IjfIjtrsrr z sr Tr

lound that overhead sprmkler systems cou!d Z^^^ COnSUming dmC-,f 1 W - I could ask my wife : ^ase turn on all or parr of the system and run it for a specified time. But it is perkily 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 folly appreciate how much water your soil will take in when sprayed with n0ZZle for a given amount of time.

What a sprinkler \ 111 c I

accomplish

When you irrigate or when ir 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 tar 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 roors can't extract it. If soil gets dry enough, the remaining moisture clings so hard that evaporation at normal temperatures can't remove ir. To get soil completely dry, you would have to heat it to exceed the boiling point of water. Even the hottest, never-rained-here-cver desert soil still holds a little moisture.

"Flic 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 .5 third of the water it potentially could hold. But well before the permanent wilt-ing 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"tenv porary 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.

How much to water

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.

Modem 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 so.1 has dned to about 70 percent of its moisture-holding capacity, it should b wa r d 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. H 'Cne D

If you 11 contemplate Figures 6.4 and 6.5 and do a little arithmetic you'll see that m moderate chmates it would be wise to water semi-intensive raised

I beds (Column 2) back up to capacity every two to five days ~ quently (giving less water) on sandy soil; less often, but applying more when you do water, on heavier soils. 1 he basic plan should be to replace lost mois-rure 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 sprinklers "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 sprinklers application rare 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-til! test. If the ball feels quite damp and sticks together solidly (unless you have very sandy soil, in which

166 happening when it counts case this test won't work at all), the soil moisture is above 70 percent ff moist soil ball sticks together firmly but breaks apart easily, the moisture ^ rent is around 70 percent. If the soil feels damp bur won't form a ball when 2 squeeze it hard in your fist, and if the soil contains over 10 percent clay yo°u" 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 knowl-

edgeably 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 veg-enables with two-foot-deep (60-centimeter) toot systems can easily accept 1 to 1 % 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 mo,st when seed is sprouting. when you are nursing recently trans-

Ltl" g$ mg 'r WeMher' species with unusually high

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 „ot 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 our ro be tar less expensive. For rhe nearest supplier, cheek 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 rhe 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

Comparison of high- versus low application-rate sprinkler performance

Nozzle diameter in inches *

Operating pressure in PSI **

Discharge in gallonst per minute

Throw radius in feet tt

Spacing in feet

Application rate in inches per hour

Vl6

30

0.45

33

20x20

0.11

J/16

60

0.79

36

20x20

0.19

7/64

30

1.94

33

20x20

0.47

7/64

60

2.66

36

20x20

0.64

13/64

30

6.78

40

25x25

1.05

"/64

60

9.53

. 45

25x25

1.46

  • Multiply by 2.54 for centimeters.
  • Multiply by 7 to obtain kpa (kilopascals); multiply by 1.42 to obtain meters of head.

t Multiply by 3.785 for liters tt Multiply by 30.48 for centimeters

Figure 6.6

droplets before they hit the ground, most lawn sprinklers issue big dr0p|cts and produce high precipitation rates - apparently a nmesaving conveniencc for busy homeowners, even though sod leaches as eas.ly as vegetable pl0Cs with die same consequences. Consider how much overwatering can happen lf one of these monster sprinklers runs forgotten for a few hours.

Sprinkler systems that apply less than halt an inch (1.25 centimeters) pcr hour arc 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 arc 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 i, I , , quarter of an inch (six millimeter) per hour X " ^ , T ,f an inch to three quarters of an inch (12 to M" ^ 3 ^ ** sprinkle for a fewlours in the ear^^^ ** ^ sun gets strong. 8 breczcs sta" "p and the

Although nozzles even smaller than the ones noted in P , able, '/it-inch (1.8-millimeter) bores are about the minil * ** ^

m 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 cant spray far enough to achieve even lower application rates, so you need to use many more sprinklers ro cover the same area. This gets expensive.

As the bores in nozzles get larger than 7/m inch (2.75 millimeters), they start emitting droplet sizes too massive for a veggie garden. These might be fine for pastures, go It 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 ,3/m inch (five millimeters) and larger, each sprinkler drawing in excess of five gallons (20 liters) per minute.

Sprinkler designs. It seems to be impossible ro design the perfect crop sprinkler, a mingle 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 ro solve this problem. Use any sprinkler made by any manufacturer you care to choose — whether lawn, garden, agricultural, or commercial. Nor only does no single sprinkler 1 know of accomplish perfectly uniform coverage,

Figure 6.7: The formula for the area of a circle is: A=Ur2. 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 (3.14x25x 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.

