Sunday, October 5, 2014

Christine Jones on Soil Carbon

Newton Community Farm

Deborah:  more carbon has come out of the soil than out of smokestacks and industry.

Flemish scientist (Van Helmand) from 1640s weighed soil in a tub, planted a willow in it, and after 5 years weighed the tree and weighed the soil.  The freeways over 149 pounds and the soil sighed only a few ounces less than originally.  The tree came from the air - carbon, hydrogen, oxygen, nitrogen.  Air is 78% N, 21% O, and all the rest are trace gases.  Carbon is only 0.04% of the atmosphere.

Most of the nitrogen fixing microbes refuse to be cultured in the lab.  Plants need about 60 different elements to grow and be healthy and associates with microbial and fungal communities in order to get them. Plants build soil at the roots through aggregates.  There's more water in the aggregate than outside and less oxygen than outside and right at the root tip in association with microrrhyzal fungi.  These aggregates can fix nitrogen even if they are not associated with legumes.  Bacteria can't fix nitrogen at atmospheric levels of oxygen.

Humus is formed inside the aggregates and needs 60% carbon, 8-10% nitrogen, 1-2% phosphorus, 0.8-1.2% sulfur to form, with the remainder being aluminum, iron….

Soil is 50% oxygen bound to other elements and 30% silicon, and then aluminum and iron (20%) which act as catalysts. Degrading soils have more free aluminum.

Humus is an organo-mineral complex formed inside the aggregates.  Humus is honey-colored, a gel-like substance and looks like crude oil under the microscope.

Organic matter in the soil breaks down into CO2 and plants take it up through the underside of the leaves. For some plants, this is the most important source of CO2. This is the soil respiration rate and this carbon can be the limiting factor in plant growth:  labile carbon.

Grasses build soils.  Van Helmand's experiment would have found that there was more soil in his tub than when he started.

90% of the roots of most plants are in the top 50 centimeters (18 inches) of the soil.

Measure of plant photosynthesis:  brixing
Superphosphate inhibits mycorrhizal fungi.

Grasses build soils through producing humus.  Grasses depend upon good soil and thus put carbon back into the soil.  Grasses build soil better than anything else.  Soil is a product of photosynthesis and microbial resynthesis so soil is not the base of the pyramid, photosynthesis is.  Only the growing root tips grow new soil and this active growing of grasses need grazing animals.

There is the decomposition pathway for carbon, catabolic pathway, and the liquid carbon pathway, an anabolic pathway which builds up humus which produces a non-labile form of carbon, stable carbon.  Increase our capacity for photosynthesis, becoming light farmers, never leaving bare ground.

Mycorrhizal fungi take carbon from the roots and provide other nutrients to the plants.  This is natural carbon trading.  Have a soil restoration credit rather than simply a commoditized carbon credit.  Every farm becomes a carbon sink rather than a carbon source.

Liquid carbon is where carbon is being moved to the most actively growing roots, at the depth of 12-16 inches.  Up to 80% of the carbon can become humus at a rate of up to 30 tons per year.  In humus, the carbon is in ring form rather than chains and is much harder to breakdown.

A healthy soil is a net sink for methane through methantrophs.

Annual grasses use photosynthesis more efficiently than perennials.

Cover crops:  ryegrass, vetch, clover for over winter
oats, field peas, buckwheat for winter kill
And do multi-species cropping.  Cocktail cover cropping.