When it comes to irrigation, many people like to rant on about ‘deep watering’ and how this is the best way to get healthy plants and lawn. Unfortunately what isn’t explained is that throwing a lot of water at your top soil in one cycle doesn’t always work. Deep watering can’t always be achieved in one watering period each week. There is one simple reason for this that is overlooked, Top Soil and its type.
Top soil type plays a big part in how long and how often you can water your garden. How can this help me save water?
There are several types of top soil from sandy right through to clay. If you live around Victoria, you are unfortunately in a moderately clay based top soil region.
How does top soil affect irrigation?
Top soil affects irrigation in two ways. Firstly if you are in a clay based soil area then water takes along time to get through the ground to be used by plants, if you’re in a sandy area then water runs through and its hard to get it to stay there.
Secondly with a clay soil, once the water is in the soil, then clay soil will retain it for longer, as opposed to sand that has very little water retaining qualities to it at all.
Now having taken top soil into account and established what type of soil you have. Now comes the technical part.
If I have clay soil what can I do?
Don’t despair, just because you have clay soil. Clay soil just means you have to have a slightly different irrigation plan of attack.
Firstly with any irrigation it is best to look at the whole picture. Yes, you just want to get water to your plants and lawn, but no you don’t want to waste money or water doing it. This is what a lot of landscaping / irrigation companies don’t take into account. If you want to keep plants and turf healthy, you can just set your irrigation to water for an hour once a week, because it just wont work……why? Evapotranspiration.
What is Evapotranspiration?
Evapotranspiration is the process of getting water into the top soil and what factors affect it.
When you run your irrigation there are several factors that need to be taken into account.
- Top Soil – what type of soil do you have and how well does it take water?
- Time – when are you watering.
- Slope – how much slope is affecting water run off?
- Weather – sun, wind, temperature
Simply put ‘evapotranspiration’ is the rate of water going into the ground to the rate of water evaporating, and the amount running off the top soil.
So imagine you have a clay soil lawn which is 10ft x 10ft (100sqftf) with a slight slope, irrigation heads have been installed perfectly with the correct head spacing (say each corner at 10ft apart). Now its time to set the clock for watering, your irrigation company has said 1 hour once a week . That’s good if you want to pay for water that will run down the drain after probably 15 minutes of watering. What irrigation heads do you have in that lawn? Rotors…that means that each is pushing out 1+ gallons per minute. That’s 4 gpm or 240 gallons per hour.
Rate of absorption for clay soil; 0.25 – 1.25cm per hour
The irrigation companies like rainbird, Toro etc have calculated that to get 1” of water to your lawn take 0.62 of a gallon per sqft.
1”(2.5cm) of water for 100sqft is 62 gallons
With this calculation, we can quickly see that a clay top soil will only take approximately 30gallons per hour.
Having figured this out, now we can start to look at alternative options.
The best option is to look at reducing zone running time. If the zone is putting out 4 gpm, then it is best to run the zone for 7 minutes and then give the lawn time to take the water in before running for additional 7 minutes. I would maybe have one watering time in the morning and the second in the evening. This will give the lawn time to utilize the water from the first running time before adding additional water.
With this method you can monitor your lawn and adjust zone watering times, through carefully visually monitoring your lawn to see if you can increase or decrease your zone running time.
However with this example we have now just made a saving of 178 gallons in one watering time, that’s over 9000 gallons in a year! Now thats saving water!
The condition of the soil is the single most important factor in gardening. A healthy soil discourages disease, grows strong plants to survive insect attacks and encourages abundant crops. More problems or disappointments stem from poor soil preparation than from any other cause. If your soil is not properly prepared, you’re finished before you’ve even begun. The better the soil, the better the harvest. All plants need air, water, and nutrients from the soil in order to grow. Every soil needs preparation every year. The preparation steps to take depend on the type of soil. There are three basic types: clay, loam, and sand.
