Everand Logo

Welcome to Everand!

  • Discover millions of ebooks, audiobooks, and so much more with a free trial

    From $11.99/month after trial. Cancel anytime.

    The Soil
    The Soil
    The Soil
    Ebook429 pages6 hours

    The Soil

    By B. N. K. Davis, N. Walker, D. F. Ball and Alastair Fitter

    ()

    Read preview

    About this ebook

    The soil is one of the great unsung disappearing resources, with over 100m tonnes being destroyed every year. This edition is exclusive to newnaturalists.com

    The soil is the work place of farmers and gardeners, but it is also a fascinating environment inhabited by insects that can leap into the air to a record height, multilegged scavengers that are vital to the decomposition of plant matter and the long, thin, entwining strands of thousands of species of fungi.

    Although soil plays a vital role in the functioning of the world, it has often been overlooked, mainly because it contains a huge range of different fields, all of which have become specialities in their own right. This book brings together specialists in these fields to give a broad overview of the staggering advances that have been made since Sir John Russel's The World Of Soil was published in this series in 1947.

    The first two chapters introduce the physical structure of the soil. The next four chapters deal with the specific animals and plants and how they exploit this environment. The final four chapters describe how these animals interact and how man has used and abused the soil in his striving to gain more and more from this resource.

    LanguageEnglish
    PublisherHarperCollins UK
    Release dateApr 11, 2013
    ISBN9780007406647
    The Soil

    Related to The Soil

    Titles in the series (98)

    View More
    View More

    Related ebooks

    Agriculture For You

    View More
    View More

    Related podcast episodes

    Related articles

    • UNLIMITED

      Make Peace With Weeds

      Dec 2, 2021

      Make Peace With Weeds
      4 min read

    • UNLIMITED

      Soil assessment 101

      Aug 27, 2018

      Soil assessment 101
      3 min read

    • UNLIMITED

      May-august

      May 5, 2022

      May-august
      2 min read

    • UNLIMITED

      How To Garden Like A Nonno

      Dec 5, 2021

      There is nothing better than having a nonno, and I should know: I had two of them. Nonnos are no-nonsense, hard-working and cheeky. They know how to fix things, how to make things, how to grow things, how to care for things. They basically know all t

      6 min read

    • UNLIMITED

      Regenerative Soil Solutions

      Apr 26, 2020

      Regenerative Soil Solutions
      1 min read

    • UNLIMITED

      The Constant Gardener

      Apr 20, 2022

      The Constant Gardener
      3 min read

    • UNLIMITED

      Rewilding

      Dec 29, 2020

      Rewilding
      8 min read

    • UNLIMITED

      COPING with CLIMATE CHANGE

      Aug 25, 2022

      COPING with CLIMATE CHANGE
      5 min read

    • UNLIMITED

      Climate Farming Practices

      May 14, 2021

      Climate Farming Practices
      5 min read

    • UNLIMITED

      Why Soils Are Dying, And How We Can Save Them

      May 28, 2021

      The majority of soils in South Africa are degraded, with areas receiving less than 600mm of rain a year at particularly high risk. The overuse of agricultural chemicals such as fertilisers, pesticides and herbicides contributes to soil degradation. A

      4 min read

    • UNLIMITED

      Black Magic

      Nov 1, 2022

      Black Magic
      3 min read

    • UNLIMITED

      Our Favourites To Suit Your Needs

      Dec 23, 2020

      Our Favourites To Suit Your Needs
      1 min read

    • UNLIMITED

      A Growing Choice

      Jun 5, 2021

      Direct drills are firmly back in vogue as the emphasis shifts towards boosting soil health as well as cutting establishment costs. Some machines will only perform to their best in no-till conditions – working into the firm surface underneath stubble,

      13 min read

    • UNLIMITED

      The Full Monty

      Oct 20, 2022

      It is raining here, raining hard. The water butts are overflowing and the puddles straddling half the garden paths. The ground is skiddy with mud. Three months ago, when we were desperate for water, this would have been an idyllic picture but now it

      3 min read

    • UNLIMITED

      Panayoti Kelaidis

      Aug 25, 2022

      PANAYOTI KELAIDIS is a lifelong Colorado gardener who has worked at Denver Botanic Gardens for more than 40 years. Known for his expertise in rock gardening and alpine plants, he is a longtime member of the North American Rock Garden Society. This in

