# Soil Health and Soil Quality: - The Fundamental Keys to a Sustainable and Productive Agriculture

Ajeet Kumar

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Ajeet Kumar. Soil Health and Soil Quality: - The Fundamental Keys to a Sustainable and Productive Agriculture. International Symposium on Management of Rice based agricultural system under stress prone environment, Rajendra Agricultural University, Pusa, Samastipur, Bihar, Mar 2016, Samastipur, India. pp.48-54. hal-04972899

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Distributed under a Creative Commons Attribution 4.0 International License
International Symposium
on
Management of rice based agricultural System
under stress prone environment

(17 to 19 March, 2016)

Souvenir

Rajendra Agricultural University

Pusa, Samastipur, Bihar (INDIA)

www.pusavarsity.org.in
# Soil Health and Soil Quality: The Fundamental Keys to a Sustainable and Productive Agriculture

Ajeet Kumar

Regional Research Station (RRS), Madhopur, West Champaran-845454, Bihar, India
(Rajendra Agricultural University, Pusa (Samastipur), Bihar, India)

Corresponding author: E-mail: ajeetrau@gmail.com, ajeetbau@gmail.com

## Introduction

Healthy agricultural soils are able to balance a range of functions to meet the demanding needs of farming communities. Healthy soils function to sustain soil biota and plant life, store and cycle water and nutrients, decompose organic matter, inactivate toxic compounds, suppress pathogens and protect water quality. Soil health is a systems concept that implies that the soil functions as a balanced living system. It implies that the interactions among the soil's internal components are optimal and that the interactions of the soil with its external environment and the production system are sustainable.

Soil health is defined as the continued capacity of soil to function as a vital living system, by recognizing that it contains biological elements that are key to ecosystem function within land-use boundaries. These functions are able to sustain biological productivity of soil, maintain the quality of surrounding air and water environments, as well as promote plant, animal, and human health. The concept of soil quality emerged in the early 1990s and the first official application of the term was approved by the Soil Science Society of America Ad hoc Committee on Soil Quality. Soil quality was been defined as "the capacity of a reference 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." Subsequently the two terms are used interchangeably although it is important to distinguish that, soil quality is related to soil function, whereas soil health presents the soil as a finite nonrenewable and dynamic living resource. The concept of soil health directly includes interactions between plant inputs and soil in creating a healthy environment. Because of the numerous alternative uses of soil, the meaning of the terms soil health and soil quality depend on the defined purpose such as for agricultural use. In agriculture, the main attention on plant and animal productivity as these would be of greatest importance in cultivated soils. Protection of soil quality under intensive land use is a major challenge for sustainable resource. The basic assessment of soil health and soil quality is necessary to evaluate the degradation status and changing trends following different land use and management interventions. In India, the adverse effects on soil health and soil quality arise from nutrient imbalance in soil, excessive fertilization, soil pollution and soil loss processes. Soil degradation and poor water quality are symptoms of poor soil health. Soil biological activity, surface cover, organic matter content, pH and water availability are highly interactive and hence important soil health properties. My focus on examining the development of soil health approaches as well as the content of soil health and soil quality information and its application to farming community, since these are the regions where loss in soil quality is expected to be continued to a negative impact on productivity and long term sustainability. This paper describes soil health and how it relates to soil properties and management practices in agricultural production systems.

Soils are dynamic ecosystem that supports diversity of life. Therefore the concept of soil health is not difficult to understand when system is viewed as a whole. The main challenge is to manage soils such that they are able to do perform various uses they are put to without degradation of soils themselves or environment.
Soil health has been defined by Doran and Zeiss (2000) as 'the capacity of soil to function as a vital living system, within ecosystem and land use boundaries, to sustain plant and animal production, maintain or enhance water and air quality, and promote plant and animal health'. Healthy soil functions optimally through balanced interactions amongst its biological, physio-chemical and mineral components. The mineral component consists of sand, silt and clay particles; the physio-chemical component consists of soil aggregates, pore space, reactive surfaces, and organic and inorganic compounds; and the biological component consists of roots, insects, invertebrates and microorganisms.

