Soil Horizons Issue 24, December 2015

Breaking in the Pumice LandsFIGURE 3 Drained productive pastures support the economy of theManawatu region todayEncouraged by farmers, local authorities, and GovernmentDepartments, they researched ways to overcome thelimitations of wet, poorly drained soils for cultivation andagricultural production, to enable the local economy todevelop.As one travels through the farming districts of New Zealand,and of the North Island in particular, one cannot help beingstruck by the fact that there are thousands of acres on thiscountry crying out to be drained .There is no doubt that astime goes on, more and more if it will be drained, and it hasbeen the object of Mr Hudson and his assistant Mr Hopewellto get to the bottom of some of the more unsatisfactoryaspects of drainage so that the work of development may becarried out with the minimum of mistakes and waste of money.G.S.Peren, 1940, Massey Agricultural College,Palmerston NorthSoils research played a pivotal role in the successfulconversion of thousands of hectares of poorly drainedsoils in the Manawatu region into productive freer drainingpastures. The Drainage Extension Service were activeright into the beginning of the 21st Century, at which stageother commercial companies took over the installation andmaintenance of the mole and tile drain networks laid by themin the preceding decades.One of the most mystifying agricultural problems in thefirst part of the 20th century was the wasting illnesstermed ‘bush sickness’ that affected sheep and cattleintroduced onto recently converted tussock plains andshrublands on pumice parent materials in the centreof the North Island. Scientists originally diagnosed theproblem as a form of iron deficiency, and it took morethan 20 years for the exact cause to be identified.This research pioneered the way for many futureresearch projects investigating the relationship of animalmetabolism to soil characteristics.Before they were solved, these animal health problemshad led to the conversion of the recently establishedpastoral farming on pumice soils (Fig. 1) to exotic forestry.Pinus radiata trees were planted into a large area, nowknown as the Kaingaroa Forest. This forest became thelargest exotic forest in the world, with world-beatinggrowth rates. The exotic forestry development was verysuccessful, forming the basis of New Zealand’s futureexotic timber industry.Meanwhile, soil scientists were determined to discover thereasons for the ‘bush sickness’ problems. Soil surveys inthe mid-1930s by Les Grange and Norman Taylor studiedvolcanic ash deposits and showed that bush sicknessonly occurred where tephras had been deposited duringthe Taupō and Kaharoa eruptions (about 200 AD and1314 AD). Chemical analyses revealed that the sicknesswas caused by a deficiency in the trace element cobaltand that other trace elements, selenium and copper, werealso deficient.By the late 1930s the widespread use of cobaltisedsuperphosphate had successfully controlled bushsickness and opened the way for successful pastoraldevelopment of these problem areas.The development of this soil and water research disciplinelaid the foundation for our ability to tackle current issuessuch as the quality of drainage water, irrigation and effluentmanagement. Now, in some regions of New Zealand,research is underway to understand which specific parts ofdrained landscape, might need to be reverted to wetlands toslow-down losses of nitrogen and phosphorus, in drainagewaters, into surrounding waterways and groundwater.CAROLYN HEDLEY – LANDCARE RESEARCHE: hedleyc@landcareresearch.co.nzFIGURE 1 Pumice soil profiles5

