The effect of the boundary layer is most noticeable
during hot conditions and is the reason why plants
will wilt on hot days even in moist soil.
The way around this problem is the send the
water directly to the plant, bypassing the soil. This
is not hydroponics, which does not use soil at all. In
Direct Irrigation, the grower deploys a water reservoir
beneath the plants. As roots grow into the soil, they
are attracted to the water reservoir and the roots enter
it. When they touch the water, they form a separate
set of roots, the water roots, in addition to the usual
soil roots. The formation of two sets of roots is one
of the unique features of Direct Irrigation. The water
roots undergo a startling transformation: they lose
their bark and metamorphose into thin, unbranched,
spaghetti-like strands that emerge from a common
point. The water roots, although submerged, are not
suffocated because they are in properly aerated water,
not in saturated soil loaded with bacteria and fungi. In
saturated soil, oxygen is removed from the soil solu-
tion by the biological oxygen demand of bacteria and
fungi. In Direct Irrigation, there are very few bacteria
and fungi in the water, and the water is kept in con-
tact with the air.
42
As the plants absorb water from the reservoir,
they increase the concentration of solutes in the water
reservoir. If this is permitted to go on indefi nitely,
the water in the reservoir will grow increasingly con-
taminated with solutes, decreasing the concentration
difference, which will halt further absorption. There-
fore, periodically, the water reservoir is replaced with
fresh water, forcing overfl ow and moistening the soil.
This fl ushing process moistens the surrounding soil
and eliminates the need for overhead watering. In
case of brackish water, instead of being fl ushed, the
water reservoir is drained of water containing excess
solutes. This salinated water is then disposed of into
the ocean where it will do no harm. The entire cycle
of fi lling, fl ushing or draining is, of course, automatic.
The result of this process is rapid growth with huge
water savings.
One key factor is the use of demand feeding of
the plants. As the plants absorb water, the level in the
water reservoir goes down. This activates the fl oat
valve which refi lls the water reservoir to its proper
level. There is no guesswork. The plants control the
water fl ow into the water reservoir by this simple
feedback mechanism. No water is wasted by giving
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May 2018