      11 min read

    • UNLIMITED

      Farming For The Future

      Jun 14, 2023

      Farming For The Future
      8 min read

    • UNLIMITED

      Grow Green Manure

      Apr 10, 2020

      Grow Green Manure
      8 min read

    • UNLIMITED

      Best Smartphones For Macro

      Apr 8, 2023

      Best Smartphones For Macro
      7 min read

    • UNLIMITED

      The Hidden Half Of The Garden

      Oct 21, 2021

      The Hidden Half Of The Garden
      3 min read

    • UNLIMITED

      Cotton: The Ideal Crop For Reducing Carbon Emissions And Poverty

      Feb 4, 2022

      What impact is climate change having on South Africa’s cotton farmers? Hennie Bruwer (HB): Ironically, we’re currently seeing, and will continue to see, an increase in the number of cotton farmers in South Africa as a result of climate change. This i

      6 min read

    • UNLIMITED

      Product Reviews Soil Testing

      Dec 31, 2019

      Product Reviews Soil Testing
      5 min read

    Related categories

    Reviews for The Soil

    0 ratings

    0 ratings0 reviews

    What did you think?

    Tap to rate

    Review must be at least 10 words

      Book preview

      The Soil - B. N. K. Davis

      EDITORS’ PREFACE

      We are all familiar with the plants and animals with which we share the world above the soil surface. We are much less familiar with the inhabitants and processes in the ubiquitous but inaccessible world of the soil. The organisms in this hidden world are often microscopic, small enough to live in the maze of narrow pores, and are concealed by the opaque matrix in which they live. Taxonomic difficulties add a further barrier to exploration. The Soil is an account of the soil as a living system, in which moles, minerals, molecules and microbes interact with vegetation, under the influence of climate and man.

      The soil, the earth’s skin, has been scarred, peeled off or incurably bruised over much of Britain. It is all too easy for heavy machinery to destroy in minutes a soil profile that has taken centuries to develop. Perhaps this book will help us to appreciate those precious sites where its structure remains intact. It also shows how, if compaction can be avoided, heavy machinery can have a positive role in the large-scale restoration of soil capable of supporting vegetation on mine or industrial waste.

      Processes in the soil matter to farmers and gardeners, moles and oak trees. To understand them is a necessity for agronomists, an aspiration of ecologists, and a pleasure for others. Many policy decisions on agriculture and conservation depend on the ability to understand and manipulate soil processes. This is an area where informed public opinion has an important part to play in moulding public policy. Those who read this book will be in a better position to understand some of the more controversial aspects of man’s impact on the soil.

      Research has advanced on many fronts since Sir John Russell wrote The World of the Soil in this series in 1957. Until now many of those advances have been accessible only to specialists. The authors of this book are in a unique position to introduce us to this new material and to provide an exceptional guide to the ecosystem we tread on every day. It is a credit to the subject that it has advanced far enough in 34 years to merit this new approach, and a credit to the series that it has lived long enough to include this second book.

      AUTHORS’ PREFACE

      Soil science came of age in Britain with the publication in 1912 of the first edition of E. J. Russell’s Soil Conditions and Plant Growth. Forty-five years later, after retiring as director of Rothamsted Experimental Station, Sir John Russell published The World of the Soil in the New Naturalist series to bring the burgeoning subject to a wider audience. Fifty years ago he wrote in his preface, this book would have been much easier to write than it has been today. Enough was then known about the wonders of the soil to show that deeper mysteries lay beyond. The facts gleaned were simple, the generalisations were broad and easily comprehended…Now it is all very different. Vast numbers of learned memoirs have been written about [the subject]. If this statement were true then, how much more so today. The subject has continued to grow in breadth as well as depth with several international journals on soil biology starting since 1957 and a string of published symposia. Soil Conditions and Plant Growth, revised by E.W.Russell and now edited by A. Wild, is in its 11th edition (1988), and is still a standard reference work.

      With growth has come increasing specialization – in soil physics, pedology, soil biology, microbiology and applied aspects, such as agriculture and land restoration. The student and professional scientist is now well supplied with monographs on all these topics but there is increasing need to see the world of the soil as a whole; to appreciate the complex and delicate structure of this thin skin on the earth’s surface, the activities of microorganisms in the cycles of decay and renewal, the interwoven lives of animals and plants below and above the soil surface, and man’s ability to use or abuse this vital resource. It is difficult to do justice to this broad spectrum, and we have had to be selective in our coverage. We have tried to illuminate a wide range of themes which interest us and which we thought would interest the non-specialist reader. Inevitably, this selection leaves many gaps but if we succeed in whetting an appetite for more information we will be well satisfied.