Figure 6.7: The formula for the area of a circle is: A=Ur2. 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 (3.14x25x 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.

bur mosr fail miserably. The reason? With a circular partem, a sprinkler milst deposit nearly ten times as much water on the perimeter as ,t does in the ccn. J Every point in between receives a different amount.

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 diffuscr 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 m regular geometric patterns so that one sprinkler's heavily watered area is overlapped by another sprinklers 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 r^ i field « ofco„«q„

nuy be essential to keep fringe areas within your own yard if T ovcrspray out of neighbors' yards or off windows. Y C° P

Dryish fringe area Dryish fringe area

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 (co 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 our 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. I he 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 rh assorted nozzle sizes, designated in metric. The besr arc rhe 1.8 0r C2°oXotre nozzles, which is close to ^a inch. Naan, are available through hi, irrigation and farm suppliers, who can order them through chcir wholesale souses if they don't actually stock them. I have used Naan sprin. U ■ -C the early 1980s. The best of the Naan range .s designated as model SOIL! because che 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 (about inch), quick-disconnect barbed fitting at the end — all ready to go. If the supplier you contact does not have the 501U in stock, dont 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 sprinklers 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

,. I.,, , mtorm average possible and, interestingly, the ability to cover part circles without incre lsi, | .

cation rate. This design was initially intended for in*.-;.-,,..- U ^ '

institutional situations, where sprinklers have ro be located close to buildings and windows and wher, the user wants prec.se coverage in order to avoid sidewalks, oversaving w"

dows, and so forth. Gardeners with fat wallets and an interest in hiilcch irrigation should consider these.

High- and low-angle sprinklers. Agrieultural-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-an^le sprinklers are more strongly affected by wind, which can disperse the water stream, blow it of f 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 lor 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. I hey Ye 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 tew hints it 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 nozzles bore to the water pressure is especially important. It the water stream is propelled from the nozzle by a pressure too low tor the design, the stream (jet) doesn't break up and spray (or diffuse) properly. I he impulse arm, as expected, causes much water ro be laid down near the sprinkler, and the tight, undiffuscd stream carries water to the fringes, bur few droplets .ire landing between these extremes — little water is laid down in the middle or rhe pattern.

Consider the opposite effect. Run at excessively high pressure, the water jet mists and breaks up too much —sprays too much/'as a fanner would mv actually shortening the throw of the water, greatly increasing the rate of near the sprinkler, and making the more distant parts of «, C0Vcr.

agC NoiTes are designed to spray properly at pressures ranging from ten to 100 pounds per square inch (700 kpa), with most rcqmnng from 30 to 60 psi (210to 420 kpa). Once piped water gets past your houses pressure regulator, L pressure is usually between 30 and 45 psi (210 to 315 kpa). The pressure in unregulated water mains can be considerably higher or, unfortunately, some-rimes 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 arc less bothered by wind and are usually spaced at 75 percent of their radius.

Buy agricultural sprinklers from a farm supply or irrigation company. It 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 h.gh enough to hold sprinkler heads above vegetable crops. Veggie gardeners need supports standing about three feet (90 centimeters) above the soil. (As menuoned earlier, the Naan 501U. atop a tall metal spike takes care of this for you.) One way to improvise risers is to due , sprinkler spike into the end of a long piece of heI r P' ' P '

centimeter), white plastic pipe. Cut off the bottom endT^'lf1 ^ angle so that you can push it into the soil. The so ' U F>ÍpC at a Sh'irP

through a barbed push-in connector in a black AR<T, Sp'ke 'S suPPIiecl b P astic 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 suppliers, 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 rail stand supplied by an ordinary hose. Move it around the garden and run it for attach sprinkler head here sprinkler spike glue feeder tube water pipe plastic water pipe

Figure 6.9: An improvised sprinkler-head riser.

attach sprinkler head here sprinkler spike glue feeder tube

Figure 6.9: An improvised sprinkler-head riser.

water pipe plastic water pipe

garden ing when it counts

t -A. in carefully determined positions. I did it this way for the first Cq PCtn a trials ground (before my seed business made any serioUs rTi ade a stand with a sack of ready-mix concrete, a five-gallon (20. Mpb-ric bucket, four feet (120 centimeters) of galvanized pipe, and a few fiCd DriP systems and microirrigation. I do not recommend drip systems for rhe 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 thc Watcr straight down through sand without spreading out horizon-tally, leaving large areas of totally dry S°l1 Chat thc Plants can't root into.

Figure 6.10: An improvised single-head sprinkler system.

High-quality long-lasting drip lines might be useful for permanent planting such as raspberries ,„ heavier soils, but given a choice between drip system 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 arc 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 usefiil 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 il 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.

chapter

Was this article helpful?

0 0

Post a comment