to eat. Another experimental garden of equal size was entirely
unirrigated. There I tested larger plots of species that I hoped
could grow through a rainless summer.

By July, growth on some species had slowed to a crawl and they
looked a little gnarly. Wondering if a hidden cause of what appeared
to be moisture stress might actually be nutrient deficiencies, I
tried spraying liquid fertilizer directly on these gnarly leaves, a
practice called foliar feeding. It helped greatly because, I
reasoned, most fertility is located in the topsoil, and when it gets
dry the plants draw on subsoil moisture, so surface nutrients,
though still present in the dry soil, become unobtainable. That
being so, I reasoned that some of these species might do even better
if they had just a little fertilized water. So I improvised a simple
drip system and metered out 4 or 5 gallons of liquid fertilizer to
some of the plants in late July and four gallons more in August. To
some species, extra fertilized water (what I call "fertigation")
hardly made any difference at all. But unirrigated winter squash
vines, which were small and scraggly and yielded about 15 pounds of
food, grew more lushly when given a few 5-gallon,
fertilizer-fortified assists and yielded 50 pounds. Thirty-five
pounds of squash for 25 extra gallons of water and a bit of extra
nutrition is a pretty good exchange in my book.

The next year I integrated all this new information into just one
garden. Water-loving species like lettuce and celery were grown
through the summer on a large, thoroughly irrigated raised bed. The
rest of the garden was given no irrigation at all or minimally
metered-out fertigations. Some unirrigated crops were foliar fed
weekly.