CLAY: A potter’s pleasure but a gardener’s nightmare. The particles of clay soil hold water and force out air, forming a solid mass that is slow to dry out and when it does, becomes rock hard. When organic matter is worked into clay soil, the clay will effectively hold the nutrients that vegetables need to grow.
SAND: Ideal at the beach but trouble in the garden. Sand particles leave plenty of space for air but water and nutrients wash right out, making it hard for all but very drought tolerant plants to survive.
LOAM: Gardener’s gold. This is what we all strive for. Somewhere between clay and sand, containing organic material that gives it a fluffy, light texture. The best soil in any garden is the top few inches where decaying plant roots, leaves and other organic matter naturally decay. This is called the top soil. For a vegetable garden more than for any other kind of garden, you need a deep loam 8 or 12 inches deep. Loamy soils are physically easy to prepare, and weeding and watering are easier too.
This isn’t difficult to achieve, but will be more time-consuming the first year than in years to come. Every year compost will have to be dug into the soil. As you continue to grow crops, they deplete the soil of nutrients which must be replenished. Compost adds nutrients, increases water retention , and is light enough to allow air to stay in the soil.
S tips for Preparing the Soil
Like all living things, plants need air, water, and sunshine and two of these three reach the plants through the soil. The better the soil, the better the harvest.
Whether preparing a new gar den or readying the soil of an established one, you start by spading or rototilling the soil to at least spade depth, 8 to 10 inches. This loosens and aerates the soil, providing a good home for your crops and assuring their development and healthy growth. Whenever possible, be gin the preparation of your garden in the fall.
“Top dress” the garden with your choice of humus-building materials: compost, peat moss, manure. Rototill or spade the garden again to mix and improve the soil, and carry the nutrients down to the depth that the vegetable roots will reach.
Also, if you’ve dug away some of the lawn to enlarge your vegetable plot, be sure to re move all of the grass from the area. Grass grows so quickly as to crowd out seedlings. You can either bury i t a foot deep in your garden to add nutrients to the soil as i t decomposes or throw it on your compost pile.
Come spring, continue your effo1ts to improve your soil. Vegetable gardens need yearly replenishment of nutrients and humus; what you take out, you must give back. If you did not add fertilizer in the fall, now is the time to do so, but a word of warning . . . don’t work the soil when it is wet; wait until the surface has begun to dry out
And the soil below the surface is only moist. Working with soil when it’s too wet can ruin its structure by compacting its particles, and this kind of damage can take a long time to correct. If you live in an area of the country known for its mud season, you should prepare soil in the fall. You’ll add weeks of growing to your season because you won’t have to wait for the soil to dry out before it can be planted. Raised beds are also a good solution to mud problems, providing better drainage and allowing the soil to warm more quickly.
TESTING THE SOIL
For the tastiest vegetables possible at harvest time, test the condition of the soil. That is the best way to find out what it needs to bring it to its most fertile state for the seeds or seedlings it will nourish and grow.
A soil test is easy. You can buy a simple, inexpensive soil kit or, if you prefer, arrange a complete soil test from an independent laboratory, your local county extension service, or agricultural college. A complete soil test will evaluate the nutrients in the soil and the pH. You can buy a pH meter yourself, to test for acidity or alkalinity in the soil. Put the prongs into the soil and you get an instant reading. The reading will tell you if your soil is acid (sour) or alkaline (sweet). This condition is rated on a scale of 1 to 14.
Take readings at different locations in the garden, since soil condition varies even from one spot to the next in your own backyard. Collect topsoil samples from different spots and mix the samples together. You’ll need about 8 ounces of soil to make your tests. Your test results will show a pH reading and tell you how much lime or sulfur to add per 100 square feet to bring the condition to ideal. Generally, soils do not vary too far from neutral and need only minor adjustments in ph. For growing vegetables, you will want a pH reading of around 6.5 (between 6 and 7 is fine). Because both lime and sulfur work slowly, it’s best to incorporate one or the other into the topsoil in the fall; over the winter months, they will adjust the condition of the soil.
