Organic and Sustainable Farming. 11:00-12:30 Capturing the Organic Market 2:00-3:00 Organic Pest Management 4:30-5:30 Alternative Soil Management

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1 Organic and Sustainable Farming 11:00-12:30 Capturing the Organic Market 2:00-3:00 Organic Pest Management 4:30-5:30 Alternative Soil Management

2 The 2012 Educational Program Committee is pleased to share conference educational materials with you under the condition that they are used without alteration for educational and non-commercial use only. All materials are protected by copyright law. The authors kindly request their work is properly cited, including the date of publication. For more information on Small Farms, visit our website at: or contact your local County Extension Agent. For inquiries about this topic, please contact: Danielle Treadwell, Educational Program Chair. Phone: (352) Suggested Citation: Author Full Name. Title of Presentation or Handout University of Florida-IFAS and Florida Agricultural and Mechanical University-CAFS Florida Small Farms and Alternative Enterprises Conference. July 27-29, Kissimmee, FL.

3 Soil Health and Disease Suppression in organic versus conventional plant production Prof. Dr. Ariena van Bruggen Emerging Pathogens Institute and Plant Pathology Dept. University of Florida in Gainesville, FL

4 Outline: Organic and conventional crop management, soil quality and soil health Root disease suppression in organic compared to conventional soil Root diseases in crop mixtures versus pure stands Nematode suppression in organic soils Suppression of human pathogens in organic soils Reasons for pathogen suppression in organic soils Conclusions

5 Differences between conventional and organic management Conventional Organic synthetic pesticides natural and mineral pesticides synthetic fertilizers organic amendments short rotation longer rotation rarely cover crops frequently cover crops rarely plant mixtures more frequently plant mixtures sometimes biological control rarely biocontrol applied (fungi, bacteria) applied rarely soil disinfestation sometimes soil disinfestation (by heat)

6 Differences between conventional and organic management: agrobiodiversity Org - Conv Org - Conv Differences in plant diversity in time and space can have a major influence on plant diseases Photographs by Frans Smeding

7 Differences between conventional and organic soils Conventional pesticide residues high NO 3 and P 2 O 5 contents low organic matter content poor structure lower microbial diversity and activity lower soil animal diversity and numbers conduciveness to root diseases Organic no pesticide residues low NO 3 and P 2 O 5 contents higher organic matter content sometimes better structure higher microbial diversity and activity higher soil animal diversity and numbers suppressiveness to root diseases

8 Soil quality and soil health Quality: mainly physical and chemical characteristics Health: mainly biological characteristics; diversity, ability to withstand stress Left: old grassland, no fertil. Right: reseeded, fertilizer Left: good quality soil, crumbly Right: poor quality soil, blocky Photo s on the right by Jan Bokhorst

9 Tomato corky root severity in organic, low-input and conventional plots in California 20 Lesions/root system ORG LOW Corky root CONV CONV2 0 Year 8 Year 9 ORG, LOW and CONV 4-yr rotations, CONV2 a 2-yr rotation Effects of rotation and of management were significant Van Bruggen et al., unpubl.

10 Tomato root rot by Pythium in organic, low-input and conventional plots in California % rotted tips/root system Pythium root rot Year Year 9 ORG, LOW and CONV 4-yr rotations, CONV2 a 2-yr rotation Effects of rotation and of management were significant Van Bruggen et al., unpubl.

11 Take-all disease on barley in conventional and organic soils DISEASE RATING 6 BARLEY 0% INOCULUM DISEASE RATING C-C C-S O-C O-S 6 BARLEY 0.5% INOCULUM C-C C-S O-C Less disease in organic than in conventional soil Pseudomonas fluorescens was not responsible for disease suppression in organic soils O-S Hiddink et al., 2005

12 Relation between take-all disease on triticale and bacterial diversity in conventional, transitonal and organic soil Disease rating Relative disease C-L CO-S O-S Relative diversity index Greater microbial diversity in organic soil was associated with less take-all disease Hiddink et al., 2005

13 Effects of plant diversity on root diseases Take-all disease severity on triticale alone or in a mix with clover Soil NO3 content in a triticale crop or in a mix with clover % Diseased roots NO3 mg/kg soil Triticale Triticale-clover Triticale Triticale-clover Hiddink et al., unpubl. Hiddink et al., unpubl.

14 Effects of plant diversity on root diseases Clubroot incidence on Brussels sprouts grown alone or in a mix with barley % Diseased plants B.SPROUTS MIX Hiddink et al., unpubl.

15 Effects of soil heating by steam on relative survival of J2 juveniles of root knot nematode (Meloidogyne incognita) in organic greenhouse soils J2 survival (unpast/past) 0,8 0,7 0,6 0,5 0,4 0,3 0,2 0,1 0 A A A AB AB Steamed in past AB Never steamed B C C C CD CD CD DE E N M E Q B I X Y S G D O F C L Greenhouse soils Root knot nematode larvae were more suppressed in nonsterilized soil Slow-growing predatory nematodes did not come back in steamed soil Berkelmans et al., unpubl.

16 Effects of soil heating by steam on root knot nematode index (RKI) in pots inoculated with J2 of M. incognita RKI (median) 5,5 5 4,5 4 3,5 2, ,5 1 0,5 0 Steamed in past A Never steamed B BC BC C C D control L O M S F I Farmers Root knot nematode index was lower in nonsterilized soil Slow-growing predatory nematodes did not come back in steamed soil Berkelmans et al., unpubl.

