Perhaps somewhere in the world, the key to successful gardening is simply dropping seeds into the ground and watching them spring forth. But most garden soils require careful attention and preparation.
Choosing a Plot
A common mistake among beginning and experienced gardeners alike is to plant more than they can care for. A successful vegetable garden plot does not need to be big. A small, well-tended garden will grow as much or more produce than a larger one that the owner cannot keep up with.
Choose a sunny location where water is readily available to create a garden plot. Most vegetables do best in full sun, but if the plot does not receive full sun all day, try to find a place that gets at least six hours of sunlight.
If a plot has never been used as a garden before, it will probably need to be cleared. If grass or sod is growing in the soil, remove it from the plot. Do not try to mix the sod into the soil. Grass roots are tenuous and tightly intermingled, making it difficult to break up and smooth out grass clumps. These clumps may also sprout later and become weeds. Remove large weeds, while tilling under the smaller weeds. Large stones or other foreign objects should be removed from the area leaving a clear area for the garden to grow.
Try to select a spot with good, rich soil. Good garden soil is deep, loose, fertile, well drained, rich in organic matter, and has a neutral pH. The ideal garden soil composition is about five percent organic matter; twenty-five percent air; twenty-five percent water; and forty-five percent mineral matter with a neutral pH of about seven. Soils in desert areas are alkaline and are not naturally fertile. Plan to work to improve what is there.
Get acquainted with the soil in the plot. A soil test will reveal fertilizer needs and composition of soil. Soil testing is available for a nominal fee through area extension services and some private testing labs. Soil testing for home gardens is recommended every three to five years.
Soil tests determine the pH, salt concentration and level of nutrients. On a scale with a pH of seven being neutral, many vegetables will grow quite well from 6.0 to 8.4. With the analysis, the lab or extension service will provide information on needed soil improvements.
Although crops prefer a perfect soil, most will adapt and grow satisfactorily in a wide range of soil conditions from sand to clay provided they are handled correctly. Avoid the temptation to haul in topsoil to improve on what is already there. It is almost always better to work with existing soil than to haul in topsoil.
There are no legal definitions for topsoil, so providers can sell soil of nearly any composition and call it topsoil. Hauled in soil may not be any better than the existing soil in the garden plot. It could be a source of noxious weeds with a less than favorable pH or of worse texture than what is there. When fill is needed to raise the level of the yard or to fill in a coarse gravel bed, soil must be hauled in. Be aware that it may or may not improve the area where it is placed.
The minerals in soil are tiny particles of weathered rock. Texture refers to how the relative sizes of the particle structure deal with their arrangement.
Most soils contain varying sizes of minerals. The relative amounts of sand silt and clay determine the type of soil in your garden. Soil scientists use a soil triangle to illustrate the relative proportions and resulting soil structure. Very large soil particles are sand, medium sized particles are silt and fine particles are clay. The different sizes of the particles do not mesh tightly, allowing for tiny pores between them that allow the water, nutrients and air to move through the soil to the roots. An even mixture of the three makes the best garden soil. Since most soils are not an even mixture, compensate for the parts that keep the garden from producing as it should.
Knowing what type of soil is in the garden makes planning and cultivation easier. Sandy soil, which warms early in the spring and allows water to drain freely, is less likely to compact than other types. However, it does not hold water well.
Clay soil, composed of tiny particles that cling together readily holds moisture and locks air out. Typically it feels heavier than sandy soils because it holds water so well. Roots do not develop as well in clay soils because they have to penetrate the dense material and because they have difficulty getting enough oxygen for optimum growth.
Loam soils contain somewhat equal proportions of sand, silt and clay. Loam soils hold moisture and nutrients around the root zone, and drain well enough to deliver needed oxygen to the roots.
Between the three basic types of soil, very light sand, heavy clay, and loam are other variations – sandy loam, loamy clay, etc.
To determine the type of soil in a garden plot, test it by turning over a shovel full of soil and squeeze it together. If it does not stick together well, the soil is probably sandy, if it forms a sticky ball that does not easily come apart, the soil is clay. Soil that forms a ball, crumbles easily and is not particularly sticky is considered loam.
