M.G. Kibblewhite

Generic Issues on Broad-Scale Soil Monitoring Schemes： A Review

Numerous scientific challenges arise when designing a soil monitoring network (SMN), especially when assessing large areas and several properties that are driven by numerous controlling factors of various origins and scales. Different broad approaches to the establishment of SMNs are distinguished. It is essential to establish an adequate sampling protocol that can be applied rigorously at each sampling location and time. We make recommendations regarding the within-site sampling of soil. Different statistical methods should be associated with the different types of sampling design. We review new statistical methods that account for different sources of uncertainty. Except for those parameters for which a consensus exists, the question of testing method harmonisation remains a very difficult issue. The establishment of benchmark sites devoted to harmonisation and inter-calibration is advocated as a technical solution. However, to our present knowledge, no study has addressed crucial scientific issues such as how many calibration sites are necessary and how to locate them.

Biochars in soils: towards the required level of scientific understanding

Key priorities in biochar research for future guidance of sustainable policy development have been identified by expert assessment within the COST Action TD1107. The current level of scientific understanding (LOSU) regarding the consequences of biochar application to soil were explored. Five broad thematic areas of biochar research were addressed: soil biodiversity and ecotoxicology, soil organic matter and greenhouse gas (GHG) emissions, soil physical properties, nutrient cycles and crop production, and soil remediation. The highest future research priorities regarding biochar’s effects in soils were: functional redundancy within soil microbial communities, bioavailability of biochar’s contaminants to soil biota, soil organic matter stability, GHG emissions, soil formation, soil hydrology, nutrient cycling due to microbial priming as well as altered rhizosphere ecology, and soil pH buffering capacity. Methodological and other constraints to achieve the required LOSU are discussed and options for efficient progress of biochar research and sustainable application to soil are presented.

Predicting the preservation of cultural artefacts and buried materials in soil

This study identifies factors affecting the fate of buried objects in soil and develops a method for assessing where preservation of different materials and stratigraphic evidence is more or less likely in the landscape. The results inform the extent of the cultural service that soil supports by preserving artefacts from and information about past societies. They are also relevant to predicting the state of existing and planned buried infrastructure and the persistence of materials spread on land. Soils are variable and preserve different materials and stratigraphic evidence differently. This study identifies the material and soil properties that affect preservation and relates these to soil types; it assesses their preservation capacities for bones, teeth and shells, organic materials, metals (Au, Ag, Cu, Fe, Pb and bronze), ceramics, glass and stratigraphic evidence. Preservation of Au, Pb and ceramics, glass and phytoliths is good in most soils but degradation rates of other materials (e.g. Fe and organic materials) is strongly influenced by soil type. A method is proposed for using data on the distribution of soil types to map the variable preservation capacities of soil for different materials. This is applied at a continental scale across the EU for bones, teeth and shells, organic materials, metals (Cu, bronze and Fe) and stratigraphic evidence. The maps produced demonstrate how soil provides an extensive but variable preservation of buried objects.

On Soil Carbon Monitoring Networks

The design of a Soil Monitoring Network (SMN) poses numerous scientific challenges, especially for the assessment of national or continental areas. The task is particularly challenging because soil carbon content and stocks are driven by controlling factors of disparate origins and scales. Various approaches to the establishment of SMNs are reviewed here. Frameworks for soil monitoring exist in numerous countries, especially in Europe. Although some countries work using standard monitoring methodologies and coverage, there is considerable variation in approaches to the monitoring of soil carbon even within a country. In addition to achieving harmonization, there are generic issues which must be addressed when SMNs are established and operated: the SMN should be effective for different soils, and it must enable the detection of change in soil carbon at relevant spatial and temporal scales with adequate precision and statistical power. We present examples which address these issues and summarize previous reviews on this topic. It is essential to establish an adequate sampling protocol which can be applied at each sampling location and time. The design must address the questions that the user of data has and provide information with accuracy and precision at the spatial and temporal scales that match the users’ needs. Furthermore, the design must match the methods of analysis so that statistical assumptions can be justified. At the global scale, the question of harmonizing sampling and analytical methods is difficult. Here, we propose the establishment of benchmark sites devoted to harmonization and inter-calibration. We present a case study from France which addresses scientific issues such as how many calibration sites are necessary and how they should be selected.

Managing declining yields from ageing tea plantations.

Strong growth in the demand for tea requires further increases in the productivity of plantations. Declining or stagnant yields are commonly observed in older plantations. Possible controlling factors for yield decline are reviewed including ageing of plants, chronic disease and sub-optimal soil conditions such as excess soil acidity and low soil organic matter. Management options for addressing these factors are evaluated, including replanting. A systematic approach to decision-making about replanting is presented. Practice for replanting is reviewed and it is concluded that evidence to support a general case for replanting is limited, unless based on the introduction of more productive clones and/or better plant spacing.

Broad-Scale Soil Monitoring Schemes

Soil resources provide many important ecosystem goods and services. However, they are at risk from a variety of threats operating over a broad range of scales. Political awareness that soil is threatened by increasing pressures has been rising for several years (European Commission 2006). Indeed, the demand for soil information is increasing continuously (Richer de Forges and Arrouays 2010). Although rates of soil degradation are often slow and only detectable over long timescales, they are often irreversible. Therefore, monitoring soil quality and condition is essential in order to detect adverse changes in their status at an early stage.

Field assessment of the balance between greenhouse gases and ammonia emissions from grassland under various N-management regimes

Materials and methods A field-plot experiment (2 x 1.5 m per plot, n=3) was carried out, with grass-derived and maizederived slurries of high and low dry matter (DM) content. Plots were spread using splash-plate application. In addition, one of the combinations of maize-derived slurry DM content was spread on three additional plots simulating trailing shoe, in order to compare both slurry application techniques. Control plots include no N fertilization and 60 kg N ha of calcium ammonium nitrate (CAN) fertilization. Two treatment applications were carried out in April and July 2009 under contrasting climatic conditions. Continuous flux measurements were taken after slurry application. Ammonia was measured using a photo-acoustic analyzer (INNOVA 1412 Trace Gas Analyser, INNOVA Instruments, Copenhagen, Denmark) coupled to a dynamic chamber. Carbon dioxide and nitrous oxide were measured using static chambers and an Infra-Red Gas Analyzer (CO2, PP Systems EGM-4, PP Systems, Hitchin, Herts., UK) or a gas chromatograph (N2O, Varian) for the analysis of the gases. Ancillary data (air and soil temperature, rainfall, soil moisture, soil ammonium and nitrate concentration) were also collected. Cumulative fluxes were calculated for the first week following fertiliser application (Figure 1). Background fluxes (control plots) were subtracted from fluxes calculated for treatments plots. These treatments were compared using ANOVA with slurry dry matter and slurry types as main factors.