17 Risk of human pathogens in food production systems Reservoirs: cows pigs chickens Salmonella low medium high E. coli O157:H7 high low low Campylobacter low medium high Most cases/outbreaks linked to animal products Increased association between food-borne diseases and fresh vegetables manure Salmonella Franz et al., 2008 Klerks et al., 2007

18 Risk of human pathogens in food systems Survival of E.coli O157:H7 in manure and soil log CFU/gdw Time (days) GMH GH SH GML GL SL log CFU/gdw org/sand conv/sand org/clay conv/clay Time (days) E. coli O157:H7 declined faster in fibrous manure from cows on a high fiber diet (with straw) than on a low fiber diet (with corn silage) E. coli O157:H7 declined faster in organic than in conventional soil Franz et al., 2005

19 Internalization of Salmonella in tomato plants BSL II greenhouse log CFU/gdw One-week post inoculation Two-week post inoculation Salmonella Typhimurium inside inoculated leaflets. Green=sand; Red=conventional soil; Yellow=organic soil Salmonella declined faster in leaves of plants in organic than in conventional soil Gu et al., 2011

20 Internalization of Salmonella in tomato plants Correlation of decline rates with bacterial diversity and soil nutrients Salmonella declined faster in organic soils Decline rates were higher at higher bacterial diversity and Ca and Mg concentrations in soil Gu et al., 2012

21 Internalization of Salmonella in tomato plants Salmonella enters a leaf through stomates or hydathodes (different kinds of openings for movement of gas and liquid) A trichome (leaf hair) and a stomate (leaf opening) with Salmonella cells Water droplets emerging through hydathodes (openings) on the margins of leaflets The tip of a leaflet with hydathode; Salmonella cells inside leaf and conducting vessels Gu et al., unpubl.

22 Internalization of Salmonella in tomato plants Salmonella moves from leaves into stems (phloem) and fruit Conducting tissues: xylem on left and phloem on right (in box) Phloem cells with Salmonella cell inside Gu et al., 2011

23 Internalization of Salmonella in tomato plants Salmonella inside tomato fruits on leaf-inoculated plants contaminated fruits control fruits Gu et al., 2011

24 Internalization of Salmonella in tomato plants 1 Number of plants with internally contaminated leaves 2 Number of fruits that were internally contaminated, 9 fruits on 1 plant 3 Number of fruits that were internally contaminated, 5 fruits on 1 plant, 2 fruits on another plant. Gu et al., 2012

25 Reasons for pathogen suppression in organic soils In the soil and rhizosphere Greater diversity of microbiota (bacteria, fungi, nematodes etc.) -> a greater chance of the presence of antagonists and predators Root exudates consumed by abundance of microbes -> no rhizosphere effect -> pathogens cannot find roots Fewer nutrients and substrate available for pathogens to grow In the plants Lower nitrogen levels, higher Mg and Ca levels -> sturdier plants Greater induced resistance throughout the plants Better soil structure, drainage, water-holding capacity -> less stressed plants

26 Bacterial composition 2 Similarity of microbial communities in rhizosphere versus bulk soil from organic and conventional farms 3 ˆ B B R R R 2 ˆ B B R R B B B R R B R BBR RB R B B R R R R R 1 ˆ B B BB R B R BB B B B R BB B RBBR R R R B R R R 0 ˆ R R R R R R R R R R B RB 1 ˆ RR R R B R R R B B R R B 2 ˆ B B B B B B 3 ˆ B B 4 ˆ BB B B 5 ˆ B 6 ˆ Šƒƒˆƒƒƒƒƒƒƒƒƒƒƒˆƒƒƒƒƒƒƒƒƒƒƒˆƒƒƒƒƒƒƒƒƒƒƒˆƒƒƒƒƒƒƒƒƒƒƒˆƒƒƒƒƒƒƒƒƒƒƒˆƒƒƒƒƒƒƒƒƒƒƒˆƒƒƒƒƒƒƒƒƒƒƒˆƒ ƒ Each dot is a soil sample R Conventional Rhizosphere samples B Conventional Bulk Soil samples R Organic Rhizosphere samples B Organic Bulk Soil samples Bacterial composition 1 Van Diepeningen et al., 2006

27 Conclusions Usually: root disease severity is lower in organic than in conventional farms Frequently: a positive correlation of root disease severity with N availability, and a negative correlation with microbial activity and diversity Usually: soil sterilization has a long-term negative effect on natural pathogen and nematode suppression Commonly: enteric pathogens are suppressed in fibrous manure and well aerated (organic) soil Rarely: enteric pathogens can enter through roots or leaves, move inside the plant and contaminate a plant internally

28 Conclusions Survival and movement of Salmonella in tomato plants is less in organic than conventional soil Greater bacterial diversity in plants grown in organic soils may lead to greater resistance to internal colonization of Salmonella as well as plant pathogens It is important to maintain soil health by diverse cropping systems, addition of organic matter to soil, and avoidance of any kind of soil sterilization (soil solarization and biological soil disinfestation are ok) It is important to prevent contamination with human pathogens: properly composted manure, clean water

29 Acknowledgements University of California Davis: all people of the SAFS project, especially Howard Ferris, Kate Scow, Sean Clark Wageningen University: Aad Termoshuizen, Wim Blok, Gerbert Hiddink, Anne van Diepeningen, Robert Berkelmans, Eelco Franz, Michel Klerks, Oscar de Vos University of Florida: Ganyu Gu, Juan Cevallos- Cevallos, Ellen Dickstein