      We have tried to be up to date in concepts and discoveries but, even while preparing the book, the agricultural scene has changed radically. To increase productivity has ceased to be the driving force behind so much of the research on soils that has marked the past 50 years. Crops, however, are just one expression of a soil’s potential: to create and manage diverse ecosystems is no less a challenge; amongst other things, it entails research on reducing soil fertility.

      Each section of the book has been read and criticized among ourselves but, in addition, comments have been obtained from outside experts on particular topics: micro-arthropods – M. Luxton, woodlice – P. T. Harding, millipedes and centipedes – R. E. Jones, spiders – E. Duffey, ants – T. J. King, other insects – R. C. Welch, earthworms – B. M. Gerard, nematodes – K. Evans, snails and slugs – B. Eversham, agriculture – B. G. Davies, land restoration – S. G. McRae. We are most grateful to all these, and hope to have avoided errors even if we have not presented a topic in the way they would have done.

      The sources of illustrations are given with the captions and we would like to thank the following for providing photographs: J.M. Anderson, T. Bauer, Broom’s Barn Experimental Station, A.F. Brown, G.P. Buckley, J. Day, B. Dickerson, K. Evans, R. Evans, R.D. Finlay, Frank Lane Picture Agency Ltd, J.A. Grant, Christine Hepper, Dick Jones, T.P. McGonigle, S.G. McRae, R.H. Marrs, J. Miles, National Museum of Wales, J.A. Thomas and T.C.E. Wells. S.V. Green and R.C. Welch kindly made original drawings of snails, woodlice and beetles. Figures 45 and 46 were drawn by Paul Joyce. C.A. Howes generously provided original data on mole distributions.

      We gratefully acknowledge the kind permission of the following journals and institutes to reproduce copyright illustrations: Pedobiologia (Figs 1, 31), Journal of Soil Science (Fig. 6), Blackwell Scientific Publications Ltd (Fig. 7), Plenum Publishing Corporation (Fig. 9), Soil Survey and Land Research Centre (incorporating the Soil Survey of England and Wales) (Fig. 11), Transactions of the British Mycological Society (Fig. 16), Naturwissenschaften (Fig. 23), Behavioural Ecology and Sociology (Fig. 30), Netherlands Journal of Zoology (Fig. 39), John Wiley and Sons (Fig. 45), Geoderma (Fig. 49), North Holland Publishing Company (Fig. 50), Institute of Terrestrial Ecology (Fig. 51), Journal of Ecology (Fig. 52), Grassland Research Institute (Fig. 57), Central Electricity Generating Board (Fig. 67), Ready Mixed Concrete (United Kingdom) Ltd (Fig. 69).

      Finally, I should like to thank K. Mellanby for his encouragement in writing this book (B.N.K.D.).

      UNITS OF MEASUREMENT

      Science now uses metric units almost exclusively but it is often easier for many people to visualize an acre rather than a hectare, or to appreciate altitude in feet rather than metres. We have therefore given both in many instances, especially when dealing with historical data. In some cases, English units have become disused except by a few but it would be inappropriate to quote wheat yields in the Middle Ages in anything except hundredweights.

      CHAPTER 1

      ARCHITECTURE OF THE SOIL WORLD

      We live on the rooftops of a hidden world

      Peter Farb 1959

      It is difficult to visualize the world of the soil as it appears to a worm or a woodlouse, a mole or a microbe. We may dig a pit in a woodland, grassland or arable soil and describe the different sections exposed to view; or feel the distinctive textures of a peaty moorland soil and a sandy heathland soil. We can measure the sand, silt and clay contents, or analyse a soil for its available plant nutrients – nitrogen, phosphorus and potassium. From our perspective, such apparent abstractions are a necessary step towards understanding a soil, but this is a long way from knowing how an individual plant rootlet will behave as it grows; or how a parasitic eelworm makes its way through the soil to attack the growing root.

