Lecture 5 - Soil Flashcards
1
Q
Plant Roots & Exudates
A
- roots don’t grow deeper in dry periods (they shrink)
- roots extend the crown
- new feeder roots grow from outward the crown line, so mulch there
- most nutrient roots are found within 15cm, few up to 46cm, deeper is usually just for water uptake
- only very few trees (>2%) have a taproot
- roots can pump up water from deep and redistribute it in upper soil layers
- exudates consist of carbohydrates, sugar and small portion protein
- plants exude different exudates at different parts of the plant
- to attract bacteria and fungi and trade for micronutrients, and even pre-sysnthesized fats
- economy in the soil: plants produce the sugars from the energy of the sun, then trade that for nutrients and form the soil around each root according to their needs (micro climates)
- this only works in a functioning soil food web with all the members in right proportion
2
Q
Synthetic Fertilzer
A
- Romans killed their soils, tilled 6-12 x a year, brought this to Africa
- like them with European imperialism, western Europe exported its soil degrading agricultural techniques all over the globe
- in the tropics these have a even worse effect than in temperate climates
- industrialization amplified these degrading techniques to be even more degrading
- Haber-Bosch process: turn fossil fuels into NPK
- this lead to increased food production, population growth and soil degradation
- farmers all over the world became dependent on fertilzer and GMO contracts
- synthetic fertilizer are the gasoline to the fire
- synthetic fertilizer are salts that create salt layers, destroy soil food web, compact the soil, and more
3
Q
Soil Food Web - Trophic Layers
A
- First/Basal Layer: living and dead plant material (roots, plant litter, manure)
- Second Layer: organisms that feed on organic matter and exudates: decomposers, herbivores, plant parasites, they store nutrients: bacteria, fungi
- Third Layer: organisms that feed on bacteria and fungi (also decomposers) that make their nutrients available for the plants: protozoa, small nematodes, small micro-arthropods
- Fourth layer: larger micro-arthropodes and nematodes that feed on smaller ones
- Fifth layer: predatory macro-arthropods like beetles, centipedes that feed on smaller ones
4
Q
Soil Food Web - Members
A
- bacteria: fore runners, feed on organic matter, make glues for micro-aggregates. population stays stable throughout progression, bacteria-dominated soil (overpopulation) are weedy soils
- protozoa: consume bacteria and release micro-nutrients, marker for soil health under microscope
- nematodes (predator/root-feeding): regulators that keep populations in check, root-feeding ones can be a problem
- arthropods (micro/macro): consume and shred organic matter, fungi and bacteria, break things down and make them available to other members
- fungi (saphrotic/mycorrhizal/pathogenic): hyphae, mycellium, the complex connector within the soil food web, can digest what others can’t, the biggest carbon sequesters, orchestrate and facilitate all the trading
- plant roots: form symbioses, trade through exudates, change pH around the root area
5
Q
Top Soil
A
- 15-20cm where roots get most of their nutrients, most available nutrients, most connections of the soil food web
- this will tell you most about the quailty of the soil on your site
- never, never mix top soil with subsoil, if you dig it up seperate it and put it back the same way
- plants roots go laterally within this layer
6
Q
Nitrogen cycle
A
7
Q
Nitrogen fixing
A
- rhizobia enter the plan through a infection thread into the root hair that sends out hormones
- plant delivers sugars to the bacteria and the root hair swells to a nodule
- rhizobia cretae amino acids by fixing the nitrogen from the air and the carbon from the plant in an anaerobic reaction
- once the nodule has reached its amino capacity, then the bacteria share it with the plant
- there are other forms os nitrogen-fixing through symbiosis like Frankia bacteria
- most legumes (fabacea) are N-fixing, alder (alnus / Erlen)
- nodules don’t form in a pH >5 (acidic) or in
8
Q
pH
A
- alkaline (>7): bacteria dominant
- acidic (<7): fungi dominant
- healthy soils change and have diverse pHs throughout, depends on many factors, the plants and microbes change the pH according to their needs in different zones (that’s why no till is so effective in soil regenreation)
- above pH 7 = nitrate (NO3-) release (annuals + weeds grow well), chicken manure, vegetative growth, not fruit producing
- below pH 7 = ammonium, reproductive growth (seeds, fruits)
- with different compost teas, pH of the soil can be influenced at different times
- when used at the right time we can increase growth and fruit production
- with succession the soil gets more fungal dominant and acidic (beach alkaline, forest acidic)
9
Q
Nutrients
A
*
10
Q
Hydrophobic soil
A
- cement, concrete, hardpan, etc.
