MAHADEV SHINDHEID No:MA1TAE0135

Department of Plant Pathology

COA, Shivamogga

On

Soil Health Paradigms and Implications for Disease Management

Seminar

OutlineIntroduction

Definition

Factors influencing soil health

Management practices

Case studies

Conclussion

In one teaspoon of soil there are… Bacteria 100 million to 1 billion

Fungi 6-9 ft fungal strands put end to end

Protozoa Several thousand flagellates & amoebaOne to several hundred ciliates

Nematodes 10 to 20 bacterial feeders and a few fungal feeders

Arthropods Up to 100

Earthworms 5 or more

Introduction

Definitions Soil: An ecological system consisting of

inorganic minerals, decomposing organic matter, living organisms and growing plants

Soil: A farmer's "Silent Partner“

SOIL HEALTH:

• Soil health is a capacity of the soil to function as a vital living system to sustains biological productivity maintain environmental quality and promote plant, animal, and human health.

• “A healthy soil should be capable of supporting life processes such as plant anchorage and nutrient supply, retain optimal water and soil properties, support soil food webs, recycle nutrients, maintain microbial diversity, remediate pollutants, sequester heavy metals, and contribute to disease suppression”

(Wang and Hooks, 2010).

Properties healthy soil

8

CHARACTERISTICS OF HEALTHY SOILS

Sufficient supply of nutrients. High biological diversity Ability to maintain the integrity of nutrient cycling and energy flow Suppression of multiple pests and pathogens Ability to improve plant health Maintenance of water and air quality Good soil tilth Good internal drainage Low populations of parasites High populations of plant-health promoting Organisms Low weed pressure No toxic chemicals that harm plants

Wang and Hooks (2010)

Soil MoistureSoil TemperatureSoil pH Organic MatterNutrientsBeneficial Microorganisms

Factors influencing soil health

Organic amendmentsCrop rotationCover crops and Green manuresSoil typesTillage practicesIntercropping

Factors influencing soil health

Soil health management practices

Manage organic matterMinimize disturbancesDiversify soil biotaMaintain soil coverCrop rotation Cover crops and green manuresOrganic amendmentsConservation tillage

Soil health and disease management

Crop rotation

Soil moisture, pH, temp

Nutrient management

Organic amendments

Cover crops and green manures

Beneficial organisms

Conservation tillage

Soil moistutre

Pathak and Srivastava (2001) reported that, with increasing soil moisture and decreasing soil temperature, decreases the incidence of Rhizoctonia bataticola in sunflower

Soil Moisture Increase Phytophthora spp. Rhizoctonia spp. Pythium spp. Soil Moisture Decrease Fusarium spp. Verticillium spp. Armillaria spp.

Soil pH

• It affects nutrient availability and microbial activity.

• Most plants and microorganisms prefer a pH range of 6-7.

• Raising the soil pH to 6.5–7 by using nitrate nitrogen in place of Ammonical nitrogen will decrease the development of Fusarium wilt

Potato scab is more severe in soils with pH levels above 5.2. Below 5.2 the disease is generally suppressed.

Club root of crucifers can be reduced by raising pH(alkaline)

Fusarium wilt disease (i.e. the more acidic the soil, the more severe the disease).

Takeall of wheat disease- Gaeumannomyces graminis, is favored by alkaline pH.

Soil pH have a strong effect on infective juveniles survival.

Survival and pathogenicity nematodes declined slightly as the soil pH decreased from pH 8 to pH 4.

Acidic soil with pH levels below 4.0 may limit the nematodes host-finding

(Kung et al., 1990)

SOIL TEMPERATUREWarm, moist soils with high levels of carbon to nitrogen will have higher levels of microbial activity and a relatively higher level of suppression

Most of the soil organisms function best at an optimum soil temperature of 25 to 35 C⁰

Soil temperature can greatly affect the activity of locomotion, infection and reproduction of nematodes

High temperature can manage- Verticillium spp.

Decreasing soil temperature, decreases the incidence of Rhizoctonia bataticola

ORGANIC AMENDMENTS Animal Manure

Green Manure (Crop Residues)

Composts

Peat

Blood Meal

Compost Tea

Fish Meal

Poultry Manure

How does compost suppress disease?

Improves soil physical and chemical properties Improve soil structure and fertility Enhanced activities of antagonistic microbes Increased competition against pathogens for resources that

cause fungistasis Release of fungitoxic compounds during organic matter

decomposition Induction of systemic resistance in the host plants

Pathogens:

• Fusarium spp.• Phytophthora spp.• Pythium spp.• Rhizoctonia solani • Sclerotinia spp. • Sclerotium spp.• Thielaviopsis basicola • Verticillium dahliae

CROP ROTATION• Break disease cycle by

reducing pathogen level

• Alter the soil characteristics

• Inhibition of pathogens by chemicals

BENIFICAL CROPS PATHOGEN REDUCED PRECEDING CROP (host)

Rice Verticillium dahliae CottonPeas Gaeumannomyces graminis Wheat

Maize , Wheat, Sorghum

Ralstonia solanacearum Tomato and potato

Legume crops Streptomyces scabis PotatoGround nut Meloidogyne incognita Tomato

Wheat Heterodera schachtii Sugarbeet

cereals Xanthomonas campestris pv. campestris

Cabbage

Effect of Rotation on Pathogens

Growing of cover crops:

Reduce erosion

Improves the physical condition of soil

Increase organic matter

Increase soil microbial diversity by enhancing the soil

microflora.