Soil Science in the New Zealand Forestry SectorThe predominant production system followed by the NewZealand forestry sector is a low input, short rotation model.This results in significant disturbance to forest soils on amuch more frequent basis than occurs in other countries,e.g. rotation lengths of 30 years compared with 60 years.This increased pressure placed on soil resources has thepotential to degrade the ability of the soil to support forestestablishment and growth, resulting in reduced yield overmultiple rotations.In response, Crown Reserach Institute for forestry, Scion,has conducted extensive research into the factors that affectthe ability of soil to support productive forests. This researchhas extended over time from simple assessments of soilnutrient pools to assessments of the stability of soil processesthat determine the flux and availability of those nutrients,the activity of the soil microbial communities that influenceforest health and growth, and the importance of the physicalstructure of soil to the sustainability of forestry operations.Although this research has identified a range of opportunitiesto develop improved forest management systems, to date ithas resulted in only limited changes to silvicultural practices. Akey reason for this is unfamiliarity with soil itself as an indicatorof site productivity. Analysis of foliar tissue has long beenconsidered the simplest method to determine if a forest standis deficient in key nutrients. To further explore issues in theuse of soil-based data in forest management, we surveyedopinions on the role of soil research across the forestry sector.The survey collected information from 130 respondents,including farm foresters, small-block owners, corporateforesters, and independent forestry consultants across mostregions of New Zealand. Survey information indicated thatthe vast majority of respondents regarded soils as relevantFIGURE 1 Workshop attendees observing the preparation of a soilsurface for sample collection in a mature stand of radiata pineFIGURE 2 Equipment required to deal with the various issues encounteredwhen collecting soil bulk density soil samples in plantation foreststo forest productivity and were interested in making useof soil data. However, it was equally apparent that mostrespondents considered themselves unable to conduct soilsampling effectively, or to take soil data and translate it intopractical actions that could be incorporated into their forestmanagement strategies.To address this lack of confidence, Scion has instigated aseries of forest soil sampling workshops to provide the sectorwith greater understanding of methods for soil sampling(Fig. 1). Issues discussed included the use of mappingsystems and sufficient replication to ensure soil samples arerepresentative of the area in question, the timing of samplingefforts within the life of the forest stand, and the level ofresolution in sampling across the landscape – balancedagainst the cost-effectiveness of investment in soil collectionand analysis. The workshops comprised a field component,allowing the attendees to become familiar with the varioustools and techniques used to obtain the different kinds of soilsamples, which is a critical element in understanding the timerequired to conduct such sampling (Fig. 2).Through the “Growing confidence in forestry’s future”(GCFF) research programme, Scion works closely with thesector to address the successful use of soil data to informforest management. This spans a diverse range of projects,including issues of precision nutrient management, enhancingthe activity of beneficial soil microbes, and maintaininglicense to operate through assessment of the environmentalsustainability of management.SIMEON SMAILL – SCIONE: simeon.smaill@scionresearch.com6

Looking to the future of land evaluationand farm systems analysisFuture shape of land evaluationLand evaluation is formally defined as ‘the assessmentof land performance when used for a specified purpose’and has a long history of describing and quantifying thedifferences between units of land. The procedure uses limitingfactors arising from climate, hydrology, landforms, soils andvegetation as the basis for evaluation of sustainable yields,with critical values determining the boundaries of suitability. InNew Zealand, land use capability classification is the basis forassessing suitability for sustained production.Two new trends emerging from land evaluation frameworksglobally are the recognition of the wider functions provided bylandscapes and the need for greater stakeholder participationin exploring the balance between economic, environmental,social, and cultural outcomes. With increasing demandson the finite land resource, land evaluation must go beyondassessment of land suitability for primary production aloneand consider the performance of all services provided by acombination of land type, climate, land use, and managementpractices, as well as impacts on receiving environments.A rapidly emerging multi-disciplinary approach to assess themulti-functionality of natural resources is the ecosystemsapproach based on the concepts of natural capital andecosystem services. Natural capital is defined as the ‘stocksof natural assets that yield a flow of ecosystem goods orservices into the future’. This concept comes from trying toframe the contribution of natural resources to the economyalongside built capital (factories, buildings), human capital(labour, skills), and social capital (education, culture).Ecosystem services are defined as ‘the benefits people obtainfrom ecosystems’ – not only food, but also flood mitigation,nutrients filtration, greenhouse gas regulation or pestregulation.Adding an ecosystems approach to land evaluation enablesthe supply of ecosystem services to be directly linked to theperformance of a combination of land type, land use andmanagement intensity to deliver specific outcomes.Emerging farm systems analytical capabilityFarms are often an assemblage of multiple landscapes witha mixture of topographies and soil types, both of whichinfluence pasture and crop production, as well as otherecosystem services. Importantly, these land units showdifferent responses to inputs and practices. Today’s intensiveagricultural systems are the product of successfully combiningbuilt capital with diverse natural resources (e.g. land, water) toproduce food and fibre for profit. Future analysis of the farmsystem will need to be extended to include the implicationof decision-making not just on food and fibre production,FIGURE 1 Combining land capability with resource condition under a land use to quantify ecosystem services provision for multi-function land evaluation7