The biological and organic component and functions of soils depend on, and emerge from, the physiochemical and mineral components. Hence the abundance, diversity and functioning of these organisms is a key indicator of soil health. The main function of soil organisms is to cycle and transform nutrients and energy by decomposing organic matter. This process occurs within a complex food chain and is highly dependent on environmental factors such as moisture content and temperature. Soils are part of the life cycles of many types of organisms including insects, earthworms, mites, springtails, bacteria, algae, blue-green algae, fungi, protozoa and nematodes. A healthy soil performs the following functions: - sustain biological productivity, store and cycle water and nutrients, decompose O.M., inactivate toxic compounds, suppress pathogens, protect water quality and enhance soil health.

The concept of soil health and soil quality has consistently evolved with an increase in the understanding of soil quality attributes. Soil quality cannot be measured directly, but soil properties that are sensitive to changes in management can be used as indicators. The soil health approach is better applied when specific goals are defined for a desired outcome from a set of decisions. Therefore the soil health soil quality as an evaluation process consists of a series of actions viz. Selection of soil health indicators, Determination of a minimum data set (MDS), Development of an interpretation scheme of indices and On-farm assessment and validation.

## Soil Health Indicators

Even though the properties that constitute a healthy soil are not the same in all places and all the situations, there are some important soil properties that indicate soil health. The quality of soil is dynamic property and it affects the sustainability and productivity of land. It is controlled by chemical, physical, and biological components of a soil and their interactions. Indicators, however, will vary according to the location, and the level of sophistication at which measurements are likely to be made. Therefore, it is not possible to develop a single short list which is suitable for all purposes. The commonly used indicators of soil health upon which soils community agreed upon are as mentioned in table 1.

<table><caption>**Table 1.** Commonly used indicators of soil health</caption><thead><tr><th>Biological indicators</th><th>Chemical indicators</th><th>Physical indicators</th></tr></thead><tbody><tr><td><ul><li>Microbial biomass</li><li>Earthworm populations</li><li>Nematode populations</li><li>Arthropod populations</li><li>Mycorrhizal fungi</li><li>Respiration rate</li><li>Soil enzyme activities</li><li>Pollutant detoxification</li><li>Decomposition rate</li></ul></td><td><ul><li>pH</li><li>Organic matter oTotal carbon</li><li>Total nitrogen oCation exchange capacity oMajor and minor nutrients oElectrical conductivity</li><li>Heavy metals and plant toxins</li></ul></td><td><ul><li>Texture</li><li>Bulk density</li><li>Penetration resistant</li><li>Aggregate stability</li><li>Water holding capacity</li><li>Infiltration rate</li><li>Depth of hardpan</li><li>Depth of water table</li><li>Porosity</li><li>Erosive potential</li><li>Aeration</li></ul></td></tr></tbody></table>
## 1. Biological indicators

Identification of biological indicators of soil quality is critically important because soil quality is strongly influenced by microbiologically mediated processes (nutrient cycling, nutrient capacity, aggregate stability etc.). It is essential to identify those components that rapidly respond to changes in soil quality. Biological indicators of soil quality that commonly measured are soil organic matter, respiration, microbial biomass (total bacteria and fungi,) and mineralizable nitrogen. Soil organic matter plays a key role in soil function, determining soil quality, water holding capacity and susceptibility of soil to degradation. In addition, soil organic matter may serve as a source or sink to atmospheric CO₂ and an increase in the soil C content is indicated by a higher microbial biomass and elevated respiration. It is also the principal reserve of nutrients in the soil, may contain large quantities of mineral nitrogen.

## 2. Chemical indicators

In order to achieve high crop yields farmers have to provide soil nutrients in large quantities. Therefore it is possible to alter the pool of available nutrients by adding inorganic fertilizers, incorporating cover crops, and using other organic materials in form of manures and composts. Results of chemical tests are soil quality indicators which provide information on the capacity of soil to supply mineral nutrients, which is dependent on the soil pH. Soil pH is an estimate of the activity of hydrogen ions in the soil solution. It is also an indicator of plant available nutrients. High activity is not desirable and the soil may require liming with base cations Ca or Mg in order to bring the solution back to neutral.

