Introduction to Soils for the Master Gardener

1. Introduction to Soils for the Master Gardener Dick Wolkowski Extension Soil Scientist Department of Soil Science University of Wisconsin - Madison

2. 700 different • soils • in Wis.

3. Productive soil must be fertile • physical fertility • texture, structure, drainage, tilth • chemical fertility • nutrient supply • soil testing • nutrient additions • biologically fertile • microorganisms • organic materials • soil environment

5. Soil formation-’weathering’ • physical • freezing, thawing, wetting, drying, organisms • chemical • dissolved minerals moved in water • soil horizons formed • 1 inch - 100 years

6. Soil = f (Climate, Parent material, Living organisms, Topography, Time ) Deciduous Coniferous Prairie

7. Soil texture • classes - sand, silt, clay • names based on proportions • loam, silty clay, loamy sand • changing proportions not recommended • clay also group of minerals • montmorillinite, kaolinite.… • nutrient storehouse

8. Textural classes

9. Soil organic matter • plants, animals, microorganisms • living, dead, decay products • humus • complex, dark-colored, reactive • soil acidity reservoir • nutrient storehouse • difficult to significantly increase

10. Soil structure • particles ‘glued’ into aggregates • organic matter, clay, bacterial secretions, Fe/Al oxide coatings • granular, platy, blocky • finer aggregates in ‘topsoil’, massive in subsoil • improve by adding organic residues • decay: 90% CO2 + H2O

11. Problem: ‘heavy’ soil • aggregates tightly packed • small pores • poor drainage, roots suffocate • ‘cloddy’ if tilled wet • compact easily • improve with organic residues • better crumb stability • larger pores • sand + clay = cement

12. Problem: ‘light’ soil • aggregates too big to pack tightly • large pore spaces • droughty • improve with organic residues • ‘sponge’ • better water holding capacity

13. Organic residues • compost, grass clippings, crop residues • annual gardens - 1 bu / 20 sq ft • perennial gardens - 1 bu / 10 ft • do not add to tree/shrub planting hole • green manure, fall cover crops • green topgrowth tilled under • extra N needed for high C residues • microorganisms ‘tie-up’ N • wood chips, sawdust, oat straw

14. Organic residues • provides ‘food’ for microorganisms • for every 100 lb. added, 90 lb. converted to water, carbon dioxide • 10 lb. stable 1st year • 1 lb. stable 2nd year • microbial decay process • more ‘glue’ for better crumb stability • nutrients released • fresh surfaces for nutrient holding

15. How to remember the 17 essential elements C HOPKINS CaFe is Mighty Nice, But Many More Prefer Clara’s Zany Cup • Required for the plant to complete life cycle • Directly involved in metabolism • Can not be substituted by another nutrient • Essential for a wide range of plants

16. Food for plants? • plant, animal nutrition very different • plants manufacture basics • protein, carbohydrate, sugar…. • framework with C, H, O • 14 essential soil elements • N, P, K - primary • Ca, Mg, S - secondary • B, Cl, Ni, Cu, Fe, Mn, Mo, Zn – trace or micro • animals (we) eat basics

17. Nutrient supply • clay main ‘nutrient storehouse’ • negative charge • attracts, holds positive ions • Ca ++, Mg ++, K +, NH4+ • easily displaced, exchanged • plant uptake • some leaching on sandy soils • negative ions remain in soil solution • NO3-, Cl-, SO4=

18. Nutrients must be soluble plant root pore space soil solution Nutrient exchange between clay and soil solution

19. Would Calvin be a good master gardener?

20. Soil testing is the only preplant method of knowing nutrient need! • WHAT SOIL TESTING TELLS US • Crop N need • Plant available P and K • Crop P and K need • Soil organic matter • Soil pH and lime requirement • Other tests if requested

21. A shovel is OK too, mix a small amount in a clean bucket

22. Soil test • rapid chemical analysis • index of potential nutrient supply • deficiency • excess • sample to show ‘true’ variation • Composite • UWEX lab in Madison

23. Sampling soils • sample depth • established turf - 4 inches • new turf, gardens - 6 inches or tillage depth • raised beds - depth of bed • probe best, spade OK • combine 5 subsamples – composite

24. Avoid unusual areas: backfill, wet spots, etc.

25. Sampling soils • when • annual gardens, new turf • fall, spring before tillage • perennials, problems, established turf • anytime • suspected salt damage • very early spring • sample each area separately • repeat every 2-3 yrs

26. Useful laboratory tests • routine • soil pH, ‘buffer’ pH • organic matter % • available P and K • other • Ca, Mg, S, Zn, B, Mn • no good test/need • N, Fe, Cu, Cl, Mo, Ni • ‘problem solving’ • texture, soluble salts • Cl, Pb, As,... UW Soil and Plant Analysis Lab 8452 Mineral Point Rd, Verona 53593 (West Madison Ag. Research Station)

27. Soil test report • potential for deficiency • which nutrient needed • how much to apply • fertilizer for nutrient need • lime, sulfur amendments for pH change • when to apply • when to STOP!

