Gardening When It Counts

Before the 1930s, few farms had electricity. Many vegetable gardens were grown without running water. Before 1880, when 90 percent of all North Americans (and probably Australians and New Zealanders) lived on family farms or in tiny villages, it would be a fair guess that over 90 percent of all vegetable gardens were grown without running water. In those days, after a few weeks without rain, many would begin talking about drought and of how their gardens or crops were suffering. But other gardeners in the vicinity wouldn’t be complaining much.

In 1911 John Widstoe wrote Dry Farming, a book about large-scale farming in semi-arid places.Widstoe had a different take on what a drought (or “drouth,” as he called it) actually is.He said:

Drouth is said to be the archenemy of the dry farmer, but few agree upon its meaning. For the purposes of this volume, drouth may be defined as a condition under which crops fail to mature because of an insufficient supply of water. Providence has generally been charged with causing drouths, but under the above definition, man is usually the cause. Occasionally, relatively dry years occur, but they are seldom dry enough to cause crop failures if proper methods of farming have been practiced. There are four chief causes of drouth: (1) Improper or careless preparation of the soil; (2) failure to store the natural precipitation in the soil; (3) failure to apply proper cultural methods for keeping the moisture in the soil until needed by plants, and (4) sowing too much seed for the available soil-moisture.[emphasis added]

I emphasize Widstoe’s fourth point because this is the factor that most pertains to veggie gardening. I also emphasize it because choosing plant spacing is the single most important decision the gardener will make.

These days, having piped water is normal. Veggie gardening styles have adapted to this situation and to the needs of suburbanites living on smaller lots, who buy most of their produce instead of growing it. This shift in vegetable-growing methods was named “intensive.” The idea: put the vegetables much closer together in massed plantings on raised beds so the yield from postage-stamp-sized gardens becomes greater per square foot. The gardener loosens the bed to two feet deep (60 centimeters), supposedly so the root systems can go down instead of out.The high plant density sucks the soil dry so rapidly the gardener must water almost daily during the growing season. However, the yield from the amount of water used is supposed to be greater. And, of course, the gardener must make the soil super-fertile to support this intense growing activity.

The intensivists say that putting vegetable rows far apart is a waste of garden space and that gardeners do it only in foolish imitation of farmers, who have to do it so that machinery can work the field. This assertion is not correct. The reason people traditionally spread out their plants (and why farm machinery was designed to match this practice) was so that the vegetables could go through rainless weeks without damage or moisture stress. Most of the intensivist claims listed in the preceding paragraph are also not quite true, as I will soon demonstrate.

I expect many North American cities and towns will start to experience more severe water shortages, if only due to increases in population.This is also happening in the U.K., Australia, and New Zealand. But under economic stress,many people may again wish to grow a substantial amount of their own food. What little irrigation their gardens will get may have to be recycled household water or rainwater off the roof, trapped in tanks, which is how most rural Australians still live. Plenty of piped, chlorinated water may be available in some areas, but unless alternative and large-scale energy sources are developed, the cost of this water will increase with the inevitable increase in the price of oil.

Going back to old-style gardening won’t actually be a sacrifice. In fact, it may work out to be a big gain for most people. Instead of having to water the garden constantly and finding that a veggie garden makes a problem about going on a week’s holiday during summer, people will discover the old-style garden can look after itself. In my experience, the supposed advantages of intensive raised beds are largely an illusion. Instead of growing many small, crowded plants that take a longer time to harvest (and clean), people will spend less time harvesting larger, more attractive-looking, more delicious vegetables. Species that produce an ongoing harvest, like tomatoes and cucumbers, will surprise the intensivist by yielding a lot more toward the end of the season because when these plants are crowded together, they produce well for a few short weeks and then virtually stop yielding, their root development stopped by overcompetition.

Please study Figure 6.1, a regrettably complex table of plant spacing possibilities. The crop spacings listed in Column 1 are typically what intensivists recommend. A crop canopy forms quickly at those spacings, and from then on watering will be necessary almost daily during sunny weather. I do not recommend using these spacings. Column 2 is my recommendation when you have abundant irrigation. Use Column 3 where there is sufficient rain during the growing season to comfortably support a garden; generally this means areas that were once covered with large trees, which describes all of North America east of the 98th meridian (a north-south line running through Dallas, Texas), the densely settled east coast of Australia, and most of the U.K. except the dryish east of England. Column 4 may be used where there is a fair depth of moisture-retentive soil (over four feet/120 centimeters) and where winter rains or snowmelt have charged that soil with water to its full depth. Column 4 assumes that what little rainfall there may be during the growing season will happen with many weeks of separation between.This describes the semi-arid parts of the North American prairie states after there has been good snowmelt from winter and also describes Maritime climates with their winter rains and dry summers.

* On raised beds. **Grow in hills, two to three plants per hill. *** Potatoes are hilled up as they grow.

† In raised rows. †† Most items in this group are better grown in hills; see Chapter 9 for details.

‡ To convert to centimeters, multiply inches by 2.5.

A note on spacing: Generally the first number is the in-the-row spacing; the second number is the between-row spacing. A 24 x 24 spacing on a four-foot-wide (120-centimeter) raised bed means a double parallel row down the bed the long way. A 36 x 48 spacing means a single row of plants three feet (90 centimeters) apart down the center of a four-foot-wide raised bed. Il_9781550923858_0019_001

Most current garden books and government agricultural publications, having been written by academics who are trained to regard earlier similar publications as “authoritative,” parrot Everybody Else’s recommendation to use these plant spacings. I do not recommend using Column 1. It is here only so that you may compare the opinion of Everybody Else to something I consider practical. For example, when Column 1 says “Beets, 4 x 4” it means 16 square inches (roughly 100 square centimeters) per plant. Compare that to Column 2, which recommends 4 x 18 or 72 square inches (465 square centimeters), which allows each plant nearly five times as much room.

Once ultra-crowded plants have formed a crop canopy (in other words, the crop has fully covered the bed with growing leaves), moisture loss is so rapid during sunny weather that to prevent moisture stress, you will need to give the beds at least half an inch (1.25 centimeters) of water every other day in hot spells. If the soil doesn’t retain much moisture, you’ll apply less water, but you’ll apply it every day. I’ve seen sandy intensive beds need irrigation twice daily in really hot weather. This requirement tightly shackles gardeners to their gardens.

