Preparing the Best Soil for Crops

How Amendments, Green Manure, and Mulch Techniques Improve Crops

best-soil-for crops

By Anita B. Stone

How do you prepare the very best soil for crops? What makes good soil? Learn four organic methods for healthier harvests.

To enjoy a profitable, sustainable and green garden, each one of our homesteads requires care using a variety of procedures and testing to maintain the integrity of the landscape. Because soil amendments are simple and require little energy to improve the physical properties of any garden and crop system, it is preferable to use major amendments when working to provide top-notch soil.


Amending is not the same as mulching although some mulches are also used as amendments. Mulch is considered a major soil amendment and is placed on the soil surface, eventually becoming mixed into the soil for full effectiveness. If left unprotected, the amendment will interfere with water, air movement and root growth for potential crops.

The best soil amendments increase water and nutrient holding capacity and improve aeration and water infiltration. Wood products can tie up nitrogen in the soil. Sphagnum peat is top quality to other types of peat. Alternatives to using peat moss include decomposed tree bark, sawdust, and shredded newspaper. Just be careful not to use glossy paper or paper with color links. Many homesteaders use leaf mold, which does a good job of fluffing up the soil. Just collect or rake a big pile of leaves, allowing them to sit for a year or so and you not only capture an organic material but a responsible and effective way to get rid of those annoying leaves.

Another substitute for peat moss is coir, the hair-like fibers on coconut shells which also add fungi to protect plants from some diseases.

There are two categories of soil amendments; organic and inorganic. Organic come from something that is or was alive. They include sphagnum peat, wood chips, including redwood and cedar, hardwood bark, grass clippings, straw, compost, manure, biosolids, sawdust and wood ash. Inorganic amendments are either mined or man- made to include vermiculite, perlite, tire chunks, pea gravel, and sand.

Organic matter improves soil aeration, water infiltration and both water and nutrient holding capacity. Many organic amendments act as organic fertilizers and serve as important energy sources for bacteria, fungi and earthworms that live in the best soil for crops.


A unique form of compost is often referred to as squiggle power. Worm compost has about five times the nitrogen, ten times the potash and seven times the phosphate than soil that hasn’t been worked on by worms. The small garden worms recycle 15 tons of soil and organic matter per acre every year and offer about twice as much usable magnesium.

When selecting an amendment, decide how long it will last in the soil, consider the soil texture, the plant reactions to salts and salt content and pH of the amendment.

If your soil has less than three percent organic matter, you can apply three cubic yards of an organic amendment per 1,000 square feet. To avoid salt buildup, do not apply more than this amount. It is recommended to test the soil before adding amendments.

If you plan to apply wood chips or sawdust, you may need to apply nitrogen fertilizer to avoid nitrogen deficiency, which moves into plants. Sphagnum peat is an excellent amendment, especially for sandy soil, which will retain more water after sphagnum is applied. Peat offers a low pH and helps grow plants that require a more acidic soil. Be aware of salts in soil amendments. High salt content and high pH are common problems in certain soils so avoid amendments such as wood ash. Sphagnum peat and compost made from pure plant sources are low in salts and good choices for amendments. Request an analysis of the amendments that you are considering and choose wisely. If no analysis is available, test a small amount prior to purchasing a large quantity of amending product.

Wood products can control nitrogen in the soil and cause a deficiency in your plants. Tiny organisms in the soil use nitrogen to break down the wood. Within a short time, the nitrogen is released and becomes available to the plants. The problem is magnified with sawdust because it has a larger surface area than wood chips. If you apply wood chips or sawdust, you may need to apply extra nitrogen. When amending sandy soils, use organic amendments well decomposed like composts or aged manures so the goal increases the soil’s ability to hold moisture and store nutrients. With clay soils increase aeration and drainage using peat, wood chips, tree bark or straw.

Testing How-tos

Soil testing is imperative to discover the nutrition of the best soil for crops, including the acidity or alkalinity and the level of essential nutrients as phosphorus, potassium, calcium, magnesium and the list continues. Test results will help you make decisions regarding plant selections, soil preparations, and fertilization. A soil test determines soil pH. It is a measure of the hydrogen activity. The pH scale contains 14 divisions known as pH units. Values below 7 constitute increasing acidity, and values above 7 make up alkaline range. Therefore a soil pH of 4 is ten times more acidic than soil with a pH of 5.

Most inexpensive soil test kits from garden centers, hardware stores or home improvement stores are available, but most have proven to be unreliable. They do not indicate the amount of lime needed. Reliable results can be obtained by submitting samples to a soil testing lab. Most every state offers s a county agricultural extension center where trained technicians analyze soils for both commercial and home-growing landscapes. Simply request free forms and boxes from the county agent for soil samples. Once the analysis is completed, you can find results online in some states or you may request a printed report be mailed directly to you.

Routine soil sample analysis may be taken any time of the year. Avoid using brass, bronze or galvanized tools, which may contaminate the sample with copper and/or zinc. Place the sample into a clean bucket or a box provided by the county extension. Scrape leaves, mulch and other debris from the surface.

It is best to collect soil samples with stainless steel or chrome-plated tools. Dig a small hole into the soil then scrape the dirt from the side of the hole, one stroke, bottom to top. Dig a sample six to eight inches deep in the garden soil and two to six inches deep in lawns. For vegetable gardens take samples six to eight inches deep and for trees and shrubs, a depth of six to ten inches is recommended.

Repeat this procedure in six to eight areas to obtain a variety of samples for testing.

