Soil Functions and Diversity in Organic and Conventional Farming

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Supradip Saha

Abstract Intensification of modern agriculture is one of the greatest threats worldwide and it has led to growing concern about conserving biodiversity and its role in maintaining functional biosphere. It is now clear that agricultural intensification can have negative local consequences, such as increased erosion, lower soil fertility, and reduced biodiversity; negative regional consequences, such as pollution of ground water and eutrophication of rivers and lakes; and negative global consequences, including impacts on atmospheric constituents and climate. Concerns about the ability to maintain long-term intensive agriculture are also growing. Organic farming is now seen by many as a potential solution to this continued loss of biodiversity due to recycling of natural resources and no negative impact of synthetics. Though almost all soil processes are regulated by soil microbes, the link between micro-bial diversity and soil function is not well understood.

This review article assesses the impacts on biodiversity of organic farming, relative to conventional agriculture, through a review of comparative studies of the two systems, in order to determine whether it can deliver on the biodiversity benefits. It also identifies and assesses soil processes regulated by microbes under organic and conventional management practices. It also highlights changes during conversion from conventional to organic cultivation regarding biological processes as well as abundance of microbes. It emphasized tools to measure functional diversity and activity of microbes including molecular tool. The review also draws attention to four key issues: (1) differences in functional diversity under organic and conventional management practices; (2) variation in soil processes due to organic management practices; (3) molecular tools and comparative studies related to analysis of microbial biomass or characterization; and (4) changes during conversion to organic farming.

Concerning environmental protection, in general, the risk of adverse environmental effects is lower with organic than with conventional farming methods,

Indian Council of Agricultural Research,

Vivekananda Institute of Hill Agriculture, Almora -263 601,

Uttarakhand, India e-mail: [email protected]

E. Lichtfouse (ed.), Sociology, Organic Farming, Climate Change and Soil Science, Sustainable Agriculture Reviews 3, DOI 10.1007/978-90-481-3333-8_10, © Springer Science+Business Media B.V. 2010

though not necessarily so; with reference to soil fertility and nutrient management, organic farming is suited to improve soil fertility and nutrient management markedly on the farm level; regarding biodiversity, comparison studies show that organic farming has more positive effects on biodiversity conservation. Organic farming identifies a wide range of soil microbial community that benefit from organic management through increases in abundance and/or species richness. Management practices used in organic farming are particularly beneficial for farmland wildlife. Although the continuing debate on the issue of adoption of organic farming has not come out with clear-cut resolution in many parts of the world, the biodiversity aspect in soil functions will be on the positive side for the foreseeable future.

Keywords • Comparison • Functional diversity • Molecular tool • Organic farming • Soil processes

Abbreviations

AMF

Arbuscular mycorrhizal fungi

ARDRA

Amplified rDNA restriction analysis

C/N

Carbon-to-nitrogen ratio

FAME

Fatty acid methyl esters

FISH

Fluorescent in situ hybridization

PCR-DGGE

Denaturant gradient gel electrophoresis

PCR-TGGE

Temperature gradient gel electrophoresis

Pg

Pico gram

PLFA

Phospholipid fatty acids

RT-PCR

Reverse transcription polymerase chain reaction

T-RFLP

Terminal restriction fragment length polymorphism

USLE

Universal soil loss equation

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