These spacings are how I currently garden.Most of my garden, except for the sprawling vines and a block of sweet corn, is grown on 4 x 25 foot (1.25 by 7.5 meters) raised beds; the spacings reflect layouts on beds like this. This more generous spacing will still result in a crop canopy that completely covers the bed, but the canopy does not form so quickly. Because each plant has far more soil room to fill with its roots, such a canopied crop needs watering only every four to seven days in sunny warm weather.One reason this garden will go longer between irrigations is that the plants are sufficiently spaced to benefit from capillarity flow, which partly recharges their root zone with subsoil moisture.

The volume of harvest on this spacing is about 90 percent what you’d get using Column 1, but you will put in less than half the number of hours to get it. The smaller vegetables are arranged in four-foot-long (120-centimeter) rows running across the beds the narrow way.Tightest of all are salad radishes, given only 12 inches (30 centimeters) between rows, which is still far enough apart to pass a hoe between the rows until one week before harvest. Using Column 2, the vegetables become larger and more succulent and tender because growth has not been slowed by overcompetition; consequently harvesting (and washing/trimming) takes much less time.

In this system, small plants are grown on wide raised beds, larger ones in slightly raised single rows, sprawling ones in hills rather far apart, and crops like corn or okra, large plants that don’t need to start in a finely raked seedbed, are grown on flat ground. Even after crop growth makes it difficult to walk between the rows or hills, a garden using Column 3 may go through rainless weeks without significant moisture stress. The plants have spread sufficient roots to greatly benefit from capillarity. Their ever-expanding root systems continue to discover large amounts of soil water held in storage, like money in a bank account (think of deep subsoil moisture rising through capillarity as being like substantial interest). Yields per square foot are only slightly lower than those you’ll gain by using Column 2 spacing. In dry years, irrigation would increase yields, but in most years, rainfall will be adequate; watering will not be essential. Because the rows are so far apart, hoeing weeds is easy. I grew my variety trials grounds in this style and during the main growing season, when the weeds were growing their fastest, could keep a half acre weed-free with only one short morning’s hoeing each week.

Column 3 has been used by English-speaking North Americans ever since the Native Americans taught them how to garden here, based on the millennia of their own experience.

Column 4 contains my spacing suggestions for regions with relatively dry summers and with not much water for irrigation. Unirrigated gardening in such a situation works only if the soil goes into the growing season fully saturated to considerable depth, if weed competition is meticulously eliminated, and if the soil is kept loose at the surface with regular cultivation, forming what is termed a dust mulch. An inch (2.5 centimeters) of loose surface soil acts much like a straw mulch, virtually eliminating moisture loss from sun shining on bare ground. Assuming there are no weeds, the only moisture lost will be what is transpired by growing crops.

In the North American summer, rainfall often comes as intense showers and thunderstorms. If there is a crust or hard layer on the surface, much of this rain may run off. If the surface is loose, the rain will penetrate. It is essential, therefore, that a day or so after such a rain you go out with a hoe and loosen up the surface of every accessible part of the garden.This prepares the soil to fully accept the next chance shower and also helps keep the moisture now in the earth from evaporating.

When you are gardening this way, it is essential, it is vital, it is incredibly important, it is crucial (can I express it any more strongly?) that you make sure the surface inch (2.5 centimeters) or so of soil contains a fair amount of compost or decomposed manure.This will prevent crust formation and help your soil form large stable crumbs that the wind won’t blow away when you make a dust mulch.

Widstoe’s fourth cause of drought, “sowing too much seed for the available soil-moisture,” is a little like Will Roger’s comment about speculating in the stock markets:“If you want to make money in stocks, buy one that will go up. If it didn’t go up, don’t buy it.” The reason people fail to match crop density with the available soil moisture is greed, the temptation to get a somewhat bigger harvest by having more plants in the same area.We humans tend to forget pain and loss, to hope that some recent years of higher rainfall represent what can always be expected. If, on the other hand, gardeners were to act more like pessimists and expect that every year would be a dry one, then they would plant things a bit more spaciously, more along the lines of what is suggested in Column 4.The results wouldn’t be as bad as you might think, because getting more moisture in a wet summer and having more room to grow the smaller number of plants will produce larger plants and yield more per plant. True, it won’t be as much as you might have had by increasing the plant population, but you’ll get it more securely.

If I were gardening in the eastern half of the United States or Canada and had started the season with a traditional garden design, based on the spacings in Column 3, and if it began to look like a mighty hot, droughty summer, there are some steps I could take to greatly reduce the damage.The first thing would be a brave action indeed: I’d go out with a sharp hoe and chop every second plant in every row and harvest every second carrot or beet, no matter how small it was at the moment. This would instantly reduce moisture consumption while providing double the capillary moisture to the remaining plants. The end result might not be the loss of half the crop. By preventing severe moisture stress, I might end up harvesting a lot more. And if it should start raining, you’d be surprised at how big the plants will grow in these roomy spacings.

If it didn’t start raining, I’d thoroughly wield my weeding hoe, as described above, at least weekly.

The next thing I’d do, if at all possible,would be to start fertigation,which is something that a person might want to do in any case, drought year or not, because it has such benefits. Crop scientists of Widstoe’s era noticed that it took twice as much water to make a given weight of dry plant material on soils that were infertile as it did on soil that was highly fertile. And William Albrecht explained that much of what appears to be drought damage is actually nutrient deficiency induced by dry surface soil when plant nutrients are mainly located in the plowed surface layer. This can be especially true in new veggie gardens because it can take a few years for the fertility you’re putting into the topsoil to work its way down into the subsoil.When plants are not finding water in the surface layers, they must feed in the subsoil, but if that is infertile...

To more rapidly remedy subsoil infertility when you are starting a new garden in humid regions, you may want to spread a full dose of fertility-building materials at the end of summer the year before the land will become a veggie garden. This will allow the autumn rains and the spring snowmelt to carry this nutrition into the subsoil.

The fertigation bucket economically and effectively places moisture and nutrition below a growing plant. In the early 1990s I did dry-gardening experiments in Oregon, where the entire hot summer is dependably rainless. Each unferti-gated winter squash vine grown on the spacings suggested in Column 4 yielded 20 pounds (nine kilograms). But other plants of the same variety on the same spacing that were given five gallons (20 liters) of fertigation four separate times between the solstice and the equinox (20 gallons total) yielded 50 pounds each (22 kilograms). Thirty pounds (13 kilograms) of additional squash for 20 gallons of water seems a pretty good exchange to me.

Fertigation is especially useful for big plants: tomatoes, melons, cucumbers, squash. It can make all the difference for Brussels sprouts or big cabbages, for a broccoli or a thriving pepper bush. The results can be remarkable.