Optimum plant growth occurs in soils that hold water and nutrients around roots, yet drains well enough to allow oxygen into the area. It should also offer support for plants. Always correct soil imbalances before planting.
The effects of watering, settling, and pressure eventually compact the mineral particles in the soil, inhibiting water movement to various degrees. Soil must be loosened to allow air circulation to the roots. Plant roots require oxygen to function properly. Small air holes in loose soil allow efficient water drainage and the introduction and circulation of needed oxygen. Till, fork, or spade soil about eight inches deep to soften it and break up large clods. It is not necessary to over-prepare the soil – marble sized particles can be smoothed away with a rake.
Many gardeners damage soil by rushing to prepare it before it is dry enough. Test to see if the soil is dry enough to work. Take a handful from about three to four inches beneath the surface, and compress it into a ball. Toss it up and down in your hand or drop it on a hard surface. If the ball shatters, the soil can be worked. If it does not shatter, do not try to rototill.
Till as deeply as possible to break up the soil beneath. If a garden is tilled to the same depth each year, a hardpan layer may develop just below the usual tilling depth. Hardpan forms an impermeable “floor” where water accumulates and cannot soak through. Plants do not grow well unless this layer is penetrated and broken up.
Soils should contain five percent organic material. Nearly all soils, whether clay, sandy or humus, benefit from the addition of organic matter. Spread a layer of organic matter two to three inches thick over the soil surface and incorporate it six to eight inches deep. Organic matter breaks up clay allowing for air and water circulation, and helps hold water in sandy soils. Good sources of organic matter include straw, twigs, leaves, peat moss, sawdust, grass clippings and well-rotted manure.
In sandy soil, almost any type of organic matter will improve its structure and water-holding capability. Use coarse organic matter like sawdust or leaves to lighten clay soils. Peat moss is not a good additive to clay soils because peat moss has great water-holding capabilities just as the clay does. Together they hold too much water.
It may take several years of applying organic matter to significantly improve clay soil, but it is well worth the effort. Be careful in adding sand to clay soil – sand and clay mixed with water form a low grade concrete! The process involves extra work and expense and should only be attempted if adding bounteous organic matter and if organic matter, which breaks down will be added yearly.
Organic matter ties up nitrogen as it decays. Add nitrogen fertilizer to the organic matter to aid in the decomposition process. This addition of nitrogen is not intended to aid future plant growth, but to act as a facilitator to help in decomposition. More fertilizer will be needed when planting. Use one pound (one pint) of ammonium sulfate, or 2/3 pound of ammonium nitrate, or 1/2 pound of urea for each inch of organic matter placed on one hundred square feet of soil.
Manures vary in quality. If mixed with large amounts of bedding materials, there may not be enough nitrogen to decompose it and feed the crop. When using well-rotted manure for organic matter, reduce the fertilizer rate by 1/2.
Many areas of the country have acidic soils. If it is determined that your soil is acidic, add lime, gypsum or dolomite to loosen the soil and reduce acidity.
Gypsum is neutral and will not acidify alkaline soils, although it is sometimes promoted as an "alkali fighter." It can be used in areas of very high sodium soils known as "black alkali" areas where crops grow poorly, if at all.
Little can be done to neutralize alkaline soil, but adding iron sulfate or ground sulfur will help. Iron sulfate alters the pH more quickly than sulfur, but it also breaks down more quickly. Ground sulfur will stay in the soil for years.
Another good way to lower the pH slightly is to add an organic matter such as peat moss, wood chips, leaf mold, or sawdust.
Composting is the decomposition of organic material into humus. It is a natural phenomenon that gardeners can use to their advantage to improve garden soils. Compost can be purchased or created in a home garden by recycling kitchen and garden waste.
Composted materials make excellent mulches to cover or amend the soil. Using organic waste to make compost makes sound ecological sense. About thirty percent of the waste that reaches the landfill could be composted, lengthening the time that the landfill is useful. In addition, it improves the soil by increasing fertility, water holding capacity, and drainage.
