Chemical Innovation for Sustainable Agriculture by Investing in Soil Health

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doi:10.2533/chimia.2021.700 Chimia 75 (2021) 700–703 © Swiss Chemical Society
A Perspective on Chemistry and Society
A Column on the Occasion of the 75th Anniversary of CHIMIA
Syngenta Crop Protection AG
Chemical Innovation for Sustainable Agriculture by
Investing in Soil Health
Claudio Screpanti*
*Correspondence: Dr. C. Screpanti, E-mail: claudio.screpanti@syngenta.com
Soil Health Centre, Crop Protection Biology Research, Syngenta Crop Protection
Research Stein, Schaffhauserstrasse 101, CH-4332 Stein, Switzerland.
Claudio Screpanti is an agronomist
working in Syngenta R&D organization
in Switzerland. He has several years
of experience in agricultural research.
He obtained his PhD in agronomy
from the University of Bologna, Italy
in 2003. He carried out additional
studies in molecular biology and
genetic engineering at the University
of Louvain-la-Neuve, Belgium. Later, Claudio joined the
Syngenta R&D organization, covering different scientific roles
always in relation to soil biology. In 2018 he became a Syngenta
Fellow, a company award recognizing outstanding scientific
achievements. In his current role, Claudio leads the Soil Health
Centre in Stein (Switzerland) and acts as Syngenta soil expert
looking at the behavior and effects of new small molecules
in the soil-crop systems. The aim is to support the discovery
and development of new and more sustainable crop protection
solutions.
Agriculture and Current Challenges
There is an increasing urgency for a more resilient and
sustainable way to produce food, feed and fibers. Science
and technologies can play a pivotal role in these endeavors. A
broad array of new promising technologies is steeply growing
in the farming area spanning from precision agriculture
techniques, advanced modeling and predictive approaches to
optimize inputs, new crop breeding programs up to microbiome
harnessing to improve crop performance and resilience against
the major climatic and pest threats.[1,2]
Beside this technological panoply, there is an emergent trend
towards new and exciting opportunities to support sustainable
agriculture using chemical innovation. In the following
paragraphs, new perspectives on how chemistry can contribute
and support food production in the context of some of the major
challenges of this century will be presented.
Soil Health and Priorities for the Global Challenges
More than 95% of food comes from soil. However, there is an
increasing concern about the rapid degradation of soil resources.
New actionable programs have been put in place to preserve this
non-renewable resource.[3] Soil health, as an emerging concept,
has gained increasing attention in several scientific, social, and
political areas in recent years. Soil health can be defined as “the
capacity of a living soil to function, within natural or managed
ecosystem boundaries, to sustain plant and animal productivity,
maintain or enhance water and air quality, and promote plant
and animal health”.[4] New policies aiming at preserving soil
were promoted in several geographies like Switzerland, EU and
beyond.[5–7]
Using soil health as criterion to drive innovation in agriculture
requires a solid evaluation framework to profile any new and
promising technology.[8–10] Identifying the best approach to
measure soil health is still a matter of debate,[8–11] here, a
framework suitable for crop protection R&D is presented. Three
major priorities reflecting the global challenges are considered:
promote soil biodiversity, preserve soil from major threats and
mitigate climate changes (as indicated in Fig. 1). These priorities
enable to identify eight targets to evaluate the impact of new
technologies.
Several enabling technologies and agronomical
management practices have been disclosed as impactful to
support and improve the soil health addressing one or more of
the highlighted targets,[4,11,12] yet in this context, the potential
role of chemical-based technologies has been often neglected
and discounted, even though a tremendous role is played by
natural small molecules on a multitude of processes below
ground.[13–15] It is worth mentioning the striking and not yet
75th AnniversAry of ChimiA CHIMIA 2021, 75, No. 7/8 700
Fig.1. Framework with soil health
priorities and associated targets.

75th AnniversAry of ChimiA CHIMIA 2021, 75, No. 7/8 701
fully uncovered chemical diversity that can be found below
ground with thousand different chemical features isolated from
the roots of different plant species.[14,16] The next section aims
to provide a historical perspective of the role of chemistry in the
soil and crop sciences and how it evolved in the last centuries.