It is important when fertigating that the water sinks right in, making a surface wet spot no larger than the little plate under a teacup. This way the moisture penetrates straight down into the subsoil.The speed the water comes out of the bucket determines how widely the moisture spreads. Exactly how large the drainhole should be depends on the soil type; sandy soil usually accepts moisture rapidly, and the water naturally goes deep and not wide. Clay soils are slower to take in moisture, and it spreads out much more broadly when applied from a single drip source. If the soil has 20 percent clay or more, then five gallons (20 liters) will be about right, given every three weeks. But if the soil has little clay, it has far less ability to hold moisture. In that case, perhaps half as much water, say 2½ gallons (10 liters), given every ten days would work better.

Fertigation can be a wise practice even when the plants are otherwise getting enough water. If the soil needs no more moisture, you can make the fertilizer solution a bit stronger and give less volume because it will thin itself out with the moisture already present in the earth.

The traditional fertigation solution is manure or compost tea. Fill a barrel (these days it will probably be a garbage can) with water, dump in a bucketful or two of fresh manure or compost, and allow it to brew for a week. Stir the brew every few days.When it’s ready, dip out buckets of fertigation concentrate. Periodically refill the barrel with fresh water and add more manure or compost. You’ll determine how much you need to dilute this tea according to your results in using it.When the barrel starts getting too full of solids, empty it out, spread the solids on the garden or toss them into the compost heap, and start a new batch. A variation: Put armloads of comfrey leaves in the brew instead of manure. Other forms of organic matter containing a fair amount of proteins that you could toss into the brew include alfalfa (lucerne), seedmeal, or a quart or two (liter or two) of tankage, meatmeal, or even highly potent bloodmeal (this would really put up the nitrogen content). Urine would also work excellently.

These days, someone makes a product for doing everything, and fertiga-tion is no exception.Organic gardeners will see an excellent (and rather costly) result using fish emulsion fertilizer, diluted as suggested, which is usually about one part concentrate to 100 parts water. Soluble chemical fertilizers are also highly effective if they contain trace elements as well as NPK. As long as these chemicals do not replace regular additions of organic matter, their use will not damage soil life because they are applied in a highly dilute form.

There is a simple procedure that shows precisely how much clay your soil contains. Every gardener should do this test if for no other reason than to know what their soil profile is to at least three feet (90 centimeters) deep (if it goes that far).

Dig a hole. If you have a soil augur or posthole digger, the hole doesn’t need to be any larger in diameter than the tool. Otherwise, neatly excavate a short, hip-wide ditch that is at least 36 inches (90 centimeters) deep. It is normal to find more than one sort of soil below any field.The first 6 to 12 inches (15 to 30 centimeters), the “topsoil” layer, are usually darker in color because they contain almost all the organic matter. Sometimes the same sort of soil particles continue down further, but become lighter in color. Typically, in climates where there is more than about 30 inches (70 centimeters) of rainfall a year, and also in soils that developed slowly out of the rocks they sit atop (upland soils), you’ll encounter a change as you dig, almost as though the land were a layer cake. Below some point you will find a layer of clay. In dryer climates this may not occur. If there is such a change, then take a pint-sized (500-milliliter) sample of both types, or all three types if there are three distinct soils as you go down.

Ask yourself a question as you dig: Is this soil loose enough, friable enough, that roots can penetrate it? As you dig are you finding roots? Some soils, especially some clay subsoils, are so dense and airless that almost no roots can exist in them. If you run into that sort of clay, there is little point in going deeper; in fact, in that kind of soil it will be difficult to dig further. If you’re gardening on alluvium (soil deposited by flooding rivers or creeks) instead of an upland soil, and if as you dig you run into a layer of nearly pure gravel, there is also no point in going deeper. Few plants will be able to root through it, and gravel serves as a complete barrier to moisture rising to the surface by capillarity — your garden will require considerable irrigation.

So now you’ve assessed the resource that lies below your feet. I wouldn’t want to garden anywhere without having this valuable information.

With samples in hand, the next step is to do a “soil fractional analysis” test. Don’t be daunted by the big name. It’s a piece of cake.The idea is to determine the makeup of your soil by breaking it into constituent particles and finding out how long they stay suspended in water. The smaller the soil particle, the longer it will stay suspended in water. Clay particles are so tiny that only the most powerful microscope can see one, and they stay suspended in water for many hours, sometimes days. The main thing we want to know is how much clay there is mixed into the larger particles of your soil.

To do the test, get a quart (liter) canning jar or something similar with a good lid. Take about one pint (500 milliliters) of soil, remove any roots or small rocks, break it up as finely as possible, and put it in the jar. Get a felt pen that will write on glass and mark on the side of the jar where the top of the soil comes to.Alternatively, stick a strip of adhesive tape on the glass and mark the top of the soil on the tape.Now fill the jar with water to within about one inch (2.5 centimeters) of the top and add a teaspoonful (five milliliters) of ordinary dishwashing detergent — a low-suds type is best, but low-sudsing is not critical. Seal the jar and shake it hard. And shake. And shake some more. Now shake really hard. Shake for five to ten minutes. Shake until every particle of soil in the jar that had aggregated (formed clumps that resist coming apart) has been separated from every other particle (this is the reason for the soap). If you’re lazy or like efficiency, take the jar to the local hardware store and ask them to put it into their paint shaker for a few minutes, then take it home and briefly shake it again. But the second shaking will only take a minute or so because all the soil aggregates will have already been broken up.

Now comes the measurement. Stop shaking and immediately put the jar down in bright light, say on a windowsill.Wait exactly two minutes, by the clock, from the moment you stopped shaking. Then look closely, using a bright flashlight if necessary to see into the murky water. Unless what you’ve been shaking is pure clay, some of the soil will probably have settled out and will be resting on the bottom. That deposit is your “sand fraction.”Mark the depth of the sand fraction on the side of the jar.Now go away for a while, but come back exactly two hours after you stopped shaking, take another look, and make another mark.What settled after the first two minutes but within two hours is the silt fraction. Silt particles are finer than sand but are still just tiny broken and rounded-off bits of rock.

At this point, all that remains suspended in the water is the clay and maybe the organic matter. Clay can take a long time to settle out — days, sometimes weeks. If you wanted perfect accuracy you’d wait until the water was clear and then make another line, but, practically speaking, the first mark you made, showing where the dry soil came to when you first filled the jar, will be close enough. If the clay fraction settles within 12 hours, that’s a good sign you have a relatively coarse sort of clay. Any soil that contains much fine clay will be harder to work.

