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Collection Highlights

Encyclopedia of Soil Science, Third Edition Rattan Lal

Soil Water and Agronomic Productivity 1st Edition Rattan

Lal

Sustainable Agriculture Reviews 45 Legume Agriculture and

Biotechnology Vol 1 Praveen Guleria

Soil and Fertilizers-Managing the Environmental Footprint

1st Edition Rattan Lal (Editor)
Sustainable Agriculture Reviews 35 Chitin and Chitosan
History Fundamentals and Innovations Grégorio Crini

Sustainable Management of Soil and Environment Ram Swaroop

Meena

Sustainable Agriculture Reviews 47: Pesticide Occurrence,

Analysis and Remediation Vol. 1 Biological Systems
Inamuddin

Sustainable Agriculture Forest and Environmental

Management Manoj Kumar Jhariya

Soil Degradable Bioplastics for a Sustainable Modern

Agriculture 1st Edition Mario Malinconico (Eds.)
Sustainable Agriculture Reviews 29

Rattan Lal
Rosa Francaviglia Editors

Sustainable
Agriculture
Reviews 29
Sustainable Soil Management:
Preventive and Ameliorative Strategies
Sustainable Agriculture Reviews

Volume 29

Series Editor
Eric Lichtfouse, CNRS, IRD, INRA, Coll France, CEREGE, Aix-Marseille
Université, Aix-en-Provence, France

Advisory Editors
Shivendu Ranjan, School of Bio Sciences and Technology, VIT University,
Vellore, Tamil Nadu, India
Nandita Dasgupta, Nano-food Research Group, School of Bio Sciences and
Technology, VIT University, Vellore, Tamil Nadu, India
Sustainable agriculture is a rapidly growing field aiming at producing food and
energy in a sustainable way for humans and their children. Sustainable agriculture is
a discipline that addresses current issues such as climate change, increasing food
and fuel prices, poor-nation starvation, rich-nation obesity, water pollution, soil
erosion, fertility loss, pest control, and biodiversity depletion.
Novel, environmentally-friendly solutions are proposed based on integrated
knowledge from sciences as diverse as agronomy, soil science, molecular biology,
chemistry, toxicology, ecology, economy, and social sciences. Indeed, sustainable
agriculture decipher mechanisms of processes that occur from the molecular level to
the farming system to the global level at time scales ranging from seconds to
centuries. For that, scientists use the system approach that involves studying
components and interactions of a whole system to address scientific, economic and
social issues. In that respect, sustainable agriculture is not a classical, narrow
science. Instead of solving problems using the classical painkiller approach that
treats only negative impacts, sustainable agriculture treats problem sources. Because
most actual society issues are now intertwined, global, and fast-developing, sustainable
agriculture will bring solutions to build a safer world. This book series gathers review
articles that analyze current agricultural issues and knowledge, then propose alternative
solutions. It will therefore help all scientists, decision-makers, professors, farmers and
politicians who wish to build a safe agriculture, energy and food system for future
generations.

More information about this series at http://www.springer.com/series/8380

Rattan Lal Rosa Francaviglia
•

Editors

Sustainable Agriculture
Reviews 29
Sustainable Soil Management: Preventive
and Ameliorative Strategies

123
Editors
Rattan Lal Rosa Francaviglia
Carbon Management and Sequestration Research Centre for Agriculture
Centre and Environment
The Ohio State University Council for Agricultural Research
Columbus, OH, USA and Economics (CREA)
Rome, Italy

ISSN 2210-4410 ISSN 2210-4429 (electronic)

Sustainable Agriculture Reviews
ISBN 978-3-030-26264-8 ISBN 978-3-030-26265-5 (eBook)
https://doi.org/10.1007/978-3-030-26265-5
© Springer Nature Switzerland AG 2019
This work is subject to copyright. All rights are reserved by the Publisher, whether the whole or part
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recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission
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The use of general descriptive names, registered names, trademarks, service marks, etc. in this
publication does not imply, even in the absence of a specific statement, that such names are exempt from
the relevant protective laws and regulations and therefore free for general use.
The publisher, the authors and the editors are safe to assume that the advice and information in this
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authors or the editors give a warranty, expressed or implied, with respect to the material contained
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This Springer imprint is published by the registered company Springer Nature Switzerland AG
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Preface

“Soil management is sustainable if the supporting, provi-

sioning, regulating, and cultural services provided by soil
are maintained or enhanced without significantly impairing
either the soil functions that enable those services or biodi-
versity. The balance between the supporting and provision-
ing services for plant production and the regulating services
the soil provides for water quality and availability and for
atmospheric greenhouse gas composition is a particular
concern”.

FAO 2017. Voluntary Guidelines for Sustainable Soil

Management Food and Agriculture Organization of the
United Nations, Rome, Italy.

Humankind is facing tremendous challenges in agriculture: Climate is changing,

global population is growing quickly, cities are expanding, diets are undergoing
major shifts and soils are becoming increasingly degraded. In this fast-changing
world, and given the urgent need to eliminate hunger and ensure food security and
nutrition, understanding and attaining sustainable soil management have never been
more important.
Soils are the foundation of food production and many essential ecosystem ser-
vices. It has been shown that sustainable soil management contributes to increasing
food production, enhancing the nutrient content of food, and adapting to and mit-
igating climate change.
Indeed, the sustainable development goals identify the need to restore degraded
soils and improve soil health. There is widespread agreement that we must preserve
the full potential of soils and be able to support food production while storing and
supplying more clean water, maintaining biodiversity, sequestering carbon and
increasing resilience in a changing climate. This is a goal that requires the universal
implementation of sustainable soil management.
This book presents reviews on preventive and ameliorative strategies addressing
sustainable soil management. The first chapter by Biswas et al. reviews the current
knowledge on soil health related to organic carbon and biological resources,
particularly microorganisms, and their effects on potential agricultural productivity.

v
vi Preface

Scheme of soil health in agricultural productivity, Chap. 1.

Factors and processes affecting the soil organic carbon dynamic, Chap. 2.

In Chap. 2, Morari et al. address the existing knowledge about the amount of SOC
stored in soils globally and explore factors and processes controlling its distribution.
The topic of organic matter management in cereal-based systems is presented in
Chap. 3 by Amanullah et al. Spiegel et al. review the past and current use of
P fertilizers and present the results of two Austrian long-term P field experiments in
Chap. 4. Loum et al. evaluate soil organic carbon mapping by testing the
Preface vii

effectiveness to include remote sensed data in Chap. 5. The last chapter by Cornelis
et al. presents the problem of drought and floods from a soil-water management
perspective.
The book reinforces the following principal concepts: 1) the health of soil,
plants, animals, people, and the environment is one and indivisible, 2) soil
restoration and sustainable management is crucial to achieving the sustainable
development goals, especially those with regard to zero hunger, climate action, and
life on land, 3) sustainable soil management is critical to reconciling the need for
advancing food and nutritional security with the absolute necessity of mitigating the
climate change and improving the environment, and 4) health of the planet and
future of the humanity are intricately interconnected with the judicious use of the
finite but essential soil resources.