Soil moisture will not affect soil test results. But it’s better if the soil is slightly damp to dry, but not wet when you collect samples. If the soil is too wet to till, it’s too wet to sample and could damage the box during shipment.

When you complete a soil report form, fold the form so it is inserted between the flaps in the top of the box or tape it to the sample box. If you have plants in one area that are not doing well, send a soil sample from the problem area and another from a good area for comparison. Fill out the Diagnostic Soil Sample Information Sheet Form AD2 instead of the regular soil sample sheet. You will receive an analysis including crop information. Lawn and other forage will also be included upon request. Test results and suggested lime and fertilizer application rates will be mailed to you. The speed at which results become available varies with the time of year.

Green Manures

When planted into the soil, green manure, also known as a cover crops for gardens, is a major influence in adding nutrition to otherwise lackluster dirt. Plant a cover crop early in the season to improve the best soil for crops. After you turn it under wait about four weeks, then plant warm season vegetables. If plants start to flower, cut them down and dig them in to increase fertility. Green manures are essential for annual cropping systems that are sustainable. Historically, green manure can be traced to the original fallow cycle of crop rotation, where we waited and alternated soil and crops. But green manure crops today are a major part of organic agriculture known to suppress weeds and prevent soil erosion and compaction once plowed under while green or shortly after flowering. Nitrogen release is beneficial from the green manure crops. When selecting crops you should weigh the following information. Select a fast or a slow growing crop to if the time span that the land will be left barren. The season of the year is important as not all varieties will survive the winter cold. Decide if you want your crop to fix nitrogen and determine the soil type and how much drainage is available.

Once the plant material is released additional decomposition permits nutrients to instill themselves on the farm such as NPK (Nitrogen, phosphorus and potassium), calcium, magnesium, and sulfur. All beneficial to the health of the soil and permits easily tilled land areas. Green manures can be planted in the fall or as part of your crop rotation during the growing season. If you plant green manure crops to grow fall or winter, they double as a cover crop and help keep the topsoil from washing away. The crops are also turned into the best soil for crops in early spring. This is done when the soil is not warm enough to plant but is dry enough not to get compacted by working with it. If you have heavy soil, it is a good idea to turn the green manure into the soil later in the fall so that it decomposes over the winter. It is better than working with wet, heavy soil. You should not work or try to work with wet soil.

Choosing the proper green manure crop depends on when you want to seed and what type of soil you have. Some green manures require you to seed in the winter and others in the spring. It is best to combine more than one green manure and rotate what you plant from year to year.

There are two types of green manures; legumes and non-legumes. Legumes are plants whose roots work with the bacteria in the soil to suck in nitrogen from the atmosphere. Legumes include cowpeas, vetch, sesbania, and velvet beans, as well as non-leguminous crops such as Sudan grass, millet, ryegrass, buckwheat, and oats. Oats and rye have been used as winter cover crops for years. Fava beans, mustard, clover, lupine, fenugreek, hemp, alfalfa, velvet bean are included in the list. Comfrey, field beans, and sunflowers may be used as green manure plants along with Winter rye grows well in very cold zones and should be ready to turn under in early spring. Check with your county extension office to decide the best green manures for your area. Whatever green manure you choose, it will add organic nutrition to your best soil for crops.

To plant green manure properly, you will want to do so when it is going to rain. It is necessary that the seed not dries out during the germination period. For a small herb garden, you can broadcast the seeds by hand in an even manner. Once spread, rake the soil to cover the seeds allowing them to germinate. Green manures perform fertilization. Always select green manure crops based on the growing area and rain amounts to ensure proper growth and use of the cover crops.


Deep mulch gardening reduces moisture loss, weed emergence and certain diseases coming from the soil that causes rot when vegetables rest on the bare ground. One disadvantage in mulch may serve as harborage for some pests, mainly snails and slugs, squash bugs and crickets.

Mulching is probably one of the most effective methods to weed control. Various types of mulches may be divided into organic and inorganic mulch. Organic mulches include straw, leaves, paper, compost tree bark, and sawdust. Inorganic include plastics and petroleum by-products. Mulches come in a variety of colors, including red, orange and black. You can purchase top-grade mulch at special mulch

Organic mulches applied to a weed-free soil surface prior to direct seeding or transplanting of crops, may also be applied after crops show up but before weeds emerge. Mulching with a material should be done with care, spread evenly over the surface of the soil and not consist of large particles. One-half inch thick over the soil prevents light weed penetration. Mulch should be free of weed seeds, insects, diseases, and chemicals. Mulch materials should be heavy enough so it will not be easily displaced by wind and water. Look out for sawdust containing tree sap or wood binding glue. Organic mulch is preferred over inorganic mulch.

Black plastic is widely used as a ground cover mulch. Mulching with this inorganic substance is simple, but somewhat expensive and doesn’t allow proper amounts of moisture to penetrate the soil. If cost is not a negative factor, irrigation problems are easily solved.

Mulch materials should be heavy enough or densely packed so that it will not be easily displaced by wind or water. Mulch made of paper, sawdust and tree bark are usually free of weeds, disease, and insects. Sawdust, however, may contain amounts of tree sap or wood binding glue found in sawdust from boards such as plywood and press -wood. Make sure you know the source of the sawdust.

Because the best soil for crops is of primary importance on the landscape, it is imperative that preparation time is given to the planning, planting, and maintenance to get the best crops possible. To achieve this goal, testing, amendments, mulch, and green manures require careful selection and implementation for the best and most lucrative crops from farm or homestead to the table.

How do you cultivate your best soil for crops? Let us know!

Originally published in Countryside March/April 2012 and regularly vetted for accuracy.


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