## 3. Physical indicators

Soil physical properties are estimated from the soil's texture, structure, tilth, bulk density, porosity, water-holding capacity (Hillel, 1982). The presence or absence of hard pans usually presents barriers to rooting depth. All of these properties are improved through additions of organic matter in soils. Therefore, the suitability of soil for sustaining plant growth and biological activity is a function of its physical properties. There are several criteria to consider when selecting soil health and soil quality indicators. In general, appropriate indicators should be: (easy to assess, able to measure changes in soil function both at plot and landscape, scales, assessed in time to make management decisions, accessible to many farmers, sensitive to variations in agro-ecological zone, representative of physical, biological or chemical properties of soil, assessed by both qualitative and quantitative approaches).

<table><caption>Table 2 Summary of soil health indicators used to assess soil functions.</caption><thead><tr><td>Indicator</td><td>Soil function</td></tr></thead><tbody><tr><td>Soil organic matter (SOM)</td><td>Soil structure, stability, nutrient retention; soil erosion (Carter, 2002)</td></tr><tr><td>Physical: soil aggregate stability, infiltration and bulk density</td><td>Retention and mobility of water and nutrients; habitat for macro and micro fauna (Swift et al., 2004)</td></tr><tr><td>Chemical: pH, extractable soil nutrients, N-P-K and base cations Ca Mg & K</td><td>Soil biological and chemical activity thresholds; plant available nutrients and potential for N and P as well as loss of Ca, Mg & K (Drinkwater et al., 1996)</td></tr><tr><td>Biological: microbial biomass C and N; potentially mineralizable N</td><td>Microbial catalytic potential and repository for C and N; soil productivity and N supplying potential (Cadisch and Giller, 1997)</td></tr></tbody></table>

In several literatures, it is postulated that basic soil quality indicators should reflect criteria which are relevant to existing soil data bases. Based on these propositions a list of basic soil properties that should be indicative of soil
quality was established in Table 3. This list has been included in the MDS by Larson and Pierce (1994), and expanded with a few biological aspects of soil quality, namely microbial biomass C and N, and soil respiration.

## Concept and Application of Minimum Data Set:

A minimum data set (MDS) was proposed to measure soil quality and its changes due to management practices through selection of key indicators such as soil texture, organic matter, pH, nutrient status, bulk density, electrical conductivity and rooting depth (Larson and Pierce, 1994). Collecting a minimum data set helps to identify locally relevant soil indicators and to evaluate the link between selected indicators and significant soil and plant properties. It is a minimum set of indicators required for understanding of the soil attributes. More importantly they serve as a useful tool for screening the condition, quality, and health of soil.

<table><caption>**Table 3.** Proposed minimum data set of physical, chemical, and biological indicators for assessing soil quality</caption><thead><tr><th>Indicators</th><th>Rationale for assessment</th></tr></thead><tbody><tr><td></td><td><strong>Biological indicators</strong></td></tr><tr><td>Microbial biomass C and N</td><td><ul><li>☐ Describes microbial catalytic potential and repository for C &amp; N.</li><li>☐ Provides an early warning of management effects on O.M.</li></ul></td></tr><tr><td>Potentially mineralizable N</td><td><ul><li>☐ Describes soil productivity and nitrogen supplying potential</li><li>☐ Provides an estimate of biomass</li></ul></td></tr><tr><td>Soil respiration</td><td><ul><li>☐ Defines a level of microbial activity</li><li>☐ Provides an estimate of biomass activity</li></ul></td></tr><tr><td></td><td><strong>Chemical indicators</strong></td></tr><tr><td>Soil organic matter pH</td><td><ul><li>☐ As a proxy for soil fertility and nutrient availability</li><li>☐ biological and chemical activity thresholds</li></ul></td></tr><tr><td>Electrical conductivity</td><td><ul><li>☐ plant and microbial activity thresholds</li></ul></td></tr><tr><td>Extractable N, P, and K</td><td><ul><li>☐ Describes plant-available nutrients and potential for N loss</li><li>☐ Indicates productivity and environmental quality</li></ul></td></tr><tr><td></td><td><strong>Physical indicators</strong></td></tr><tr><td>Soil texture</td><td>Indicates how well water and chemicals are retained and transported<br>Provides an estimate of soil erosion and variability</td></tr><tr><td>Soil depth and rooting</td><td>Indicates productivity potential<br>Evens out landscape and geographic variability</td></tr><tr><td>Infiltration and soil bulk density (n̂b)</td><td>Describes the potential for leaching, productivity, and erosion is used to correct soil analyses to volumetric basis</td></tr><tr><td>Water holding capacity</td><td>Describes water retention, transport and erosion<br>Available water is used to calculate soil bulk density and O.M.</td></tr></tbody></table>

