Spectral mapping of soil organic carbon

This chapter first reviews recent pilot studies covering limited areas often with exposed bare soils. Then we focus on the challenges for large-scale application of spectral mapping when the soil and parent material are heterogeneous and surface conditions are unknown. In order to deal with these constraints we discuss i) calibration of spectral models based on large spectral libraries, ii) surface conditions that disturb the soil signal, and iii) time series of images in order to delimit cropland fields and increase the extent of bare soil that can be mapped. Finally, a case study deals with a SOC prediction map derived from the spectra of a Sentinel-2 image and calibrated using the LUCAS spectral library.

Advances in techniques to assess soil erodibility

Soil erodibility is the susceptibility of soil to the erosive forces of rainsplash, runoff and wind. It is a significant factor in determining present and future soil erosion rates. Focusing on soil erosion by water, this chapter shows that erodibility is determined by static and dynamic soil properties that control a range of sub-processes affecting soil erosion, but there is no standardised test procedure, making comparison of erodibility assessment techniques and their results challenging. Most researchers agree that aggregate stability is the best indicator of soil erodibility. Selection of techniques to measure aggregate stability need to consider the type of disruptive forces and breakdown processes to which field aggregates are subjected. New indices must incorporate spatial and temporal variabilities in erodibility; the different erosion processes operating; the impact of climate change; and the role of soil biology. New analytical techniques such as computer aided tomography show promise in considering soil erodibility as a dynamic continuum operating over 3 dimensions.

Advances in measuring mechanical properties of soil in relation to soil health

Although mechanical properties of soil are fast and easy to measure, they have not been used as indicators of soil health apart from cone penetration resistance. The confined compression test is traditionally used for the prediction of soil compaction risks. Other mechanical tests such as soil rheometry, miniature indentation test, and tensile strength are used for assessing the impact of certain amendments on the stability of the soil. Rheological techniques are appropriate to investigate microstructural stability of soil on a particle-particle scale. Miniature indentation test is very useful to perform when mechanical properties of soil are required to measure at the mm scale. Measurement of the tensile strength of soil has an advantage as it eliminates the effect of water content. There is clearly a need for more practical and rigorous testing on comparing different mechanical properties of the soil to test how they perform relative to each other.

Advances in visual soil evaluation techniques

Soil structure is a complex and dynamic soil property that constitutes a key aspect of soil health. Soil structure assessment can be evaluated in the field by visual soil evaluation techniques. Development and improvement of these techniques/methods have been the focus of numerous soil scientists worldwide since the mid-20th century. Divided into topsoil and soil profile methods, they differ in principle and level of detail of the assessment. The development and protocols of selected methods are presented in this chapter in chronological order of development, to show differences in methodological approaches. The description given for each of the methods includes guidance for the appropriate selection of the method to be used by stakeholders. Two case studies are given as examples of i) how visual techniques can contribute to achieving the challenges for developing sustainable agricultural management focused on nurturing soil fertility, and ii) the use of visual techniques as tools to assess and monitor soil health in developing countries.

Developing soil health indicators for improved soil management on farm

A range of chemical, physical and biological processes are important for sustained productivity and environmental quality in agricultural systems. Farmers and scientists share a concern with soil health, and this leads to questions for both measurement and management. An essential step is to define the context and the key functions required of a soil at the scale of interest (e.g. farm, drinking water catchment, region). Only then can appropriate indicator measurements be selected. Current soil health frameworks across the world commonly use organic matter (carbon), pH, extractable phosphorus, and various indicators of soil structure/water storage. A framework of interpretation shows whether the measured values are acceptable or whether one or more soil functions are constrained. A number of the soil health frameworks in practical use present the soil health indicators in a scorecard using traffic light coding to direct users towards guidance for improved soil management on-farm.

Imaging soil structure to measure soil functions and soil health with X-ray computed micro-tomography

The use of non-invasive imaging techniques expands opportunities to characterize soil health and functioning, complementing the information from the traditional soil structure analyses. Soil pore architecture drives water and gas fluxes, chemical transport, activity and movement of soil biota; and imaging techniques are particularly suitable for quantifying it. Here we discuss the potential for X-ray computed micro-tomography (X-ray µCT) as a tool to characterize key parameters of soil pore architecture, such as measures of macroporosity, pore connectivity, pore shape, and solid-to-pore distance. We also provide a brief overview of the principles behind X-ray µCT, examples of the latest literature that implemented these pore measures for soil characterization, and recommendations for the methods that can be used to determine these characteristics using publicly available software ImagJ. We also assembled a list of resources where in-depth information and comprehensive reviews of the current literature can be found.

Developing decision support systems (DSS) for farm soil and crop management

This chapter provides a review of decision support systems (DSS) in agriculture and addresses several key questions about them. Why are they important, and why are they necessary for the future? What kind of systems currently exist? Different aspects of agricultural DSS design, implementation and operation are covered. These aspects include the fundamentally spatial consideration of DSSs, the need for and use of sensor technology within such systems, modelling and software components, system-operator interfaces, the potential (and current) use of DSSs for directly controlling agricultural management, and a discussion of what is needed to make DSSs more successful and widely-used in agriculture

Assessing soil health by measuring fauna

This chapter provides examples of the impact of soil fauna on soil health within different ecosystems and how the soil habitat changes in relation to this biodiversity. It focuses specifically on mesofauna in agriculture, grasslands, woodlands and as bioindicators, before concluding with an overview of how the development of mesofauna as bioindicators is important in establishing a healthy soil.

Characterisation of fungal communities and functions in agricultural soils

One of the main drivers for the recent interest in utilising fungi has been the development of molecular technologies which allow us to investigate fungal communities in detail. We have made significant steps forward in understanding numbers and functions of fungal communities in soil. If we are to make progress in harnessing fungal communities for improving the sustainability of our production systems, we need to improve our ability to accurately monitor species composition, abundance and interactions, and to increase our understanding of functional traits. This chapter presents recent advances in the study of these ubiquitous and vital components of all terrestrial ecosystems.

Quantifying earthworm community structures as indicators of soil health

Earthworms are a symbol that farmers use to indicate soil health, but is this an intuitive observation that will lead to sustainable soils? This chapter describes the co-development of an assessment method to the ecological group level (epigeic, endogeic and anecic earthworms) in the UK. The process resulted in a Twitter based #WorldWormWeek initiative, a connective network of organic and conventional farmers and the Rothamsted Research experimental farm between 23 – 31st March 2019. There was an unexplained absence of epigeic (28 % fields) and anecic (18 % fields) earthworms in fields surveyed by UK farmers.