permaculture

[Lawrence London <lfljvenaura@gmail.com>]

Crush the right rock and spread it on farms to help soil and the climate |
Ars Technica
https://arstechnica.com/science/2018/02/spreading-crushed-rock-on-farms-could-improve-soil-and-lower-co%E2%82%82/

A new paper from a group of authors led by David Beerling
<https://www.sheffield.ac.uk/aps/staff-and-students/acadstaff/beerling> of
the University of Sheffield argues the case that something that sounds a
little wild—spreading crushed basalt over the world’s croplands—could
actually be pretty practical.

Basalt and some other types of rock loaded with silicate minerals remove CO2
from the atmosphere as they weather thanks to chemical reactions with
water. Carbon dioxide dissolved in rainwater is turned into bicarbonate,
which trickles away in groundwater or rivers and eventually reaches the
ocean. This process has had a huge impact on greenhouse gas concentrations
over Earth’s history but does so only slowly. It would have to be put on
steroids to be helpful within the next century.

You might be surprised to learn we already commonly do something like this
on agricultural land—just with the wrong kind of rock. Farmers often add
crushed limestone to their fields to counteract soil pH changes resulting
from fertilizer application. Unfortunately, acidic soils can actually cause
some of that limestone (which is calcium carbonate) to transform into CO2,
which is released into the air.

But crushed basalt could do the same pH-adjusting job while providing a
variety of additional benefits. Weathering basalt minerals will release
nutrients, including phosphorus. (Think of the fertile soils that develop
in volcanic areas—basalt is a volcanic rock.) Basalt could help maintain
good soil structure and slow erosion.