Columbus, OH, USA Rattan Lal

Rome, Italy Rosa Francaviglia
Contents

1 Environmental Microbial Health Under Changing Climates:

State, Implication and Initiatives for High-Performance Soils . . . . . . 1
Bhabananda Biswas, Ramkrishna Nirola, Jayanta Kumar Biswas,
Lily Pereg, Ian R. Willett and Ravi Naidu
2 Deep Carbon Sequestration in Cropping Systems . . . . . . . . . . . . . . . 33
Francesco Morari, Antonio Berti, Nicola Dal Ferro and Ilaria Piccoli
3 Organic Matter Management in Cereals Based System:
Symbiosis for Improving Crop Productivity and Soil Health . . . . . . 67
Amanullah, Shah Khalid, Imran, Hamdan Ali Khan, Muhammad Arif,
Abdel Rahman Altawaha, Muhammad Adnan, Shah Fahad
and Brajendra Parmar
4 Impact of Mineral P Fertilization on Trace Elements
in Cropland Soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
Heide Spiegel, Andreas Baumgarten, Georg Dersch, Erwin Pfundtner
and Taru Sandén
5 Remote Sensing and Sustainable Management of SOC
in the Sahelian Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111
Macoumba Loum, Alioune Badara Dieye, Mar Ndiaye,
François Mendy, Samba Sow and Pape Nekhou Diagne
6 Building Resilience Against Drought and Floods:
The Soil-Water Management Perspective . . . . . . . . . . . . . . . . . . . . . 125
Wim Cornelis, Geofrey Waweru and Tesfay Araya

Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143

ix
Chapter 1
Environmental Microbial Health Under
Changing Climates: State, Implication
and Initiatives for High-Performance
Soils

Bhabananda Biswas, Ramkrishna Nirola, Jayanta Kumar Biswas,

Lily Pereg, Ian R. Willett and Ravi Naidu

Abstract Soil fertility and its productivity are the two pillars for maintaining agri-
cultural output and it is a measure of soil performance. Growing concerns about
climate change have recently focused on the fate of high-performance soils. Soil
biological health is an important aspect of agricultural productivity and a global

Author deceased in January 2019. Professor Lily Pereg was expert in soil microbial ecology with
long-standing experience. We have lost a very active scientist in this field. All co-authors extend
the deepest condolence to family, friends and colleagues of Prof Pereg.

B. Biswas (B)
Future Industries Institute, University of South Australia, Mawson Lakes,
SA 5095, Australia
e-mail: Bhaba.Biswas@unisa.edu.au
B. Biswas · R. Naidu (B)
Cooperative Research Centre for Contamination Assessment and Remediation of the
Environment (CRC CARE), The University of Newcastle, ATC Building, Callaghan,
NSW 2308, Australia
e-mail: Ravi.Naidu@newcastle.edu.au
R. Nirola
Cooperative Research Centre for Contamination Assessment and Remediation of the Environment
(CRC CARE), Mawson Lakes campus of University of South Australia, Mawson Lakes,
SA 5095, Australia
J. K. Biswas
Department of Ecological Studies and International Centre for Ecological Engineering,
University of Kalyani, Kalyani, Nadia 741235, West Bengal, India
L. Pereg
School of Science and Technology, University of New England, Armidale,
NSW 2351, Australia
I. R. Willett
Department of Food and Agriculture, The University of Melbourne, Parkville,
VIC 3010, Australia
R. Naidu
Global Centre for Environmental Remediation (GCER), The University of Newcastle, ATC
Building, Callaghan, NSW 2308, Australia

© Springer Nature Switzerland AG 2019 1

R. Lal and R. Francaviglia (eds.), Sustainable Agriculture Reviews 29, Sustainable
Agriculture Reviews 29, https://doi.org/10.1007/978-3-030-26265-5_1
2 B. Biswas et al.

concern due to its vulnerability to climate change impacts. We reviewed the cur-
rent knowledge on soil health related to organic carbon and biological resources,
particularly microorganisms and their effects on potential agricultural productivity.
We critically reviewed the challenges associated with changing climate and outlined
emerging technologies to help maintain high-performance soils. Our main finding is
the adverse impact of climate change on soil microbiota resulting in less than optimal
soil functionality. Alteration of bacterial community composition and fungal coloni-
sation patterns in the rhizosphere and soil-root interface cause suboptimal nutrient
availability for plant growth. Several green and climatically benign soil amendments
can be implemented to obtain high-performance soils under extreme climatic condi-
tions. Minerals and rocks, such as clay mineral, zeolite, mineral formulation, organic
and biological inoculation could be helpful to maintain or enhance soil fertility par-
ticularly in the event of soil warming and drought. Besides the traditional postulates
on climate changes, we uncover further challenges such as chemical pollutants in the
environment and important research areas to improve our understandings on climate
change-driven soil productivity. The remedy to this is to probably adopt green and
efficient technologies to enhance the soil productivity over limited non-renewable
agricultural landscape.

Keywords Soil biodiversity · Soil biological health · Soil microorganisms ·

High-performance soils · Soil productivity · Changing environments · Climate
change · Soil pollution · Soil amendments · Biocompatible materials

1.1 Introduction

Burgeoning population and ever-increasing demand for food production from finite
areas of agricultural land have led to an urgent need for sustaining and enhancing soil
productivity. Soil performance is crucial to crop and other agricultural production
(Reddy and Hodges 2000). Soils’ functions are dominated by the flow and transforma-
tion of mass, energy and genetic information in the Earth’s “critical zone” (Banwart
et al. 2017), and therefore significantly control the above and below-ground systems
of this zone. In the Anthropocene (the age with significant human impacts on the
environment), the critical soil zone, which is essential for increasing the production
of food, has been exposed to the consequences of global change (Richter and Mob-
ley 2009). Climatic changes, particularly extreme events including drought, heavy
rainfall and global warming can affect soil quality. For example, based on the current
climate-driven impact model, it is estimated that the agricultural production of key
commodities including wheat, sugar and cattle in Australia would decline 9–10%
by 2030 and is likely to further decline to 13–19% by the middle of this century
(Gunasekera et al. 2007), and the recent analysis of food security also raised similar
concern (Turner et al. 2018). Another report also estimated that approximately one-
tenth of the expected Canadian cereal production would be lost due to water scarcity
and warming conditions over the four decades between 1964 and 2007 (Lesk et al.
2016). Climate change is expected to be followed by changes in water availability
1 Environmental Microbial Health Under Changing Climates … 3

and soil organic carbon (SOC) content (Kang et al. 2009; Doetterl et al. 2015). At
a global scale, soil is the third largest repository of organic carbon and the effects
of climate change will have impacts on organic matter (OM) dynamics, strongly
influencing carbon (C) storage as well as impacting crop production (Lehmann and
Kleber 2015). Biological processes in the soil are key players in determining soil
structure and function, including cycling of nutrients (Brevik et al. 2015). Therefore,
crop nutrition depends on the biological health of soil where moisture and OM prop-
erties of soil influence the biotic health. There is compelling evidence that climate
changes alter soil biodiversity and functions (Allen et al. 2011; Bellard et al. 2012).
Some regions of the world, such as Syria are already is suffering from inadequate
food production related to extreme climatic episodes (Kelley et al. 2015). The con-
cept of ‘high-performance soil’ has recently emerged due to research on the potential
stressors of soil functions, which aimed at developing technologies for improving
soil fertility and maintaining crop and animal production per unit area of land (Soil-
CRC 2017). Here we review the roles of microbiological components in maintaining
soil productivity and how their functions are being impacted by climate change. We
conclude with suggestions on technologies and management practices to increase
soil performance for supporting crop production.