- needs to be cut/ripped and filled with organic matter, so it doesn’t wash out
- might need constant watering the first season
- introduce humidity through swales, earthworks
- rippers with compost tea injectors because the clay will seal up right after opening the soil and plant trees/plants with roots to break it up
- bad soil might need to be plowed once to break the layer of compacted salts, anaerobes, etc. to then innoculate it with the right microbes
11
Q
Aeration
A
- we want much aeration, easy to compress loam
- no heavy machinery
- no animals trampling
- broadfoarks, Yoeman plow, chisel plow
- aerobic bacteria
- easy for roots to penetrate
- critters need oxygen
12
Q
Soil Ethics
A
- use less land
- build soil
- conserve healthy soil
- build with soil
- use legumes & cover crops
- make good habitat for insects & worms
- innoculate with beneficial bacteria (rhizobia, EM) and fungi (EnM, EcM, AM)
- create windbreaks
- reduce compaction
- restore nutrient cylcles (include humanure)
13
Q
Reading landscape
A
- soil depth: if you know tree species present. juding by their specific growth (height), you can tell if soil is shallow or deep
- water: wet spots, depression area, where plants are congregating, etc.
- pH: knowing the pH preferences of certian species
- compaction: knowing plants with certain roots (ex. dandelion in compacted, bahia grass in loose soil)
- minerals: certain plants can indicate minerals, lack of nutrients can be observed in plants
- fire: see for burned areas, affected soil life
- frost pockets: less activity in colder months
- drainage: are there wet areas?
- overgrazing: very short plants, superficial layer of compaction
- animal activity: observe for burrows, attacked trees, trampled plants
14
Q
Vermicompost
A
- worm castings = worm manure, dark brown, nutrient rich structures, innoculated by useful bacteria
- stimulates plants growth and reduces pathogens
- creates healthy environment for useful bacteria
- red wigglers: eisenia fetida
- do research before you introduce new worm species, some earth worms might be invasive
- worm tea ≠ worm leachate (what drips out of worm compost)
- worm tea: take worm castings, suspend them in sack to water and aerate it a certain amount of time (aerobic)
- 0,5 - 1 kg vermicompost for every 20 l water (generous)
- aeration depends on temperature of liquid but never more than a couple of days, use aeration pump (aquariums)
- use chlorine-free water, as it kills beneficial bacteria
- worm tea can be diluted if needed
- worm leachate: has not necessarily gone through worm digestion, so it can contain harmful/pathogenic microbes
- worm leachate needs to be diluted 1:10 ratio and aerate that solution for at least 24 hours to be used safely, test on few plants first
- if you have a lot leachate, might be a sign for too much moisture
15
Q
Vermicompost - Applictation
A
- test the soil: nutrients/trace minerals and toxins, universities and state might offer these for cheap
- no hot peppers, onions, garlic, bones and citrus for vermicompost as they ususally take longer (worms don’t like them)
- worms need lots of ventilation (holes!)
- drainage for excess water/humidity
- in the beginning slowly integrate food scraps, no oil
- couple of slices of/hollowed out watermelon helps migrating the worms for harvest
- prevent your vermicompost from frost in winter
16
Q
Vermicompost - Worms
A
- hermaphrodites
- can double their population every 90 days
- 2-3 months to become adult
- baby worms hatch after 3 weeks
- worms can process multiple times their own weight in optimal conditions a day
- can process 0,25 - 0,5x their weight of fresh food waste
- moisture 70-80%
- 12 - 26°C
- food source: straw, shredded newspaper, organic scraps, egg shells
- need lot of oxygen, bulky bedding (toilet paper rolls, leaf litter, etc.)
