Page 277 - Environment: The Science Behind the Stories

the sCIeNCe BehINd the stORy

how Productive Is How can organic fields produce
Organic Farming? decent yields without relying on syn-
thetic chemicals? The answer lies in
the soil. Mäder’s team found that soil in
Organic farming puts fewer synthetic
chemicals into the soil, air, and water the organic plots had better structure,
than conventional industrial farming better supplies of some nutrients, and
does. But can organic farming pro- much more microbial activity and inver-
duce large enough crop yields to feed tebrate biodiversity (Figure 1).
the human population? The world’s Studies are continuing at the
two longest-running field experiments Swiss scientist dr. Paul Mäder (center) Swiss plots today, producing new
visits colleagues at Pennsylvania’s rodale
on the topic—in Switzerland and in institute. research results. As one example, Jens
Pennsylvania—suggest that the answer Leifeld and two colleagues at a Zurich
is yes. Researchers record crop yields research institute analyzed soil carbon
Let’s first visit Switzerland, where
one in every nine hectares of agricul- at harvest each year. They analyze 80
the soil regularly, measuring nutrient
tural land is managed organically (the content, pH, structure, and other 70
fifth-highest rate in the world). Back in variables. They also measure the
1977, Swiss researchers established biological diversity and activity of 60
experimental farms at Therwil, near microbes and invertebrates in the soil.
the city of Basel. Long-term studies Such indicators of soil quality help 50
are rare in agriculture and in ecology. researchers assess the potential for Percent increase over conventional plots supplemented with manure 40
They are highly valuable, because long-term productivity.
they can reveal slow processes or In 2002, Paul Mäder and col- 30
subtle effects that get swamped out leagues from two Swiss research insti- 20
by year-to-year variation in shorter- tutes reported in the journal Science
term studies. results from 21 years of data. Over this 10
At the Swiss research site,
wheat, potatoes, and other crops are time, the organic fields yielded 80% of 0 Soil Soil Soil
what the conventional fields produced.
activity
grown in plots cultivated in different Organic crops of winter wheat yielded chemistry structure Microbial
treatments: invertebrates
90% of the conventional yield. Organic
• Conventional farming using chemical potato crops averaged 58–66% of
pesticides, herbicides, and inorganic conventional yields because of nutrient Figure 1 organic fields developed better
fertilizers deficiency and disease. soil quality than conventional fields
• Conventional farming that also uses Although the organic plots pro- supplemented with manure. Values for
organic fertilizer (cattle manure) duced 20% less, they did so while soil chemistry (6 variables), structure
• Organic farming using only manure, receiving 35–50% less fertilizer than the (3 variables), invertebrates (5 variables),
mechanical weeding, and plant conventional fields and 97% fewer pes- and microbial activity (6 variables) were
compared. Organic fields outperformed
extracts to control pests ticides. Thus, Mäder’s team concluded, conventional fields without manure (not
• Organic farming that also adds natu- the organic plots were highly efficient shown) still more. Data from Mäder, P., et
ral boosts, such as herbal extracts in and represent “a realistic alternative to al., 2002. Soil fertility and biodiversity in organic
compost conventional farming systems.” farming. Science 296: 1694–1697.

Organic agriculture . . . is based on minimal use of off-farm U.S. states and over 80 nations have laws spelling out organic
inputs and on management practices that restore, maintain, standards.
and enhance ecological harmony [and] minimize pollution For farmers, organic farming can bring a number of ben-
from air, soil, and water . . . The primary goal of organic ag- efits: lower input costs, enhanced income from higher-value
riculture is to optimize the health and productivity of interde- produce, and reduced chemical pollution and soil degradation
pendent communities of soil life, plants, animals, and people. (see The Science behind The STory, above). In many cases more
pests attack organic crops because of the lack of chemical pes-
California, Washington, and Texas established stricter ticides, but biocontrol methods (p. 256) can help keep pests in
276 state guidelines for labeling foods organic, and today many check. Moreover, the lack of synthetic chemicals maintains

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