So now you know that you have so many inches of sand, so many of silt and so many of clay.Dredge up your grade-school math and calculate the percentage of each. (This calculation is far easier when measurement is done in millimetres.) For those readers whose math is weak, you can determine the percentage by dividing the height of the dry soil into the height of the layer in question.

One benefit of knowing the percentage of each type of soil in your garden is that the mix of soil particles indicates how much water that soil can hold for the benefit of growing plants (see Figure 6.4).

A sand soil is defined scientifically as one with less than 10 percent silt or clay.A medium soil could be any mix of sand and silt that has at least 20 percent clay but less than 35 percent clay; this sort of soil is commonly called a “loam.” A clayey soil is made of more than 35 percent clay. If it contains no more than half clay, it can be an excellent soil to grow a garden in. If it is more than half clay, it can be a difficult soil to work.

Okay, now you’ve got some solid information about your soil. Especially important, you’ve got an idea of how much moisture it will make available to plants. A sandy topsoil with a clayey subsoil that is open to root penetration can make more water available than it might seem when you just consider the top few inches. If the subsoil is a deep, open clay, there will be a huge reserve of moisture. On a soil like this you may see plants wilt a bit in midafternoon during the hottest weather, but they will seem restored the next morning (although they aren’t entirely restored because any wilting is a shock to a tender vegetable plant).

Wise gardeners do everything possible to help their plants avoid moisture stress and especially to avoid wilting. If you’re not irrigating at all, then by increasing spacing you give each root system a greater area of soil to mine for water and give capillary uplift a greater chance to effectively recharge your plants’ root zones. If you are fertigating, your soil fractional analysis will tell you if you should add water in small increments more often to sandy soil or if you can add water in larger amounts less frequently because there is enough clay to hold the moisture. If you are irrigating regularly and spacing your plants according to Column 2, you will need a bit more information to irrigate most effectively.

Amount of water lost per day in midsummer

Temperature in summer	Region	Inches lost per Day
Cool	Western Washington, coastal southern B.C., Canadian Maritimes, Scotland, and western U.K. Western Oregon, northern US,	0.2
Moderate	Western Oregon, northern US, Southern Canada, Tasmania, New Zealand (S. Is.), eastern U.K.	0.25
Hot (humid)	Eastern US, east coast Australia, NZ (N. Is.)	0.3
Hot (dry)	Prairie states, northern California, Coastal southern California, southwest Oregon	0.35
Low desert	Southwest desert states, southern California	0.45

Figure 6.4 showed how much water loss you should allow before irrigating to prevent moisture stress.The amount of water that is extracted from soil each day depends on the air temperature, the humidity of the air, the strength of the wind, how dense the crop canopy is, etc. But as a rough guide, Figure 6.5 shows, roughly, the amount a crop that has made a canopy will draw up and evaporate during midsummer.

Suppose I have the gardener’s dream, an infinitely deep loam. I have plenty of irrigation water, so I have used Column 2 spacings. After I bring it to its water-holding capacity, my soil can give up about an inch (2.5 centimeters) of water before the crops will experience any moisture stress. If I can prevent moisture stress, the garden will grow better and produce more. Suppose I am gardening in Maryland and it is a hot, sunny, rainless week in mid-July.Most of my vegetables have formed a dense leaf canopy, so my ground is losing about 0.3 inches (seven millimeters) per day. I must add about an inch of water to the soil every three or four days.Of course, if there is a spell of cloudy weather, much less water will be lost. If it drizzles insignificantly, at least during that time, no moisture will be lost from the ground. If it rains, I can add that amount to the moisture balance of my soil. But if I owe the garden an inch of water, and just before I irrigate it rains two inches (five centimeters), this account isn’t the type that can go into surplus. Any extra moisture will move into the subsoil and can only assist the plants after rising slowly by capillarity. So even though I just got two inches of rain, when the soil has lost an inch a few days from now, it will still be time to add another inch.

When I was doing dry-gardening experiments, I noticed that if, instead of fer-tigating, I sprayed liquid fertilizer at the same strength with which I’d fertigate on the leaves of plants that looked as through they were moisture stressed, then the plant almost instantly looked quite a bit better. Not as much better as it would had I fertigated, but still, considerably better.This practice is called foliar feeding. If you are so short of water that finding a few hundred gallons a week for fertigation is not possible, then perhaps a few gallons a week mixed into the sprayer would be the next best choice.

A few hints: If you’re going to foliar spray homemade teas, they need to be perfectly filtered first. Farmers in India have discovered that one of the best possible foliar sprays is half-strength Coca Cola. It contains significant amounts of phosphoric acid, and there is something about the sugar that helps plants a lot. If you should encounter a half bottle of flat Coke, why not give it a try?

Regular foliar feeding is not a bad practice in any case. Kelp tea is one of the best organics to use for this purpose when the plants don’t need more nitrates. Kelp contains phytamins and a full range of trace mineral nutrients. A mixture of kelp tea and fish emulsion sprayed once a week will make the plants grow much faster. So will a complete soluble chemical mix if it has trace minerals in it too.

If you’ve designed an intensive garden that depends on regular irrigation, or if you plan to irrigate as an emergency measure in the event of a longer-than-usual dry spell, this section will help you become systematic about watering. You need a system based on science because both watering too little and watering too much can hugely reduce the garden’s performance.

It soon becomes obvious to the new gardener that even short periods of moisture stress reduce vegetable quality.This stress does not have to reach the point of wilting to cause a lot of damage.Moisture stress can happen to regularly irrigated gardens, too.Underwatering may be so subtle that no temporary wilting occurs, thus going unnoticed, but it still produces serious consequences.

Many gardeners wet down their gardens almost daily with hose and fan nozzle because they want to make sure the beds provide abundant moisture all the time. This method, done properly, works quite well, so long as you enjoy the task. However, if the garden is watered daily but too briefly, the plants can become water-stressed, although on casual inspection the soil seems moist.What is happening is that the surface inches stay damp, but the gardener never discovers that, deeper down, the soil has become bone-dry. Under these conditions vegetables will not wilt, because they never quite suck the surface layer dry, but they’ll become severely stunted due to lack of root development.

Recognizing this possibility, John Jeavons, the “father” of intensive gardening in North America, in his book How To Grow More Vegetables ..., recommends using a fan nozzle daily, continuing on each bed until the entire surface sparkles (becomes shiny wet). This sparkling results from water that has not yet flowed into the bed beading up on the surface. The shine only lasts a second or so initially, but as the deeper soil becomes saturated, the shine lasts longer and longer. Jeavons says that when it lasts long enough (one to ten seconds), the bed has been given enough water.