28. Soil test results • excessively high • common for residential areas • not detrimental • adding more not beneficial • avoid balanced blends, most organics • low • buildto optimum • turf fertilizer blends

29. Soil test results - pH • measure of acidity, alkalinity • scale 1 - 14, optimum 6 - 7+ • add lime only if recommended • incorporate 6 - 8 inches • add aluminum sulfate to acidify • new turf • if strongly alkaline • blueberry, rhododendron

30. Effect of soil pH on nutrient availability

31. Optimum pH for turf and gardens • depends on species** pH range • kentucky bluegrass 6.0 - 7.6 • creeping red fescue 5.3 - 7.5 • sweet corn 6.0 • potato 5.4 – 6.0 • green bean 6.8 • tomato 6.0

32. Soil test results - organic matter • 2 - 4% most soils • impractical and difficult to change • nutrient reservoir • used for calculating N and lime recommendations

33. Soil test results - N • no direct measures on report • N rec from crop need, organic matter • promotes leaf growth • excess N • delays maturity • moves below root zone and may contaminate ground water

34. Soil test results - P • stimulates root growth and flowering • shallow rooted greater need • optimum soil test P for turf and gardens - established turf 11 - 15 ppm - sweet corn 16 - 25 ppm - green bean 16 - 25 ppm - tomato 31 - 45 ppm - potato 161- 200 ppm

35. Soil test results - K • promotes disease resistance, winter hardiness • root crops require most • optimum soil test K for turf - established turf 41 - 60 ppm - sweet corn 101 - 120 ppm - green bean 101 - 120 ppm - tomato 121 - 180 ppm - potato 121- 160 ppm

36. Inorganic fertilizer • sold on a percent by weight basis • N + P2O5 + K2O • chemically simple • N in air plus natural gas • rock phosphate, potash mined, sized and cleaned very soluble salts easily blended must be careful with rates

37. Inorganic fertilizer Nutrient Type N P2O5 K2O --------------% --------------- urea 46 0 0 ammonium nitrate 33 0 0 triple super P 0 46 0 ordinary super P 0 20 0 muriate of potash 0 0 60 potassium sulfate 0 0 50 di-ammonium phos. 18 46 0

38. Recommended fertilizer Gardens • avoid high N fertilizers for most crops • sweet corn, potato are exceptions • uniform, low grade (e. g.10-10-10) • does not match plant need • over supply P and K • micronutrients generally not needed • adjust pH as necessary

39. Organic fertilizer • chemically complex, contains C • naturally occurring • byproducts • microorganisms must degrade • slow release, rate ??? • improve structure with long-term use

40. Organic fertilizer Nutrient Type N P2O5 K2O ---------------%---------------- blood meal 13.0 1.5 0.6 bone meal 2.2 27.0 0 seaweed 1.5 1.0 4.9 tree leaves 0.7 0.1 0.8 greensand 0 1.4 6.3 activated biosolid 6.0 3.0 0.2

41. Organic fertilizer • may contain • unnecessary nutrients, compounds • nonessential elements • does not add nutrition, improve flavor, enhance food safety and quality • often more expensive per pound of nutrient

42. Foliar sprays: fruits, sensitive ornamentals • trace, secondary elements • soil Fe, Mn ‘fixed’ at high soil pH • supply by spraying leaves • temporary ‘fix’, requires repeating • emergencies • no substitute for soil applied nutrients • leaf burn, expensive, extra work • most spray falls on soil

43. Recommended fertilizer Turf blends • regular or maintenance - ‘high N’ • soil test P, Koptimum, above • starter - ‘high P2O5’ • soil test P below optimum • winterizer - ‘high K2O’ • soil test K below optimum • use a “Holiday” schedule • sweep off driveways and sidewalks

44. Other turf management considerations • Mowing • no shorter than 2.5 in. • cut no more than 1/3 at any time • normal height in fall • Thatch • natural buildup • verti-cut, power-rake, core • Water • 1 in. per week in summer, less in spring and fall • soak rather than sprinkle • Shade • seed fescue • prune trees • mow higher • less water and fertilizer

45. Compost

46. What is Compost ? • Material left after the aerobic decomposition of organic material(s) Organic Material + “bugs” + O2  Compost + CO2 + H2O

47. General Characteristics • N availability much lower than fresh materials like manures, biosolids, food processing wastes (<10% of TN) • Diverse array of “feedstocks” used to make compost • Variability in quality of finished compost • Comes with lots of “things” besides macro-nutrients

48. Assessment of maturity • High concentrations of ammonium-N indicate immature compost • - should be less than 40 ppm • Measure microbial respiration under optimal • moisture, temperature conditions • - High respiration= high activity= unstable • - Low respiration=low activity= stable • Test compost or compost blend BEFORE using

49. Fresh Vs. Composted Organic Matter • Fresh Wastes • High biological activity • Some have high nutrient availability • Can immobilize nutrients during early stages of decomposition • Highly variable in physical traits • Instability can increase Pythium damping off of certain crops • Compost • Already gone through decomposition, stable • Mature compost should provide some nutrients • Improves drainage and other physical properties • Provides for biological control of Phytophthora root rot

50. Making Your Own Compost • Build a “bin” 5 x 5 x 5 ft. • Add organic materials and adjust to 40-60 % water content • Use bulking agent for wet materials, add water to dry materials • High C:N materials take longer • Maintain aeration by frequent turning • Compost is finished when pile doesn’t re-heat and it is difficult to distinguish initial materials