1.2 Soil Biological Fertility and Soil Health

Soil health depends on physical such as texture, aggregation, porosity, chemical

such as pH, cation exchange capacity, soluble salts and biological such as fauna,
flora and microorganisms factors that are interrelated (Fig. 22.1). We will focus on
‘soil biological fertility’ which was described as “the capacity of organisms living in

Fig. 22.1 A schematic presentation of soil health in agricultural productivity (OM = organic
matter). Sustainable agriculture is the outcome of economic sustainability, social variability and
environmental quality whereas soil quality is an integrated part of environmental quality. Biological
factors such as microbial health, diversity and biomass are one of the key elements attributed to
maintaining soil quality. The scheme has been modified based on Anonymous (2011)
4 B. Biswas et al.

soil (microorganisms, fauna and roots) to contribute to the nutritional requirements

of plants and foraging animals for productivity, reproduction and quality (considered
in terms of human and animal wellbeing) while maintaining biological processes that
contribute positively to the physical and chemical state of soil” (Abbott and Murphy
2007). As presented in Fig. 22.1, the biological components of soil contribute to soil
quality, which ultimately promotes sustainable and large crop yields and biological
factors are greatly influenced by OM, pedoturbation and biodiversity (Riches et al.
2013; Pulleman et al. 2012; Wolters 2001).
Soil organic matter (SOM) is a key soil component derived from living and dead
flora and fauna and is essential for the growth of plants (Bot and Benites 2005).
SOM influences physical properties such as bulk density and aggregate stability,
and the retention of water (Arthur et al. 2013). It significantly contributes to ion
exchange in soil and influences pH and nutrient buffering capacity (Willett 1994). The
decomposition of OM releases various forms of nutrients such as N, P, S depending
on its nature, quantity and quality, making them available to plants (Dungait et al.
2012; Powlson et al. 2011; Sarkar et al. 2016). Soil health can be impaired if its
OM content is depleted. Some reports suggest that levels lower than 2% as SOC
or 3.4% as SOM limit the fertility of agricultural soils (Lal 2004; Greenland et al.
1975; Loveland and Webb 2003). However, Lehmann and Kleber (2015) suggested
that the role of OM in agricultural productivity is related more to the continuum
of its decomposition products than to the stock of OM in the soils. Therefore, soil
biodiversity is crucial for the functioning of soils. For example, soil (micro)organisms
contribute to biomass and decomposition of OM, play an important role in nutrient
cycling and involve in a cross-layer mobilization of soil particles; such process by
earthworm, arthropods and nematodes is known as pedoturbation. Furthermore, the
soil biodiversity maintains a dynamic food web in soil, which ultimately provides a
variety of ecosystem services (Wolters 2001; Ferris and Tuomisto 2015; Pulleman
et al. 2012; Brevik et al. 2018).
A detailed description of the services provided by soil biodiversity was presented
by Turbé et al. (2010). Microorganisms, especially bacteria and fungi, are the dom-
inant biota in soils and can have a great contribution to agricultural ‘bioeconomy’
(Rengalakshmi et al. 2018). As a general estimation, 1 g of agricultural soil contains
1 billion bacterial cells of 10,000 different genomes (Torsvik et al. 2002), and they
constitute 3–5% of the total organic carbon in the soil (Turbé et al. 2010). In the
rhizosphere, the most abundant soil-root-microorganism microhabitat, microbes can
be manipulated to increase soil quality (Chaparro et al. 2012). The flow from OM
to plants via soil microorganisms is depicted in Fig. 22.2, showing the conversion
of organic macromolecules into available plant essential nutrients. It is important to
note that abundance alone may not ensure soil function, since some species may not
be active in the soil under a certain condition (Wolters 2001). Therefore, increased
microbial diversity with a variety of microbes capable of a specific function may
better facilitate soil fertility.
1 Environmental Microbial Health Under Changing Climates … 5

Fig. 22.2 Simplified schematic of the microbial role in the nutrient release from OM through
mineralization, making them available to plants in soils. N, S, P represent nutrients in the form of
nitrogen, sulphur, phosphorus, respectively.

1.3 Soil Performance and Climate Changes

1.3.1 Impacts of Climate Changes on Soil Microbial

Diversity and Abundance

Climate change is largely driven by global warming due to the accumulation of CO2
in the atmosphere, leading to regional changes in the intensity and frequency of
rainfall and increasing extreme events such as floods and droughts.
The soil microbial activities, such as microbial respiration responds positively
to soil warming. In the climate change model, the temperature quotient Q10 , which
means an approximate double rate of respiration for every 10 °C increase, is often
used. Based on such model, recent studies argued that at a fixed Q10 of 2, a tem-
perature increase of 2–2.6 °C should directly increase the respiration rates of soil
microorganism by 15–20% (Luo et al. 2001). However, soil microbial respiration
pattern linked to increased temperature cannot be generalised due to the limitations
of long-term studies at field scale on various soil systems (Classen et al. 2015).
Studying the temperate forest soil for 2 years, Hicks Pries et al. (2017) reported that
6 B. Biswas et al.

