Organic Fertilizers
For organic gardeners, creating a living soil rich in humus and nutrients is the key to growing great fruits and vegetables, abundant flowers, and long-lived ornamental trees and shrubs. The overall fertility and viability of the soil, rather than the application of fertilizers as quick fixes, is at the very heart of organic gardening.
But like
all gardeners, organic gardeners have to start somewhere. Your soil may
be deficient in certain nutrients. It may not have excellent soil
structure. Its pH may be too high, or too low. Unless you’ve lucked into
the perfect soil, you’re going to have to work to make it ideal for
gardening.
Chemical Vs. Organic
Many organic
materials serve as both fertilizers and soil conditioners—they feed both
soils and plants. This is one of the most important differences between
a chemical approach and an organic approach toward soil care and
fertilizing. Soluble chemical fertilizers contain mineral salts that
plant roots can absorb quickly. However, these salts do not provide a
food source for soil microorganisms and earthworms, and will even repel
earthworms because they acidify the soil. Over time, soils treated only
with synthetic chemical fertilizers lose organic matter and the
all-important living organisms that help to build a quality soil. As
soil structure declines and water-holding capacity diminishes, more and
more of the chemical fertilizer applied will leach through the soil. In
turn, it will take ever-increasing amounts of chemicals to stimulate
plant growth. When you use organic fertilizers, you avoid throwing The manufacturing process of most chemical fertilizers depends on
nonrenewable resources, such as coal and natural gas. Others are made by
treating rock minerals with acids to make them more soluble.
Fortunately, there are more and more truly organic fertilizers coming on
the market. These products are made from natural plant and animal
materials or from mined rock minerals.
However, the national standards
that define and distinguish organic fertilizers from chemical
fertilizers are complicated, so it’s hard to be sure that a commercial
fertilizer product labeled “organic” truly contains only safe, natural
ingredients. Look for products labeled “natural organic,” “slow
release,” and “low analysis.” Be wary of products labeled organic that
have an NPK (nitrogen-phosphorus-potassium) ratio that adds up to more
than 15. Ask a reputable garden center owner to recommend fertilizer
brands that meet organic standards.your
soil into this kind of crisis condition.
Using Organic Fertilizers
If you’re a
gardener who’s making the switch from chemical to organic fertilizers,
you may be afraid that using organic materials will be more complicated
and less convenient than using premixed chemical fertilizers. Not so!
Organic fertilizer blends can be just as convenient and effective as
blended synthetic fertilizers. You don’t need to custom feed your plants
organically unless it’s an activity you enjoy. So while some experts
will spread a little blood meal around their tomatoes at planting, and
then some bonemeal just when the blossoms are about to pop, most
gardeners will be satisfied to make one or two applications of
general-purpose organic fertilizer throughout the garden.
Convenient products like dehydrated organic cow-manure pellets and
liquid seaweed make it easy to fertilize houseplants and containers too.
(Don’t use fish emulsion indoors, though, because of its strong odor.
Save it for your outdoor containers and garden plants.)
You can also make custom mixes to address your plants’ specific needs.
For example, you can use bat and bird guano, composted chicken manure,
blood meal, chicken-feather meal, or fish meal as nitrogen sources.
Bonemeal is a good source of phosphorus, and kelp or greensand are
organic sources of potassium.
Dry Organic Fertilizers
Dry organic
fertilizers can consist of a single material, such as rock phosphate or
kelp (a type of nutrient-rich seaweed), or they can be a blend of many
ingredients. Almost all organic fertilizers provide a broad array of
nutrients, but blends are specially formulated to provide balanced
amounts of nitrogen,
potassium, and phosphorus, as well as micronutrients. There are several
commercial blends, but you can make your own general-purpose fertilizer
by mixing individual amendments.
Applying Dry fertilizers
The most common way to apply dry fertilizer is to broadcast it and then hoe or rake it into the top 4 to 6 inches of soil. You can add small amounts to planting holes or rows as you plant seeds or transplants. Unlike dry synthetic fertilizers, most organic fertilizers are nonburning and will not harm delicate seedling roots.
