Agriculture Reference
In-Depth Information
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
cropping in the rotation, as this crop earned high prices. The organic sys-
tem was the most profitable of the four-year rotations because of organic
price premiums. Problems in the organic system were related to high ni-
trogen demand and weed management costs. This study exemplified the
complexity of crop comparisons, as the organic system had a complicated
rotation of crops that built soil fertility: cover crop, safflower, cover crop,
corn, oats/vetch, bean, cover crop, tomato. The two-year conventional rota-
tionwas simply tomato, wheat, tomato, wheat (and soil fertility was supplied
by agrichemicals). Given the profitability of tomatoes, it is clear why some
farmers would choose this two-year rotation. Organic farms must be guided
by longer-term goals and ecological balance. And the authors note that this
study did not include the long-termbenefits of increased soil organicmatter,
nutrient storage, or reduced erosion.
The Sustainable Agriculture Farming System Project in the Sacramento
Valley provided information to study the long-term effects of organic, low-
chemical input and conventional farmmanagement (Colla et al. 2002). The
data was detailed: From 1989 to 2000 the specific field methods such as
planting dates and input names were logged. The soil chemical properties,
crop yields, and cropmineral compositions were compared. Results showed
that the organic soils developed the highest levels of carbon, nitrogen, sol-
uble phosphorus, exchangeable calcium, and potassium. Organic tomato
yields were similar to the conventional and low-chemical input yields. Or-
ganic tomatoes contained higher levels of phosphorus and calcium, while
conventional tomatoes had higher levels of nitrogen and sodium. While the
levels may not lead to human health concerns, the 38 percent higher nitrate
levels in conventional tomatoes would likely cause metal storage containers
to corrode. Over the long term, organic practices produced tomato yields
similar to conventional farmingmethods,with richer soil andmoreminerals
in the food crop.
The “purported drawbacks” of organic tomato farming that “include
an increased incidence of pest damage and higher risk of pest outbreaks”
were investigated in California (Letourneau and Goldstein 2001, 557). This
fascinating study compared tomato production on eighteen commercial
farms (half were certified organic) and found that damage to tomato fo-
liage and fruit did not differ between certified organic and conventional
farms. Specifically, this research focused on arthropod communities (that
means “bugs” to most of us: spiders, beetles, ants, etc.). Both types of farms
had arthropod damage, but there were big differences in the community
structures - organic farms had higher richness of species and natural en-
emies. This indicated that any one particular pest bug would be “diluted”
[47],
(8)
Lines: 102 to 106
———
0.0pt PgVar
———
Normal Page
PgEnds: T
E
X
[47],
(8)
