Research Approaches to Sustainable Biomass Systems || Soil Fertility and Soil Microorganisms

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    Potential Productivity

    Classification 117

    Organic Matter 118

    5.2.1. Carbon Dynamics on



    Continuous Cropping 129

    5.4. Microbially Mediated Soil

    EnvironmentalBiomass in Japanese

    Agricultural Soils 133the Earth Scale 118

    5.2.2. Factors in the Increase

    and Decrease of SOC 118

    5.2.3. Principle of

    Rothamsted Carbon

    Model 119

    Impacts 131

    5.4.2. Nitrogen Cycles

    Through Microbial

    Biomass in Soils 132

    5.4.3. Nitrogen Cycle

    Through Microbial5.2. Soil Management and SoilFertility 131

    5.4.1. Productivity andRes

    CopClass 117

    5.1.5. Improvement of

    5.3.5. Soil Sickness due toProductive CapabilityClassification

    5.1.4. Expression of109Classification

    5.1.3. Factors Affecting the


    5.1.2. Soil Potential

    Productivity108Chapter Outline5.1. Soil Fertility

    5.1.1. Definition of Soil108aruo Tanaka, Akane Katsuta, Kokiicroorganisms

    oil Fertility andearch Approaches to Sustainable Biomass Systems. http://

    yright 2014 Elsevier Inc. All rights reserved.Biomass 1

    5.3.2. Habitats 1

    5.3.3. Taxonomy 1

    5.3.4. Microbial Functions 122

    235.3. Soil Microorganisms 1

    5.3.1. Abundance andModified RothC 120

    22and Paddy Soils 1

    5.2.5. Application of20RothC for Andosols5.2.4. Modification ofToyota and Kozue SawadaSoilChapter



    In lassification (National Conference ofSo 1979) is used to evaluate soil fertility;th ificat yHa

    prod ereup

    108 Research Approaches to Sustainable Biomass SystemsJapan, Soil Potential Productivil Conservation and Survey Proe soil potential productivity classmazaki and Micosa (1991).Classification of soil potentiality Cject,sults of soil surveys. It is a practicalon their limitations or hazards for cropuctivity is a form of interpretinion is presented based on the report b

    g thHaruo Tanaka

    5.1.1. Definition of Soil Fertility

    Soil fertility is defined as the quality of a soil that enables it to provide nu-trients in adequate amounts and in proper balance for the growth of specifiedplants or crops (Soil Science Glossary Terms Committee, 2008). It is not onlybased on the natural conditions or peculiar property that the soil has but also thehuman activities such as growing various crops by applying different cultiva-tion methods. Soil fertility is the most important factor to affect the productionof biomass in a field. Usually, sustainable high yields of biomass can beexpected from fertilized soil. For land that is not fertile, application of a largequantity of natural or chemical fertilizer with high labor demand is necessary tomaintain high biomass production.

    An agro-ecosystem is viewed as a subset of a natural ecosystem. Tradi-tionally, the agro-ecosystem is characterized as having a simpler speciescomposition and simpler energy and nutrient flows than a natural ecosystem.The soil has the function as the decomposer in the agro-ecosystem to decom-pose the organic matter such as composts or plant residues applied to the soilinto inorganic matters biologically by animals and microorganisms inhabitingthe soil. However, excessive application of organic matter causes environ-mental pollution such as the groundwater contamination with ammonium. Inaddition, as a producer, the soil supports the growth of plants that absorbnutrients and water from the soil to grow under solar irradiation. Hence, soilproductivity is a synonym of soil fertility.

    5.1.2. Soil Potential Productivity Classification5.4.4. Management of

    Microbial Biomass

    Nitrogen During

    a Crop Growth Period 136

    5.4.5. Future Prospects 139

    References 140method to grade or group soils basedproduction and/or risk of soil damage

  • to jeopardize crop production; all these concerns are closely related to soilsphysical and chemical properties. The objective of land capability classificationis to eliminate limitations for increasing crop productivity. There are four soilcapacity classifications, i.e. I, II, III, and IV, defined as follows:

    l Class I Land has almost no limitations or hazards for crop productionand/or risks of soil damage.

    l Class II Land has some limitations or hazards and/or risks of soil damage,and some improvement practices are required for normal crop production.

    l Class III Land has many limitations or hazards and/or risks of soildamage, and fairly intensive improvement practices are required.

    l Class IV Land has great natural limitations, so it is difficult to use as

    more than 15 cm is classified as class I, because paddy or grassland crops are

    109Chapter j 5 Soil Fertility and Soil Microorganismscapable of growing in thinner topsoil than upland or orchard crops.

    TABLE 5.1 Thickness of Topsoil (t)


    t (cm)


    Paddy Upland Orchard Grassland

    >25 I I I I

    25e15 I II II I

  • TABLE 5.2 Effective Depth of Soil (d)


    d (cm)


    Paddy Upland Orchard Grassland

    >100 I I I I

    100e50 I II II I

    50e25 II III III IeII

    25e15 III III IV IIeIII

  • 111Chapter j 5 Soil Fertility and Soil Microorganismsand their combinations. For example, soil texture is based on the classificationused in the ISSS system; textures of S, LS, SL, FSL, L, and SiL are classified asCoarse to medium; SCL, CL, and SiCL are classified as Fine; and SC, LiC,SiC, and HC are classified as Very fine.