One to ten seconds is quite a range! Jeavons suggests trying different shiny times, combined with digging some test holes to see how deeply the soil is saturated. Without this check, gross overwatering or underwatering could result. Many clayey soils, capable of holding a great deal of water but often assimilating it slowly, could accept a lot of water before it penetrated far. So clays could show a sparkly surface for several seconds, yet be quite dry a few inches down. Coarse-textured sandy soils usually take in water rapidly, and it might be difficult to get a shine to last more than one second, if at all, no matter how much the gardener overwatered or how fast the water was put down, resulting in considerable leaching.

Then there are types of fine sands that become coated with the products of humus breakdown in such a way that, once they have become dry, water beads up on them and runs off without penetrating. It is very difficult to remoisten soils like this after their surface has dried out. Applying high-volume flows with a hand nozzle doesn’t work very well on soils like this. Gardeners must either mulch these fine sands so the surface never dries out, or make a small investment in low-application-rate crop-sprinklers (more about these shortly).

When I was a novice gardener, I hand-watered as Jeavons suggests. However, with businesses to run, I needed a less time-demanding method. I found that overhead sprinkler systems could achieve about the same result without consuming my time. If I had to be away, I could ask my wife to please turn on all or part of the system and run it for a specified time. But it is perfectly possible to water quite successfully with no more equipment than a fan nozzle and a hose — so long as you know what you are trying to accomplish and fully appreciate how much water your soil will take in when sprayed with a nozzle for a given amount of time.

When you irrigate or when it rains, each soil particle attracts to itself all the water that will stick to it before the force of gravity overcomes this attraction and pulls surplus water deeper into the ground. Thus, the surface few inches of soil can quickly become saturated, while deeper layers may still be dry. A layer of soil that has absorbed all the water it can hold against the force of gravity is said to be at field capacity. It’s like a sponge retaining all the water it can.After saturation has been reached, if more moisture is added, some starts dripping out the bottom. Continuing the irrigation brings layer after layer to capacity, and the moisture seeps ever deeper. Each and every irrigation also leaches water-soluble plant nutrients out of the surface layers and moves them down to the full depth the water has reached. If you water too long, plant nutrients are moved so far down that your vegetables’ roots can no longer access them. Result: poor growth.

The opposite of soil at field capacity is totally dry soil, something rarely — perhaps never — seen on this planet. That’s because as soil particles dry, the moisture they’re holding becomes an ever-thinner film on their surfaces. The thinner the film, the more tightly it is held, until moisture clings so tenaciously to soil particles that vegetable roots can’t extract it. If soil gets dry enough, the remaining moisture clings so hard that evaporation at normal temperatures can’t remove it. To get soil completely dry, you would have to heat it to exceed the boiling point of water. Even the hottest, never-rained-here-ever desert soil still holds a little moisture.

The point on a wet-to-dry scale where moisture clings so hard to soil particles that plants can no longer extract any moisture is called the “permanent wilting point.”Most vegetable species are not very effective at extracting moisture from dryish soil and wilt permanently at the point soil is holding about a third of the water it potentially could hold. But well before the permanent wilting point is reached, the soil comes to a degree of dryness at which vegetables experience temporary wilting during the few hours the hot midday sun increases their need for water beyond the ability of their roots to extract enough.Always imaginative, soil scientists call this degree of dryness the “temporary wilting point.”And well before their soil gets even that dry, most kinds of vegetables, being fragile, highly inbred, weakly rooting creatures, begin to experience subtle, almost unnoticeable moisture stress. It is your job to prevent this stress; as I’ve said before, any stress reduces the quality and amount of production.

Plants convert solar energy into new plant material. If photosynthetic efficiency could be increased, plant breeders could create new varieties capable of producing far more plant material in far less time. So far, this has proved impossible. As a result, when plant breeders seek to increase crop-plant productivity, about all they can do is redirect the focus of a plant’s efforts — emphasize one aspect of a plant’s activities by encouraging it to put less energy into some other area.

Vegetables are far less able to survive moisture stresses than field crops like wheat are, because vegetables have been trained over millennia to make larger edible parts at the expense of root system vigor. In the last 50 years or so, vegetables have been bred to become even weaker in this respect because to maximize profit in our industrial age of oil-driven irrigation, modern plant breeders have redesigned many vegetable varieties so they will produce even larger edible portions even more quickly at even greater cost to their root development.

Modern industrial farming aims at maximum production by maintaining vegetable field moisture levels above 70 percent of capacity, to the full depth of the vegetables’ root development. Intensive raised-bed gardeners should try to accomplish about the same thing. Once the top 12 inches (30 centimeters) of soil has dried to about 70 percent of its moisture-holding capacity, it should be watered back up to capacity again. By the time the top foot has dried to 60 percent of capacity and the next foot has dried to close to 70 percent, the bed must be watered back up to capacity.

If you’ll contemplate Figures 6.4 and 6.5 and do a little arithmetic, you’ll see that in moderate climates it would be wise to water semi-intensive raised beds (Column 2) back up to capacity every two to five days — more frequently (giving less water) on sandy soil; less often, but applying more when you do water, on heavier soils. The basic plan should be to replace lost moisture more or less at the rate it is lost, without overwatering (which leaches out soil fertility).

Judging by recommendations in garden books and magazines, and judging by the equipment most gardeners use for irrigation, I conclude that gardeners who do irrigate grossly overwater far more often than they underwater. Consumer-grade “lawn and garden” sprinklers spread water thick and fast. Although consumers don’t get accurate performance specifications, as buyers of agricultural-grade crop sprinklers do, it is easy to test any sprinkler for application rate. Simply set out a few water gauges — empty tin cans or other cylinders with straight-up-and-down sides. Put one near the sprinkler, one near the outer limit of its reach, and a couple in between. Run the sprinkler for exactly 20 or for exactly 30 minutes, measure the depth of water in each container, average those amounts, and do some arithmetic to derive the sprinkler’s “application rate per hour.” Most lawn sprinklers spread well in excess of two inches (five centimeters) per hour. Oscillating sprinklers, the kind that spread water in rectangular patterns, put down two to four inches (five to ten centimeters) per hour. The exact amount depends on sprinkler design, water pressure, and pattern adjustment knob setting. Spraying or soaker hoses and spot sprinklers designed to cover small areas usually put out an even higher rate. How much leaching do you suppose the average gardener causes by running one of these sprinklers for only one hour? (Please contemplate Figures 6.4 and 6.5 again.)

