Pesticide and Environmental Update
Soil Microbes Like Organic Fertilizer
Hard-working soil microorganisms help plants get the nutrients they need to
thrive. Agricultural Research Service studies in Weslaco, Texas, are
helping to reveal exactly how organic fertilizers and conservation tillage
enhance the microbes' activity.
Soil scientists Joe M. Bradford and Larry M. Zibilske of the ARS Integrated
Farming and Natural Resources Research Unit lead the experiments. The unit
is part of the ARS Kika de la Garza Subtropical Agricultural Research
For their tests, the researchers are working with specialists from three
Texas companies that produce organic-based fertilizers: Earthwise Organics,
Inc., of Harlingen; Ag Organics, Inc., of Houston; and Gardenville
Fertilizer Corp., of San Antonio. All-natural, organic fertilizers are
those approved for producing certified organic crops.
The scientists are using the fertilizers to grow strawberries--as a model
plant--in greenhouses. So far, microbes have released nutrients from the
fertilizers at an impressive rate, according to Zibilske. And, soil
microbes seem to unlock the nutrients at the time the developing strawberry
plants need them the most. Now the researchers want to find out whether
soil microbes in organic fields perform differently than those in
conventionally managed soils.
In experiments with cotton and corn, Zibilske and Bradford are using
conservation tillage. Unlike traditional tillage, conservation tillage
requires leaving crop residue on the field surface after harvest where it
Zibilske and Bradford report that conservation tillage improved the uptake
of phosphorus, iron and other nutrients by both cotton and corn plants. The
decaying crop residue likely nourished the soil microbes and bolstered
Allowing residues to decay on top of soil doesn't hurt crop growth or yield
in subtropical environments like southern Texas, according to Bradford,
leader of the research unit. It also decreases erosion and reduces
evaporation of needed water from the soil surface. In addition, not
plowing-under the residues helps farmers save on costs of labor, fuel and
equipment such as tractors.
Our Golden Harvest Natural Fertilizer will feed your soil!