How Much Water Is Just Right?

While there is no one answer to the question of how much water is just right for all gardens, there are some useful general guidelines. The most efficient and cost-effective way to water any plant is to fill the entire root zone with water, and let the soil become almost dry be fore the next watering. The amount of dryness depends on the plant. Let the top 2 or 3 inches dry out for most established plants. Let the soil around a large tree dry down several inches, but keep new or tiny plants moist to the top inch or so of soil.

Water most plants deeply and infrequently. When using a sprinkler, measure how many inches of water you apply by setting jars at intervals along sprinkler pathways. This will also tell you if the sprinkler gives even coverage.

Remember soil type affects how much water is necessary. Water sandy soils more frequently than clay soil. To make sure you are delivering enough water to where it is needed, use a soil probe or shovel before you water to determine the extent of dryness. Repeat the process after watering to see how deeply the water has penetrated into the soil.

Lawns. Use an overhead sprinkler. Water to a depth of at least 6 inches as soon as grass fails to spring up after walking on it. Avoid frequent, shallow waterings as they lead to shallow roots, which are far more susceptible to heat or drought. Aeration, or removal of soil plugs, helps send water to the root zone. Renting an aerator every other year or so also will help to reduce thatch build-up and combat compaction.

Vegetables, Bedding Plants, and Perennials. Water 6 to 12 inches deep every four to ten days for established plants. Don't wait for plants to wilt before the next watering. Wilting slows growth and reduces crop yields.

Soaker hoses or drip irrigation are efficient ways to water here. They can save up to 60 percent of the water used by a sprinkler. Place mulch over the hose to prevent evaporation.

A cheap version of drip irrigation is container watering. Bury a container, such as a plastic 1-gallon milk jug that has had 2 or 3 holes punched in the bottom, next to or between individual plants. Keep the containers filled with water and allow them to seep water directly into plant root zones. Tailor the size of the container to the size of the plant.

Sprinklers are not the best for vegetable gardens because they waste a vast amount of water. More water lands on the leaves, where it evaporates, than anywhere else. Hand watering is as much a waste of time as it is water. Unless you stand there for a few hours with a water wand, you cannot wet the soil deeply enough to do a worthwhile job.

Cultivate unmulched soil to increase water absorption. Crusted soil forms a barrier against water penetration.
Trees, Shrubs, and Landscape Plants. Water throughout the drip line of plants for the most efficient intake of water. Soaker hoses (see page 31) allow you to wind around individual plants. They are great for such shrubs as roses that are susceptible to moisture-loving disease organisms. Since no water rests on the leaves the diseases can't establish their spores. To allow water to slowly seep down into the soil, mound a ridge of soil around the outside of the drip line to form a basin and fill with water. Remove this soil during rainy weather to prevent waterlogged roots.

Plants on landscape berms. Check and water more frequently since they have more exposed soil from which water may evaporate.

New woody transplants. Water thoroughly both the nursery soil within the root ball and the native soil surrounding it. Failure to do so may prevent the roots from venturing into the surrounding soil, which can eventually kill the plant. Dead plants are an investment wasted.

Plants in containers. Water as soon as the surface feels dry. Keep a close eye on thirsty plants such as fuschias, which often need watering once or twice daily in hot, dry weather.

Watering your plants

If you still use a lawn sprinkler to water a vegetable garden or landscape planting, or if you use an overhead watering system on hot, windy days you are wasting water. The idea of watering is to deliver an adequate amount of water to plant roots, no more, no less, and nowhere else.

There are several factors that determine how much water you need to apply and the best method of application. For starters, rainfall is a factor. No matter what plants you are watering in what type of soil, the amount of watering necessary depends on how much nature already supplies.

Another factor is the soil type. Remember that sandy soils drain quickly and that clay holds moisture for a longer period of time. These are functions of how the water moves through the soil, which affects its availability to plant roots. One inch of water applied in sandy soil will percolate down 12 inches. In good loam 1 inch of water will go down 6 to 10 inches, and in clay it will penetrate about 4 or 5 inches. Once water has filtered down beneath plant root zones it is effectively gone.