Such perspectives will help to highlight possible trajectories for
the chemical innovation for future agriculture.
Soil and Chemistry: A Historical Perspective.
The importance of chemistry in soil and the relevance for
crop production goes back to the nineteenth century with the
first attempts by von Thaer in Germany,[17] Davy in England,[18]
and Boussingault in France[19] to shed light on the essential role
of soil to support plant growth by providing nutrients. Later Way
unveiled the ability of soil to exchange ions and the underlying
the ion-sorption processes;[20] and then together with Liebig’s
work[21] they set up the foundations for the soil fertilization
and ultimately contributed to the soil fertility concept. Other
milestones followed in the twentieth century and marked the
contribution of the chemical innovation in the agriculture
particularly with the Haber-Bosch process through which it
became possible to synthesize ammonia from atmospheric
nitrogen with the help of iron-based catalyst, paving the way
for modern agriculture and use of synthetic fertilizer.[22]
From the 1950s onwards chemical innovation sustained a
growing crop protection industry with many – among others
– soil-applied agrochemicals.[23] This innovation led to a
significant increase in labor and land productivity[24] as well
as in food security.[25,26]
Whilst the past technological efforts were devoted to
more abundant and safer foods, the future emerging direction
points to the urgent needs of more sustainable food production
addressing the major interconnected global challenges like
climate change[27] and biodiversity and soil losses.[3] Thus, this
historical perspective leads to enquiry how chemical innovation
can support sustainable agriculture by targeting soil health?
Chemical Innovation Targeting Soil Health
As indicated in Fig. 1, the framework for implementing soil
health science in crop protection R&D identified eight major
targets. For succinctness purpose, only a few of them will be
discussed in this section.
Minimizing residues of future chemical crop protection
solutions is one of the highest priorities to support soil health.
To this end, information about the environmental degradability
of early chemical leads should be available as early as
possible and drive a rational chemical design. Therefore, new
alternative predictive approaches able to provide swiftly and
in a high-throughput manner indications about degradation
are highly valuable.[28,29] A few recent investigations harvested
some encouraging results, the published approach hinged on
the fast evaluation of the degradation kinetics of a wide range
of compounds on activated sludge systems and used this to
predict soil half-lives from studies with a regulatory setting.
Satisfactory predictions across a wide range of agrochemicals
were observed and were superior to other approaches relying
on other available predictive models.[28]
Protecting the soil microbial community and promoting the
microbial nutrient cycles hold great potential. In this respect
the naturally occurring below-ground chemicals particularly
in the rhizosphere – the thin interface between plant roots
and near soil – represents unique and fascinating examples of
‘Chemistry-in-action’ underpinning a vast range of biological
interactions and biogeochemical processes with a fundamental
ecological relevance and exceedingly important agronomical
implications. Plants strongly contribute to such a ‘Chemical
parade’ by deploying up to 50% of their photosynthates in the
rhizosphere[14] as primary or secondary metabolites (Fig. 2).
They regulate several interactions as plant-plant; microbes-
plant, plant-pest and nutrient assimilation.
Chemical signals like flavonoids are involved in the plant-
microbe interactions and the recruitment of beneficial N-fixing
rhizobial bacteria by the leguminous plants. Benzoxazinoids
are multifunction molecules acting as phytosiderophores for
iron assimilation and also mediate the recruitment of other
beneficial microorganisms[30] or attract herbivore insects.[31]
Similarly, soil microorganism use signals to communicate
and coordinate growth and other behavior features like
competitions, symbiosis, or diseases. Several recent studies
showed that rhizosphere microorganisms can produce
antimicrobials like DAPG (2,4-diacetylphloroglucinol), PHZ
(phenazines) and PRN (pyrrolnitrin) which can be active
against pathogens causing different soil borne-diseases.[13,32]
Soil microorganisms release also other classes of molecules
acting as phytohormone compounds (i.e. auxins, gibberellins,
and cytokinins) which influence the development and other
physiological processes in plants.
If an anthropomorphic consideration would be allowed here,
it could be stated that plants speak chemistry and use small
molecules to call for food, cry for help and compete for space.