Another benefit of doing this water-gauge test is that you’ll see the uniformity of distribution (or lack of it) that you’re getting. Try it! You may be saddened by your results. However, any sprinkler that wets the ground fairly uniformly, even a high-output one, can water a garden effectively without leaching if you know the sprinkler’s application rate and know how thick a layer of water you wish to spread.

Now you need to determine when to water. Soil moisture is best judged five to six inches (12 to 15 centimeters) below the surface. Firmly squeeze a handful of soil into a ball — the classic ready-to-till test. If the ball feels quite damp and sticks together solidly (unless you have very sandy soil, in which case this test won’t work at all), the soil moisture is above 70 percent. If the moist soil ball sticks together firmly but breaks apart easily, the moisture content is around 70 percent. If the soil feels damp but won’t form a ball when you squeeze it hard in your fist, and if the soil contains over 10 percent clay, your vegetables are experiencing moisture stress. They may look okay, but they are still at least mildly stressed.

Another, more convenient, way to determine when to water is to knowledgeably guesstimate the amount of moisture recently lost from soil. The amount of water that sun, wind, and heat remove from soil varies with the season and the amount of vegetation the soil supports, but does not vary with the type of soil. Regardless of their texture, all soils lose water at about the same rate because it is not the sun shining on the earth that dries soil out; it is the sun evaporating moisture from plants’ leaves.

If you’re going to base your additions of water on the figures in Figure 6.4, remember to adjust for cloudy days (when far less loss will occur) and for any rain received (even if it is only a drizzly fraction of an inch that stops the soil from losing moisture). Reduce the rate of loss for areas that aren’t covered by a leaf canopy — bare soil hardly loses moisture at all, especially if it has been cultivated and has formed a dust mulch.

Sandy gardens should be irrigated after losing about half an inch (1.25 centimeters) of water so as to reduce leaching.Clayey soils growing larger vegetables with two-foot-deep (60-centimeter) root systems can easily accept 1 to 1 ½ inches (2.5 to 4 centimeters) of water without danger of leaching.You may need to apply more frequent, lighter irrigations on heavier soils to keep the surface moist when seed is sprouting, when you are nursing recently transplanted seedlings during hot weather, or for species with unusually high moisture requirements, such as radishes and celery.These extra needs are best supplied with a hose and fan nozzle.

Agricultural-grade sprinklers spread water more uniformly than the consumer-grade stuff home gardeners usually use. Agricultural sprinkler heads spread water at a known, specified rate and are not designed to wear out quickly, as too many consumer-grade ones are. In the long run, paying whatever is necessary and travelling as far as necessary to a supplier of commercial-grade equipment works out to be far less expensive. For the nearest supplier, check the Yellow Pages under “Irrigation.”

Your choice of sprinkler size can make quite a difference. Although it takes a larger number of low-application-rate sprinkler heads to cover a given area (small-bore nozzles, shorter throw radius), it is better to use this sort in the home garden because (1) they put out lighter droplets, and (2) a smaller throw radius helps keep the water where you need it and off adjoining buildings and noncritical vegetation.High-application-rate sprinklers put out large heavy droplets that can cause significant soil compaction, reducing root development and making cultivation and weeding more difficult. Large droplets pounding on the surface may also contribute to forming a soil crust. Because crusts don’t form on sod, and because the lawn itself breaks the force of large droplets before they hit the ground, most lawn sprinklers issue big droplets and produce high precipitation rates — apparently a timesaving convenience for busy homeowners, even though sod leaches as easily as vegetable plots, with the same consequences. Consider how much overwatering can happen if one of these monster sprinklers runs forgotten for a few hours.

* Multiply by 2.54 for centimeters.

** Multiply by 7 to obtain kpa (kilopascals); multiply by 1.42 to obtain meters of head.

† Multiply by 3.785 for liters †† Multiply by 30.48 for centimeters

Figure 6.6

Sprinkler systems that apply less than half an inch (1.25 centimeters) per hour are best for the garden but do have drawbacks. Sun, wind, and high air temperatures can combine to break up fine streams of water and evaporate them nearly as fast as the sprinkler puts moisture out.Most criticism of sprinkler irrigation coming from drip enthusiasts (or drip equipment salespersons) is based on this misuse of the method. Small sprinkler heads are not useless, but you should not use them when the sun is strong and the wind is blowing. Sprinkling when it is calm and the sun is lower or hidden by clouds is more efficient, too, because little or no water is lost before it enters the earth.

It is possible to design a system with such a low application rate that you can water a clay soil all night long, from bedtime to breakfast, without risk of overwatering. At night there is rarely any wind, and for rural homesteaders with limited-output wells, this is also the time when there is no competition from showers, dishwashing, and so on.Watering at night is widely believed to be harmful to plants, but it may actually be the best time to water if your heavy soil allows you to do it all night without leaching. Plants are naturally dampened by dew for the last few hours of the night; during summer they quickly dry off in the morning.You can harm plants by watering them just before dark, stopping the irrigation, and leaving the plants damp all night. These are ideal conditions for the multiplication of disease organisms.Watering all night continuously washes bacteria and fungus spores off the plants before they can do any damage. This principle is well understood by nurseries that propagate healthy plants from root cuttings under a continuous mist.

On lighter soils, the best sprinkler design is one that spreads about a quarter of an inch (six millimeters) per hour, allowing you to apply a layer half an inch to three quarters of an inch (12 to 19 millimeters) thick when you sprinkle for a few hours in the early morning before breezes start up and the sun gets strong.

Although nozzles even smaller than the ones noted in Figure 6.6 are available, 1/16-inch (1.8-millimeter) bores are about the minimum effective size for veggie gardening. Systems designed around this nozzle size cover the largest amount of ground while using the smallest possible number of gallons per minute to do it. Bores with a smaller diameter can’t spray far enough to achieve even lower application rates, so you need to use many more sprinklers to cover the same area. This gets expensive.

As the bores in nozzles get larger than 7/64 inch (2.75 millimeters), they start emitting droplet sizes too massive for a veggie garden. These might be fine for pastures, golf courses, or corn fields, but to run several of them at once requires a larger water supply than most home gardeners have available. Large-scale farmers routinely use sprinklers with nozzles of 13/64 inch (five millimeters) and larger, each sprinkler drawing in excess of five gallons (20 liters) per minute.

Sprinkler designs. It seems to be impossible to design the perfect crop sprinkler, a single sprinkler that uniformly spreads water over a circle or a square while it sits in the middle of the space.The water-gauge test described a couple of pages earlier will show you how difficult it is to solve this problem. Use any sprinkler made by any manufacturer you care to choose — whether lawn, garden, agricultural, or commercial.Not only does no single sprinkler I know of accomplish perfectly uniform coverage, but most fail miserably.The reason? With a circular pattern, a sprinkler must deposit nearly ten times as much water on the perimeter as it does in the center. Every point in between receives a different amount.