Finally, consider the plants you are watering. Some plants need much more water than others. New plants, from seeded lawns to bedding transplants and burlap-balled shrubs, require lots of frequent watering to establish their roots. On the other hand, established native plants need very little rainfall supplementation; they have naturally adapted to the area. Some plants, such as madrona, flannel bush, and western dogwood, suffer if watered in the summer.

Understanding Soil Acidity

Acidity and alkalinity describe measurements of the pH balance. The pH level is measured on a scale from 1 to 14. 1 is extremely acidic, 14 extremely alkaline, and 7 is neutral. Each number represents a tenfold difference in acidity or alkalinity. Soil that has a pH of 6 is ten times more acidic than soil with a pH of 7. Most plants prefer a slightly acidic soil, while some, such as blueberries, prosper only in very acidic soils. Very high or very low pH affects the availability of soil elements to plants, which makes pH a key factor in nutrient supply.

Gardeners commonly alter pH with lime and sulfur products. Lime raises pH (reduces acidity) and sulfur lowers pH (raises acidity). Since young plants are very sensitive to pH levels, add amendments the season before you plant to give the additive time to change the acid balance. Often gardeners are impatient and don't give purchased products a fair chance to work, simply another waste of money. Also, apply lime at least thirty days prior to using fertilizers; they bind each other up when applied together, essentially wasting the money spent on both products.

Other soil additives also affect pH balance. When applied heavily, manures, sludge, peat moss, coffee grounds, and high-nitrogen fertilizers raise acidity.

A Guide on Organic Fertilizers

You know you want humus or organic matter and also that other nutrients are necessary for soil and plant health. But before you run down to the garden center, let's consider some alternative low-cost soil
amendments, where you can get them, and how they will help your garden.

Compost. Your own backyard is the best and cheapest place to find this valuable soil amendment . You also will find it in the garden center's soil amendment section. Also, cities and counties are getting into the act with community composting. You can find huge heaps of the stuff near your local trash dump. Bring your own containers or a pick-up truck, and get your share for nothing or a nominal fee.

Mushroom compost. If you happen to live near a mushroom grower, they are an excellent source for low-cost or free compost. Mushrooms are grown indoors in huge containers filled with fine, dark, crumbly compost. Before growers plant mushroom spawn in containers, they steam-sterilize the compost. After a couple of months, growers harvest the mushrooms and clear out the bins. This used compost is still rich in nutrients and organic matter. A few little mushrooms may pop up, but since you know they are an edible variety, eat up.

Sewage sludge. Plants treat sewage for disposal using two methods, anaerobic digestion and air activation. Digested sludge is much lower quality as a fertilizer than the activated type. Activated sludge is usually much more expensive. Either type of heat-treated sludge is safe to use around your yard and garden. Inquire at your local treatment plant.

Green manures. When you spade green vegetation into the soil, you add precious organic matter, nutrients, and moisture. Green leaves, weeds, grass clippings, and cover crops such as clovers, buckwheat, rye, and oats return nitrogen, carbon, trace minerals, and other nutrients to the soil when turned under. Legumes, such as clover and alfalfa, make exceptional cover crops because they take nitrogen from the air, and convert it into a usable form for plants. One word of caution: If your plants go to seed, don't turn them into your garden soilunless you want more of them.

Animal manures. Where there are animals, there will be manure. The first rule is never use cat, dog, or swine manure in your garden. These types of manure harbor parasites and disease organisms that can be harmful to your health.

Racetracks, livestock breeding farms, dairy farms, rabbit runs, poultry farms, petting zoos, and non-petting zoos often are overjoyed to have someone actually volunteer to haul the manure away! Most manures should not be used fresh in the garden; salts will burn plant roots. Compost it first, or spread it over the soil in the fall so it has time to mellow.
Rendering plants. Organic gardeners are familiar with additives such as blood meal (rich in nitrogen), hoof and horn meal (high in nitrogen, phosphorus, and calcium), and bone meal (rich in nitrogen, phosphorus, and calcium). These are by-products of the slaughtering process and originate at rendering plants. Purchased in small quantities, these products are usually quite expensive. Most rendering plants sell these only in bulk, such as 25-ton tractor/trailer loads. Make friends with a plant worker who may be able to get you a smaller quantity!