The most common way to apply dry fertilizer is to broadcast it and then hoe or rake it into the top 4 to 6 inches of soil. You can add small amounts to planting holes or rows as you plant seeds or transplants. Unlike dry synthetic fertilizers, most organic fertilizers are nonburning and will not harm delicate seedling roots.
During the growing season, boost plant growth by
side-dressing dry fertilizers in crop rows or around the drip line of
trees or shrubs. It’s best to work side-dressings into the top inch of
the soil.
Liquid Organic Fertilizers
Use
liquid fertilizers to give your plants a light nutrient boost or snack
every month or even every 2 weeks during the growing season. Simply mix
the foliar spray in the tank of a backpack sprayer, and spray all your
plants at the same time.
Plants can absorb liquid
fertilizers through both their roots and through leaf pores. Foliar
feeding can supply nutrients when they are lacking or unavailable in the
soil, or when roots are stressed. It is especially effective for giving
fast-growing plants like vegetables an extra boost during the growing
season. Some foliar fertilizers, such as liquid seaweed (kelp), are rich
in micronutrients and growth hormones. These foliar sprays also appear
to act as catalysts, increasing nutrient uptake by plants. Compost tea and seaweed extract are two common examples of organic foliar fertilizers.
Applying Liquid Fertilizers
With flowering and fruiting plants, foliar sprays are most useful during
critical periods
(such as after transplanting or during fruit set) or periods of drought
or extreme temperatures. For leaf crops, some suppliers recommend
biweekly spraying.
With flowering and fruiting plants, foliar sprays are most useful during
When using liquid fertilizers,
always follow label instructions for proper dilution and application
methods. You can use a surfactant, such as coconut oil or a mild soap (¼
teaspoon per gallon of spray), to ensure better coverage of the leaves.
Otherwise, the spray may bead up on the foliage and you won’t get
maximum benefit. Measure the surfactant carefully; if you use too much,
it may damage plants. A slightly acid spray mixture is most effective,
so check your spray’s pH. Use small amounts of vinegar to lower pH and
baking soda to raise it. Aim for a pH of 6.0 to 6.5.
Any
sprayer or mister will work, from hand-trigger units to knapsack
sprayers. Set your sprayer to emit as fine a spray as possible. Never
use a sprayer that has been used to apply herbicides.
The
best times to spray are early morning and early evening, when the
liquids will be absorbed most quickly and won’t burn foliage. Choose a
day when no rain is forecast and temperatures aren’t extreme.
Spray
until the liquid drips off the leaves. Concentrate the spray on leaf
undersides, where leaf pores are more likely to be open. You can also
water in liquid fertilizers around the root zone. A drip irrigation
system can carry liquid fertilizers to your plants. Kelp is a better
product for this use, as fish emulsion can clog the irrigation emitters.
Using Growth Enhancers
Growth enhancers
are materials that help plants absorb nutrients more effectively from
the soil. The most common growth enhancer is kelp (a type of seaweed),
which has been used by farmers for centuries.
Kelp
is sold as a dried meal or as an extract of the meal in liquid or
powdered form. It is totally safe and provides some 60 trace elements
that plants need in very small quantities. It also contains
growth-promoting hormones and enzymes. These compounds are still not
fully understood, but are involved in improving a plant’s growing
conditions.
Applying Growth Enhancers
Follow the directions for spraying liquid fertilizers when applying growth enhancers as a foliar spray.
Follow the directions for spraying liquid fertilizers when applying growth enhancers as a foliar spray.
You
can also apply kelp extract or meal directly to the soil; soil
application will stimulate soil bacteria. This in turn increases
fertility through humus formation, aeration, and moisture retention.
Apply
1 to 2 pounds of kelp meal per 100 square feet of garden each spring.
Apply kelp extract once a month for the first 4 or 5 months of the
growing season.
If fresh seaweed is available,
rinse it to remove the sea salt and spread it over the soil surface in
your garden as a mulch, or compost it. Seaweed decays readily because it
contains little cellulose.
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