Increasing Soil Fertility Saves Water





Does crop growth equal water use? Most people would say this
statement seems likely to be true.
Actually, faster-growing crops use much less soil moisture than
slower-growing ones. As early as 1882 it was determined that less
water is required to produce a pound of plant material when soil is
fertilized than when it is not fertilized. One experiment required
1,100 pounds of water to grow 1 pound of dry matter on infertile
soil, but only 575 pounds of water to produce a pound of dry matter
on rich land. Perhaps the single most important thing a water-wise
gardener can do is to increase the fertility of the soil, especially
the subsoil.
_Poor plant nutrition increases the water cost of every pound of dry
matter produced._
Using foliar fertilizers requires a little caution and forethought.
Spinach, beet, and chard leaves seem particularly sensitive to
foliars (and even to organic insecticides) and may be damaged by
even half-strength applications. And the cabbage family coats its
leaf surfaces with a waxy, moisture-retentive sealant that makes
sprays bead up and run off rather than stick and be absorbed. Mixing
foliar feed solutions with a little spreader/sticker, Safer's Soap,
or, if bugs are also a problem, with a liquid organic insecticide
like Red Arrow (a pyrethrum-rotenone mix), eliminates surface
tension and allows the fertilizer to have an effect on brassicas.
Sadly, in terms of nutrient balance, the poorest foliar sprays are
organic. That's because it is nearly impossible to get significant
quantities of phosphorus or calcium into solution using any
combination of fish emulsion and seaweed or liquid kelp. The most
useful possible organic foliar is 1/2 to 1 tablespoon each of fish
emulsion and liquid seaweed concentrate per gallon of water.
Foliar spraying and fertigation are two occasions when I am
comfortable supplementing my organic fertilizers with water-soluble
chemical fertilizers. The best and most expensive brand is
Rapid-Gro. Less costly concoctions such as Peters 20-20-20 or the
other "Grows," don't provide as complete trace mineral support or
use as many sources of nutrition. One thing fertilizer makers find
expensive to accomplish is concocting a mixture of soluble nutrients
that also contains calcium, a vital plant food. If you dissolve
calcium nitrate into a solution containing other soluble plant
nutrients, many of them will precipitate out because few calcium
compounds are soluble. Even Rapid-Gro doesn't attempt to supply
calcium. Recently I've discovered better-quality hydroponic nutrient
solutions that do use chemicals that provide soluble calcium. These
also make excellent foliar sprays. Brands of hydroponic nutrient
solutions seem to appear and vanish rapidly. I've had great luck
with Dyna-Gro 7-9-5. All these chemicals are mixed at about 1
tablespoon per gallon.
Vegetables That:
Like foliars
Asparagus Carrots Melons Squash
Beans Cauliflower Peas Tomatoes
Broccoli Brussels sprouts Cucumbers
Cabbage Eggplant Radishes
Kale Rutabagas Potatoes
Don't like foliars
Beets Leeks Onions Spinach
Chard Lettuce Peppers
Like fertigation
Brussels sprouts Kale Savoy cabbage
Cucumbers Melons Squash
Eggplant Peppers Tomatoes
Fertigation every two to four weeks is the best technique for
maximizing yield while minimizing water use. I usually make my first
fertigation late in June and continue periodically through early
September. I use six or seven plastic 5-gallon "drip system"
buckets, (see below) set one by each plant, and fill them all with a
hose each time I work in the garden. Doing 12 or 14 plants each time
I'm in the garden, it takes no special effort to rotate through them
all more or less every three weeks.
To make a drip bucket, drill a 3/16-inch hole through the side of a
4-to-6-gallon plastic bucket about 1/4-inch up from the bottom, or
in the bottom at the edge. The empty bucket is placed so that the
fertilized water drains out close to the stem of a plant. It is then
filled with liquid fertilizer solution. It takes 5 to 10 minutes for
5 gallons to pass through a small opening, and because of the slow
flow rate, water penetrates deeply into the subsoil without wetting
much of the surface. Each fertigation makes the plant grow very
rapidly for two to three weeks, more I suspect as a result of
improved nutrition than from added moisture. Exactly how and when to
fertigate each species is explained in Chapter 5.
Organic gardeners may fertigate with combinations of fish emulsion
and seaweed at the same dilution used for foliar spraying, or with
compost/manure tea. Determining the correct strength to make compost
tea is a matter of trial and error. I usually rely on weak Rapid-Gro
mixed at half the recommended dilution. The strength of the
fertilizer you need depends on how much and deeply you placed
nutrition in the subsoil.
Water-Wise Gardening Year-Round





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