Figure 6.7: The formula for the area of a circle is: A=πr2. Imagine a sprinkler with a 25-unit radius (for the convenience of American readers, assume that the “unit” is feet, but it can be any measure, metric or imperial). The innermost five units of the sprinkler pattern occupies 78.5 square units (3.14 x 5 x 5). The area in the outer five feet of the pattern is 706.5 square units, calculated this way: the area of the full circle (3.14 x 25 x 25) minus the area in the inner 20 feet of the pattern (3.14 x 20 x 20). Thus the nozzle must deposit nearly ten times as much water on the outermost five units of the pattern to end up with the same thickness of coverage as on the innermost five units.

Many design tricks are used with agricultural sprinklers to approach the ideal of equal water distribution, but even the best of them probably puts twice the amount of water on the inner half of its coverage. Surprisingly, the design that seems to so cleverly overcome this problem by watering in squares and rectangles instead of in circles — the oscillating sprinkler — is usually the worst culprit of all. I suspect the reason for this is that the cam arrangement that rotates the spray arm is inevitably a loose fit that pauses the arm too long at the turnaround point, so this type of sprinkler errs by putting too much water at the ends of its rectangular pattern and too little above the sprinkler itself. Do you have one? Measure it yourself !

The impact sprinkler can’t apply water uniformly because the rocker arm passing through the nozzle jet (its bouncing rotates the sprinkler head) dumps too much water close to the sprinkler while too little is thrown to the extremes.Most consumer-quality impact sprinklers come with a diffuser paddle or adjustable needle-tipped screw of some sort to shorten the water throw by diffusing the spray. But more than the slightest amount of diffusion increases the tendency to grossly overwater the center while leaving the fringes too dry. The more the radius is shortened by breaking up the nozzle stream, the worse this effect becomes. Agricultural-quality impulse sprinklers do not use diffusers; instead, they have nozzles with scientifically designed bores that, if used at the correct pressure, diffuse the stream (spray) properly all by themselves, putting only about twice as much water near the center of their coverage as on the outer half. Again, if you have one, measure it yourself !

To compensate for this inherent limitation of sprinkler design, farmers set out many overlapping sprinklers, all going at one time.These are arranged in regular geometric patterns so that one sprinkler’s heavily watered area is overlapped by another sprinkler’s deficiently watered area, and the differences roughly average each other out. Any multiple-sprinkler pattern still leaves a dryish fringe area, where fewer overlaps occur. On the farm, these fringes beyond the margins of the field are of little consequence; in the backyard, it may be essential to keep fringe areas within your own yard, if only to keep overspray out of neighbors’ yards or off windows.

Figure 6.8: Simultaneously operating several correctly spaced sprinklers creates overlapping water patterns, permitting uniform coverage. The optimal spacing between sprinklers is about 60 to 70 percent of the sprinkler’s throw radius. Left side: Sprinklers arranged in triangular patterns. Right side: Sprinklers correctly overlapped, arranged in square patterns.

The less-watered fringes can, however, be useful for growing a dry garden or for locating tall perennials, especially if you’re using low-angle sprinklers (to be explained shortly). Putting a line of raspberries or climbing beans right along the beginning of the dry fringe intercepts all the overspray so that it drips off the leaves and concentrates in this row. In this way, the hedge gets about as much water as is deposited in the middle of the sprinklers’ patterns, and nothing much goes past it.

Sometimes sprinkler patterns are laid out in squares, sometimes in triangular patterns. The triangular method spreads water slightly more uniformly, but the square pattern may lend itself better to the backyard situation. The shorter the designed radius of the sprinkler is, the smaller the fringe area will be, making short-radius, low-angle sprinklers preferable for backyard gardens.

Probably the single most useful, inexpensive, and highly durable agricultural-quality impulse sprinkler available is the Naan 501, made in Israel. It comes with assorted nozzle sizes, designated in metric.The best are the 1.8 or 2.0 millimetre nozzles, which is close to 1/16 inch. Naans are available through many big irrigation and farm suppliers, who can order them through their wholesale sources if they don’t actually stock them. I have used Naan sprinklers since the early 1980s.The best of the Naan range is designated as model 501U, because the 501 all by itself is nothing but the sprinkler head, which requires supports and feeder systems for proper installation. The cost of all these bits exceeds the price of the sprinkler. However, the “U” model comes with a one-meter-tall (slightly over one-yard-tall) metal support rod that holds the sprinkler head well above most vegetable crops, and a feeder pipe with a seven-millimetre (about¼ inch), quick-disconnect barbed fitting at the end — all ready to go. If the supplier you contact does not have the 501U in stock, don’t let him or her fob off the lesser items on you. Demand a special order and wait a few weeks until it comes in.

If you are using these, I strongly suggest you also purchase a special seven-millimetre punch to insert the barbs into the supply lines. If you make these holes with a nail, they’ll leak. The punch only costs a few dollars and will last a lifetime.

Some gardeners try to eliminate fringe areas by using impact sprinklers with part-circle mechanisms, locating sprinklers at the edges or corners of the garden. Generally this practice has more disadvantages than the gardener realizes. Keep in mind that cutting the arc in half doubles the rate of application; cutting it to 90° quadruples the rate of application. Part-circle sprinklers have two other flaws. First, you need a rather large-bore nozzle to create enough force to actuate the part-circle mechanism, and such a nozzle puts out a powerful stream with high application rates and big droplets. And second, when the sprinkler’s mechanism is in its reverse cycle, it dumps a lot more water close in, further accentuating the undesirable tendency to overwater close in.

The best (but not cheapest) alternative to the impact sprinkler was invented by the Toro Company. This design is now made by several other companies too, including an Australian manufacturer. It uses an internal water-powered turbine to rotate the sprinkler head.This type also has multiple-nozzle heads with various emission rates that provide the most uniform coverage possible and, interestingly, the ability to cover part circles without increasing the application rate. This design was initially intended for institutional situations, where sprinklers have to be located close to buildings and windows and where the user wants precise coverage in order to avoid sidewalks, overspraying windows, and so forth. Gardeners with fat wallets and an interest in high-tech irrigation should consider these.