FEEDING THE SOIL
Gardeners often refer to the “tilth” of their soil, by which they mean the physical condition that enables it to support good plant growth. Good soil should be friable (free from caking) and have a high content of organic matter for good plant nutrition and root aeration. The key here is to keep the humus content of your soil high. Even when tilt is good, it is important to continue adding humus-building materials. You can never add too much humus to your garden soil.
Fertilizers, on the other hand, should be added thoughtfully, and they are most effectively added in early spring. Add fertilizer before you turn the soil over, to incorporate. The nutrients uniformly throughout the soil, at least a couple of weeks prior to planting so they have time to break down. Otherwise, fertilizers can burn tender roots.
One of the questions most frequently asked is, “what is the difference between chemical and organic fertilizers?”
From the point of view of the plant there is no difference in usability or in the plant’s growth. Environmentally, though, there is a big difference. The danger with chemical fertilizers comes from excessive use which can damage you r soil by killing beneficial microorganisms and repelling worms, pollute water supplies as excess nitrogen seeps into the water table, and burn plants’ roots if the chemical fertilizer comes in contact with them. In addition , chemical fertilizers do nothing to help improve the condition of the soil, whereas organic fertilizers improve the tilth and aeration of the soil.
A complete chemical fertilizer contains the three most important plant nutrients: nitrogen, phosphorus and potassium. Packaged chemical fertilizers identify these nutrients by their percentages of nitrogen (N), phosphorus (P) and potassium (K) or potash in the package. A formula of 5-10-5 garden fertilizer , the most popular all-around formula for vegetable gardens, contains 5% nitrogen, 10% phosphorus, and 5% potassium. The other 80% of the package is inert material that helps distribute the chemicals evenly.
Nitrogen promotes the rapid growth of green stems and leaves which is why it is especially important for such leaf crops as broccoli, lettuce, and spinach. Nitrogen deficiency causes yellowed leaves and stunted growth, while an excess of nitrogen produces excessive vegetative growth at the expense of the fruit in vine crops, like tomatoes, or root crops, like beets and carrots. Phosphorous stimulates early root formation and is necessary for fruit, flower, and seed formation. A deficiency will show up in purple coloring of the leaves and small and spindly plants. Potassium helps the plants manufacture sugar and starches, as well as aid in their transport throughout the plant. A deficiency will cause dry , discolored leaves and stunted plants.
Don’t automatically sprinkle or spread a chemical fertilizer on your garden every spring or fall. You could be doing more harm than good. Here is where a soil test is important. Your test reading may show that you need only one or two nutrients, not a complete fertilizer, in which case you can buy what you need separately , in the quantities you need, at your gar den store or nursery .
If you use a chemical fertilizer, make sure it is a slow-release fertilizer. Organic fertilizers are preferred, though. The ideal method is to spread an inch or more .of compost over the entire garden every spring or fall, dig it in and let it work for you. Plan to grow crops that are heavy feeders and need largeamounts of nitrogen in a location where beans grew the year before. Peas, beans and other legumes, if planted with a legume soil inoculant will release nitrogen into the soil as they grow. After you have harvested the beans , till the vines into the soil to improve its composition and to add nitrogen for next year’s leaf crops.
“Side dress” vegetables that need a boost during the growing season by mixing fish emulsion, well-rotted manure , compost , or slow-release fertilizer into the soil around or alongside them. For an organic “side dressing,” the amount can be a handful or more. You can’t harm the plants with too much organic “side dressing,” but with chemical fertilizers i t i s important to follow the directions carefully. Vine crops like extra fe1tilizer when the vine begins to run and again when the flower buds are forming. Most other vegetables like it about three weeks after transplanting or when fruit is starting to form.
Here are some sources of organic nutrients:
Decomposed cow manure, available commercially bagged in a deodorized form at your local garden center, is a soil-improving humus that supplies nitrogen, phosphorous, and potassium to plants . Hu m us is an all-important part of th e soil , derived from decomposed organic matter rather than minerals. Humus is organic matter in the last stage of decomposition before becoming carbonic acid , ammonia, water, and various trace elements. It is an ingredient that makes the soil crum bly , soft, and workable–a key to gardening success.
