OUR FOOD, OUR SOIL: sustainable agriculture in the 21 st century. Sina Adl Department of Biology Dalhousie University

Transcription

1 OUR FOOD, OUR SOIL: sustainable agriculture in the 21 st century Sina Adl Department of Biology Dalhousie University

2

3 fertilizers composted manure grazing manure and urine Producer subsystem CO 2 Decomposer subsystem

4 Long term impact of agriculture Exponential decrease in soil organic matter Loss of soil structure Wind/water erosion Nutrient depletion Poor water retention Loss of decomposition efficiency Yield decrease, disease susceptibility, weather sensitivity Long term footprint on soil

5 Paustian et al Compilation

6 The land use history ( ) of a mixed hardwood forest in western Belgium and its relationship with chemical soil characteristics Verheyen et al. (1999)

7 Conventional mitigation of impact Fertiliser Disrupted soil community Replaces natural N fixation Pollution Pesticides & herbicides Bioaccumulation Non-target effects Dispersal to ecosystems Pollution, toxicity Irrigation Soil erosion Salinity built-up Loss of ground water Compensation, subsidies

8 Impact of agriculture on soil Compaction Aeration, drainage Temperature Moisture retention Reduced biological decomposition, nutrient cycling

9 Is there a crisis in agriculture? Naturally poor vs Ag degraded soils Inhabiting fertile soils Water resources (oil, dams, ground water, waste)

10 Summary of criticisms Loss of organic matter Causes erosion and yield decline Pollution Water intensive Unsustainable yields Diversity loss Loss of biological function

11 Composts reverse soil degradation Organic matter input Return biological activity Improve mineral availability Reduce compaction Improve water retention Reduce pollutant leaching Improve chemical degradation Improve yields

12 Soil community structure

13 Fungi Responsible for most of organic matter decomposition

14 Mycorrhizae

15 Ameobozoa scale bar 10 microns

16 scale bar 50 microns Testate amoebae

17 Soil flagellates feed on bacteria 10 6 to per gram

18 Nematodes feed on bacteria, fungi, protozoa and other nematodes predatory nematode

19 Soil mites feed on fungi, decomposing organic matter, or prey

20 Pseudoscorpions

21 Insect larvae

22 Earthworms (Oligochaeta) Enchytraeids

23 COMMON COMPOSTING PROBLEMS Unwanted material (metals, plastic, etc.) Toxic material (medical, pesticides, solvents, household chemicals, etc.) Stink prior to collection Pest reproduction Poor fermentation management Stinky fermentation Stalled fermentation Poor composting Poor quality product Variable product quality

24 SOLUTIONS Collection frequency, container design Source separation Facility design (smell and waste) Microbiological monitoring of fermentation Management of input organic composition Product quality control Whole system set of legislated standards Companies will do things as cheaply as the legislation and contract permits

25 Recommendations Source separation/triage before composting Implement industry standards and quality control Waste-collection is separate from product manufacture & marketing Hire fermentation & decomposition specialists Measure metal bio-availability in soil rather than total content

26 Uses for good quality composts: Organic matter amendment to agriculture Can substitute chemical fertilizers Including use of compost teas Metal levels well below guidelines Some salts may be high Moisture and C/N ratio is adjustable Can be a high quality product Doesn t need to end in landfill Mine site remediation, ecological restoration

27 Uses of composted MSW

28 Recovery of ped structure

29 Soil recolonisation rate Georgia USA, conservation farming chicken litter cotton no tillage

30 SOIL %C C/N ratio 5 Douglas COTTON soil %C SPRING FALL Spring Fall FIELD (YRS conservation) 0-20

31 Compost amendment can reverse soil degradation 120 Morphotypes g Flagellate Gymnamoebae Testacea Ciliata R in FIELD (Years in no-till)

32 Tillage thousand yrs ago Tigris, Euphrates,Nile, Indis, Yangtze valleys 8,000 YBP SE Europe Jethro Tull, populariser US moldboard plow Thomas Jefferson 1784 John Deere, mass market Accelerated erosion Tractors, dust-bowl 1930s Faulkner 1942, Plowman s Folly Short term fertility Long-term decline 95 million ha no-till today

33 Organic agriculture? Agriculture without Pesticides Herbicides Fertilisers Transgenic crops Lower-yield varieties Susceptible to disease Tillage management Storage limitations Off-site contamination, recalls

34 Axis 2 Soil quality indicators, management practices, month: comparison of organic and potato in Maritimes 1.6 Soil Quality Indicators CCA Biplot July 0.6 Nematode Organic 0.3 Microbial Biomass PH % Moisture Testate Amoebae Microarthropod September -0.6 Bulk Density C:N ratio -0.3 Conventional May Vector scaling: Axis 1 Nesbitt thesis, SRES, 2006

35 Mathematical model of increased area under organic management (Adl, Iron & Kolokolnikov) Organic agriculture addresses pollution and chemical issue only Issue of food security, and food safety cannot be set aside

36 Towards sustainability Soil organic matter management Society C waste recycling, MSW composting Urban to rural C transfer Rethinking urban waste management Reduced tillage Improved soil properties, water budget, reduced pesticides/herbicides Biological approach to soil nutrient management Crop rotations, locally adopted varieties Rebuilding soil N fixation Both provide stable complete soil food-web improving decomposition

37

38 Concluding remarks Balancing competing interests Farm machinery, fertilisers, seeds, biotechnology Short term politics, business greed Public education on food production issues Managing how to feed the world is too serious an issue Must be detached from fads and pseudo-science

39 Main points Decades for natural recovery of soil diversity and function, can be accelerated through management Cheap sources of organic matter for recovery of ped structure and micro-habitats Main drivers for remediation are societal and political Healthy environments Carbon trading and carbon credits

40 from Gary Larson