Understanding the hidden language of crops particularly
below ground can be a way forward to synthetize natural
Fig. 2. Naturally above- and
below-ground chemicals
produced by plants and
microbes and controlling several
processes.

702 CHIMIA 2021, 75, No. 7/8 75th AnniversAry of ChimiA
molecule or invent and optimize new compounds inspired by
the natural chemical signals.
An example of innovation in this area is represented by
strigolactones. Strigolactones are terpenoid-derived natural
molecules acting as phytohormones and controlling several
physiological and development processes in planta. They
act also as potent rhizosphere signals with many potential
applications in modern agriculture.[33] Interestingly, they are
involved in the establishment of relevant symbiotic interactions
between crops and arbuscular mycorrhizae and/or rhizobium.
Moreover, new evidence suggests that strigolactones can
influence the composition of the root microbiome.[34] The role of
strigolactones on the promotion of mycorrhization is particularly
relevant for soil health. Arbuscular mycorrhizae are considered
keystone taxa supporting many important ecosystem processes
like carbon, nitrogen and phosphorus cycles, biodiversity soil
structure promotion.[35,36] Recent studies showed how synthetic
mimics of strigolactones are active to promote key steps in the
symbiotic relationship (Fig. 3).[37,38]
Successful total synthesis of natural strigolactones like
sunflower-specific heliolactone[39,40] and orobanchol in rice[41]
represent interesting chemical leads to promote soil health.
In the context of climate change, reducing greenhouse gas
emission is an unavoidable challenge requiring the involvement
of public and private organizations. According to a recent ICPP
report[42] about 23% of greenhouse emissions derive from
agriculture and other land uses. Nitrogen fertilization is of
massive importance for crop production at farm level and it is
associated with nitrous oxide release. This is a potent greenhouse
gas accounting for about one third of the total agriculture and
other land use greenhouse emissions.[43] The current consensus
is that fertilization practices and other interventions are the
most effective approaches to control the soil N-cycle and reduce
greenhouse gas emissions.[27] However, small molecules can
have profound and specific effects on different steps of the
soil N-cycle. A broad range of natural or synthetic compounds
– encompassing several agrochemicals – have been shown to
interact directly with different steps of the soil N-cycle.[44–46]
The soil N-cycle is a multi-step process mediated by microbes.
[46] Any shift in one step will also have indirect consequences on
N pools’ partitioning and thus on other cycle steps. To manage
the soil N-cycle effectively, it is necessary to consider the
processes’ holistic nature and control N availability, leaching,
and emissions.
Conclusive Remarks
Since the inception of the agriculture sciences in the
nineteenth century, chemistry has been at the cornerstone of
crop productivity, nutrients, and soil fertility concepts. Chemical
innovation supported almost two centuries of exceptional
development in agriculture securing access to food, feed and
fibers.
Yet, today climate change and other global challenges
are threating our food production system. Therefore, a more
resilient and sustainable agriculture is urgently needed. A way
forward is through the promotion of soil health. Although the
concept is open to many definitions and interpretations, three
clear priorities can be used to drive the innovation: promoting
soil biodiversity, preserving soil resources from major threats
and mitigating climate change. New chemical solutions can
address these targets. An exciting and very promising venue for
innovation lies with new non-cidal molecules miming rhizosphere
signals controlling important biogeochemical processes with
a tremendous agronomical relevance. Knowing and mastering
the chemical lexicon of the plants can support a healthy crop by
promoting a healthy soil.
To build the future using wisdom gained from the past, the
following quote from Liebig sounds timely “Perfect Agriculture
is the true foundation of all trade and industry – it is the system
of Agriculture cannot be formed without the application of
scientific principles; for such a system must be based on an exact
acquaintance with the means of nutrition of vegetables , and with
the influence of soils and action of manure upon them . This
knowledge we must seek from chemistry”.[21]
The Swiss Chemical Society is leading the way with many
new and thrilling initiatives.[47] For instance, by establishing
and promoting new thematic communities like Chemistry and
the Environment, Green & Sustainable Chemistry and Chemical
Ecology; without doubt important steps to reap future benefits.
Received: July 12, 2021
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