Composting can be a casual or scientific endeavor. Kitchen and yard wastes can be piled up in the garden, but must be allowed time to decompose. More sophisticated systems use containers to turn and mix the material to hasten decomposition.
Organic wastes naturally decompose through microorganisms, insects and earthworms feeding which break it down. To function properly, the decomposing organisms need oxygen, water, nitrogen and heat mixed into the organic matter. If the right amounts of oxygen and water are incorporated, the decomposition takes place rapidly and the mixture produces enough heat to kill weed seeds and plant disease pathogens.
Incorporate air into the mixture to hasten the decay process and keep it from developing foul odors. Turn compost frequently to keep oxygen levels high. The faster the process takes place, the better the source of fertilizer it becomes.
Add nitrogen fertilizer to the composting product to hasten the decomposition process. A ratio of one part nitrogen per fifteen to thirty parts compost is about the right mix.
Using the easiest method of composting, make a pile of organic waste, turn it periodically to keep oxygen levels high and reduce foul odors, and let nature do the rest. The resulting compost will improve soil tilth, but will not be as high in fertilizer value as compost made using more sophisticated methods.
A compost bin makes the process tidier and more efficient. Make the bin about six feet high, and three to four feet square. Use building materials that allow air to get into the composting mixture such as wire, or board slats with air spaces between slats. Add moisture, and a few handfuls of lime each week to speed up the process.
Other sophisticated bins and plans are available. Consult your local county agent for more detailed information.
Mulch is spread over the soil surface to keep moisture in and weeds down. Mulch also helps keep the soil from getting over heated or from getting too cold.
Generally, mulches fall into two categories: organic and inorganic.
Organic mulches include materials like bark, shredded leaves, composed products, pine needles, and shredded newspaper. Inorganic mulches include plastic, rock, and landscape fabric. Clear all weeds from a garden before mulching for best weed control.
The advantage of organic mulch over plastics and other non-organic types is that organic materials eventually break down and improve soil structure. Mulches are sometimes used in the fall over perennial plants to keep soil temperatures constant. The purpose is not necessarily to keep soil from freezing, but to keep it from an alternating freeze/thaw, freeze/thaw cycle that may heave plants out of the ground, damage roots, or allow plants to break dormancy during a thaw, exposing them to potential damage during a freeze.
When using grass clippings as mulch, scatter them in thin layers allowing them to dry out between applications. Grass tends to clump together and develop mold and other micro-organisms. Spread in thin layers it quickly desiccates and new layers can be added to achieve the proper depth. Grass is not a great soil amendment because it is mostly water and deteriorates very rapidly.
Inorganic mulches, particularly black plastic and landscape fabrics are good for holding down weeds.
Clear plastic mulches have the specific benefit of warming the soil while holding moisture in. These clear plastics warm the soil more than black plastic. Many garden annuals grow and develop much faster in warmer soil. Planting crops through clear plastic aids in rapid growth and production.
Putting clear plastic over soil provides a greenhouse effect in the early part of the season allowing weeds to spring up under the plastic along with the desired plants. Lift the plastic and hoe or pull weeds while they are small. As the season progresses, the heat that builds up under the plastic will burn off weeds as they emerge. The tops of the plants above the plastic will not get overheated, while the roots beneath the plastic receive needed warmth.
Clear plastic is particularly effective in hastening the progress of melons and winter squash. Melons develop more sugar when they ripen in warm weather
To apply plastic mulches, lay the plastic in place and dig a shallow trench along the edges allowing the edge of the plastic to drop down into the trench. Cover with soil to keep wind from getting under the edges of the plastic and lifting it. In windy areas, rocks or piles of soil can be placed on various spots on top of the plastic to help hold it down.
Cut holes or make x-shaped slits where plants will be placed. Fold flaps on x-shaped slits underneath to prevent the flaps from falling on the emerging seedling and overheating it. Cut holes and slits only as big as needed for plant emergence and development.
If using drip hose, turn the water on for a short time before planting so that you can see where emitters are and make holes in the plastic over the wet spots. Put soil over the edges of the holes to keep wind from getting in through the planting holes. Later in the season, as plants develop and spread, the weight of the plant will keep the plastic in place.