Chapter1 soil quality and soil health .pptx

soil health and soil quality

1. Dr. A. V. Rajani Assistant Professor Department of Agricultural Chemistry & Soil Science College of Agriculture Junagadh Agricultural University Junagadh, Gujarat. 2018 As per the Fifth Dean Committee Recommendations for the B. Sc. (Hons.) Agri. Course Curriculum Lecture note * Ag. Chem. 3.3 * Problematic Soils and their Management (2+1) Prepared & Compiled By 1

2. Contents Suggested Reference Books: Textbook of Soil Science (2017) by R. K. Mehra , ICAR, New Delhi Introductory Soil Science (2013) by D.K. Das, Kalyani Publishers, New Delhi Fundamentals of Soil (2000) by V.N. Sahai , Kalyani Publishers, New Delhi Soil science An introduction (2010) by ISSS, New Delhi Concept of Soil Science (2012) by S.G. Rajput , , Kalyani Publishers, New Delhi Alkali Soils their Reclamation and management (1990) by L.L. Somani, Divyajoyti Prakashan , Jodhpur The Nature and Properties of Soil (1990) by N.C. Brady, Macmillan Publishing Company, New York (USA ). 2 Chapter No. Title Page No. 1 Soil Quality and Soil Health 2 2 Problematic soils and their management 10 3 Eroded Soils/ Soil erosion 49 4 Compacted Soils and Polluted Soils 62 5 Quality of Irrigation Water 69 6 Remote Sensing and GIS techniques 81 7 Soil Classification 85 8 Multipurpose Trees: Their selection and role in land-use systems 88

3. Ag. Chem. 3.3: Problematic Soils and their Management (2+1=3) Theory Soil quality and health, Distribution of Waste land and problem soils in Gujarat and India. Their categorization based on properties. Reclamation and management of Saline and sodic soils, Acid soils, Acid Sulphate soils, Eroded and Compacted soils, Flooded soils, Polluted soils. Irrigation water – quality and standards, utilization of saline water in agriculture. Remote sensing and GIS in diagnosis and management of problem soils. Multipurpose tree species, bio remediation through MPTs of soils, land capability and classification, land suitability classification. Problematic soils under different Agroclimatic zones of Gujarat. Practical Preparation of saturated paste of problematic soil. Determination of pHs and ECe of saturation extract of problematic soil. Estimation of water soluble and exchangeable cations in soil and computation of SAR and ESP and characterization of problematic soil. Determination of Gypsum requirement of alkali/ sodic soil. Determination of lime requirement of acidic soil. Determination of Quality of irrigation water (pH, EC, Ca, Mg, Na, CO3, HCO3, Cl, SAR and RSC). 3

4. Chapter 1 Soil Quality and Soil Health It takes half a millennia to build two centimeters of living soil and only seconds to destroy it - Anne Glover "The multiple roles of soils often go unnoticed. Soils don ’ t have a voice, and few people speak out for them. They are our silent ally in food production." Jose Graziano da Silva, FAO Director-General Soil is a natural finite resource base which sustains life on earth. It is a three phase dynamic system that performs many functions and ecosystem services and highly heterogeneous. Soil biota is the biological universe which helps the soil in carrying out its functions. Often soil health is considered independently without referring to interlinked soil functions and also based on soil test for few parameters. Physical condition of soil and biological fertility are overlooked in soil health management which needs revisiting of soil users. Recognizing the importance of soil health in all dimensions, 2015 has been declared as the International Year of Soils by the 68th UN General Assembly. Food and Agriculture organization of the United Nations has formed Global soil partnership with various countries to promote healthy soils for a healthy life and world without hunger. India, the second most populous country in the world faces severe problems in agriculture. It is estimated that out of the 328.8 m ha of the total geographical area in India, 173.65 m ha are degraded, producing less than 20% of its potential yield (Govt. of India, 1990). 4

5. 5 Whitney (1982) Hilgard (1892) Dokuchaiev (1900) Joffe (1936):   Soil is a natural body of mineral and organic constituents differentiated into horizons usually unconsolidated, of variable depth which differs among themselves as well as from the underlying parent material in morphology, physical makeup, chemical properties and composition and biological characteristics.   SSSA (1970): ( i ) The unconsolidated mineral matter on the surface of the earth that has been subjected to and influenced by genetic and environmental factors of parent material, climate (including moisture and temperature effects), macro and microorganisms and topography, all affecting over a period of time and producing a product, that is “SOIL” that differs from the material from which it is derived in many, physical, chemical, biological and morphological properties and characteristics. (ii) The unconsolidated mineral material on the immediate surface of the earth that serves as a natural medium for the growth of land plants.