but also on the services our farm systems provide. Thisecosystems approach creates the ability to define ‘ecologicalboundaries’ within which resources should be managed,addressing the purpose of the Resource Management Act1991 (Section 5).In our research programme, we are developing a new farmsystems model “INFORM” (Integrated Farm Optimisation andResource Allocation Model) that integrates biological datafrom each land management unit (similar natural resourcesand management practices) (LMU) within the farm. It usesLMU information to identify the mix of production enterprisesand management regimes that maximise profit (EBIDTA) forthe business.This method helps isolate and examine the value ofinvestments targeted at specific parts of the farm on thewhole farm business, and could potentially offer analysis thatwill make best use of resources within defined boundaries, fortargeted performance of ecosystem services delivery.ALEC MACKAY, ESTELLE DOMINATI, JOHN RENDEL –AGRESEARCHE: alec.mackay@agresearch.co.nzUsing aerial survey and remote sensing to assess bank andcliff erosion in Hawke’s BayLandcare Research scientists have been collecting videofootage of bank erosion in Hawke’s Bay to help them studythe stability of the landscape.The new information will be used to improve SedNetNZ, aprocess-based sediment budgeting model being developedby Landcare Research (see Soil Horizons issue 21,September 2012), because the model will benefit from moredetailed bank erosion data.Bank erosion data are normally collected using groundreconnaissance, but this is time-consuming and often limitedby accessibility problems (e.g. see Fig. 1).Therefore we used a helicopter to fly hand-held, highresolution video cameras along selected river channels,covering approximately 100 kilometres of river channel inabout two hours’ flying time. An example of the imageryobtained from this method is shown in Figure 1.The video footage was then interpreted on-screen, inconjunction with an ortho-rectified image of the areas flown,to identify the total length of river banks and cliffs affected bydifferent erosion types. This information was then digitised inGIS software using a river centreline subdivided by erosioncategory (Fig. 2), and statistics generated on the length ofbank and cliff affected by erosion as a proportion of the totallength of river channel.Erosion categories identified and mapped were cliff erosion(erosion of bedrock cliffs), alluvial bank erosion, undercutslab failures, surface erosion, gullies, slumps, and shallowlandslides, along with categories for those channel marginsthat were not eroding or were obscured.8The aerial survey approach was very successful for thefollowing reasons: Continuity of coverage: High-resolution video gives a nearcontinuous, high-quality, interpretable, qualitative recordof erosion types along channel margins. Videos can befreeze-framed to yield a good-quality still photograph ofany scene along the flight path. By comparison, obtaininga comparable record from the ground is not feasible. Ability to interpret and map from video imagery: Using arecent vertical aerial photographic survey as a base, wewere able to use the video imagery objectively to map thefull extent (length) of erosion along entire channels. Fromthis we could quickly derive the total proportion of channellength affected by different erosion types, and assesstheir relative significance. Many of the erosion featureswere not clearly visible on vertical aerial imagery, furtherunderpinning the usefulness of the video survey. Cost: The aerial survey, while presenting a relatively largeup-front cost, yielded data that would have been morecostly to acquire using traditional ground-based methods,and impossible to collect from inaccessible parts of theriver bank.We intend to develop this method in future work, with thepossibility of deriving three-dimensional measurements oferosion features through stereo image analysis and/or theincorporation of LiDAR data to help us better understandsediment fluxes from these sourcesNOTE: LiDAR: Light Detection and Ranging is a remote sensing methodused to examine the surface of the Earth.HARLEY BETTS AND MIKE MARDEN – LANDCARE RESEARCHE: bettsh@landcareresearch.co.nz

FIGURE 1 Video image of “Cliff erosion” from the upper Tutaekuri catchmentFIGURE 2 Erosion mapping for part of the Mangaone catchment, with randomly coloured segments corresponding to mapped erosion classes. Achange from one segment to another indicates an erosion class change on at least one bank. Grid interval is 500 m9