    TABLE 5.4 Ease of Plowing (p)

    Dependent factors

    Class Criteriaa b c d






    Easy to slightly difficult






    Moderately difficult






    Very difficult

    aTexture of top soil (Coarse to medium: 1; Fine: 2; Very fine: 3).bStickiness of topsoil (Non-sticky to slightly sticky: 1; Sticky: 2; Very sticky: 3).cConsistence of topsoil when dry (Loose to soft: (2); Slightly hard: 1; Hard: 2; Very hard to extremely

    hard: 3).dMoisture condition of topsoil (Dry to moderately dry: (2); Moist: 1; Wet: 2; Very wet: 3). Moisture

    condition refers to the major part of the year and/or 2e3 days after considerable rainfall.e. Permeability Under Submerged Conditions (l; only for paddyfields; Table 5.5)

    This soil permeability affects the movement of water in the soil, soil temperature,and leaching of nutrients or development of reduced condition of the soil. It isevaluated mainly by the combination of soil texture and the presence of acompact layer within 50 cm of the surface as dependent factors. The measure-ment of the water permeability coefficient and/or water requirement in depth hasbeen widely used, and hence the permeability data are handy for carrying out thesoil permeability classification. The dependent factors that are relevant to clas-sifying the soil are as shown in Table 5.5. This table shows similar classificationsof finest soil texture as in Table 5.4, but the ratings are different. To determine themaximum compactness within 50 cm of the surface, Yamanakas core pene-trometer is used. Value ranges of >24, 2411, and

  • 112 Research Approaches to Sustainable Biomass SystemsTABLE 5.5 Permeability under Submerged Conditions (l; only for

    paddy fields)of easily decomposable organic matter in topsoil, Contents of free ironoxides in topsoil, and Degree of gleyzation are used. Organic matter that iseasily decomposed is represented by NH4-N cg kg

    1 in air-dried soil (A) andNH4-N cg kg

    1 in soil after the soil sample has been incubated at 30C for4 weeks (B). The easily decomposable organic matter is classified as Low


    factors Class

    (Paddy) Criteriaa b

    1 1 I Poorly to imperfectly permeable1 2 I

    2 2 II Moderately to well permeable3 2 II

    3 3 III Well to excessively permeable

    aFinest soil texture within 50 cm of the surface (Very fine: 1; Fine: 2; Medium to coarse: 3).bMaximum compactness within 50 cm of the surface (Very compact to compact: 1; Medium

    to loose: 2; Very loose: 3).

    TABLE 5.6 State of OxidationeReduction Potentiality (r; only for paddy


    Dependent factors Class



    (Risk of root damage)a b c

    1 1 2 I None to weak1 3 2 I2 1 2 I

    1 1e2 3 II Moderate to strong1 3 3 II2 1e2 3 II3 1 2 II

    2 3 3 III Very strong3 2 2 III3 1 3 III3 3 2 III

    aContents of easily decomposable organic matter in topsoil (Low: 1; Medium: 2; High: 3).bContents of free iron oxides in topsoil (High: 1; Medium: 2; Low: 3).cDegree of gleyzation (Weak: 1; Moderate: 2; Strong: 3).

  • (A < 10, B < 10), Medium (A: 1020; B: 1015), and High (A: >20; B:>15). If based on the content of free iron oxides (cg kg1), the topsoil can beclassified as High (>1.5), Medium (1.50.8), and Low (200 is High, 200100 is Medium, and

    113Chapter j 5 Soil Fertility and Soil Microorganisms

  • 2 1 2 I

    114 Research Approaches to Sustainable Biomass Systemsh. Inherent Fertility of the Soil (f; Table 5.8)

    1 2 3 II Medium2 1 3 II1 3 1 II1 3 2 II

    1 3 3 IIIeII Infertileemedium3 1 1 III Infertile

    2 4 2 IIIeII Infertileemedium

    aNutrient holding capacity (High: 1; Medium: 2; Low: 3).bNutrient fixation power (Very low: 1; Low: 2; Medium: 3; High: 4).cBase status of the soil (Good: 1; Medium: 2; Poor: 3).TABLE 5.8 Inherent Fertility of the Soil for Upland, Orchard,

    and Grassland (f)

    Dependent factors

    Class Criteriaa b c

    1 2 1 I FertileThe soils inherent fertility is evaluated by using combinations of thefollowing three dependent factors: nutrient-holding capacity, nutrient fixa-tion power, and base status. Nutrient-holding capacity is evaluated based oncation exchanged capacity (CEC; cmolc kg

    1 soil) as High (>20), Me-dium (206), and Low ( 5.5), medium(pH between 5.5 and 5.0), and poor (pH < 5.0). Table 5.8 shows theclassification for upland, orchard, and grassland, while other tables are usedfor paddy fields.

    i. Content of Available Nutrients (n; Table 5.9)

    Available nutrients in topsoil are closely related to the inherent soilfertility, but evidently influenced by the combination of the followingdependent factors: contents of exchangeable Ca, exchangeable Mg,exchangeable K, content available P (determined by using the Truogmethod), available N and Si (for paddy), and micro-elements (evaluatedby using the risk of deficiency), as well as soil acidity as indicated by thepH (H2O) value.

