Agriculture Reference
In-Depth Information
in a healthy soil. The bacteria
Paenibacillus
found in California
soils prevents tomatoes from being contaminated with salmo-
nella, and some microbes help plant roots uptake phospho-
rus from the soil. Chemical fertilizers—especially anhydrous
ammonia—can kill these microorganisms, although research
generally finds their impact on microbial communities to be
small. However, in cases where the impacts are larger, there
are ways to respond without giving up chemical fertilizer. The
absence of worms can be compensated for by aerating the soil
mechanically. Companies like Terra-One sell fungi and other
microorganisms to inject back into the soil. Gardeners have
been buying such microorganisms for decades.
Healthy soils are also high in organic matter (mostly the
decaying residues of previous crops), which help to prevent
soil erosion and increase the soil's capacity for retaining mois-
ture. Farmers can also return organic matter to the soil by
adopting no-till methods, where the soil is not penetrated by a
plow. They have also employed alternatives to chemical fertil-
izer, like livestock manure. Planting legumes between crops
(what is called a “cover” crop) not only increases nitrogen in
the soil (legumes are great at doing this) but since the legume
is not harvested it remains on the field and becomes assim-
ilated into the soil as organic matter. One American farmer
adopting these innovations has even put a monetary value on
this organic matter: $3,775 per acre.
Finally there is the pH issue. Through the application of
chemical fertilizers (and other practices) soils are becom-
ing more acidic over time, and once the pH balance is too
low, plant yields fall. The solution is simple: put something
on the ground to raise the pH. Organic fertilizers can some-
times achieve this, but the most common solution—a solution
centuries old—is to apply lime. Some regions like the state of
Washington have no local source of lime and the transporta-
tion costs are too high to import it, so farmers have watched
their pH levels fall with no immediate solution. There is talk
of a company creating something called “liquid lime” that