6. Soil is the essence of life on earth. It serves as a natural medium for the growth of plants that sustains human and animal life. Healthy soils provide us with a range of ecosystem services such as resisting erosion, receiving and storing water, retaining nutrients and acting as an environmental buffer in the landscapes. Soils have undergone unabated degradation at an alarming rate by wind and water erosion, desertification and salinization resulting from misuse and improper farming practices. Soil quality, antonym for soil degradation, has deteriorated due to the natural and anthropogenic activities particularly with the advent of the intensive management practices. Present day need is to understand the definition and concept of soil quality and soil health and associated concepts, computation and assessment of soil quality and finally the influence of management practices on the soil quality with an overall objective of identifying the soil-quality-promoting practices. An attempt has been made in this chapter to elucidate different facets associated with soil quality and soil health. 6

7. Soil Functions Five soil functions as enunciated by Karlen et al. (1997) are: Sustaining biological activity, diversity and productivity Regulating and partitioning water and solute flow Filtering, buffering, degrading, immobilizing and detoxifying organic and inorganic materials, including industrial and municipal by-products and atmospheric decomposition Storing and cycling nutrients and other elements within the earth's biosphere Providing support to socio-economic structures and protection for archaeological treasures associated with human habitation. Thus, soil acts to supply nutrients and offer favorable physico-chemical conditions to plant growth, promote and sustain crop production, provide habitat to soil organisms, ameliorate environmental pollution, resist degradation and maintain or improve human and animal health. 7

8. Soil Quality and Soil health Soil Quality Defined The term and concept of soil quality evokes various responses depending on our scientific and social backgrounds. For some, soil quality evokes an ethical or emotional tie to the land. To others, soil quality is an integration of soil processes and provides a measure of change in soil condition as related to factors such as land use, climate patterns, cropping sequences and farming systems. Most comprehensive and accepted definition of soil quality is the one given by Soil Science Society of America ( Karlen et al. 1997) which inter alia reads 'Soil quality is the capacity of a specific kind of soil to function within natural or managed ecosystem boundaries to sustain plant and animal productivity, maintain or enhance water and air quality and support human health and habitation'. 8

9. Soil Quality vs. Soil Health The term soil quality and soil health are often used interchangeably in the scientific literature and popular articles, with agricultural and environmental scientists in general preferring the term soil quality and farmers or producers preferring the term soil health. Some others prefer the term soil health because it depicts soil as a living, dynamic organism that functions holistically rather than as an inanimate or non-living mixture of sand, silt and clay. Others prefer the term soil quality as descriptor of its innate quantifiable physical, chemical and biological characteristics. Soil quality is the capacity of soils within landscapes to sustain biological productivity, maintain environmental quality and promote plant and animal health. On the other hand, soil health is the 'fitness' (or condition) of soil to support specific uses (e.g. crop growth) in relation to its potential as determined by the inherent soil quality and is more sensitive to anthropogenic disturbance and is severely limited in extreme environments. Both of these terms relate soil to other concepts of health such as environmental health, human health, plant health, and animal health. Soil health and soil quality are functional concepts that describe how fit the soil is to support the multitude of roles that can be defined for it. Therefore, soil quality can be regarded as soil health. 9

10. 10 Many others view that soil health may be considered as the state of the soil at a particular time equivalent to the dynamic soil properties that change in the short term. Examples of dynamic soil properties are: organic matter content, diversity and number of organisms and microbial constituents or products. In a broad way, soil quality may refer to both permanent soil properties and soil condition.

