Organic Potting Media for Vegetable Transplants

1. Organic Potting Media for Vegetable Transplants Anu Rangarajan Cornell University Dept. of Horticulture

2. Evaluating a potting mix • Physical Properties • Particle size appropriate to container • Density will hold up plants • Good aeration and waterholding capacity • 20-30% air space, water (40-50% common) • Chemical Properties • Nutrients levels low to moderate • Salts and EC below 1.5 dS/m • pH between 5.5 and 7.5 • Biological Properties • No plant pathogens • Decomposition rate should be low • Consistency

3. Plant roots, Soil and Soil organisms interact Rhizosphere microbial communities establish Beneficial RZ microbes Growth Promotion Nutrient cycling, hormones Disease Suppression Parasitism, competition, ISR Rhizosphere www.chesco.com/~treeman/ SHIGO/RHIZO2.jpg

4. Microbial Activity of Compost Mixes

5. Organic Challenge = Nutrients • Need adequate supply for growth • Organic sources often inconsistent • Compost based media • Soluble fertilizer sources • Release of nutrients from organic sources difficult to predict • Some will result in ‘composting’ • Others increase salts

7. Monitoring Electrical Conductivity • Soluble salts (K, Na, Cl, NO3, NH4) • Symptoms of high EC • Poor germination • Restricted root growth • Restricted water uptake and wilting • Marginal burning on foliage • Reduced flowering and yields • Saturated paste, 1:2 dilution or 1:5 dilution, based upon dry wt soil

8. EC levels 1 dS/m= 1 mmhos/cm= 1 mS/cm=1000 uS/cm

9. Alfalfa Rates Fresh Wt EC

10. Compost-based transplant mixes • Source • Manure based vs. plant based and N content • Dairy and horse vs. poultry • Quality • Curing/maturity to get media C:N ratio between 15-20 • Particle size (<2-3 mm, 50% of compost) • Salt content/phytotoxicitiy (dS/m<3) • Rate • 10-50% of media, 20% common • Storage

11. Growth tests for Phytoxicity • Cress (Lepidium sativum L.) or Chinese Cabbage as indicator crops • Compare germination in +/- amended peat mix • Compost rate • 20%-30% of mix • Count emergence after 10-12 days

12. What are potential alternatives to compost for organic transplant media? Compost is a biologically active project, and is always changing

13. Questions: • Potential nutrient sources • Thermophillic compost • Vermicompost • Alfalfa meal, soy meal, sesame meal, blood meal (crab, feather) • Rates • Particle size • Influence on crop growth

14. Base mix: 70 peatmoss : 30 vermiculite (v/v) 5 lbs. lime per cubic yard of mix Bloodmeal mix: Base plus 7lbs. bloodmeal, 7 lbs. rock phosphate, and 7 lbs. greensand per cubic yard of mix Vermicompost Rates and Plant Growth

15. Vermicompost Rates and Root Growth

16. Compost vs Meals ‘05 • Thermophillic compost (20%) • Vermicompost (20%) • Sesame meal (1%, 2.5%) • Alfalfa meal and Bradfield (5%)

17. Thermophilic compost (TC) www.musc.edu Vermicompost (VC) Continuous flow through reactor system: microbes & epigeic earthworms (Eisenia fetida) www.hri.ac.uk/recoveg

18. Compost vs. Meals EC Fresh Wt

20. Field evaluation

21. Do the potting mixes effect germination, growth and yield?

22. Yield

23. Expanded trial • Alfalfa meal 1, 2.5, 5% • Bradfield Alfalfa meal 1, 2.5, 5% • Sesame Meal, 1, 2.5% • Soybean Meal, 1, 2.5, 5% • Thermophillic compost- RT • Vermicompost- RT and Hog • Bloodmeal • Thermo-, vermic + bloodmeal • Thermo-, vermic + Brad1%

24. Alfalfa meals

25. Plant Amendments

26. Compost Blend Mixes

27. Thermophillic compost + other amendments

28. 2007 Tomato Transplant Dry Wts

29. EC of mixes

30. Suggestions for improving organic transplant media formulation: • Vermicompost provides more consistent performance than thermophillic compost • Use combinations of plant and compost amendments • Reduce vermicompost rates and combine with blood meal or alfalfa meal (1%) • 1 to 2.5% of plant meals support vegetable seedling growth for 6 weeks • Alfalfa meal most readily available source • Sesame meal more difficult to find

31. Suggestions for improving organic transplant media management: • Record amendment wt and volume added • Mix nutrient source into media 1 week prior to use • Fill flats and wet/leach if possible • If mix in advance, store dry • Screen all amendments to a uniform size • Grind plant amendments to 2 mm mesh for better distribution • Monitor EC prior to seeding and then for minimum of first two weeks. Leach if high EC

32. Rhizosphere sampling June Original plug July October

33. TC TC & VC VC BASE SUN SM1 AM5 Manure based compost amendments SM25 SUN & BASE Plant based amendments POTTING MIXES TYPE OF ORGANIC MATTER

34. TC VC BASE Manure based compost amendments P SUN June SM1 July C AM5 P SM25 C Potting media Plant based amendments October COMPILED DATA – ENTIRE SEASON TIME

35. Conclusions • Organic amendment influenced tomato transplant and early season growth, but not yield • Plant based mixes had higher bacterial pops. • Amendment type supported different bacterial communities around the roots • These differences persisted well into the middle of the season in the field • Selection of a transplant media may become a strategy to address particular field site challenges