The odyssey of a national soil carbon modelThe Ministry for the Environment (MfE) established the LandUse and Carbon Analysis System (LUCAS) for reportingon New Zealand’s land use, land-use change, and forestry(LULUCF) sector in the national greenhouse gas inventory,submitted each year to the United Nations FrameworkConvention on Climate Change (UNFCCC). As part of LUCAS,the Soil Carbon Monitoring System (the ‘Soil CMS’) wasdeveloped to extrapolate national soil carbon stocks andestimate and report the effect of land-use change on the soilcarbon pool to meet the UNFCCC reporting guidelines. Underthose guidelines, countries can rely on simple, prescribedmethods using global default values (called a Tier 1 approach),use country-specific data with Tier 1 methods (a Tier 2approach), or implement more specific and sophisticatedmethods, such as process-based models (a Tier 3 approach).The tier structure is hierarchical, with higher tiers implyingincreased accuracy of the method and/or emissions factorsand other parameters used in the estimation of the emissionsand removal. Following the IPCC good practice guidance,countries are expected to use appropriate available data andmethods at the highest tier possible depending on nationalcircumstances, especially for reporting on important (“key”)categories of greenhouse gas emissions and removals. Inaddition, the principle of continuous improvement encourageseach Party to refine and improve its approach through time.1990s: The Soil CMS Model emergesFrom the outset, New Zealand sought to report on soil carbonusing a Tier 2 approach, setting it on an odyssey of meetingboth scientific research and international policy challenges.After the UN Conference on Environment and Development,the “Earth Summit” held in Rio de Janiero in 1992, LandcareResearch Scientist Kevin Tate recognized the need to pulltogether New Zealand’s soil data for the future reportingrequirements, and MfE initiated the development of the SoilCMS in 1996. The main focus of this first version was thethen major land use change in New Zealand of afforestationof former pastures. The underlying principle was to calculateFIGURE1 Soil carbon accumulates in topsoils10the difference between assumed equilibrium soil C stockswhere land-use change occurs, applying the IPCC defaultof linear change to a new equilibrium over a 20-year period(the approximate duration of exotic forests being harvested).With that aim in mind, the soil CMS model was developedbased on biophysical principles using existing national soildata sets to estimate SOC taking into account site variablessuch as climate, topography, soil type, and land use. Thesoil CMS model was further developed with additional data,and a move from a linear regression model to a generalleast squares fitting procedure and a correction for spatialautocorrelation.2010: International reviewThe soil CMS met resistance from an “external review team”(ERT) of New Zealand’s 2010 submission (for the 2008reporting year), its first annual submission for CommitmentPeriod 1 (2008–2012) of the Kyoto Protocol. The ERTcommended New Zealand for undertaking the Tier 2approach but questioned its statistical validity, especiallydetecting the effect of particular land-use transitions on soilcarbon stock changes. The ERT encouraged New Zealand tore-examine the methodological approach, as well as collectmore data for land-use categories under-represented in thecalibration data set.2015: A refined Soil CMS ModelThe LUCAS programme sought to meet ERT expectationsby collecting additional data and recalibrating the model.Although the first attempts to add new data sets (for croplandsoils) were helpful in terms of expanding the data set, themodel improvements were deemed insufficient to meet theERT critique. So, New Zealand reverted to using a Tier 1approach for estimating and reporting soil carbon emissionsand removals for the 2010 and 2011 reporting years(submitted in 2012 and 2013, respectively). Further modeldevelopment and recalibration involved adding a wetland soilsdata set to the calibration data and a thorough investigationinto approaches used to model SOC and determine thesignificance of land-use transitions, resulting in an improvedversion of the soil CMS that could be used for a Tier 2approach. Thus, in 2014, New

contributions by New Zealand soil scientists advancing soil research. This issue of Soil Horizons shows how our traditional approaches to soil science, collecting data, research - and even the way we view soil - have changed. Rapid advances in technology are opening many new soil research opportunities, and these advances are combining with the