Source: Doran *et al.*, 1996; Larson and Pierce, 1994; and Doran and Parkin, 1994

## On-farm soil health assessment

On-farm assessment of soil quality and health is recommended to assist farmers to evaluate the effects of their management on soil. This approach also permits interaction between researchers, extension and policy personnel
when providing interpretation to link on-farm knowledge to soil health information. The main objective is to develop
soil quality and soil health standards to assess changes which are practical and useful to farmers. For instance,
linking soil health measurements with farmer perceptions of soil quality can bridge the gap in interpretation of
complex data sets. **Scorecards:** The use of scorecards for on-farm soil quality assessment is emphasized where
qualitative observations of soil health are scored to obtain an overall measure of soil quality soil health. These cards
may be developed to evaluate soil health through farmer observations of soil physical, chemical and biological
properties. These soil characteristics are classified in terms of descriptive indicators which are interpreted on a
graded scale. **Soil quality test kits:** Assessment tools such as soil quality test kits focus on farmer-based evaluations
and education regarding various soil management practices. Further, they aim to produce an educational tool to
increase public awareness of the importance of soil quality. Such kits, which are commercially available, provide for
measurements of soil respiration, infiltration, bulk density, water content, electric conductivity (EC), pH, soil nitrates,
aggregate stability, slake test and earthworm numbers (USDA, 1999). **Soil quality indices:** Finally, various soil
quality indexing approaches are available and can be applied to derive a range of critical test values within which
soil quality and soil health assessments can be defined.

Sensing Soil Health

Assessments of soil chemical properties normally rely on laboratory data, required to adequately characterize
spatial variability of nutrients. Shepherd and Walsh (2002) have developed a promising approach that directly estimates
several soil properties simultaneously from diffuse reflectance spectra in rapid nondestructive ways. The soil
reflectance spectral data successfully predicted crop yields of an 18-year field experiment in testing different levels
of fertilizer, manure and crop residue management. Since spectral techniques allow large numbers of samples to be
rapidly analyzed, resources can be directed towards thorough characterization of the soil and its spatial variability
within a target region.

The concept of soil quality is in the process of evolution and progressively moving from a concept focused on
yield potential and nutrient levels to one of environmental quality, food safety and human health.

Soil and Climate Change

Global climate change is dramatically increasing the variability of weather conditions and soil is a critical buffer
medium for hydrologic and biogeochemical processes and therefore can mitigate the effects of extreme weather
conditions and uncertainty in the availability of water resources. The present threats of global climate change and
ozone depletion, through elevated levels of certain atmospheric gases and altered hydrological cycles, necessitate a
better understanding of the influence of land management on soil quality (Doran and Safley 1997).

Soil Health Resources

Training materials should be developed because most of the farmers still lacking the basis on which to evaluate
the complexity of soil quality changes. The literatures provides the foundation for sustainability through processes
such as nutrient and hydrological cycles, filtering and buffering of soil, decomposition of crop residues and organic
matter inputs.

