d lowering plant density as much as this book suggests equally
lower the yield of the plot? Surprisingly, the amount harvested does
not drop proportionately. In most cases having a plant density
one-eighth of that recommended by intensive gardening advocates will
result in a yield about half as great as on closely planted raised
beds._

Internet Readers: In the print copy of this book are color pictures
of my own "irrigationless" garden. Looking at them about here in the
book would add reality to these ideas.

Chapter 3

Helping Plants to Need Less Irrigation

Dry though the maritime Northwest summer is, we enter the growing
season with our full depth of soil at field capacity. Except on
clayey soils in extraordinarily frosty, high-elevation locations, we
usually can till and plant before the soil has had a chance to lose
much moisture.

There are a number of things we can do to make soil moisture more
available to our summer vegetables. The most obvious step is
thorough weeding. Next, we can keep the surface fluffed up with a
rotary tiller or hoe during April and May, to break its capillary
connection with deeper soil and accelerate the formation of a dry
dust mulch. Usually, weeding forces us to do this anyway. Also, if
it should rain during summer, we can hoe or rotary till a day or two
later and again help a new dust mulch to develop.

Building Bigger Root Systems

Without irrigation, most of the plant's water supply is obtained by
expansion into new earth that hasn't been desiccated by other
competing roots. Eliminating any obstacles to rapid growth of root
systems is the key to success. So, keep in mind a few facts about
how roots grow and prosper.

The air supply in soil limits or allows root growth. Unlike the
leaves, roots do not perform photosynthesis, breaking down carbon
dioxide gas into atmospheric oxygen and carbon. Yet root cells must
breathe oxygen. This is obtained from the air held in spaces between
soil particles. Many other soil-dwelling life forms from bacteria to
moles compete for this same oxygen. Consequently, soil oxygen levels
are lower than in the atmosphere. A slow exchange of gases does
occur between soil air and free atmosphere, but deeper in the soil
there will inevitably be less oxygen. Different plant species have
varying degrees of root tolerance for lack of oxygen, but they all
stop growing at some depth. Moisture reserves below the roots'
maximum depth become rel