Restaurants. Coffee grounds from espresso bars or coffee brewers are a good source of nitrogen. Ask the brewer to empty coffee grounds into a container for you to pick up once a week. The grounds are fairly acidic and useful in lowering pH levels when heavily applied.

Lumber mills. Sawdust is the by-product of turning trees into boards. Composed of cellulose, sawdust is a good form of organic matter for your garden. Don't add more than 2 inches each year as it requires a lot of nitrogen to decompose. For each ton of sawdust, a garden burns about 31/2 pounds of pure nitrogen. Offset this by adding 17 pounds of ammonium sulfate, 11 pounds of ammonium nitrate, or 8 pounds of urea. Avoid cedar sawdust, because it is toxic to some seedlings. Alderwood dust decomposes more quickly than others, such as fir or hemlock.

Don't waste money giving plants more nutrient supplements than they can absorb.

The major elements are those listed on plant food labels as N (nitrogen), P (phosphorus), and K (potassium, available as potash or K2O). Many soils are naturally high or low in any of these, but nitrogen is the most water soluble, and therefore the most likely to leach away (and into ground-water supplies). Adding more nitrogen than plants can take up is a waste of money.

The elements plants use less of are called secondary elements. They are no less critical to healthy growth than the major elements; plants just require smaller doses of them. They are calcium (Ca), magnesium (Mg), and sulfur (S). Don't waste money by adding these to your soil on a yearly basis, because plants take them in slowly, and they don't leach away. A single application usually lasts several years.
Trace or micronutrients are those that plants require only small amounts of. They include boron (B), manganese (Mn), copper (Cu), zinc (Zn), iron (Fe), molybdenum (Mo), and chlorine (Cl). Short of a soil test, the best way to tell if you need to add any of these is by plant response.

Is Your Soil Nutritious?

So you agree humus is good stuff. But will your soil contain all the nutrients necessary for healthy plant growth if all you add to it is humus? You already know incorporating organic matter that becomes humus means you will probably have to add nitrogen. Plants also need many other nutrients.
With the exception of carbon, which plants take from carbon dioxide in the air, as well as hydrogen and oxygen, which they derive from water, all other elements plants use must come directly from the soil. So what do they need?

Start with healthy soil for healthier, longer-lived plants

Thou shalt not skimp on soil preparation! The more you put into your soil, the more you will get out of it. What, you may ask, is the big deal? Dirt is still dirt, right? The truth is your soil health predicts the health of your entire garden. Rich, healthy soil sustains healthy plants that are more productive and give you the best possible return for your gardening investment. They also cost little or nothing in pesticides, fertilizers, and replacement.

For a better understanding, look at the functions of soil in your garden. Soil provides physical support for the plants and a reservoir for

nutrients, water, and oxygen. Some soils do the second part better than others. Sandy soils drain quickly, providing plenty of oxygen, but they also lose water, and dissolve nutrients too quickly. Clay holds minerals and moisture well, but drains poorly. The magic ingredient for improving either type of soil, or any type in between, is humus.

Humus is organic matter that has gone through a degrading experience. Organic matter is the remains of previously living things, such as plants, micro-organisms, bugs, and us. When added to sandy soils, humus improves water retention by attracting water molecules. When added to clay, humus improves drainage by breaking up the clay particles that naturally cling together. Humus also provides fuel for millions of micro-organisms that reside in the soil. As they break it down, the micro-organisms release elements necessary for plant growth.

High levels of humus are a sign of well-managed soil. It is best to add small amounts of humus each year and build it up, rather than dump it all on in one application. This is important because in the process of decaying organic matter, micro-organisms tie up precious soil nitrogen, which must be replenished. A good rule of thumb is to add not more than 4 inches of organic matter each year to any garden area.

Incorporating humus into your garden can be as cheap or expensive as you make it. Not surprisingly, the cheaper ways are more work than the expensive ones. The ideal way to incorporate humus is to compost. Barnyard manures also provide plenty of partially processed organic matter. Of course, garden centers offer bags of dried organic matter in the form of peat moss, processed compost, and steer manure. The advantage of compost, manures, or commercial products containing fertilizers is they also contain soil nutrients, usually including necessary nitrogen. So while it is less expensive to compost your own, the good news about buying bags of fertilizer is your money will be well-spent.