11. Inherent and Dynamic Features of Soil Quality Soil quality can be viewed in two ways: (1) as inherent properties of a soil; and (2) as the dynamic nature of soils as influenced by climate and human use and management. With respect to inherent properties, a soil is a result of the factors of soil formation - climate, topography, vegetation, parent material and time (Jenny 1941). Each soil, therefore, has an innate capacity to function, e.g., some soils will be inherently more productive or will be able to partition water much more effectively than others. These inherent properties and functions generally describe and focus on the entire soil profile (around 2 m deep), and are the reasons why there can be no single value describing soil quality for all soil resources and land uses. Such soils can be compared with regard to inherent differences in productivity and with regard to their capacity for a specific land use in the absence of human interventions ( Karlen et al. 2001). Attributes of inherent soil quality are mainly viewed as almost static soil properties ’ and usually show little change over time . 11

12. Factors Affecting Soil Quality The major causes of poor soil quality are: (1) Wider gap between nutrient demand and supply coupled with low and imbalanced fertilizer use (2) Emerging deficiency of secondary and micronutrients due to improper use of inputs such as water, fertilizers, pesticides etc. (3) Decline in organic matter content in soil and insufficient use of organic inputs (4) Acidification and Al 3+ toxicity (5) Development of salinity and alkalinity in soils (6) Development of adverse soil conditions such as heavy metal toxicity (7) Disproportionate growth of microbial population responsible for soil sickness (8) Natural and man-made calamities such as erosion and deforestation occurring due to rapid industrialization and urbanization, etc. 12

13. When the human population explosion became evident, to meet the challenges forced by this perception, scientists and their farmer collaborators developed and put to use intensified soil, water and crop management systems that gave unparalleled increases in food production, especially in the developing countries. The vastly increase production resulted from farming system that integrated newly created high-yielding cereal varieties (wheat, corn and rice) with increased water availability through irrigation and dramatic increase in nutrient inputs from chemical fertilizers. Monoculture systems were intensive used, and two or three crops were harvested annually. 13

14. Soil Quality indicators Soils have chemical, biological and physical properties that interact in a complex way to give a soil its quality of capacity to function of performs. Thus, soil quality cannot be measured directly, but must be inferred from measuring changes in its attributes or attributes of the ecosystem, referred to as indicators. Indicators are a composite set of measurable attributes which are derived from functional relationships and can be monitored via field observations, field sampling, remote sensing, survey or compilation of existing information. Indicators signal desirable or undesirable changes in land and vegetation management that have occurred or may occur in the future. By measuring key attributes of a system, indicators show the condition and trend of the resource being used. Indicators of soil quality should be used to assess the change in soil function within land use or ecosystem boundaries. 14

15. (1)respond to change in management practice and provide trends over time, (2)integrate soil physical chemical and biological properties and processes, (3)be easily measured, (4)have expected or threshold values, (5)have low error associated with measurement, (6)be stable in short term to enable measurement, not be required to be frequently measured, (7)be cost-effective, (8)have the ability to be aggregated from paddock or site to farm/catchment region, be mapeable in space and time, and (9)have community acceptance and involvement. 15 Soil indicators should:

16. These indicators should be sensitive enough to detect effects of management practice, but should not be affected by short-term weather patterns. The indicators used by different researchers or in different regions may not be the same because soil quality assessment is purpose- oriented and site-specific. Good indicators provide reference material to measure trends and patterns and relate soil quality to other components of the system. 16

17. Classification of Soil Quality Indicators Soil quality indicators may directly monitor the soil, or monitor the outcomes that affected by the soil, such as productivity, vegetation, water and air quality. The indicators that directly monitor the soil are grouped as ( i ) visual, (ii) chemical, (iii) physical and (iv) an biological indicators. The indicators that indirectly monitor the soil health are: crop yield/ unit area/unit time, plant biomass/unit area/unit time, ratio, legume/non-legume crop ratio, water use efficiency/unit time, nutrient use efficiency/unit water used/unit time, and produce quality such as cereal grain protein, concentration of toxic elements in food grains, vegetables, fruits etc. Some of the soil physical, chemical and biological properties suggested as soil quality indicators are listed in below. 17