soil warming by +4 °C could increase soil respiration by 34–37% mainly due to the
decomposition of decadal-aged carbon in 0–100 cm depth. On the other hand, under-
taking a year-long study on tall grass Prairie ecosystem, Luo et al. (2001) reported
that soil respiration did not change significantly rather an acclimatisation trend was
observed. The underlying functions in such microbial feedback could lead to changes
in their diversity and abundance (de Vries et al. 2018). For example, it was reported
that the abundances of ammonia-oxidizing bacteria (0.32–8.71 × 107 copies of amoA
gene per gram soil) and archaea (0.66–6.31 × 104 copies of amoA gene per gram soil)
were not impacted by the addition of fertilizers in either warming or non-warming
conditions. The authors concluded that the interaction of fertilizers and warming
conditions reduced the abundance of ammonia oxidizing bacteria in temperate soils
(Long et al. 2012). In the case of community composition, the ammonia oxidizing
genes were affected more under fertilizers than the warming condition (Long et al.
2012). Hence, a high number of Nitrosospira group present in fertilizer treatments
made that difference while only one or two clones of this group were apparent in the
warming treatments.
Changes in water availability also directly impact microbial activity. Evans and
Wallenstein (2014) modelled the impacts of 10 years’ climate change regime, with
heavy rainfall and long droughts, and concluded that soil bacteria changed their eco-
logical strategies, that is the individuals’ fitness for survival and adaptation to the
drying-rewetting regime. Using metagenomics techniques (16S rRNA gene sequenc-
ing) the authors predicted that the adaptation of these bacteria to climate change sce-
nario was due to DNA mutations. However, de Vries et al. (2018) claimed that the
soil bacterial resilience might be weak in a long-term drought. Using rain-out plots
with transparent polythene cover, the drought condition was simulated in a grassland,
UK, reporting that long-term drought—a 100 years simulated period—destabilized
the bacterial co-occurrence networks (de Vries et al. 2018). As reported in this study,
fungal communities were more resilient to the prolonged drought. However, alterna-
tion in bacterial composition, particularly in the relative abundance of denitrification
and nitrous oxide reduction genes were reported and that might pose a long-lasting
impact on soil bacterial community (de Vries et al. 2018). As such, changes in soil
water (i.e., abiotic) potential (−0.2 to −0.34 MPa) altered microbial communities
(i.e., biotic) showing significant relationships between these abiotic and biotic com-
ponents in soils (Bouskill et al. 2016). Cregger et al. (2012) found that the timings
of monsoon rainfall also changed the soil microbial communities in pinyon-juniper
woodland. Fungal abundance, in particular, has increased by as much as 4.7 times
during monsoon rainfall than during the dry period. The shortage of fungal communi-
ties in the event of drought can affect carbon degradation in soil (Cregger et al. 2012).
Changing organic carbon concentrations is another impact of climate change on soil
microbiology (Doetterl et al. 2015). Repetitive and prolonged drought conditions
might alter the microbial community towards greater production of the extracellular
enzyme that could harness organic carbon from the soil (Bouskill et al. 2016). In this
way, some soil bacterial communities change their functional composition due to
controlled intermittent drying-rewetting patterns as the organisms gradually develop
tolerance traits for effective adaptations (Evans and Wallenstein 2014). As a result,
1 Environmental Microbial Health Under Changing Climates … 7

the soil bacterial community implies a survival life strategy of mutation, and one
of the species was of special interest and prominently studied to uncover the bacte-
rial property to understand these environmental conditions (Evans and Wallenstein
2014). With the rhizosphere being a prominent niche in the soil and a centre for
microbial-plant interactions, microbial functional changes might impact plant pro-
ductivity during the period of such brief mutations (Naylor and Coleman-Derr 2018
and Barnard et al. 2014).

1.3.2 Impact of Climate Change on Rhizospheres

The rhizosphere is the zone of soil surrounding plant roots, and it has the important
role in nutrient cycling in terrestrial ecosystems through plant-microbial interactions
(Bhaduri et al. 2015; Toal et al. 2000). Various rhizospheric microbes are engaged in
beneficial activities, such as increasing the organic carbon pool, minimizing green-
house gas emissions, enhancing plant growth, inducing disease resistance and reme-
diating contaminated land (Dubey et al. 2016; Estruch et al. 2017). In a laboratory
simulation of the decomposition of SOM, it was found that increasing the tempera-
ture by the extent predicted for climate change caused genetic mutations in bacteria
(Zogg et al. 1997). The other global greenhouse and climate change impacts, such as
sea level rise, timings of seasons and rainfall patterns, not only affect the aboveground
community but also the rhizosphere communities (Drigo et al. 2017; Compant et al.
2010; Philippot et al. 2013). Figure 22.3 presents two plausible scenarios of the
effects of three major climate stresses: (i) warming and drought, and (ii) elevated
CO2 (Compant et al. 2010). Plant-growth-promoting fungi (PGPF), such as arbuscu-
lar mycorrhizal fungi (AMF), ectomycorrhizal fungi (ECM), endophytic fungi and
plant-growth-promoting bacteria (PGPB) are major microbial groups that respond to
those climatic stresses. Details of the potential mechanisms are reviewed by Compant
et al. (2010). In brief, the belowground alteration could be (i) carbon allocation, and
(ii) plant exudation patterns. These changes further induce an alteration in the com-
munity composition of fungi and bacteria in the plant root environment (Fig. 22.3). In
the altered community structure, microorganisms might encounter new competition
in the rhizosphere leading to new colonization patterns (Compant et al. 2010).
Soil respiration and rhizosphere respiration are two factors that can be studied in
relation to a climate change while the latter entails more for the crop productivity
(Toal et al. 2000). Warming and precipitation treatments increase the rhizosphere
respiration rates, possibly leading to unexpected plant biomass growth and changes
in carbon cycling (Suseela and Dukes 2013). Plants release organic compounds such
as proline on the foliar zone as a result of stress due to heat and soil toxicity that
hampers carbon cycling (Nirola et al. 2016a; Suseela and Dukes 2013). The stress
hormones are also released from roots as a result of microbial carbon mineralization
where the exudates help to decompose native soil carbon by microbes (Keiluweit
et al. 2015).
8 B. Biswas et al.

Fig. 22.3 The effects of climate changes associated with elevated CO2 , warming and drought
events on the plant-microbial interactions in the rhizosphere. PGPF = plant-growth promoting
fungi; PGPB = plant-growth-promoting bacteria. In such cases, scenario 1: warming and drought-
induced PGPF and PGPB in response to the plant’s stress and adaptation, and for elevated CO2
(scenario 2), an increased amount of C and root biomass change the PGPF and PGPB community.
Such changes in microbial community living in rhizosphere may lead to the change in the plant
community and their physiology. The scheme is based on Compant et al. (2010) with permission
of Oxford Academic (2010)

Soil physicochemical properties may also be influenced by changed rainfall pat-

tern as a result of global warming and climate change. Reduced rainfall might lead to
enhanced rhizosphere acidification due to a higher concentration of exchangeable K
and HO3 + in the rhizosphere compared to the bulk soil (Pradier et al. 2017). Nuccio
et al. (2016) reported that rhizosphere communities were mostly affected by regional
climate conditions, such as moisture and temperature, while the background soil com-
munities were influenced mainly by the soil physicochemical properties, such as pH,
EC, cation exchange capacity and clay minerals. These authors argued that grassroots
may support rare populations of soil microbes as a possible trade-off to avoid the
competitiveness in their rhizosphere. According to a result of a four-year controlled
field study on soils specific to different plants, Kardol et al. (2010) stressed that the
ecosystem functioning of habitat should be strongly controlled by the rhizosphere
ecosystem. The current information, based mostly on controlled experiments may
not be fully conclusive for predicting the impacts of climate change on microbial
functions in rhizospheres. Nevertheless, it is clear that vegetation and other primary
producers of carbon are affected by nutrient composition and availability in response
to climate change, representing indirect consequences of climate change on soil
quality (Classen et al. 2015).
1 Environmental Microbial Health Under Changing Climates … 9