- keep them in dark environment, no direct sunlight
17
Q
Fertilizer vs. Soil Microbilogy
A
- 80% of the soluble nutrients are lost and drained into rivers
- bacteria of the soil food web recycles all the nutrients from decaying organic matter and from unsoluble minerals that are present in every soil
- from NPK (50’s) to 42 essential elements (2010)
- the more we know the more elements and diversity and different nutrient cycles will be discovered
- let mother nature do it the way she came up with it for millions of years
18
Q
Building Soil
A
- mycrorrhyzal fungi
- innoculate the bare root systems when you plant trees, then mulch with wood cuttings
- innoculate seeds: coat them by soaking them in water and then dust them in myco-powder or soak them in compost tea
- crop rotations
- cover crops, nitrogen fixer in between cash crop
- might not be necessary if you use polycultures, cut & drop and feed the soil food web
- green manure
- cover crops, chop & drop, can also till it in, then cover it with earth to speed up the composting process
- green manure holds the space that weeds would take over usually
- usually used in off-season to not interfere with cash crop
- soil building crops
- C4 plants that give back lot of carbon if chopped & dropped
- hemp, corn, sugar cane, sorghum
- cowpeas: fix most nitrogen and carbon (work well with corn)
- compost
- hot compost, vermicompost, compost tea
- thermophilic compost produces pathogen and weed seed free compost
- introduce healthy compost and organic matter and the life in the soil will spread and build soil further and further away from the original compost
- vermicompost usually free of pathogenic microbes due to worm activity, but weed seeds are not affected and can still germinate, has increased volume compared to thermophilic compost
- compost tea
- suspend high quality compost in microperforated bag to infuse the organisms into the water
- then aerate and feed it (the food will determinate if it will be bacterial/fungal dominant apart from the type of compost used in the beginning)
- then spray it
- sprayers to be cleaned directly afterward, otherwise bioflim will clog it
- as the food source runs out after a certain time even while aerating it, the tea will turn anaerobic, don’t leave it for too long
- nutrient accumulator & mulch plants
- certain species that produce lots of plant material to mulch with and/or accumulate nutrients from deeper layers to the top soil layer where members of the soil food web can cycle them and make them availabale to the plants
23
Q
Berkeley method (Raabe)
A
- carbon-to-nitrogen ration should be 30:1
- bacteria use carbon for energy and nitrogen for proteinbiosynthesis
- green material (nitrogen): fresh grass clippings, manure, alfalfa meal, comfrey, vegetable waste, green prunings
- brown material (carbon): straw, cardboard, dead leaves, dried grass, paper
- right recipe when you get immediate heat (thumb rule same amount of brown and green material)
- optimal heat: consistently 60 - 70°C (measure daily with a thermometer)
- material need to be cut/chopped into small pieces to allow great surface area to catalyze the reaction of the bacteria (use shredder /chipper or run over with lawn mower)
- optimal size 1,5 - 4cm
- pile needs 50% humidity (material clumps and might drip a bit when you squeeze, but no water running out)
- layer of coarse (bigger) material on the floor to let air in, then layer shredded green and brown layers on top of each other (while mixing them a bit) and water them after each layer
- pile needs to be turned every other day when maximum temperature is reached (leave space next to the pile!)
- composting is trial and error: make many piles with different ratios and see which works best
- the turning tends to break up mycellium, so the product is usually bacterial-dominant
*
42
Q
Making Biochar
A
- make a staple from dried sticks in a pyramid kiln
- light them up from the top
- light it on the side from where the wind is coming from
- it will burn now with (almost) no smoke
- will create a bed of coal
- put a new layer of sticks on top (ca. 20cm)
- it will start burning from the top again (oxygen from below goes up to the upper layer)
- last layer: let it burn a little longer until it’s fully carbonized
- kill the fire with water (possibly innocultated)
- reuse that water for your plants
- use leaf vacuum from Stihl to collect and granulate the coal from the kiln
