7-Soil_Organic_Matter.pdf

Transcript

1. EES 140 Spring 2017 Kaizad F. Patel 1 EES 140 Spring 2017 Kaizad F. Patel 2 What is organic matter?
2. EES 140 Spring 2017 Kaizad F. Patel 2 3 Water-holding capacity, infiltration capacity Aggregate stability, structure Erosion control Soils: Physical Properties 4
3. EES 140 Spring 2017 Kaizad F. Patel 3 CEC Nutrient availability pH buffering Soils: Chemical Properties 5 Vitamins, amino acids, hormones Micronutrients Allelopathy Plant growth 6
4. EES 140 Spring 2017 Kaizad F. Patel 4 Food for heterotrophs Soils: Biological Properties 7 8 The carbon cycle
5. EES 140 Spring 2017 Kaizad F. Patel 5 9 Plant residues 10
6. EES 140 Spring 2017 Kaizad F. Patel 6 Oxidation Breakdown 11 Sugars, starches and simple proteins Crude proteins Hemicellulose Cellulose Fats, Waxes Lignin 12 Plant Residues Decreasing rate of decomposition Increasing complexity of molecular structure
7. EES 140 Spring 2017 Kaizad F. Patel 7 13 Increasing complexity of molecular structure 14 Decomposition can be aerobic or anaerobic
8. EES 140 Spring 2017 Kaizad F. Patel 8 15 Active Pool Passive Pool 16
9. EES 140 Spring 2017 Kaizad F. Patel 9 17 Plant, animal residue Large biopolymers Small biopolymers Monomers CO2 Protected/ stabilized OM (slow turnover) Protection within microaggregates Protection by sorption to mineral surfaces Labile fraction (quick turnover) Soil Continuum Model for SOM Adapted from Lehman and Kleber (2015) 18
10. EES 140 Spring 2017 Kaizad F. Patel 10 19 Generalization: C/N ratio of soil microbial community = 8:1 20 C/N ratio influences the availability of N in the soil
11. EES 140 Spring 2017 Kaizad F. Patel 11 Michael J. Singer and Donald N. Munns Soils: An Introduction, 6e Mobilization or immobilization of N High N input (low C/N ratio) Low N input (high C/N ratio) N mobilized (mineralized) N immobilized Available N in soil Microbial Activity Period of N Limitation or “Nitrate Depression” High C/N ratio organic material added to soil + - 22 Microbes producing CO2 Microbes taking up N from the soil Time
12. EES 140 Spring 2017 Kaizad F. Patel 12 23 C/N ratio influences the rate of labile SOM decomposition higher C/N ratio = slower decomposition Climate Type of Vegetation Cultivation Soil Texture Topography 24 OM input OM decomposition
13. EES 140 Spring 2017 Kaizad F. Patel 13 25 Gelisols Slow decomposition Tropics Greater plant productivity Deserts Less plant productivity 26 wet + cold Slow decomposition = More OM water saturation Soil profiles: NRCS, Michigan State University
14. EES 140 Spring 2017 Kaizad F. Patel 14 27 wet + hot High inputs Fast decomposition = Less OM Soil profile: University of Idaho 28 dry + hot Less input = Less OM Soil profile: University of Idaho
15. EES 140 Spring 2017 Kaizad F. Patel 15 Vegetation 29 Depth of OM accumulation Type of OM inputs Roots vs. litter Type of horizon A vs. O 30 Climate Vegetation type Forests Grasslands Management Illuvial accumulation
16. EES 140 Spring 2017 Kaizad F. Patel 16 Conventional tillage vs. conservation tillage Conventional vs. sustainable/ organic cultivation 31 Effect of Cultivation 32 Effect of cultivation
17. EES 140 Spring 2017 Kaizad F. Patel 17 Yanai et al. 2003 33 Effect of logging 34 Soil Texture and SOM More plant biomass OM protected from decomposition Less aeration, so less OM loss Clay > Sand More aeration = Faster decomposition
18. EES 140 Spring 2017 Kaizad F. Patel 18 35 Drainage and SOM 36
19. EES 140 Spring 2017 Kaizad F. Patel 19 37 Loss on Ignition Weigh soil Combust at 450°C for 12 hours Weigh combusted soil 38 Soils and Climate Change
20. EES 140 Spring 2017 Kaizad F. Patel 20 Soil Organic Matter 39