1.3.3 Impact of Changing Climate on Soil Biological Fertility

In general, soil fertility and agricultural productivity are vulnerable to changing cli-
matic conditions (St.Clair and Lynch 2010). This vulnerability is more prominent
in developing countries due to their limited resources and poor capacity to adapt to
changing climates (Thornton et al. 2018). The impact of the increase of greenhouse
gases could alter the microbial communities and their functions and that might affect
the microbial feedback of the C inputs on photosynthesis and respiration hampering
the agricultural crop plant physiological balance (Hoyle et al. 2011). However, in
terms of soil biological fertility, there is a knowledge gap on the direct effects cli-
mate change has on specific microbial groups, or whether specific types of crops,
if any, have been impacted due to changes in particular microbial communities.
Microorganisms in soil that influence decomposition of OM, the type and its accu-
mulation eventually influence the nutrient release from OM as one of the attributes
of climate change (Schmidt et al. 2011). Also, a survey of soil crust microbial com-
munities across arid North America predicted that an increase in temperature by a
few degrees would have impact on soil fertility due to the replacement of one species
of cyanobacteria (Microcoleus vaginatus) with another (M. steenstrupii), though the
exact consequences are unknown (Garcia-Pichel et al. 2013). Table 22.1 summarizes
some predicted scenarios where the global climatic conditions might influence the
microbial contribution to soil fertility and crop productivity. Reportedly elevated
N levels in soil, due to greenhouse effects, suppresses soil microbial activities by
shifting the metabolic potential of soil bacterial communities to render effective
soil nitrogen cycle (Liu and Greaver 2010; Ramirez et al. 2012; Singh et al. 2010).
For example, the addition of excess N might reduce the diversity of oligotrophic
bacteria, which are slow-growing and dominant in nutrient-limited habitats. These
species include Acidobacteria, Verrucomicrobia, Cyanobacteria, Planctomycetes,
and Deltaproteobacteria. The bacterial species dominant in nutrient-rich habitats
known as copiotrophs are fast growing in labile C rich environments and are repre-
sented by Actinobacteria and Firmicutes. Such microbial changes affect the release
of nutrients from SOM and therefore their availability to plants. Microbial enzymes
responsible for degrading complex C compounds are also highly sensitive to high
N in various soil systems (Sinsabaugh et al. 2005; Waldrop and Zak 2006). It was
reported that the response of soil oxidative enzyme was directly related to the input
of atmospheric NOx leading to a 20% reduction in C in a sugar-maple-basswood
ecosystem, but a 10% gain in black oak-white oak and sugar maple-red oak ecosys-
tems (Waldrop and Zak 2006).
Climate change-induced soil erosion is also a potential hazard for the biological
fertility of agricultural land (Hoyle et al. 2011). This is mainly due to the loss of
surface soil that contained a significantly higher amount of SOC than the deeper
layers. Relatively higher frequency and intensity of storms are manifestations of the
current climate change as reported by Climate Council Australia Ltd. (Steffen et al.
2017). This could lead to a significant loss of surface soil (70–300 t ha−1 ) while the
Table 22.1 The impacts of climatic stress on microorganism that potentially influence soil productivity
10

Microorganism/microbial Role in soil fertility Climatic conditions Impact References

products
Arbuscular mycorrhizal P transfer from fungi to Warming and elevated CO2 Prediction of various Evidence reviewed by Fitter
fungi plants and C transfer from impacts on crop et al. (2000)
plant to fungi productivity: neutral,
positive and negative.
However, changes in fungal
communities might affect
the plant-fungal interaction
Ericoid mycorrhizal fungi; Symbiosis in roots and Warming (+1 °C) for 3 years Fungal colonization Binet et al. (2017)
dark septate endophytes produce and release in temperate region increased (+3%), however,
phenoloxidase enzyme; this enzymatic activities
enzyme facilitates decreased (−50%)
decomposition of
recalcitrant organic
compounds and mobilizes
nitrogen for the plants
Microbial consortia Decomposition of organic Soil warming Microbial community Zogg et al. (1997)
targeting Phospholipid fatty matter in soil altered; C pool increased;
acid and Lipopolysaccharide however, any adverse impact
fatty acid on soil productivity is
inconclusive
Ammonia-oxidizing bacteria Nitrification in soil Elevated temperature along The combined climate Horz et al. (2004)
with heavy precipitation change parameters had a net
negative effect on the
abundance of
ammonia-oxidizing bacteria
(continued)
B. Biswas et al.
Table 22.1 (continued)
Microorganism/microbial Role in soil fertility Climatic conditions Impact References
products
Microarthropod Decomposition of OM and Elevated N Reduction in richness and Eisenhauer et al. (2012)
nutrient cycling potential alteration of soil
food web
Soil urease; ß-glucosidase; C and N mineralization for a Prolonged warming Warming increased soil Sardans et al. (2008)
protease mid and long term in enzyme activity; however it
Mediterranean Shrublands decreased C:N ratio due to
the microbial synthesis of
enzymes; also higher
availability of NO3 − caused
by these enzymatic activities
leads net N loss due to
heavy rainfall in the
Mediterranean region
Prolonged drought Drought decreased protease
activity; higher C:N ratio
was also observed in plant
biomass
1 Environmental Microbial Health Under Changing Climates …

Bacterial and fungal Rhizosphere health Prolonged drought Destabilization of bacterial de Vries et al. (2018)
communities co-occurring networks;
alteration of denitrification
and nitrous oxide reducing
bacterial genes; fungal
community may resilience
to the drought
11
12 B. Biswas et al.

typical loss has been reported as 60–80 t ha−1 for bare fallow, 8 t ha−1 under a crop
and 0.24 t ha−1 under pasture in a given year (Hoyle et al. 2011).
Empirical and model-based research concluded that not all of the climatic con-
ditions associated with climate change impose negative impacts on crop growth in
agricultural land. Jakobsen et al. (2016) argued that an increase in plant growth may
occur due to elevated atmospheric CO2 concentrations, leading to enhanced P suffi-
ciency, in two contrasting species (Brachypodium distachyon, a grass and Medicago
truncatula, a legume species). However, elevated CO2 might impact on the mycor-
rhizal association in plants leading to impact on C–P trade balance and eventually
reducing crop yield [see reviews by Fitter et al. (2000) and Cotton et al. (2015)].