      Partly, it is the three dimensionality of the soil environment, and partly its physical complexity and scale, which are beyond our direct experience. Quite apart from gravel and larger pieces of rock, there is more than a thousand-fold range in size between the two extremes of the spectrum of what soil scientists call ‘fine earth’: between coarse sand particles, up to 2mm in size, and those of clay minerals which are less than 0.002mm. (The sizes of the soil inhabitants cover an even larger spread, between a 200mm earthworm and a 0.002mm microbe, for example). These mineral particles, together with an intimate mixture of living and dead plant material, form a spongy matrix permeated by pores filled with air and water. The pores themselves may comprise 30–50% of the total volume in a good topsoil – plenty of space for airbreathing creatures of all sizes, and for those dependent upon an essentially aquatic way of life.

      THE SOIL SURFACE AND SUPERFICIAL PLANT REMAINS

      The soil environment can be looked at from many viewpoints: as a sequence of approximately horizontal zones of distinctive character and properties from the soil surface downwards; as a medium that provides varying levels of physical and nutritional support to plants with differing requirements; as a fabric affording many and varied niches suitable for particular soil organisms; as a reactive skin covering much of the earth’s surface that provides a sink and a buffer for rainfall and for airborne chemicals; and, overall, as a vital resource that sustains life on earth.

      These approaches are returned to in future chapters, but in considering the architecture of the soil world it is convenient to start on its roof – at the soil surface – for this is the part that is easiest to observe, and hence is most familiar. A variety of creatures are found simply by turning over stones and logs, and while some of these may not strictly be called soil animals, yet they are often very dependent upon the nature of the underlying material at some stage of their life. Many are nocturnal, and merely shelter here during the day to avoid desiccation or predation by birds. These include predatory ground beetles and spiders, and vegetarians such as woodlice and slugs. Stones that are smaller than about 10cm are of little value for providing special microclimates unless they are scattered quite thickly over the ground as in shingle, in a quarry or on a mountainside; Figure 1 shows the temperature and moisture regimes at different depths within a heap of stones inhabited by various arthropods. Large boulders, on the other hand, are usually well bedded into the ground, and if turned over will reveal true subterranean animals such as worms, or the underground galleries of ants.

      FIG. 1

      Microclimate: temperature and humidity gradients in a stony habitat in strong sunlight, and the effects on positions occupied by various small arthropods; A = bristle-tail, B = springtail, C = woodlouse. The temperature decreases from the top downwards while the relative humidity increases. When the stones are shaded, the bristle-tails move to the underside of the upper stone layer. (Adapted from G. Eisenbeis 1983.)

      Cracks and fissures in the ground serve much the same function as stones in affording protection from dry conditions for species that cannot burrow for themselves. Cracks are a common feature of clay soils during the summer, and may penetrate a foot or more in grassland or arable fields.

      Plant cover affects conditions on the soil surface in more ways than inorganic objects do because of its more varied and complex structures and thermal properties. Adhering vegetation, such as moss and algae, liverworts and lichens, harbours a rich micro-fauna of protozoa, nematodes, tardigrades, small mites and springtails. Larger moss cushions, grass tufts and rosette plants shelter a wealth of small beetles and other insects, both adults and larvae. Dead plant material not only gives shelter but offers food for a wide range of animals and fungi which fulfil a vital role in returning the store of organic material and nutrients back to the soil.

      FIG. 2

      Leaf litter, twigs and branches in a mixed oak/ash woodland in spring. Note that oak leaves remain but all the ash leaves have disappeared. (Photograph B.N.K.D.)

      A forest floor has the greatest variety of plant litter – annual sheddings from the tree canopy with occasional branches and logs, all in varying stages of disintegration and decomposition (Fig. 2). The total litter fall in a deciduous woodland in this country is around 2.5 kg a square metre (10 tons an acre). Seventy-five percent of this is leaf litter, the rest being made up of twigs, bark and seeds etc. The detailed character of this litter is important in providing habitats and food sources for different organisms. In a particular study of woodland litter, H. Heatwole decided there were three main categories. His first class consisted of leaves that roll or bend when they fall to the ground, thus producing large, round or angular spaces between them. Class 2 consisted of leaves that remain flat and so have small, narrow interspaces, and class 3 consisted of solid, woody objects. Each class was subdivided, for example to distinguish thick leathery leaves from thin papery ones and conifer needles, or accumulations of twigs from large logs. Some of these types are characteristic of natural, mixed deciduous woodland, beech hangers or pine woods in this country. A few are perhaps associated more with parks and gardens, where exotic trees and shrubs like rhododendron have been planted.