A word of warning: Fresh manure should never be applied to garden plants because it can “burn” them . Apply it in the fall and allow it to break down over the winter, or compost it first and add i t to the garden when partially decomposed , but remember that it is not odor free or weed-free until it is completely decomposed.
The best type of garden manure comes from horses or cows because of its straw texture and soil-enriching qualities. However, most people are not fortunate enough to have stable manure readily available. Fresh poultry and rabbit manure are usable but they tend to be even more caustic and likely to burn plants. Never use cat or dog manure because, as the animals are meat-eaters, the manure frequently harbors disease or parasites.
Bone meal is a slow-acting organic source of phosphorus and limited nitrogen. It is 33 percent phosphorous and 3 percent nitrogen. It must be worked into the soil where the roots of the vegetables can reach it. Bone meal won ‘t burn plant roots.
Fish emulsion supplies nitrogen and some trace elements (elements needed in very small quantities, such as iron , manganese, zinc, and chlorine). Fish meal is 10 per cent nitrogen and 6 percent phosphorous.
An excellent method of improving your soil is with a mulch. Mulch means “cover,” and this can be grass cuttings, shredded fall leaves, salt hay, wood chips, pine needles. All will enrich your garden and add the nutrients your plants constantly need; at the same time , they keep down weeds and hold in moisture.
Plastic mulch traps warmth in the soil, smothers weeds, con serves moisture and protects the developing fruit from damaging ground contact, soil bacteria, and soil insects. It can be lifted in fall and used another sea son. It’s not a difficult task to roll the plastic out on the pre pared soil where seeds or seed lings will be planted . Secure the edges with soil, stones, or u-shaped pins made from old coat hangers. To sow the seeds or set out the transplants , use a knife or garden scissors to make a slit in the plastic at the recommended intervals. A bulb planter also makes an excellent tool for cutting the holes for planting. The seed packet will give you proper spacing information.
Mulches of grass clippings, straw, compost , or wood chips are also helpful in conserving moisture and keeping the weeds down. If grass is cut weekly , it doesn’t have a chance to go to seed in your mulch pile. Grass piled several inches high creates heat and decomposes quickly; piled too high, it mats down and prevents water from reaching the rest of the pile.
One way farmers improve their soil is through use of a crop of “green manure.” You can, too. After the fall harvest , legume plants are plowed back into the ground to enrich the soil in which they are grown.
The legumes attract soil microbes to the nodules on their roots. These microbes extract nitrogen from the air and convert it to a form usable by the plants. Nitrogen , essential to. growing vegetables, gives plants their healthy, green color and helps to produce a maximum crop for harvest. When you plow the plants-stripped of their produce back under, you provide a source of valuable nitrogen to the next crops grown in that space.
The “green manure” you plow back into the soil provides large amounts of organic material (free of cost) that improve the soil structure, add abundant nutrients that enhance soil fertility, and increase the number of beneficial organisms. The deep root growth of some legumes also helps tap minerals, aerates the soil, and improves drainage. Result : better crops next year.
For the home gardener, beans and peas are the most attractive of all legumes for use as green manure because they offer the bonus of an excellent harvest. Other legumes that can be productively used are alfalfa, clover, and annual vetch, and other green manure crops are barley, wheat, buckwheat, annual rye grass, and oats.
Crop rotation on large farms permits the planting of green manure plants on part of the land each year to revitalize the soil. As a home gardener, you can accomplish the same thing.
Just plant peas and beans in a different place year after year and, after harvesting, till the plants into the soil (remove and discard any plants diseased or infected with insects first).
Green manure crops are ideal contributors to the garden’s fertility when the compost pile and other available organic materials are not sufficient for the needs of the garden, especially where the soil is poor. It’s a method of composting on a large scale, and the composting takes place over the winter, right where it is needed, giving the crops plenty of time to decompose and work into the top soil