1.4 Maintaining High-Performance Soil Health

in Changing Climates

1.4.1 Soil Microbial Health Assessment

Biomass and metabolic activity of the soil microorganisms are direct indicators of
soil health (Ferris and Tuomisto 2015). Microbial responses to increased temperature
might be effective on decaying recalcitrant OM compounds; shifting of microbial
community might bring such efficient functions (Frey et al. 2013). On the other hand,
effects of increasing temperature would be the changes in the microbial community
with associated impact, such as a decrease in biomass and enzyme activities in the
terrestrial habitat (Waldrop and Firestone 2006; Rinnan et al. 2007). Although such
discrepancy exists in the literature regarding microbial feedbacks to climate change
(Singh et al. 2010; Kirschbaum 2006), the last decade has seen the development of
cutting-edge technologies to assess the microbial profiles, including their historical
and forecasted functions (Singh et al. 2010) that has been contributing to devise soil
microbial health assessment. For example, the omics tools in the field of geomi-
crobiology and microbial geochemistry have been highly efficient technologies to
measure microbial activities in soil (Druschel and Kappler 2015). The omics tech-
nologies include molecular tools to assess microbial diversity and function, using
DNA- (genomics) or protein- (proteomics)-based analyses. Other tools are avail-
able to trace alterations in microbial activities in soil and other agricultural sites in
response to changing climate; these are:
(i) Stable isotope probes for the identification of active cells in the microbial
community (Nealson 2015);
(ii) Redox-sensor staining and fluorescence microscopy of cells to distinguish
metabolically active cells from dormant cells in the microbial community
(Crawford et al. 2002; Singer et al. 2017);
(iii) Nanoscale secondary ion mass spectrometry (Nano-SIMS) for the analysis of
single cell activities (Nealson 2015);
1 Environmental Microbial Health Under Changing Climates … 13

(iv) Synchrotron technology for imaging the metabolic activities of microbial cells
(Nealson 2015).
Using such advanced technologies, the soil can be assessed for the immediate
productivity and predictions can be made for its future performance related to the
microbial functions. This will facilitate soil amendment techniques to improve soil
performance.

1.4.2 Soil Amendments with ‘Green’ Inorganic Materials

Several natural minerals and biocompatible inorganic supplements enhance nutrient

pools in soil and thus influence soil biota and their ecosystem (Fig. 22.4). P-minerals,
gypsum, ash, lime, clay minerals, diatomaceous earth and zeolite products have
been promoted as cost-effective, and environmentally sustainable inorganic supple-
ments for improving soil biological health (Ramesh and Reddy 2011; Fischer and
Glaser 2012; Acosta-Martínez and Tabatabai 2000). Soil conditioning using gypsum
(i.e., calcium sulphate) may not directly support microbial activity. However, it can
improve the physical conditions of several soil types, ranging from highly weath-
ered acid soils to low salinity, high sodium, soils of semiarid regions, by providing
enough cations and anions electrolytes to promote flocculation and inhibit dispersion
of aggregates and surface crusting (Qadir et al. 2007). By the addition of Ca-mineral
in soil in the form of CaSiO3 , Sridevi et al. (2012) reported that microbial composi-
tion changed by 23% in organic soil of 5 cm horizon and 22% in mineral soil of 10 cm
horizon. In this process, the abundance of methane-oxidizing bacteria decreased but
the relative abundance of ammonia-oxidizing bacteria increased in the mineral soil
and decreased in the upper horizon (i.e., organic soil). Although this report (Sridevi
et al. 2012) did not include the state of soil productivity, the shift of methane and
ammonia-oxidizing bacteria could be central interest in the soil amendment strategies
in the climate change aspect.
Clay minerals, such as smectite, can improve sandy soil by promoting cation
exchange and water holding capacity due to their high adsorption sites and swelling
properties. Furthermore, clay incorporation into organic substrates, initiated by the
biological activity of soil fauna, could promote the creation of organo-mineral com-
plexes, such as humic-clays which improve soil productivity (Sulman et al. 2014).
Soil organic matter is stabilized by interactions with soil minerals (Glaser et al.
2003). Soils of semi-arid areas are characterized by poor structure, impoverished
quality and OM deficiency and are susceptible to external stresses, particularly ero-
sion, poor water holding capacity and water repellence (Hobley et al. 2018; Van Gool
2018). The productivity of soils in semi-arid areas is compounded by water repel-
lence arising from waxy organic compounds coating soil particles (Müller and Deurer
2011). These soils can be amended with clay as a management strategy to mitigate
water repellence, reduce nutrient leaching (Betti et al. 2015; Roper et al. 2015), and
14 B. Biswas et al.

Fig. 22.4 Conceptual scheme of chemical (inorganic and organic) and biological amendments
for maintenance and improvement of soil health. Plant growth can be improved by the increasing
nutrient pool. These nutrient pools can be enriched by the supplement of inorganic and organic
additives, such as minerals fertilizers and organic matter-rich compounds (e.g., manure). These
supplements can also enhance the growth of plant-growth-promoting microorganism. On the other
hand, direct addition of rhizospheric microbiota can improve soil health, promote plant growth and
function. The scheme was depicted based on DeJong et al. (2010) and Fischer and Glaser (2012)
with permission of Elsevier (2010) and IntechOpen (2012)

additionally can improve soil water holding capacity, microbial biomass, pH and
CEC (Müller and Deurer 2011).
Zeolite, a common and abundant sedimentary rock mineral has been used sev-
eral decades in agricultural soils due to its high capacity in (i) nitrogen and mois-
ture retention, (ii) control release of nutrients and fertilizers, (iii) pH balance
and many other soil benefits (Ramesh and Reddy 2011). In the case of micro-
bial health in response to zeolite, supplementing agricultural soil was found to be
non-toxic, and microbes responded in different ways (Ramesh and Reddy 2011).
1 Environmental Microbial Health Under Changing Climates … 15

Using two different zeolite supplements, namely chabazite-rich natural zeolite and
NH4 + -enriched chabazite zeolite in the sandy soil, Ferretti et al. (2018) reported that
natural zeolite (loading rate: 5% in soil) increased fungal biomass but not when the
loading rate was increased to 15%. This high amount of such adsorbents (e.g., zeo-
lite) might reduce the nutrient availability to the microorganisms for a short-term
(16 days) (Ferretti et al. 2018). On the other hand, the NH4 + -modified zeolite imme-
diately increases the total microbial biomass due to the instant increase of available
N in the soil (Ferretti et al. 2018).
Ash and urine amendments supply nutrients to soils and can enhance microbial
activity (Glaser and Birk 2012). Studying forest acidic soil in Jutland, Denmark,
Cruz-Paredes et al. (2017) reported that the wood-ash supplement dosing 3–90 t ha−1
in a relatively smaller plot of 2 m × 2 m increased bacterial biomass but decreased
fungal biomass with a net increase of soil respiration. In this case, an increase of
soil pH and addition of cadmium from the ash supplement might have influenced
the microbial community structure although Cruz-Paredes et al. (2017) argued that
up to 90 t ha−1 of wood-ash did not reduce the overall decomposer functioning.
Similarly, in the case of N enrichment using such “green” amendments, care should
be taken since they can influence microbial diversity and abundance and microbe-
mediated C turnover (Ramirez et al. 2012), and therefore the duration and quantum
of N supplements is critically important to the C:N of soils (Ramirez et al. 2012;
Janssens et al. 2010; Treseder 2008).