18. Indicator Processes and soil functions A. Mechanical Texture Crusting, gaseous diffusion, infiltration Bulk density Compaction, root growth, infiltration Aggregation Erosion, crusting, infiltration, gaseous diffusion Pore size distribution and continuity Water retention, and transmission, root growth and gaseous exchange B. Hydrological Available water capacity Drought stress, biomass production, soil organic matter content Non-limiting water range Drought, water imbalance, soil structure Infiltration rate Runoff, erosion, leaching C. Rooting zone Effective rooting depth Root growth, nutrient and water use efficiencies Soil temperature Heat flux, soil warming activity and species diversity of soil fauna Source: Lal (1994) Major soil physical indicators and related processes 18

19. Indicator Processes and soil functions pH Acidification and soil reaction, nutrient availability Base saturation Absorption and desorption, solubilization Cation exchange capacity Ion exchange, leaching Total and plant available nutrients Soil fertility, nutrient reserves Soil organic matter Structural formation, mineralization, biomass carbon, nutrient retention Earthworm population and other soil, macro fauna and activity Nutrient cycling, organic matter decomposition, formation of soil structure Soil biomass carbon Microbial transformations and respiration, formation of soil structure and organo -mineral complexes Total soil organic carbon Soil nutrient source and sink, bio-mass carbon, soil respiration and gaseous fluxes Source: Lal (1994) Table: Major soil chemical, nutritional and biological indicators and related soil processes 19

20. Visual Indicators Visual indicators of soil health may be obtained from observation or photographic interpretation. Exposure of subsoil, change in soil color, ephemeral gullies, pounding, runoff, plant response, weed species, and decomposition are only a few examples of potential locally determined indicators. Visual evidence can be a clear indication that soil quality is threatened or changing. 20

21. Chemical Indicators Dominant chemical indicators include soil pH, electrical conductivity, adsorption and cation exchange capacity, organic matter, and available nutrients. The other useful indicators, especially those which are needed for plant growth and development can also be included. Soil pH is an indicator that can provide trends in change in soil health in terms of acidification (surface and sub-surface), soil salinization, electrical conductivity' exchangeable sodium (soil structural stability), increased incidence of root disease: influence root growth, biological activity, and nutrient availability (e.g. P availability at either high pH >8.5 or low pH <5; Zn availability at high pH >8.5). Soil pH trends also provide changed capacity of the soil for pesticide retention and breakdown as well as the mobility of certain pesticides through the soil. These processes affect soil health on-farm and have effects beyond farm gate. Electrical conductivity is a measure of salt concentration and therefore, its measure can provide trends in salinity for both soil and water. 21

22. Organic matter is fundamental in maintenance of soil health because it is essential for optimal functioning of a number of processes important to sustainable ecosystems. Soil organic matter is a source and sinks of C and N and partly of P and S. It affects micronutrient availability through complexation, chelation and production of organ acids, thus altering soil pH. Conversely, it ties up metals present in toxic amounts ( e.g. Cu, As, Hg). Organic matter is essential for good soil structure especially in low clay content soils, as it contributes towards both formation and stabilization of soil aggregates. Other functions include: contribution to cation exchange capacity especially in low clay content in soils, as it contributes toward both formation and stabilization of soil aggregates. Trends in available plant nutrients, for example, N, P, S and K indicate sustainable land use, especially, if the nutrient concentration and availability are approaching but remain above the critical or threshold values. In the long-term, nutrient balance of the system (e.g. input efficiency = output) is essential to sustainability. Thus, available nutrients are indicators of the capacity to support crop growth, potential crop yield, grain protein content, and conversely, excessive amounts may be a potential environmental hazard (e.g. algal biomass, eutrophication). 22