Reduce plant diseases

Cover crops:

Sudangrass, Rye, Rapeseed, Oat, Mustard and Buckwheat

COVER CROPS AND GREEN MANURES

COVER CROPS AND GREEN MANURES

• Sudan grass-Meloidogyne hapla, Pratylenchus spp.• Hairy vetch-Thielaviopsis basicola Pythium spp. Rhizoctonia solani Fusarium spp.

Crops suitable for green manuring

Dhaincha ( Sesbania aculeata), Sunhemp (Crotalaria juncea), Cowpea (Vigna sinensis), Pea (Pisum sativum), Berseem (Trifolium alexandrinum), Lucerne (Medicago sativa)

Sunhemp Cowpea 26

Dhaincha

CONSERVATION TILLAGE• Reduced tillage systems accumulate OM and

increase the rate at which soil microfloral and microfaunal decomposition progresses

• Soils with high levels of OM have been shown to prevent common root rot of cereals (Cochliobolus spp)

NUTRIENTs Plants suffering a nutrient stress will be more

susceptible to diseases, while adequate crop nutrition makes plants more tolerant or resistant to disease.

The nutrient status of the soil and the use of particular fertilizers and amendments can have significant impacts on the pathogen’s environment.

Calcium, play a major role in the ability of the plant to develop stronger cell walls and tissues. 

How can mineral nutrition prevent plant disease?  Mineral nutrition can affect two primary

resistance mechanisms:

A) Formation of mechanical barrier (eg. Thickness of cell wall )

B ) Synthesis of natural defence compounds (eg: phytoalexins , antioxidants and flavanoids)

Nutrient Suppressing Disease

Crops

Calcium 1)Clubroot2)Fusarial wilt3)Damping off

1) Crucifiers2) Tomato, Watermelon and

cotton.3) Peanut, Soybean, Pepper,

Tomato, onion, Bean and Wheat.

Nitrate Fusarium wilt Tomato, Celery and Carnation.

Sulfur Scab PotatoPotassium Verticillium wilt CottonPhosphate Fusarium wilt Cotton and MuskmelonCopper (cu) G. graminis var

tritici Erysiphe spp.Alternaria spp.

Take all of wheat ,Powdery mildew of wheat Sunflower

(Kausadikar et al ., 2006)

NUTRIENTs in management of plant diseases

Beneficial microorganisms

Nitrogen fixing bacteria Rhizobium Azotobacter Azospirillum

P solublising bacteria• Bacillus subtilis• Pseudomonas spp.

Biofertilizers

Bio control agents T. harzianum, T. viride ,T. hamatum VAM fungi , Bacillus subtilis, Pseudomonas fluorescens Pathogens: Pythium spp. Fusarium spp. Sclerotium rolfsii Rhizoctonia solani Macrophomina phaseolina Alternaria spp. Sclerotinia spp. Verticillium spp.

Hyphae of the beneficial fungus Trichoderma wrap

around the pathogenic fungus

Rhizoctonia.

EFFICACY OF SOIL HEALTH MANAGEMENT PRACTICES FOR PLANT DISEASE

MANAGEMENTPositive effects Not sufficient to complete control 20 to 80 per cent reduces soil borne diseasesFoliar pathogens diseases

Examples Rust and mildews

Cont...

• Rhizobacteria: Induced Resistance to foliar and soil borne disease

• Compost amendments induce resistance through activation of plant defense response

• Examples: Botrytis Rot, Anthracnose, Angular Leaf spot.

• Additional control measures for foliar pathogens.

CASE STUDIES

Objective: To know the effect of cropping sequences on Root Knot Nematode population

OBJECTIVE: The role of microbial activity in the effect of soil moisture and temperature on disease severity

Dry root weight of wheat seedlings with (a) and without (b) inoculation with R. solani AG-8, at different soil temperature and moisture levels.

Objective: To determine the effect of PMR amendments on soil borne and foliar diseases of cucumber and snap bean grown on a sandy soil

Objective: To evaluate the efficacy of Brassica cover crops used as soil amendments for managing Phytophthora blight of squash

Reduction in Phytophthora blight on squash plants by soil amendments with shoots (A) or roots (B) of cover crops under greenhouse conditions. Plant tissues were used to amend infested soils at 1 or 2.5% (plant/soil, w/w).

Objective: to evaluate the effects of compost on bacterial wilt of potatoes

CONCLUSION Management practices that promote soil health by improving

soil physical, chemical, and biological properties, resulting in improved nutrition, enhanced yield and disease suppression

Contribute to building active, diverse and potentially disease-suppressive microbial communities and can provide the base of a sustainable disease management program

Biodiversity is important to make management strategies reliable

Use of soil health management practices can substantially reduce soil borne disease problems, but cannot completely eliminate them, may take time to develop, and should be used in conjunction with other approaches to achieve sustainable disease management