1.4.3 Soil Improvement with Organic Amendments

Organic amendments influence soil microbiology and health in various ways, many
of them seem to contribute to environmental sustainability (examples given in
Table 22.2). Application of vermicompost, which enhances water retention and
water-stable aggregates in soil, lead to an increase in microbial activity (Ferreras
et al. 2006). Such composts can be produced from household solid waste, animal
dung and chicken manure. Several other strategies such as biochar (Sadeghi et al.
2016), sawdust and wood ash, municipal sewage and sludge, animal manures, crop
and organic composts, other organic residues (Sadeghi et al. 2015; Chen et al. 2017),
oil mulches and biodegradable polymers (Awad et al. 2012) have been used to amend
soil physicochemical and biological properties. The impacts on the land restoration
by these organic amendments have been highly effective (Beesley et al. 2010).
The soils in semi-arid and arid regions are usually very infertile due to the lack
of organic matter, scant vegetation and slow microbial activity (Nirola et al. 2016b).
The changing climate is adding more stress to these ecosystems. In a study of soils
in semi-arid climates, Ros et al. (2003) reported that the use of urban organic amend-
ments increased soil microbial activity resulting in increased microbial biomass and
basal respiration. Likewise, the addition of urban composts resulted in better soil
aggregate stability than farmyard manure in terms of increases in organic carbon
content and increased resistance to water erosion (Annabi et al. 2011). However,
Table 22.2 Organic supplements for the improvement of soil fertility
16

Organic amendment Dose Target benefit Possible mechanisms for soil References
improvement and climatic
consequence
(An)aerobically digested 160 Mg ha−1 Higher soil respiration in All treatments increased SOC; González-Ubierna et al. (2012)
sewage sludge; Municipal solid dry-wt basis calcareous Mediterranean soils however, digested sewage
waste compost sludge supplied more labile
organic carbon than municipal
waste; aerobically digested
sewage sludge released more
greenhouse gas (CO2 )
Urban refuse/organic wastes on Various (up to More diverse Glomus group of Benefitted on application to a del Mar Alguacil et al. (2009)
highly eroded 19 years old 26.0 kg m−2 ) Arbuscular mycorrhizal fungal highly eroded Mediterranean
semiarid soil community, particularly with semi-arid soil. Likelihood of the
urban refuse at a dose of erosion to continue due to
13 kg m−2 global warming
Poultry litter with alum to Litter at More forage yield with Application in order to reduce Shreve et al. (1995)
determine forage yield 11.2 Mg ha−1 alum-amended litter at solubility of phosphate mineral
in combination 2358 Mg ha−1 compared to in the presence of rainfall
with alum mean yield of 1847 Mg ha−1 simulators. The rainfall change
pattern was impacted by climate
change
Bio-manures on sugarcane soil Press mud bio Higher yield of millable Press mud 0.5% with natural Singh et al. (2007)
physicochemical and microbial amendment (N sugarcane soil treatment that brings
properties in plant-ratoon = 150, P = 60 hormonal change-triggering
system and K = growth. A possible solution to
60 kg ha−1 ) keep the yield intact even in
presence of global warming
(continued)
B. Biswas et al.
Table 22.2 (continued)
Organic amendment Dose Target benefit Possible mechanisms for soil References
improvement and climatic
consequence
Municipal food waste compost Compost at 15, Improved soil physical property Compost added to two Iovieno et al. (2009)
and NPK fertilization 30 and 45 t and microbial activity including Mediterranean intensive
ha−1 and enzyme activity vegetable crops to preserve soil
mineral NPK at fertility. The climate change
15 t ha−1 impacts soil quality
Pine bark compost and cattle 0, 30 and 60 t Manure caused 10–50% A greenhouse experiment with Pérez-Esteban et al. (2014)
dung (horse and sheep manure) ha−1 of pine reduction of Cu and 40–80% mine soils supplemented with
bark compost accumulation of Cu in Brassica organic amendments. A solution
juncea for tackling revegetation failures
as a result of climate change
Grapevine pruning and sheep 20 Mg ha−1 Manure and leguminous mulch Mediterranean grapevine Pereg et al. (2018)
manure year−1 with improve soil chemical and production, field experiment
subsequent physical properties, as well as using organic amendments to
shallow biological N cycling potential. preserve the function of soil
ploughing or An increase in nosZ gene under facing degradation due to global
grapevine organic fertilization may warming and intense agriculture
pruning and suggest a greater abundance of
1 Environmental Microbial Health Under Changing Climates …

legume cover denitrifiers with the ability to

crop at a rate of reduce nitrous oxide to nitrogen
50 kg ha−1 gas, reducing greenhouse gas
year−1 emission
compared with
agrochemical
NPK 8/4/12 at
a rate of
250 kg ha−1
year−1
17
18 B. Biswas et al.

from a climate change perspective, the input of organic matter to agricultural soils
results in a paradox: the possibly enhanced agricultural productivity and soil quality
versus the environmental impacts of increased greenhouse gas emission (Paustian
et al. 2016). Agricultural practices with the intensive use of chemical fertilizer also
contribute to global warming. For example, an isotopic study by Park et al. (2012)
revealed that the intensive use of nitrogen-based fertilizers is responsible for N2 O
greenhouse gas production in Tasmania, Australia and Antarctica. In addition, a
meta-analysis of studies carried out between 1900 and 2016 by Ren et al. (2017)
revealed that overall the use of organic manure could reduce the emission of N2 O
and CH4 by 13 and 12%, respectively, but increase CO2 by 26% when compared
with chemical fertilizers. Other examples of the benefits of soil organic amendments
are presented in Table 22.2.

1.4.4 Biological Amelioration Through Augmentation

Soil physical and chemical properties, such as aggregate stability, bulk density, water
retention capacity, OM, C, and N are influenced by biological processes, such as soil
microbial growth and activity (Veum et al. 2014). Microbes, indigenous and those
introduced by augmentation, play roles in these properties and processes.
Soil microbes, particularly cyanobacteria and other bacteria, produce biological
soil crusts (BSCs) that can help conserve soil against wind and water-driven erosion in
semi-arid and arid conditions (Chamizo et al. 2012; Bowker et al. 2006). The process
of BSC biomineralization is initiated by establishing BSCs on soil surfaces (Valencia
et al. 2014; Zhao et al. 2014). This process is augmented by using effective inoculation
techniques to improve the physical, chemical, and biological properties of soils (Rossi
et al. 2015; Wang et al. 2009). Polysaccharides secreted by microorganisms help in
adhesion of soil particles by forming micro-networks of particles (Dorioz et al. 1993;
Kheirfam et al. 2017; Reynolds et al. 2001). This may facilitate regulating hydraulic
conductivity and increasing water retention capacity of soil (Colica et al. 2014;
Chamizo et al. 2012; Rossi and De Philippis 2015). Thus, BSC microbes modulate
soil biological and chemical properties and support soil ecosystem services, such
as nutrient cycling, C and N fixation, enhancing soil fertility (Kheirfam et al. 2017;
Sears and Prithiviraj 2012; Rashid et al. 2016; Wang et al. 2009; Rossi et al. 2015).
The relative abundance of gram-positive rhizosphere bacteria (e.g., Actinobacte-
ria) can be increased through the addition of compost, especially under water-stressed
and nutrient-scarce conditions (Lavecchia et al. 2015). Treating soil with compost,
under such adverse conditions, has triggered the sudden growth of otherwise slow-
growing gram-positive bacteria, which have outcompeted their gram-negative coun-
terparts (Manzoni et al. 2012). Therefore, examining the responses of soil bacteria
to various amendments can be a useful technique to predict functional changes of
soil bacteria and to restore microbial ecological balance (Chen et al. 2016; De Vries
and Shade 2013). The study of Drigo et al. (2017) suggests that there are certain
drought-resistant bacterial and archaeal communities that aid in ecosystem function-
1 Environmental Microbial Health Under Changing Climates … 19

