Gardening Without Irrigation: or without much, anyway | Page 5

looking for more information about dry gardening and soil/water physics. In spring 1989, I tilled four widely separated, unirrigated experimental rows in which I tested an assortment of vegetable species spaced far apart in the row. Out of curiosity I decided to use absolutely no water at all, not even to sprinkle the seeds to get them germinating.
I sowed a bit of kale, savoy cabbage, Purple Sprouting broccoli, carrots, beets, parsnips, parsley, endive, dry beans, potatoes, French sorrel, and a couple of field cornstalks. I also tested one compactbush (determinate) and one sprawling (indeterminate) tomato plant. Many of these vegetables grew surprisingly well. I ate unwatered tomatoes July through September; kale, cabbages, parsley, and root crops fed us during the winter. The Purple Sprouting broccoli bloomed abundantly the next March.
In terms of quality, all the harvest was acceptable. The root vegetables were far larger but only a little bit tougher and quite a bit sweeter than usual. The potatoes yielded less than I'd been used to and had thicker than usual skin, but also had a better flavor and kept well through the winter.
The following year I grew two parallel gardens. One, my "insurance garden," was thoroughly irrigated, guaranteeing we would have plenty 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.
Everything worked in 1991! And I found still other species that I could grow surprisingly well on surprisingly small amounts of water[--]or none at all. So, the next year, 1992, I set up a sprinkler system to water the intensive raised bed and used the overspray to support species that grew better with some moisture supplementation; I continued using my improvised drip system to help still others, while keeping a large section of the garden entirely unwatered. And at the end of that summer I wrote this book.
What follows is not mere theory, not something I read about or saw others do. These techniques are tested and workable. The next-to-last chapter of this book contains a complete plan of my 1992 garden with explanations and discussion of the reasoning behind it.
In _Water-Wise Vegetables _I assume that my readers already are growing food (probably on raised beds), already know how to adjust their gardening to this region's climate, and know how to garden with irrigation. If you don't have this background I suggest you read my other garden book, _Growing Vegetables West of the Cascades,_ (Sasquatch Books, 1989).
Steve Solomon

Chapter 1
Predictably Rainless Summers

In the eastern United States, summertime rainfall can support gardens without irrigation but is just irregular enough to be worrisome. West of the Cascades we go into the summer growing season certain we must water regularly.
My own many-times-revised book Growing Vegetables West of the Cascades correctly emphasized that moisture-stressed vegetables suffer greatly. Because I had not yet noticed how plant spacing affects soil moisture loss, in that book I stated a half-truth as law: Soil moisture loss averages 1-1/2 inches per week during summer.
This figure is generally true for raised-bed gardens west of the Cascades, so I recommended adding 1 1/2 inches of water each week and even more during really hot weather.
Summertime Rainfall West of the Cascades (in inches)*
Location April