23. Physical Indicators Physical indicators of soil health reflect the capacity to accept, store, transmit and supply water, oxygen and nutrients within ecosystem. The study of these indicators includes monitoring of soil structure through pore size distribution, aggregate stability, saturated hydraulic conductivity, infiltration, bulk density, and surface crust. Rooting depth provides a good indicator of buffering against water, air and nutrient stress. Soil surface cover can be used as an indicator of soil surface protection against raindrop impact, and hence enhanced infiltration, reduced surface crust, and reduced soil erosion and runoff. Soil water infiltration measures the rate at which water enters soil surface, and transmitted through the immediate soil depth. Rainfall is rapidly absorbed by soil with high infiltration rate. But as the soil structure deteriorates, usually with the loss of organic matter, increase in exchangeable sodium and low electrolyte concentration, the infiltration rate of a soil becomes low. This increases the tendency for soil erosion and runoff in sloping soils and water logging in flat soils. 23

24. Aggregate stability refers to the resistance of soil aggregates to breakdown by water and mechanical force. Aggregate stability is affected by quality and quantity of organic matter, types of clays, wetting and drying, freezing and thawing, types and amounts of electrolyte, biological activity, cropping systems and tillage practices . For monitoring trends in soil health, sampling procedures for aggregate stability need to be standardized. Bulk density varies with the structural condition of the soil. It is altered by cultivation, loss of organic matter, and compression by animals and agricultural machinery, resulting in compact plough layer. It generally increases with depth in-soil profile. In cracking clay soils such as Vertisols , it varies with water content. 24

25. Biological Indicators Biological indicators of soil health include soil microbial biomass and/or respiration; potentially mineralize N, enzyme activity, fatty acid profile or microbial biodiversity, nematode communities and earthworm populations. Soil microbial biomass is a labile source and sink of nutrients. It affects nutrient availability and nutrient cycling and is a good indicator of potential microbial activity and capacity to degrade pesticides. Respiration rates can be measured in the field using portable CO 2 analyzers. 25

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27. Applications of Soil Quality Approach in Sustainable Use of Soil Resources Soils play a key role in the definition of sustainable land management since they represent the basis of food production. Understanding soil quality means, assessing and managing soil so that it functions optimally now and is not degraded for future use. Few soil-related issues which cause major setback to achieve sustainable soil management are: nutrient depletion and deficiency, soil erosion and degradation, socioeconomic prices and marketing, inefficient water use, faulty research methods, unsustainable farming, soil acidity, non-adoption by farmers of improved technology, competing uses for water, lack of organic matter, inadequate fertilizer use and management, high compaction, seasonal drought and water stress, water logging and poor drainage. By monitoring changes in soil quality, a farmer or land manager can determine if a set of the practices were sustainable. The ultimate objective of sustainable soil management is to transfer healthy soil to the next generation. Soils frequently perform several functions simultaneously and not independently and quantification of these functions is essential for best output from the soil. According to Karlen et al. (1997) soil quality influences basic soil functions, such as moderating and partitioning water, solute movement and their redistribution and supply to plants; storing and cycling nutrients; filtering, buffering & immobilizing and detoxifying organic and inorganic materials; promoting root growth; and providing resistance to erosion. According to Schoenholtz et al. (2000), soil functions would be defined in terms of physical, chemical and biological properties and processes and measured against some definable standards to determine whether a soil is being improved or degraded. No soil is likely to successfully provide all these functions, some of which occur in natural ecosystems and some of which are the result of human modifications. 27

28. Strategies for Improving Soil Quality The properties of soil which represent the dynamic soil quality can be improved by several management practices which are described as follows: (1) Enhancement of Organic Matter Organic matter is considered as the main stay of good soil quality. Regular additions of organic matter improve soil structure, enhance water and nutrient holding capacity, protect soil from erosion, hard setting and compaction and support a healthy community of soil organisms. Practices that increase organic matter include: leaving crop residues in the field, choosing crop rotations that include high residue plants, using optimal nutrient and water management practices to grow healthy plants with large amounts of roots and residue, growing cover crops, applying manure or compost, using low or no tillage systems, using sod-based rotations, growing perennial forage crops and mulching. 28