ing. For example, at elevated atmospheric CO2 with the ambient plus 240 mg L−1
and low nutrient conditions, Verrucomicrobia, Armatimonadetes, Actinobacteria and
Deinococcus spp. could restore their populations and function in the rhizosphere
at significantly rapid rates following frequent wet-dry cycles (Drigo et al. 2017).
Genomic properties, especially plasmid-encoded qualities, could provide resistance
against adverse climatic conditions (Slade and Radman 2011).
Beneficial interactions between plants and microorganisms may involve free-
living or symbiotic rhizobacteria that promote plant growth through nitrogen fixation,
synthesis of siderophores, production of phytohormones (e.g., auxins and cytokinins)
and phosphorus solubilization (Burd et al. 2000; Bakker et al. 2010). Biofertilization
could be an attractive option for crop production and alternative or supplementary to
the use of chemical fertilizers, potentially minimizing the associated global warm-
ing effects (Fig. 22.4) (Miransari 2011). Isolation and augmentation of plant growth
promoting rhizobacterial consortia can also be practised in environmentally stressed
agricultural systems subject to climate change. For example, salt-tolerant, rhizo-
spheric bacterial inoculants may be exploited for the restoration of sites affected by
flood and salinity should the need arise (Kathiresan and Selvam 2006; Bledsoe and
Boopathy 2016).
The application of plant growth regulators like Indole Acetic Acid (IAA) can
play pivotal roles in cellular responses, such as photosynthesis, cell expansion, divi-
sion, differentiation, and growth of root and other parts of plants (Goswami et al.
2015; Biswas et al. 2017). The inoculation with IAA-producing bacteria, therefore,
increases root surface area and length and thereby helps plants get greater access to
soil nutrients and water (Patten and Glick 2002; Pereg and McMillan 2015). Several
other novel and promising opportunities for employing biological processes have
recently emerged to modify the properties of subsurface soils (e.g. strength, stiff-
ness, permeability) (Tecon and Or 2017). Subsurface soil constraints impact nearly
60% of the arable land in Australia and biological approaches could potentially be an
effective means of improving these soils. A bio-mediated soil improvement system
makes use of chemical reactions that are managed and controlled within soil through
biological activity and their by-products (Fig. 22.4). The native microbial population
is typically either stimulated (i.e., bio-stimulation) through the injection of nutrients
or augmented (i.e., bio-augmentation) by the introduction of additional microbes,
and these are some of the ways to improve soil qualities on a microscale to keep soil
fertility in face of global climate change (Gomez 2017).

1.4.5 Combination of Mineral, Organic and Biological

Amendments for Soil Health

Balanced use of organic and inorganic amendments for soil improvement is might
be useful as it increases the microbial biomass and soil enzymatic activities. For
example, it enhanced microbial biomass from 147 to 423 mg kg−1 and increased
20 B. Biswas et al.

urease and phosphatase activities while the soil was amended with the combination
of organic (e.g., wheat straw, farmyard or legume manure) and inorganic fertilizers
(e.g., N and P sources from urea and single superphosphate) (Goyal et al. 1999).
Both the sole-carbon-source utilization activity and the functional diversity of soil
microbial communities can be significantly enhanced by a balanced use of mineral
fertilizers (e.g., N, P, K) with organic amendments (Hu et al. 2011). Combination of
organic and synthetic amendments increased soil microbial activity, SOM and cation
exchange capacity and at the same time decreased pathogen populations (Bulluck
et al. 2002).
One of the critical contributors to global warming is N2 O emission, which is exac-
erbated by high rates of extraneous N input in agriculture (Robertson and Vitousek
2009). Since N2 O has no significant terrestrial sink, abatement is best achieved by
attenuating known sources of N2 O emissions, by altering the environmental factors
that affect N2 O production (e.g., soil N, O and C), or by biochemically inhibiting
conversion pathways using soil additives (Paustian et al. 2016). For example, nitrifi-
cation can be inhibited with synthetic additives such as nitrapyrin and dicyandiamide,
which slow ammonium oxidation so that N2 O flux can be reduced up to 40% in some
soils (Akiyama et al. 2010).
Anaerobic soil conditions with low redox potential (Eh) induce microbial
methanogenesis and emission of methane (CH4 ), a potent greenhouse gas. Main-
tenance of aerobic conditions minimizes the likelihood of CH4 emission. However,
aerobic conditions with high Eh promote nitrification, which is likely to produce N2 O,
yet another greenhouse gas. In a study of various intercontinental rice soils, Yu and
Patrick (2004) argued that a ‘window’ of optimal Eh (+180 to −150 mV) with mini-
mal production of greenhouse gases may be achieved by combined treatments of the
soil with natural minerals, organic matter-rich supplements and microbe-mediated
products. Kowshika et al. (2017) reported that the rich crop emitted less CH4 once the
soil was amended with fly ash or the combination of fly ash and silica-solubilizing
bacteria.
As shown in Fig. 22.4, agricultural productivity can be increased via a combi-
nation of chemical- and bio-engineering processes. In the case of bio-mediated soil
improvement, both the production of inorganic minerals through biomineralization
and the microbial mats (e.g., biofilms) could enhance the plant rhizosphere health
(Konhauser 2009; Swarnalakshmi et al. 2013). While rhizosphere health and plant-
microbial interactions are critically important for soil fertility (Yadav et al. 2015),
the rotation farming systems (e.g., mineral fertilizers vs. organic fertilizers; different
tillage regimes) also seem to improve the soil microbial abundance (Hartman et al.
2018). A recent bacterial atlas survey revealed that only 2% of bacterial taxa are
dominant in surface soils with a significantly higher number of rare bacterial phy-
lotypes (Delgado-Baquerizo et al. 2018). The combination of soil amendments and
crop rotation could maintain this ‘effective size’ of diverse microbial communities
and thus increase soil fertility (Hartman et al. 2018).
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