Soil Ecology: whole system approach

1. Soil Ecology: whole system approach Sherrilyn Phelps, SAFRR Jill Clapperton, AAFC Stu Brandt, AAFC

2. “When you are standing on the ground you are really standing on the roof top of a whole other world.” Dr. Jill Clapperton ?

3. “We stand in most places on Earth, only six inches from desolation, for that is the thickness of the topsoil layer upon which the entire life of the planet depends.” R. Neil Sampson

4. What is soil? • Complex mixture of mineral matter, organic matter, living organisms, air, water • Product of the environment – constantly changing, constantly evolving • Develop over time • Supports life • “skin” of the land

6. Physical properties (soil physics) • Texture • sand, silt, clay • Structure • aggregates, held together • Colour • All influenced by OM

7. Influences gain and loss of radiant energy Useful for predictions Mineral weathering OM content State of aeration Color

9. Organic Matter • All humus is OM but not all OM is humus • Raw OM = waste products or remains of organisms not yet decomposed • Humus = decomposed • OM is the primary food source for most soil organisms/animals • Quantity and quality of OM is what drives nutrient cycling

11. Effects of Organic Matter/Humus • Bulk density = decreases bulk density • Pore space = increases pore space • Structure = provides crumb structure that resists compaction • Oxygen diffusion = increases oxygen diffusion rate • Field capacity = improves soil structure

12. OM Constituents (plant) • Carbon = 42% • Oxygen = 42% • Hydrogen = 8% • Ash = 8% • Macronutrients (N, P, K, S, Ca, Mg) • Micronutrients (Fe, Mn, B, Zn, Cu, Cl, Co, Mo, Ni)

13. Macronutrients: sources • Air and water • C, H, O • Soil • N, P, K, Ca, Mg, S • Complex organic compounds (CO2, H2O, NO3+, NH4-, H2PO4-, S042-) • C:N:P:S ratio is 100:10:1:1 approximate proportions in humus and therefore target for soil

14. Carbon • Building block of life

15. Nitrogen • Component in protein, amino acids • N2 from air/rain is fixed by soil MO • C:N ratio is important to OM cycle • Influences rate of minerlization and release of nutrients • Too high C:N = slow decomposition, binds N • 20 – 30:1 is ideal for nutrient cycling

16. Adapted from The Nature and Properties of Soils by Brady & Weil

18. Phosphorus • Complex chemical reactions • Easily immobilized – fixed with Al, Fe, Ca • Most of the available P is in the form of OM, released by microbial activity • P comes from rocks/soil

20. Other Macronutrients

21. Micronutrients • Important in small amounts • Fe, Mn, Cu, Co, Ni (+) • Mo, Bo, Cl (-) • Chelated forms generally (ring)

22. Ability to store cations (nutrients) 1/1000th of a gram of H+ per 100 grams of soil Higher CEC = more nutrients it can hold Humus increases CEC Cation Exchange Capacity

23. CEC (at pH 7.0)

24. pH • Measure of soil’s acidity or alkalinity • Concentration of H+ in solution • Acid = high [H+] • Basic = low [H+]

26. Biological Properties • Life in & out of the soil • Soil Ecosystem = system made up of parts • Animals & people – unless wastes are returned to soil – the whole life-supporting process is undermined • Soil organisms – perform vast array of fertility maintenance tasks • One part of system influences other part

27. Soil Organisms • Microorganisms • Fungi, actinomycetes, bacteria, algae • Microfauna • Nematodes, protozoa, rotifers • Insects & mullulsks • Mites, springtails, spiders, sowbugs, ants, beetles, centipedes, millipedes, slugs, snails • Earthworms • Mammals • Moles, mice, groundhogs • Plant roots

28. 1 teaspoon of soil • 100 million to 1 billion bacteria • Several yards of fungal hyphae • 1000s of protozoa • 10 to 20 nematodes • Insects & mullusks – 100s / cubic foot • Earthworms – 5 – 30 per cubic foot • Plant roots = 4000 kg/ha in top 120 cm SK

30. Bacteria • Decompose OM – simple C compounds • Consume/immobilize simple nutrients from soil • azotobacter, rhizobia, nitrobacter • N-fixers, S-oxidizers, nitrifiers

32. Photo by Dr. J. Clapperton, AAFC

33. U of S

34. Bacteria – N fixation • Rhizobia & Bradyrhizobia • symbiotic with legumes • Actinomycetes • symbiotic with angiosperms • Cyanobacteria • Associative with various higher plants and MO

38. Fungi • Carry out largest share of decomposition in cultivated soils • cellulose, starch, gums, lignin, proteins, & sugars • C is energy source • Major role in humus formation and aggregate stabilization (hyphae, exudates) • Yeasts, mushrooms, molds • Some are predators of soil animals (ie., some trap nematodes)

39. Dr. Jill Clapperton, AAFC

40. Photo by Dr. J. Clapperton, AAFC

41. Fungi Benefits • Mycorrhizae association (fungus root) • Team up with plants • Sugars from root cells = energy source • Provide extension of root system = nutrient availability • Increase uptake of P and other nutrients • Prevent uptake of toxic levels of some nutrients • Evidence for protection against soil borne diseases

42. Vesicular Arbuscular Mycorrhizae (VAM)

43. Vesicular Arbuscular Mycorrhizae (VAM)

44. Dr. Jill Clapperton, AAFC

45. The relationship between some crop species and VAM fungi Potatoes and other root crops Most tropical plants and trees

46. Photo obtained from Dr. Jill Clapperton, AAFC

47. Fungi effect on more than nutrients With P. bilaii Without P. bilaii Root hairs were 33% longer with inoculation over all P levels Kevin Vessey, U of M

48. Estimated Nitrogen Balance(N supplied minus N removed [kg/ha]) Stu Brandt, Alternative Cropping Study, AAFC Scott

49. Estimated Phosphorus Balance(P supplied/P removed [kg/ha]) Stu Brandt, Alternative Cropping Study, AAFC Scott

50. Oribatid Mites [Olfert] • - Feed on microbial and higher plants • decomposer/recycler = “pooping pellets” • move up and down roots, move nutrient, carry other organisms, great tunnels • - Respond negatively to cultivation