      There is an enormous difference in the persistence and smothering effect of different kinds of leaves, ranging from ash and apple, which disappear in weeks, to beech, holly, rhododendron and conifer needles which may last for years. This difference is partly due to their size and thickness, and partly to their palatability to soil animals and susceptibility to fungal attack. The depth of litter can vary greatly depending on the density of trees, the time of year, the properties of the underlying soil, and the micro-relief of the ground. Mounds and convex surfaces may remain largely bare of litter while leaves and twigs accumulate in hollows which therefore act as foci for litter-seeking invertebrates. The student of these groups soon gets an eye for such ‘hot spots’; with experience, he can judge very accurately what species to expect.

      Where litter persists for several months or years, one can usually see three distinct organic layers above the mineral soil itself. The uppermost layer of curled and uncompressed leaves has a great deal of interstitial space. This is the zone favoured by large, active springtails which grow to 5-6mm in size, and which form the prey of many beetles and spiders. Both hunting and web-building spiders exploit this open-textured but sheltered environment. The webs may be fairly simple arrangements of criss-cross threads spun across the ends of the rolled leaves, but these suffice to entangle or delay weak prey. Experiments have shown that leaf characteristics influence the numbers of spiders in woodland litter: curled leaf litter tends to support higher densities and a greater assortment of spiders.

      Beneath this layer of relatively unaltered plant remains comes a zone of partly decomposed but still clearly recognizable plant fragments, and below this a zone of amorphous, finely divided organic matter. These three layers have been given a variety of names, but it is convenient to refer to them as the L (litter), F (fermentation) and H (humus) layers. The fermentation layer is where most of the litter decomposition takes place. This is the home of several kinds of millipedes, woodlice and fly larvae, some small earthworms, many mites and shorter-springed springtails. These are described in more detail in chapters 4 and 5.

      Grassland litter differs from woodland litter in that the dead grass does not fall to the ground in the same way but remains arched over the surface for some months, and only gradually sinks down and disintegrates. Highly siliceous grasses, such as tor grass Brachypodium pinnatum, form a distinctive and persistent litter mat which few invertebrates appear able to digest. Even palatable meadow grasses, however, can give rise to a peaty mat on the surface of the ground if earthworms are absent; this was seen in New Zealand, for example, when settlers first converted the native vegetation into pasture land with introduced grasses from Europe.

      We can move one step nearer to appreciating the structural diversity of litter if we take vertical sections and view them through a microscope. This has been done in both woodland and grassland by cutting small cores or blocks, impregnating them with gelatine, and slicing them up (Fig. 3 and Plate 1). In a study of woodland soils, J.M.Anderson recognized up to seven main classes of structures in a section through the litter, fermentation and humus layers of a sweet chestnut stand. These included not only various leafy and woody items and the cavities between them, but also plant roots with or without their fungal associations, faecal pellets of various invertebrates, and animal remains. He subdivided several of these classes to produce a total of 24 microhabitat categories which were thought to be significant for soil mites (Table 1). By examining many sections in a standard way, it then became possible to relate the number of kinds of mites identified in a section with an index of diversity computed from the number of microhabitats present. The richest zone tended to be the fermentation layer which attracted about 21 species of oribatid mites, whereas the humus layer below only supported some 10 species.

      FIG. 3

      Section through soil humus impregnated with agar jelly showing the ‘primitive’ insect Campodea staphylinus (Diplura). This species is colourless and blind but has highly developed tactile senses. It does not burrow but moves through the soil cavities using its antennae to locate a pathway when moving forward, and its equally well-developed posterior feelers’ (cerci) when moving backward under confined conditions. (Photograph J.M. Anderson.)

      This approach is clearly an advance over macroscopic analyses of litter habitats but many important criteria are still left out. We could perhaps identify the kinds of leaves present, up to a certain stage of disintegration, but their chemistry and relative palatability – the presence of sugars, cellulose, waxes, tannins and lignin – would still elude us. It is as if we tried to distinguish between caster sugar and salt by eye alone.

