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Long Term Organic Amendments Application in Vegetable Production Systems
Introduction
The vegetable growers in Florida rely completely on
methyl bromide fumigant to manage soil pathogens, nematodes, and weeds.
This production system, which generally includes raised beds, fertilizer,
polyethylene mulch and drip irrigation, has been very effective in
producing high vegetable yields. Non-chemical alternatives such as organic
amendments are as yet largely unproven, but do offer promise of more
sustainable solutions free of government regulation. The objective of this
study is to continue evaluating the long-term effects of organic
amendments on pepper (Capsicum annuum L.) and watermelon (Citrullus
lanatus [Thunb.] Manst.) growth, yield, soil chemical, and physical
properties. This research study is very unique, since is the “only”
experiment in the U.S and Canada that had been receiving a continuous
yearly organic amendment application since 1993 (10 years). Results from
the passed 10 years suggest that regular organic amendment applications to
a sandy Florida soil can increase plant growth and produce similar yields
with less inorganic nutrients than standard fertilization programs. Grower
input costs could be reduced through water and fertilizer conservation,
which would also decrease negative environmental effects.
The field experiments were conducted at the Univ. of
Florida, Southwest Florida Research and Education Center, Immokalee, FL.
The soil was
Immokalee fine sand
(sandy, siliceous, hyperthermic Arenic
Haplaquods). The experiment used a split-split experimental design with
four replications of each treatment. Main plots consisted of
organic or
non-organic amendment application, sub-plots of fumigated (i.e. methyl
bromide) and non-fumigated.
Organic amendments were applied prior to the bed
formation at different rates each year. Methyl bromide was applied at the
rate of 300 lb.acre-1. The pepper/watermelon rotations were planted each
year on raised bed 2.7 ft wide, 0.3 ft high, and 4.9 ft between centers
and 50 ft long. Beds were covered with white-faced black polyethylene
mulch. Peppers plants were planted at 45-cm spacing in double rows with 10
inches between plants giving plant populations of 17,454 plants.acre-1.
Watermelons were planted in a single row with 7 feet between plants giving
plant populations of 1,251 plants.acre-1. All fertilizer was injected by
the drip irrigation tubing and positioned in the center of the bed prior
to mulch application. Nitrogen was reduced by 50% in the organic amendment
areas to compensate the N mineralized from the organic amendment. No
granular fertilizer application at planting was used. The plants were
monitored for insects and diseases and pesticide were applied as needed
according to Univ. of Florida Extension guidelines.
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