High- and low-angle sprinklers. Agricultural-grade sprinkler heads are designed with different angles of throw. High-angle nozzles allow the stream of water to go its maximum distance, covering the largest area with the fewest number of sprinkler heads while the entire system draws the least number of gallons per minute, resulting in lower application rates. However, high-angle sprinklers are more strongly affected by wind, which can disperse the water stream, blow it off course, and cause high evaporation losses, especially if the sun is shining. High-angle sprinklers can be a wonderful solution for homesteaders who want large gardens but have low-yielding wells — if they avoid the sun and wind by watering at night or very early in the morning.

Low-angle sprinklers are best for windier positions or for daytime use. Low-angle sprinklers throw at only a few degrees above horizontal, so the radius is shortened and the stream is kept close to the ground, out of the strongest wind gusts. They’re better in tight backyard situations, too. More low-angle sprinklers are needed to cover a given area, resulting in somewhat higher precipitation rates. The Naan 501 series sprinklers have low-angle nozzles.

The fine points.When gardeners first study a commercial irrigation catalog, they sometimes become confused. Here are a few hints if you want to become educated by it instead.

Agricultural sprinklers come with recommendations for spacing and operating pressure. Operating a sprinkler outside its design limits results in poor performance. In the case of crop-sprinkler nozzles, matching the shape of the nozzle’s bore to the water pressure is especially important. If the water stream is propelled from the nozzle by a pressure too low for the design, the stream (jet) doesn’t break up and spray (or diffuse) properly.The impulse arm, as expected, causes much water to be laid down near the sprinkler, and the tight, undiffused stream carries water to the fringes, but few droplets are landing between these extremes — little water is laid down in the middle of the pattern.

Consider the opposite effect. Run at excessively high pressure, the water jet mists and breaks up too much — “sprays too much,” as a farmer would say — actually shortening the throw of the water, greatly increasing the rate of application near the sprinkler, and making the more distant parts of its coverage too dry.

Nozzles are designed to spray properly at pressures ranging from ten to 100 pounds per square inch (700 kpa), with most requiring from 30 to 60 psi (210 to 420 kpa). Once piped water gets past your house’s pressure regulator, its pressure is usually between 30 and 45 psi (210 to 315 kpa).The pressure in unregulated water mains can be considerably higher or, unfortunately, sometimes lower than this. Lucky homesteaders having their own electric pumps can, within limits, choose their water pressure. Do not attempt to use sprinklers demanding higher pressure than you have.

High-angle sprinklers should not be spaced at more than about 65 percent of their radius. This allows the proper amount of overlap in the pattern and allows for wind blowing the spray a little without making areas dry. Low-angle sprinklers are less bothered by wind and are usually spaced at 75 percent of their radius.

Buy agricultural sprinklers from a farm supply or irrigation company. If you live in or near a city, you can also buy them at landscaping firms, although you’ll probably have to chose the ones you want from a catalog and have them ordered in.These suppliers usually have a wide range of flexible plastic irrigation pipe and quick-connect fittings as well, so you can design a supply system that will handle the amount of water flow required.The dealer should be able to offer lots of good advice on how to assemble such a system.

The trickiest part of designing a sprinkler system is improvising the risers that hold the heads. In the last two decades, sprinkler-head stands have been made of inexpensive black plastic. The trouble with most of this plastic stuff is that it is designed for lawns and ornamental borders, so the risers are not high enough to hold sprinkler heads above vegetable crops.Veggie gardeners need supports standing about three feet (90 centimeters) above the soil. (As mentioned earlier, the Naan 501U, atop a tall metal spike, takes care of this for you.) One way to improvise risers is to glue a cheap, short, plastic sprinkler spike into the end of a long piece of heavy, three-quarter-inch (two-centimeter), white plastic pipe. Cut off the bottom end of the pipe at a sharp angle so that you can push it into the soil. The sprinkler spike is supplied through a barbed push-in connector in a black ABS plastic supply line laid atop the soil; the white plastic pipe holding up the sprinkler spike carries no water. If all this seems hard to imagine, spend some time at a supplier’s, handle the bits sold there, and see if all the pieces don’t fall into place.

Gardeners who know what they want to accomplish can reach their goal without ideal equipment. If a complete, permanent, multiheaded sprinkler system that turns on from a single valve is beyond your interest or budget, you can still achieve uniform irrigation with one good sprinkler head on a tall stand supplied by an ordinary hose.Move it around the garden and run it for equal periods in carefully determined positions. I did it this way for the first few years I ran a trials ground (before my seed business made any serious money). I made a stand with a sack of ready-mix concrete, a five-gallon (20-liter) plastic bucket, four feet (120 centimeters) of galvanized pipe, and a few fittings.

Drip systems and microirrigation. I do not recommend drip systems for the home garden. I used drip tubes on my trials grounds from 1982 until 1986 simply because drip was the only way I could water extensive areas during daylight hours (my property had a puny well supplying a bit less than three gallons [11 liters] per minute).

Drip tubes are expensive, even when purchased in 1,000-yard-long (around 900-meter) rolls. They are also short-lived and troublesome, but at that time I did not care what it cost in money or effort to produce my trials grounds — I was growing valuable information, not food.Drip tubes are easily cut with sharp hoes or shovels, and emitter holes tend to become plugged up at times, even if you have water filters.This means you must carefully inspect the entire system each and every time you turn it on. Drip lines also shift many inches from side to side as they expand and contract, so they won’t dependably water a line of new seedlings. They are even less suitable for germinating seeds. Drip systems are absolutely not workable on sandy soils because the water goes straight down through sand without spreading out horizontally, leaving large areas of totally dry soil that the plants can’t root into. High-quality long-lasting drip lines might be useful for permanent plantings, such as raspberries in heavier soils, but given a choice between drip systems and sprinklers, I’d always choose sprinklers.

Lately, new advances in plastics manufacturing have created a hybrid between drip and sprinkling, called microirrigation. These systems use inexpensive low-pressure plastic tubing to carry water; cheap quick-disconnect fittings for corners, plugs, connectors, and tees; cheap plastic spikes to hold sprinklers; and miniature short-radius sprinkler heads with emission rates so low they are measured in gallons (or liters) per hour, not per minute. Microirrigation systems provide an inexpensive and durable alternative under orchard trees and in vineyards.They are also being used more and more by homeowners to water ornamental beds around houses, and they are very useful in tunnel cloches to keep plants watered for a few weeks until the cloche is removed. Microirrigation bits come bubble-packed (like screws and bolts) in garden centres, but if purchased that way they are expensive compared to what you’ll find among the much broader assortment housed in the shelf bins of agricultural suppliers. If you are considering a microirrigation system, be wary about getting uniform water application. And use very effective filters! The nozzles are extremely fine.