Gardening Without Irrigation Part 10

Row 2 gets about half the irrigation of row 1 and about one-third as much as the raised bed, and so is wider, to give the roots more room. One-third of the row grows savoy cabbage, the rest, Brussels sprouts. These bra.s.sicas are s.p.a.ced 4 feet apart and by summer's end the l.u.s.ty sprouts form a solid hedge 4 feet tall.

Row 3: Kale

Row 3 grows 125 feet of various kales sown in April. There's just enough overspray to keep the plants from getting gnarly. I prefer kale to not get very stunted, if only for aesthetics: on my soil, one vanity fertigation about mid-July keeps this row looking impressive all summer. Other gardens with poorer soil might need more support. This much kale may seem an enormous oversupply, but between salads and steaming greens with potatoes we manage to eat almost all the tender small leaves it grows during winter.

Row 4: Root Crops

Mostly carrots, a few beets. No irrigation, no fertigation, none needed. One hundred carrots weighing in at around 5 pounds each and 20-some beets of equal magnitude make our year's supply for salads, soups, and a little juicing.

Row 5: Dry-Gardened Salads

This row holds a few crowns of French sorrel, a few feet of parsley.

Over a dozen giant kohlrabi are spring sown, but over half the row grows endive. I give this row absolutely no water. Again, when contemplating the amount of s.p.a.ce it takes, keep in mind that this endive and kohlrabi must help fill our salad bowls from October through March.

Row 6: Peas, Overwintered Cauliflower, and All Solanaceae

Half the row grows early bush peas. Without overhead irrigation to bother them, unpicked pods form seed that sprouts excellently the next year. This half of the row is rotary tilled and fertilized again after the pea vines come out. Then it stays bare through July while capillarity somewhat recharges the soil. About August 1, I wet the row's surface down with hose and fan nozzle and sow overwintered cauliflower seed. To keep the cauliflower from stunting I must lightly hand sprinkle the row's center twice weekly through late September. Were water more restricted I could start my cauliflower seedlings in a nursery bed and transplant them here in October.

The other half is home to the Solanaceae: tomato, pepper, and eggplant. I give this row a little extra width because pea vines run, and I fertigate my Solanaceae, preferring sprawly tomato varieties that may cover an 8-foot-diameter circle. There's also a couple of extra bare feet along the outside because the neighboring gra.s.ses will deplete soil moisture along the edge of the garden.

Row 7: Water-Demanding Bra.s.sicas

Moving away from irrigation on the other side of the raised bed, I grow a succession of hybrid broccoli varieties and late fall cauliflower. The broccoli is sown several times, 20 row-feet each sowing, done about April 15, June 1, and July 15. The late cauliflower goes in about July 1. If necessary I could use much of this row for quick crops that would be harvested before I wanted to sow broccoli or cauliflower, but I don't need more room. The first sowings of broccoli are pulled out early enough to permit succession sowings of arugula or other late salad greens.

Row 8: The Trellis

Here I erect a 125-foot-long, 6-foot-tall net trellis for gourmet delicacies like pole peas and pole beans. The bean vines block almost all water that would to on beyond it and so this row gets more irrigation than it otherwise might. The peas are harvested early enough to permit a succession sowing of Purple Sprouting broccoli in mid-July. Purple Sprouting needs a bit of sprinkling to germinate in the heat of midsummer, but, being as vigorous as kale, once up, it grows adequately on the overspray from the raised bed.

The beans would be overwhelmingly abundant if all were sown at one time, so I plant them in two stages about three weeks apart. Still, a great many beans go unpicked. These are allowed to form seed, are harvested before they quite dry, and crisp under cover away from the sprinklers. We get enough seed from this row for planting next year, plus all the dry beans we care to eat during winter. Dry beans are hard to digest and as we age we eat fewer and fewer of them. In previous years I've grown entire rows of dry legume seeds at the garden's edge.

Row 9: Cucurbits

This row is so wide because here are grown all the spreading cucurbits. The pole beans in row 8 tend to prevent overspray; this dryness is especially beneficial to humidity-sensitive melons, serendipitously reducing their susceptability to powdery mildew diseases. All cucurbits are fertigated every three weeks. The squash will have fallen apart by the end of September, melons are pulled out by mid-September. The area is then tilled and fertilized, making s.p.a.ce to transplant overwintered spring cabbages, other overwintered bra.s.sicas, and winter scallions in October. These transplants are dug from nurseries on the irrigated raised bed. I could also set cold frames here and force tender salad greens all winter.

Row 10: Unirrigated Potatoes

This single long row satisfies a potato-loving household all winter.

The quality of these dry-gardened tubers is so high that my wife complains if she must buy a few new potatoes from the supermarket after our supplies have become so sprouty and/or shriveled that they're not tasty any longer.