29. (2) Reduction in the Intensity of Tillage Reducing tillage minimizes the loss of organic matter and protects the soil surface with plant residue. Tillage is used to loosen surface soil, prepare the seedbed and control weeds and pests. But tillage can also break up soil structure, speed up the decomposition and loss of organic matter, increase the threat of erosion, destroy the habitat of helpful organisms and cause compaction. (3) Efficient Management of Pests and Nutrients Efficient pest and nutrient management means testing and monitoring soil and pests; applying only the necessary chemicals, at the right time and place to get the job done; and taking advantage of non-chemical approaches to pest and nutrient management such as crop rotations, cover crops and manure management. The terms integrated pest management (IPM) and integrated nutrient managements (INM) are very much popular nowadays. In case of IPM, the pests are managed without much dependence on the chemicals. In case of INM also, dependence on chemical fertilizers is reduced considerably. 29

30. (4) Prevention of Soil Compaction Soil compaction reduces the amount of air, water and space available to roots and soil organisms. Compaction is caused by repeated traffic, heavy traffic or traveling on wet soil. Deep compaction by heavy equipment is difficult or impossible to rectify, so prevention is essential. Subsoil tillage is only effective on soils with a clearly defined root-restricting plough pan. In the absence of a plough pan, subsoil tillage to eliminate compaction can reduce yield. Prevention is the best method to manage compaction and not the tillage. (5) Maintenance of Ground Cover Soil without adequate cover or bare soil is very much susceptible to wind and water erosion, and to drying and crusting. Ground cover protects soil; provides habitats for larger soil organisms, such as insects and earthworms and can improve water availability. Ground can be covered by leaving crop residue on the surface or by planting cover crops. In addition to ground cover, living cover crops provide additional organic matter, and continuous cover and food for soil organisms. Ground cover must be managed to prevent problems with delayed soil warming in spring, diseases and excessive build-up of phosphorus at the surface. 30

31. (6) Diversification of Cropping Systems Diversity is beneficial for several reasons. Each plant contributes a unique root structure and type of residue to the soil. A diversity of soil organisms can help control pest populations and a diversity of cultural practices can reduce weed and disease pressures. Diversity across the landscape can be increased by using buffer strips, small fields or contour strip cropping. Diversity over time can be increased by using long crop rotations. Changing vegetation across the landscape or over time not only increases plant diversity, but also the types of insects, microorganisms and wildlife that live in the soil. 31

32. Phytoremediation, Phytoextraction and Phytostabilisation Because of the high costs that are generally involved with the cleanup of contaminated land, there is large interest in alternative and lower-cost methods. Considering the ways that plants affect the bio-availability and uptake of heavy metals (and plants with their associated rhizosphere micro-organisms) could affect transformation of organic pollutants, it has been suggested to use plants to remediate the contaminated soils. Remediation of inorganic and organic compounds proceeds according to different mechanisms, and understanding the biological basis of remediation with the help of plants p (Phytoremediation) is imperative. Phytoremediation is ultimately a very simple technique - it just consists of growing plants on contaminated sites. It can be environmentally viable and economically feasible. But the effectiveness is variable and site-dependent. In the case of heavy metals, one could attempt to increase uptake (and subsequent transfer to the above — ground part) of plants. Such plants can be harvested and the pollutant removed under controlled conditions. This process is called Phytoextraction. In principle, such metals could then even be recycled. 32

33. 33 The process of Phytostabilisation consists of using plants to reduce bio-availability, and thereby prevent losses to the environment (including losses to groundwater). Immobilization in roots or binding of metals to organic matter is ways of Phytostabilisation. In order for Phytoextraction to be effective, two factors are important. (1) the bio-concentration factor (the ratio of nutrient concentration in plant roots or shoots divided by that in soil); and (2) the biomass production. From a soil biological point of view, it is important to separate bio-concentration (the ratio of a pollutant between roots and soil) and subsequent transfer (the ratio of a pollutant between shoots and roots), because heavy metal accumulation in shoots makes Phytoextraction possible, whereas accumulation in roots (with little or no transfer to shoots) make Phytostabilisation more worthwhile. Many plants also reduce the heavy metals toxicity by decreasing the transfer from root to shoot or even largely excluding them from the shoot.