Liquid fertilizers are faster-acting than
seed meals and other solid organic products, so liquids are your best choice
for several purposes. As soon as seedlings have used up the nutrients provided
by the sprouted seeds, they benefit from small amounts of fertilizer. This is
especially true if you’re using a soil-less seed starting mix (such as a
peat-based mix), which helps prevent damping-off but provides a scant supply of
nutrients. Seedlings don’t need much in the way of nutrients, but if they
noticeably darken in color after you feed them with a liquid fertilizer, that’s
evidence they had a need that has been satisfied. Liquid fertilizers are also
essential to success with container-grown plants, which depend entirely on their
growers for moisture and nutrients. Container-grown plants do best with
frequent light feedings of liquid fertilizers, which are immediately
distributed throughout the constricted growing area of the containers.
Out in the garden, liquid fertilizers can be
invaluable if you’re growing cold-tolerant crops that start growing when soil
temperatures are low for example, overwintered spinach or strawberries coaxed
into early growth beneath row covers. Nitrogen held in the soil is difficult
for plants to take up until soil temperatures rise above 50 degrees Fahrenheit
or so, meaning plants can experience a slow start because of a temporary
nutrient deficit in late winter and early spring. The more you push the spring
season by using cloches and row covers to grow early crops of lettuce, broccoli
or cabbage in cold soil, the more it will be worth your time to use liquid
fertilizers to provide a boost until the soil warms up.
Water-soluble homemade fertilizers are
short-acting but should be applied no more than every two weeks, usually as a
thorough soaking. Because they are short-acting, liquid fertilizers are easier
to regulate compared with longer-acting dry organic fertilizers, though I like
using both. With an abundant supply of liquid fertilizer to use as backup, you
can use a light hand when mixing solid organic fertilizer into the soil prior
to planting.
To explore the art of making fertilizer tea,
Brinton began by trying various ways to mix and steep grass clippings, seaweed
and dried chicken manure (roughly 33 percent manure mixed with 66 percent wood
shavings). The best procedure he found was to mix materials with water at the
ratios shown in the Homemade Fertilizer Tea Recipes chart, and allow the teas
to sit for three days at room temperature, giving them a good shake or stir
once a day.
“By the third day, most of the soluble
nutrients will have oozed out into the water solution,” Brinton says. Stopping
at three days also prevents fermentation, which you want to avoid. Fermented
materials will smell bad, and their pH can change rapidly, so it’s important to
stick with three-day mixtures and then use them within a day or two. Brinton
also studied human urine, which is much more concentrated than grass, manure or
seaweed teas, and doesn’t need to be steeped.
The lab analyzed the four extracts for
nutrient and salt content. Salts are present in most fertilizers, but an excess
of salts can damage soil and plant roots. Brinton found that chloride and
sodium salts were so high in urine that they needed to be diluted with water at
a 20:1 ratio before being used on plants. In comparison, the seaweed extract
could be used straight, and the grass clipping and chicken manure extracts
needed only a 1:1 dilution with water to become plant-worthy. Read the full
report from Woods End Laboratories.
As a general guideline, most vegetables use
the three major plant nutrients — nitrogen, phosphorus and potassium — in a
ratio of roughly 3-1-2: three parts nitrogen, one part phosphorus and two parts
potassium. This means that an N-P-K ratio of 3-1-2 is more “balanced” in
meeting plants’ needs than 1-1-1, the ratio many gardeners assume is best.
Because liquid fertilizers are a short-term, supplemental nutrient supply
secondary to the riches released by organic matter and microbes, they don’t
need to be precisely balanced. The teas made from grass clippings and urine
come closest to providing the optimum 3-1-2 ratio.
Nitrogen helps plants grow new stems and
leaves. Phosphorus is essential for vigorous rooting, and is usually in good
supply in organically enriched soils. Potassium is the “buzz” nutrient that
energizes plants’ pumping mechanisms, orchestrating the opening and closing of
leaf stomata and regulating water distribution among cells. The grass clipping
and poultry manure teas are rich in potassium, which should make for sturdy
plants with strong stems when used to feed young seedlings. Blending some grass
or manure tea with a little nitrogen-rich urine would give you a fertilizer to
promote strong growth in established plants. I like to add a few handfuls of
stinging nettles, comfrey, lamb’s-quarters or other available weeds to various
mixtures, which probably helps raise the micronutrient content of my homemade
concoctions in addition to providing plenty of potassium.
On the practical end of liquid-fertilizer
making, you may need to use a colander to remove some of the grass clippings
before you can pour off the extract. If you haven’t completely used a batch of
fertilizer within two or three days, pour it out beneath perennials or dump it
into your composter.
It’s important to relieve drought stress
before doling out liquid fertilizer. Watering before you fertilize helps
protect plants from taking up too many salts. Also keep in mind that continuous
evaporation in containers favors the buildup of salts. By midsummer, a patio
pot planted with petunias or herbs that are regularly fed with any liquid
fertilizer may show a white crust of accumulated salts inside the rim. Several
thorough drenching with water will wash these away, making it safe to continue
feeding the plants with liquid fertilizers.