The internet based resources continues to bridge the gap between the sources and users. The soil health portals
serve as a key point to access soil health information on-line. The author has tried well to enlist websites for these
purposes are as follows:-

http://www.worldagroforestry.org/sea/networks/ifm/contents.htm.

http://www.fao.org/landandwater/agll/spush/topic4.htm; http://www.rwc-prism.cgiar.org/rwc
http://www.icrisat.org/text/research/nrmp/cdlegumes/e-book/Legumes.pdf

http://www.css.cornell.edu/faculty/hobbs/; http://ipmworld.umn.edu/chapters/johnson.htm

http://ppathw3.cals.cornell.edu/mba_project/moist/mulchmail.html

http://www.ciat.cgiar.org/tsbf_institute/index_tsbf.htm

http://www.fao.org/ag/AGL/agll/soilbiod/index_en.stm

http://www.sustainableag.net/soil_health.htm; http://www.fao.org/documents

http://ppathw3.cals.cornell.edu/mba_project/CIEPCA/exmats/

http://www.gsf.de/UFIS/ufis/thesaur/soil.html; http://www.aginternetwork.org/en

http://www.fao.org/ag/agl/public.stm

http://www.soilandhealth.org/

In farms, soil health and soil quality vary dramatically from one end of field to the other. Many of the soils also respond poorly to fertilizer alone. This low efficiency can be enhanced through management of organic matter inputs, improved soil structure & water holding capacity. Soil health improvement includes consideration of the complexity of soils, long-term sustainable agricultural growth and effective use of organic & inorganic fertilizers & improved varieties.

Rapidly increasing population has made them food-insecure. With inadequate inputs in agriculture, lands are degrading rapidly and destroying ecosystems. Currently, soil resource assessment and monitoring is entering a new era. The quality of information produced by use of Geographic Information Systems and remote sensing have significantly enhanced the acceptance and use of soil health information. The uses of technology significantly increase the demand for more data. Further innovations will result in model approaches in soil genetic studies that will demonstrate the integral role of soils in ecosystems. The use of ICT (on-line delivery content through wikis, blogs and social book) pushes sharing of soil health information to a new level. The basic research is needed in order to develop proper indicators. Innovations required in setting up effective programs, which would accumulate necessary bascline soil data in order to develop appropriate minimum datasets.

## Conclusions

To maximize the soil health benefits through use of specific management practices (groundcovers, mulches, organic amendments, fertilizer strategies), there is a need to evaluate and demonstrate their use across a range of production systems and climates. This can only be achieved through an integrated research and extension strategy that brings together the necessary disciplines, programs and organizations. The adequate soil organic matter is absolutely essential to establish a healthy soil ecosystem. It is the intention of this paper to develop strategically integrated approach for soil health management.

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Carter, Martin R. (2002) Soil quality for sustainable land management: Organic matter and aggregation interactions that maintain soil functions. *Agron J* 94: 38-47

Cadisch, G. & Giller, K.E. (1997) Driven by Nature, Plant Litter Quality and Decomposition.

CAB International, Wallingford

Doran, J. W., and Parkin, T. B. (1994) Defining and assessing soil quality. Pages 3-21 in J. W. Doran et al., (eds.) Defining soil quality for a sustainable environment. Soil Science Society of America Special Publication no. 35, Madison, WI.

Doran, J.W., Sarrantonio, M., Liebig, M., (1996) Soil health and sustainability. In: Sparks, D.L. (Ed.), *Advances in Agronomy*, Vol. 56. Academic Press, San Diego, pp. 1-54.
Doran, J.W., Zeiss, M.R., (2000) Soil health and sustainability: managing the biotic component of soil quality. *Applied Soil Ecology* 15: 3-11.

Drinkwater, L.E., Cambardella, C.A., Reeder, J.D., Rice, C.W., (1996) Potentially mineralizable nitrogen as an indicator of biologically active soil nitrogen. In: Doran, J.W., Jones, A.J. (Eds.), Methods for Assessing Soil Quality. Soil Science Society of America, Special Publication 49, Madison, WI, pp. 217-229

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USDA (1999) Soil quality test kit guide. USDA, Agricultural Research Service and Natural Resources Conservation Centre. Available at: http://soils.usda.gov/sqi/kit2.html.