experiment was to measure the effect of reduced inputs on grain yield, grain quality, production costs and the profitability of the important cereal crops grown in different rotations, so that the impact of a more environmentally-friendly inputs system could be assessed and compared with conventional production systems.
    • Confirmation of co-denitrification in grazed grassland

      Selbie, Diana R.; Lanigan, Gary; Laughlin, Ronald J.; Di, Hong J.; Moir, James L.; Cameron, Keith C.; Clough, Tim J.; Watson, Catherine J.; Grant, Jim; Somers, Cathal; Richards, Karl G. (Nature Publishing Group, 2015-11-30)
      Pasture-based livestock systems are often associated with losses of reactive forms of nitrogen (N) to the environment. Research has focused on losses to air and water due to the health, economic and environmental impacts of reactive N. Di-nitrogen (N2) emissions are still poorly characterized, both in terms of the processes involved and their magnitude, due to financial and methodological constraints. Relatively few studies have focused on quantifying N2 losses in vivo and fewer still have examined the relative contribution of the different N2 emission processes, particularly in grazed pastures. We used a combination of a high 15N isotopic enrichment of applied N with a high precision of determination of 15N isotopic enrichment by isotope-ratio mass spectrometry to measure N2 emissions in the field. We report that 55.8 g N m−2 (95%, CI 38 to 77 g m−2) was emitted as N2 by the process of co-denitrification in pastoral soils over 123 days following urine deposition (100 g N m−2), compared to only 1.1 g N m−2 (0.4 to 2.8 g m−2) from denitrification. This study provides strong evidence for co-denitrification as a major N2 production pathway, which has significant implications for understanding the N budgets of pastoral ecosystems.