  • 115Chapter j 5 Soil Fertility and Soil MicroorganismsTABLE 5.9(b) Rating of Dependent Factors of Available Nutrients

    Dependent factors


    1 2 3 4

    Content of exchanged Ca (cmolc kg1) >7.1 7.1e3.6 1.2 1.2e0.5 0.32 0.32e0.17 44 44e9 20 20e10 15 15e5 6 6e5 5e4.5

  • TABLE 5.10 Hazard (i)

    Class Criteria

    I None

    II Slight

    III Moderate

    IV Severe

    I None

    116 Research Approaches to Sustainable Biomass SystemsII Moderate

    III FrequentTABLE 5.11 Frequency of Accidents (a)

    Class Criteriadetermined based on the following two independent factors: risk of overheadflooding inundation (None to slight, Moderate, and Frequent), and risk of landcreep (None to slight, Moderate, and Frequent).

    l. Slope of the Field (s; for upland and orchard; Table 5.12)

    The natural slope is the main dependent factor; its classification is decided by acombination of natural slope, direction of slope, and artificial slope.

    TABLE 5.12 Slope of the Field (s; for upland and orchard)

    Slope (%) Rating Upland Orchard

    47 5 IV IV

  • lowest class of factors. This code formula arranges briefly the information

    117Chapter j 5 Soil Fertility and Soil Microorganismsregarding the kind and the degree of limitations with each class of land. Thecode II plrn means that the land is classified class II because the factorsp (ease of plowing), l (permeability under submerged conditions), r (state ofoxidationreduction potentiality), and n (content of available nutrient) aregrouped in class II. If the soil fertility of this land is to be improved, improvingall of these factors together is necessary.m. Erosion (e; for upland orchard; Table 5.13)

    The degree of erosion or occurrence of rill or gully (Very slight, Slight,Moderate, and Severe), the power to resist water erosion for topsoil determinedusing the dispersion ratio (Strong, Moderate, and Weak), and the resistingpower wind erosion for topsoil determined using the soil bulk density (Strongand Weak) are pertinent here.

    5.1.4. Expression of Productive Capability Class

    The evaluation of these standard and dependent factors is expressed as either asimplified code formula or a detailed code formula. When a simplified codeformula, e.g. II plrn, is used, the productive capability class is placed in theTABLE 5.13 Erosion (e; for upland orchard)

    Class Criteria

    I None or very slight

    II Slight

    III Serious

    IV Very severe5.1.5. Improvement of Potential Productivity Classification

    Soil Potential Productivity Classification, which is focused on crop produc-tion, represents the inhibitory factors of the crop production clearly with asimple code formula. Now that environmental conservation has become animportant issue, these issues may include prevention of nitrogen eluviation tothe groundwater, and prevention of the emission of greenhouse gasesincluding methane and nitrous oxide. The classification must include envi-ronmental conservation functions. In addition, as far as the current situation isconcerned, the classification must consider not only chemical and physicalfactors, but also biological factors such as activity or variety of the soilorganisms.

  • and reduce SOM contained in the soil lead to the loss of about 500 Pg SOC. The

    118 Research Approaches to Sustainable Biomass Systemsamount of carbon released as a result of soil degradation is equivalent to doublethe amount of 230 Pg, which is the total quantity of carbon released byconsuming fossil fuels (Hakamata et al., 2000). If the soil degradation is restoredusing appropriate management practices, soil can become a huge sink ofatmospheric carbon through carbon sequestration. Much research has beenundertaken to study how to predict the quantitative change of SOC, and estimatethe carbon balance more accurately. This is also emphasized in the KyotoProtocol in order to prevent the expected global warming.

    5.2.2. Factors in the Increase and Decrease of SOC

    The SOC decomposition rate is affected by environmental factors as discussedin the following paragraphs:

    1. In the range of natural temperature, both the microbial activity and the SOCdecomposition rate increase at higher temperature. Hence, tropical zoneshave less SOC than frigid zones due to the temperature difference.

    2. Either higher or lower water content than the level for maximum microbialgrowth in the soil causes the SOC decomposition rate to slow down, so thatthe amount of SOC increases. If the soil water content is appropriate, micro-bial activity reaches the highest level so that more SOC is decomposed toresult in less SOC in the soil. In paddy fields, SOC accumulates becausethe paddy soil is fully submerged in irrigation water when rice is cultivated.

    3. The quantity of SOC increases when the soil is clayey.4. Soil with extreme acidity or alkalinity inhibits the activity of soil microor-

    ganisms, so that the SOC decomposition rate becomes slow, and SOC accu-5.2. SOIL MANAGEMENT AND SOIL ORGANIC MATTER

    5.2.1. Carbon Dynamics on the Earth Scale

    In recent years, the importance of soil organic carbon (SOC) in the carbon cycleon a global scale has attracted the attention of public and p...


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