      HUMUS

      We should think of this surface litter and decomposing organic matter, not just as an inert physical habitat for mites and other organisms, but more like the house which Hansel and Gretel found. This, you will remember, was made of ginger-bread, chocolate and barley sugar. The various components of fresh litter – fruits, leaves, stems and bark – differ greatly in their chemical make-up, and these differences are reflected in their rates of breakdown. The soft parts of leaves, containing sugars, proteins and starch within the cells, are quickly attacked and digested by earthworms, millipedes, springtails and other soil animals. One can often find a perfectly skeletonized leaf in which every vein has been left intact after removal of the lamina by micro-arthropods. The veins and other more woody structures are largely composed of cellulose. Snails are among the few animals that can secrete cellulase and so digest cellulose directly. Most cannot digest cellulose until it has been chemically shredded by microbial attack into simpler molecules. A few animals, ranging from termites to cattle, have evolved the trick of employing microflora in their gut for this purpose. The toughest woody fibres are composed largely of lignin which is highly resistant even to microbial attack, and these therefore remain intact for a long time. Recalcitrant, too, are waxes and resins, as can be seen in the persistence of holly leaves and pine needles.

      TABLE 1

      Microhabitat categories used in soil structure analysis (Adapted from J.M.Anderson, 1978)

      The role of soil microorganisms in plant decomposition is described in chapter 6. At a simple level, the relative rates of breakdown of plant structures reflect the ratios of carbon to nitrogen in their chemical make up. Grass leaves have a carbon : nitrogen ratio of about 5:1, barley straw about 60:1 and pine needles about 100:1. Since soil microbes have a low carbon : nitrogen ratio of 7 to 6 or even 4:1, it follows that they cannot fully exploit plant tissues that have higher proportions of carbon without drawing on other sources of nitrogen. This has practical implications in the case of straw that is incorporated into the soil after harvest, a point discussed further in chapter 8. Similar arguments apply to the carbon :  phosphorus and carbon :  sulphur ratios, though the supplies of phosphorus and sulphur are not so limiting.

      Humus is the final product of organic matter decomposition. It is a dark amorphous material consisting of complex organic molecules which can be broken down into humic and fulvic acids. There are, therefore, three interrelated organic fractions in soil. First, there are the plant (and animal) residues which form the main source of available nitrogen, phosphorus and sulphur for new plant (and animal) growth. Secondly, there is the microbial biomass which acts as a temporary store of such nutrients, and thirdly, a persistent humus fraction which is highly resistant to further breakdown but which can release nutrients very slowly. Measurements have been made of the age of humus by radio-carbon dating techniques; that is, by measuring the proportion of the radio-active isotope ¹⁴C left in the humus, and calculating the time since it must have been taken up by the living plant as carbon dioxide from the atmosphere. Such measurements give periods of several centuries, components such as humic acid persisting for over a thousand years in some instances. To use a monetary analogy, these three organic fractions – plant residues, microbial biomass and humus – might be represented respectively by goods which are traded for cash, a deposit account, and a long-term insurance policy.

      The conversion of such stores of nitrogen, phosphorus and sulphur to available, ‘cash-in-hand’, nutrients is called mineralization; the mineral forms are the ammonium cation (NH4+), and the nitrate (NO3-), phosphate (PO4³-) and sulphate (SO4²-) anions. This important topic of nutrient cycling is developed in chapter 6. The carbon in humus is oxidized to carbon dioxide and lost back to the atmosphere. Usually a steady state is reached between gains and losses of carbon, but under waterlogged conditions plant remains may accumulate as peat. It is worth remembering that the world’s vast deposits of coal, oil and gas represent the preserved surpluses of carbon built up by plant tissues in former ages. On the other hand, if peat is dried out and cultivated, as in the Cambridgeshire fens, the stores of carbon are quickly oxidized away again. We are drawing on our capital here just as we are with fossil fuels.

      The existence of distinct and persistent litter and fermentation layers characterizes what are called mor humus soils. Mor formation occurs typically on well drained, very acid soils under conifer woodland and heathland. The main deep-burrowing earthworm species Lumbricus terrestris cannot survive in such acid conditions, and in its absence the organic matter is not readily incorporated into the underlying mineral soil. In contrast, in well drained, less acidic or calcareous soils, the feeding activities of these earthworms create an intimate mixture of organic matter and mineral soil known as mull humus. This is the typical form of humus found in deciduous woodlands, lowland grasslands and in derived arable soils.

      These terms mull and mor were coined in 1878 by the Danish forester P.E.Müller who first recognized their significance as indicators of soil condition and forestry potential. W. L. Kubiena’s classic work in 1949 on The Soils of Europe recognized 16 main types of humus of which mull and mor represent two extremes. An intermediate condition, which Müller called ‘insect mull’ but which is now generally known as moder, is characterized by a well developed H layer with thin L and

      Enjoying the preview?
      Page 1 of 1