Misselbrook, T. H.

Rook, A. J.

Scholefield, D.

English

Rothamsted Repository

I G E R  I N N O VAT I O N S 2006Mult i -Funct ional  Uses  for  Pas turesMinimising pollution 44Impacts of manures on biodiversity 45Systems models 46Andrew Rook 1, Tom Misselbrook 2& David  Schole f ie ld 31 Behavioural and Community Ecology2 Manures and Farm Resources3 Nutrient Flows and System Modelling hanges in agricultural policy have led togreat emphasis being placed on the need foragricultural land to fulfil not only its traditionalfunction of food production but also to contributeother ‘ecosystem services’ such as reduction ofpollution and enhancement of biodiversity andlandscape value.  Work at North Wyke isincreasingly moving toward integrated approaches todelivery of these diverse functions with the aim ofdelivering ‘win, win, win’ outcomes.  In this articlewe describe some of the key projects in this area.Minimising pollutionUrine and faecal deposits by grazing animals arepotential hotspots of pollution to both air and water.Although potentially valuable as sources of plantnutrients, the uneven nature ofurine and faecal distributionresults in poor efficiency of useof these nutrients by the sward.The nitrogen (N) content ofurine, in particular, is very labileand may readily be lost to theatmosphere through ammoniavolatilisation and (followingnitrification and denitrificationin the soil) as nitrous oxide andn i t rogen  gas .  The  h ighconcentration of nitrogen inurine patches can also result insignificant amounts leaching asnitrate to the ground water. It isimportant to be able to quantifythese emissions (Figure 7.1), tounderstand the processesleading to them and to seekmanagement practices whichcan mitigate them. This research is underpinned bystudies of animal behaviourwhich show when and whereanimals deposit dung and urineMULT I - FUNCT IONAL  USES  FOR  PASTURESAndrew Rook,  Tom Misselbrook & David  Schole f ie ldI G E R  I N N O VAT I O N S 20064 4CMULTI-FUNCTIONAL USES FOR PASTURESFigure 7.1 Measuring ammonia volatilisation from grazing livestock(Figure 7.2).  This is important because the impact ofthe excreta and the time course of its breakdown willdepend on the substrate on which it lands, theatmospheric conditions and the overall nutrient loadwithin a given area. Multiple urine deposits to asmall area will exacerbate the polluting potential incomparison with a more uniform distribution ofurine over a larger area. Preliminary results suggestthat, the pattern of excretion differs markedly whendifferent stocking rates are used. Nitrogen concentration in dung and urine will bedirectly influenced by the composition of theherbage being eaten and may also vary throughoutthe day, as determined by animal physiology.Management of sward composition, such as theinclusion of plants containing condensed tannins orpolyphenols, offers a potential mitigation strategy.When eaten and digested by the animal, plantscontaining these compounds have been shown toI G E R  I N N O VAT I O N S 2006reduce labile N excretion. However, grazingbehaviour research is required to ensure optimalintake of such plant species within mixed swards.Improving our knowledge of the spatial andtemporal distribution of urine and faecal depositsand how this relates to the sward composition,grazing management and animal behaviour, isimportant for our overall understanding and abilityto manage the pollution risk from grazing livestock.Impacts of manures on biodiversityIn multi-functional systems, we must consider notonly the effects of manure usage on pollution butalso its effect on the biodiversity and productivity ofthe swards. An ongoing long-term study isexamining the effects of farmyard manureapplications to hay meadows.  Results from the first5-year phase of this project suggest that the impactof organic as opposed to inorganic manures ondiversity is complex and equivocal and thus a further4 5Figure 7.2 Behavioural studies on patterns of excretionMULTI-FUNCTIONAL USES FOR PASTURES3- to 5-year experimental period has commenced inorder to allow effects to develop more clearly over alonger timescale.Systems modelsThe studies described above focus on keycomponents of multifunctional pasture systems.However, if we are to understand fully the impacts ofmanagement practices we need to look at the systemholistically.  To do this in real systems is veryexpensive and therefore much of our work utilisesmathematical modelling to explore variousscenarios.The basis for our current systems modelling wasfounded in the early years of IGER North Wyke withthe development of NCYCLE – a simulation of thenitrogen flows within and from a beef grazingsystem under UK conditions. This simple mass-balance model was one of the first that enabled theI G E R  I N N O VAT I O N S 2006consideration of both production and N losses fromthe system, according to the level of inputs fromfertilisers, excretal returns and site conditions. Ittherefore provided a preliminary tool with which toinvestigate and specify the sustainability of livestocksystems in terms of animal liveweight produced, onthe one hand, and levels of environmental pollutionfrom emissions of N compounds to air and drainagewater, on the other. This model has been developedover the last 20 years through several iterations toimprove its applicability to real livestock systems.This resulted in the creation of a new model,NGAUGE, which is not only capable of simulatingN flows in different livestock systems over thewhole course of the year, taking account of particularsite conditions and previous history of management,but also of seeking an N fertiliser regime optimisedfor specified economic and/or environmental goals.This model is being used both for aiding policyformulation and implementation in relation to theMULTI-FUNCTIONAL USES FOR PASTURESFigure 7.3 A. Diagram of the inputs, outputs and interactions between the 4 models comprising the SIMSDAIRY modelling framework. 4 6ANitrate Directive and for the basis of cost-benefitanalyses of nitrate mitigation. Most recently,however, this modelling base has been furtherupgraded in capability and level of sophistication inthe development of the SIMSDAIRY modellingframework (Figure 7.3 A & B). This frameworkcomprises four simulation models: NGAUGE(IGER), PSYCHIC (ADAS), one on animal feeding(IGER-University of Reading) and one on farmeconomics (University of Exeter) linked togetherand interconnected with some sustainability‘matrices’. The modelling framework can thusconsider N and phosphorus flows, farm profit(economic viability) and environmentalsustainability from several standpoints:- air andwater quality from the baseline models and throughinclusion of the novel matrices, biodiversity andlandscape indices, animal health and welfare,product quality and soil quality. It is being used inI G E R  I N N O VAT I O N S 20064 7two modes: (i) to specify new integrated sustainabledairy systems for the UK and ways of implementingthem starting from current system typologies; and(ii) to ask ‘What if’ questions about the potentialbenefits of making improvements to each of thesystems components. The latter would includeevaluating the potential of plant and animal breedingand of closer linkage of system typologies withparticular soil and climatic conditions for optimisingall-round sustainability.MULTI-FUNCTIONAL USES FOR PASTURESFigure 7.3 B. An example of a computer screen print of the model dataBContact: david.scholefield@bbsrc.ac.ukaj.rook@bbsrc.ac.uktom.misselbrook@bbsrc.ac.uk

Multi-functional uses for pastures

https://repository.rothamsted.ac.uk/download/dfc294b7fdabfd98b1ad45c1ca26e6cf990f6a6b694e07dfd9c2db0b3089c49d/766140/06ch7.pdf

Multi-functional uses for pastures

Abstract

Similar works

Full text

Available Versions

Rothamsted Repository