Chapter 7

The Backyard

Water-Wise Gardener

I am an unusually fortunate gardener. After seven years of struggling on one of the poorest growing sites in this region we now live on 16 acres of mostly excellent, deep soil, on the floor of a beautiful, coastal Oregon valley. My house and gardens are perched safely above the 100-year flood line, there's a big, reliable well, and if I ever want more than 20 gallons per minute in midsummer, there's the virtually unlimited Umpqua River to draw from. Much like a master skeet shooter who uses a .410 to make the sport more interesting, I have chosen to dry garden.

Few are this lucky. These days the majority of North Americans live an urban struggle. Their houses are as often perched on steep, thinly soiled hills or gooey, difficult clay as on a tiny fragment of what was once prime farmland. And never does the munic.i.p.al gardener have one vital liberty I do: to choose which one-sixth of an acre in his 14-acre "back yard" he'll garden on this year.

I was a suburban backyard gardener for five years before deciding to homestead. I've frequently recalled this experience while learning to dry garden. What follows in this chapter are some strategies to guide the urban in becoming more water-wise.

Water Conservation Is the Most Important First Step

After it rains or after sprinkler irrigation, water evaporates from the surface until a desiccated earth mulch develops. Frequent light watering increases this type of loss. Where lettuce, radishes, and other shallow-rooting vegetables are growing, perhaps it is best to accept this loss or spread a thin mulch to reduce it. But most vegetables can feed deeper, so if wetting the surface can be avoided, a lot of water can be saved. Even sprinkling longer and less frequently helps accomplish that. Half the reason that drip systems are more efficient is that the surface isn't dampened and virtually all water goes deep into the earth. The other half is that they avoiding evaporation that occurs while water sprays through the air between the nozzle and the soil. Sprinkling at night or early in the morning, when there is little or no wind, prevents almost all of this type of loss.

To use drip irrigation it is not necessary to invest in pipes, emitters, filters, pressure regulators, and so forth. I've already explained how recycled plastic buckets or other large containers can be improvised into very effective drip emitters. Besides, drip tube systems are not trouble free: having the beds covered with fragile pipes makes hoeing dicey, while every emitter must be periodically checked against blockage.

When using any type of drip system it is especially important to relate the amount of water applied to the depth of the soil to the crops, root development. There's no sense adding more water than the earth can hold. Calculating the optimum amount of water to apply from a drip system requires applying substantial, practical intelligence to evaluating the following factors: soil water-holding capacity and accessible depth; how deep the root systems have developed; how broadly the water spreads out below each emitter (dispersion); rate of loss due to transpiration. All but one of these factors--dispersion--are adequately discussed elsewhere in _Gardening Without Irrigation._

A drip emitter on sandy soil moistens the earth nearly straight down with little lateral dispersion; 1 foot below the surface the wet area might only be 1 foot in diameter. Conversely, when you drip moisture into a clay soil, though the surface may seem dry, 18 inches away from the emitter and just 3 inches down the earth may become saturated with water, while a few inches deeper, significant dispersion may reach out nearly 24 inches. On sandy soil, emitters on 12-inch centers are hardly close enough together, while on clay, 30-or even 36-inch centers are sufficient.

Another important bit of data to enter into your arithmetic: 1 cubic foot of water equals about 5 gallons. A 12-inch-diameter circle equals 0.75 square feet (A = Pi x Radius squared), so 1 cubic foot of water (5 gallons) dispersed from a single emitter will add roughly 16 inches of moisture to sandy soil, greatly overwatering a medium that can hold only an inch or so of available water per foot.

On heavy clay, a single emitter may wet a 4-foot-diameter circle, on loams, anywhere in between, 5 gallons will cover a 4-foot-diameter circle about 1 inch deep. So on deep, clay soil, 10 or even 15 gallons per application may be in order. What is the texture of your soil, its water-holding capacity, and the dispersion of a drip into it? Probably, it is somewhere in between sand and clay.

I can't specify what is optimum in any particular situation. Each gardener must consider his own unique factors and make his own estimation. All I can do is stress again that the essence of water-wise gardening is water conservation.

Optimizing s.p.a.ce: Planning the Water-Wise Backyard Garden

Intensive gardening is a strategy holding that yield per square foot is the supreme goal; it succeeds by optimizing as many growth factors as possible. So a raised bed is loosened very deeply without concern for the amount of labor, while fertility and moisture are supplied virtually without limit. Intensive gardening makes sense when land is very costly and the worth of the food grown is judged against organic produce at retail--and when water and nutrients are inexpensive and/or available in unlimited amounts.

When water use is reduced, yield inevitably drops proportionately.

The backyard water-wise gardener, then, must logically ask which vegetable species will give him enough food or more economic value with limited s.p.a.ce and water. Taking maritime Northwest rainfall patterns into consideration, here's my best estimation:

Water-Wise Efficiency of Vegetable Crops

(in terms of backyard usage of s.p.a.ce and moisture)

EFFICIENT ENOUGH

Early spring-sown crops: peas, broccoli, lettuce, radishes, savoy cabbage, kohlrabi

Overwintered crops: onions, broccoli cauliflower, cabbage, favas beans