October 2020 - 25

ORGANIC
happen because nitrogen is a limiting
nutrient, but it's not something you can
tell by looking at the plants. "
A stalk test at harvest is a good measure
of any excess nitrogen and can help plan
for next year. " It's kind of like a report
card test, " Heckman said. " It gives you a
chance to ask, 'How am I doing?' "
As always, weather issues - too much
rain or temperatures that are too cold -
will always complicate a nitrogen program.
" In a cooler, wet spring, you're losing
nitrogen a couple of ways - leaching and
denitrification - and you're slowing the
nitrogen release in the soil, " Heckman said.
Soil testing will determine if the sweet
corn has its optimum soil pH of 6.5.
Liming in organic production is much
the same as in conventional agriculture
except that " burnt lime " and " quicklime "
are prohibited as soil amendments. Both
calcite and dolomite types of limestone are
allowed, widely available and commonly
used in organic crop production.
Sweet corn also needs a balance of all
other essential plant nutrients.
" There's a lot of good potassium sources
that are readily available for organic
growers, " Heckman said. Potassium sulfate
is a good choice on sandy soils because
sulphur can leach out of the root zone.
" Sulphur is important, " Heckman said.
" It may even enhance sweet corn flavor.
That's something about vegetables. It's not
just yield; it's also about quality. "
" Manure and compost are generally
good sources of
phosphorus, "
Heckman said. " If
you're applying
manure or
compost, you're
probably OK with
phosphorus. "
Manure or
compost will also
generally ensure
JOSEPH
HECKMAN
adequate sulphur fertility but a soil test is
the only way to know for sure.
If growers do need a higher phosphorus
fertility level, they may use rock
phosphate. Legumes grown in a rotation
can help make the phosphorus from rock
phosphate available. " That's part of the
organic system if you have to use rock
phosphate, " Heckman said.
Soil tests must also test for micronutrients.
Boron is important for pollination and good
kernel fill. " Make sure you test for boron.
Boron is very important to get ear fill to the
tip, " Heckman said. One to two pounds of
boron per acre is recommended if needed
based on soil test.
Manganese deficiency sometimes
occurs on New Jersey's coastal plain
soils. The treatment is foliar applications
of manganese sulfate at one pound of
manganese per acre.
Finding micronutrient fertilizer
sources is generally not a big challenge.
" As long as you can document a need,
you can pretty much use the same
micronutrient sources that you can
on conventional corn, " Heckman said.
" Check with your organic certifier if you
have any questions about the fertilizer
sources you're using. " VGN
80007-2_7.2x10.25.indd 1
VGN | OCTOBER 2020 | 13
8/11/20 8:31 PM
Morgan Composting of Sears, Michigan, mixes custom soils and products for specialty crop growers, many of whom are organic.
Photo: Stephen Kloosterman
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October 2020

Table of Contents for the Digital Edition of October 2020