Soil Test Recommendations For Organic Gardeners

I've written Soil Test Recommendations For Organic Gardening as response to the question, "I've got a report, now what?"
A report will provide you with current and accurate analysis of the composition of your garden. It gives basic information on what elements are present as well as what is missing. With this information you can begin to understand it's unique requirements. You can then restore balance and remedy potential problems. This guide is specifically written for organic remediation. A basic report shows measurements of these important elements

  • Number One, Organic Matter
  • Number Two, Phosphorus
  • Number Three, Potassium
  • Number Four, Calcium
  • Number FIve, Cation Exchange Capacity

    With the proper organic fertilization and the correct amendments, your soils fertility will improve dramatically!
    Your garden uses the nutrients and minerals available to produce healthy growth. Without replacing these components your plants produce less each season. You probably have heard the term "farmed-out", that is how it happens. Without the balancing your soils chemistry with the correct amendments, your garden (including raised beds or containers) become stressed and susceptible to a variety of diseases, insect infestation, and weed overgrowth. We have all heard of natural selection, but seldom think of how that plays out in our own gardens.

    The philosophy behind organic gardening is to create and maintain fertility which in turn sustains healthy, nutritious produce. Only use natural, organic fertilizers and amendments. These applications supply vital nutrients and micro-organisms, all of which are necessary to propagate a healthy environment in which your garden can flourish.

    Number One, Organic Matter:

    98% of your plants growth comes directly from organic matter, not enough and your plants are handicapped from the very start. Organic matter, commonly known as compost, supplies many benefits for your soil such as carbon which is a critical requirement for the propagation all living things. Carbon helps by stimulating the growth of micro-organisms, earth worms, and other beneficial creatures that comprise healthy, living soil. Compost contains microbes that secrete organic acids which help release nutrients contained in soil particles. They also secrete polysaccharides that glue soil particles into stable aggregates. The end result is abundant microbial activity that improves the overall soil structure, increases air penetration and water-holding capacity, and resists soil compaction.

    The smallest building blocks of soil structure are made by beneficial bacteria. Without bacteria, the glue that hold the soil food web together would not occur and further development of soil structure will not happen. Bacteria occupy most of the leaf or root surface and thus are most effective at consuming the food resources that disease-causing organisms would otherwise consume. In soil, bacteria have additional benefits: they retain nutrients such as Nitrogen, Phosphorus, Potassium, Calcium. They also help to decompose plant-toxic materials and plant residues while building the soil‘s aggregate structure.

    How much and how often are key components when you are considering purchasing compost to increase your organic matter levels. I read an article online that recommended adding 3-5 inches of compost to your lawn. I want to caution you about such advice. That much of any kind of compost is going to emit an odor that is not likely to please your neighbors. If it were to rain anytime soon you would have a really nasty mess. Start small, go slow but don't worry about making a mistake or doing something wrong.

    I believe a more practical procedure is to spread about than one third inch over the entire growing area in the spring, and then retest again in the fall. I use a commercial grade plastic lawn spreader to broadcast cotton burr compost to spread this on my lawn. My raised beds were filled cotton burr compost at the beginning of the season

    If you are amending your garden soil simply till it in. If you are using containers or have raised bed gardening then mix it together with a hand rake or spade.

    Remember, as you amend the soil with organic matter you are increasing soil fertility and therefore decreasing the amounts of amendments you need in the future! This is an investment in your property that will pay dividends for years to come. In the case of Mycorrhizal fungi, you generally only have to inoculate your soil only once and will never have to do it again. Organic gardening is a process not an event, take your time and enjoy the process of Nature. The longer you stay with organic methods, the lower the overall expense and the better the results.

    Ideally, you want an organic material that has been fully composted and free of pathogens. Locally available compost is always the best because you’re not paying extra for shipping Cotton Burr Compost is my personal favorite because it is local. The goal is to buy compost that is ”alive,” and it should have adequate levels fungi, bacteria, protozoa, and nematodes. Stay away from bulk-mart potting soils.

    Number Two; Phosphorus (P)

    Phosphorus is aptly referred to as the “power broker” in many publications because it controls the root system, seed, and flower development in plant life, as well as the processes of cell division and sugar formation. Perhaps a better name would be "The Pod Father"

    In order to raise a low phosphorus level, compare your reading (found on your copy of the soil test report) to the listing below and follow the guideline.

    01- 20 PPM; Apply soft rock phosphate or bonemeal at a rate of 50 lbs per thousand square feet.
    21-30 PPM; Apply at a rate of 25 lbs. per thousand square feet.
    30-50 PPM; Apply at a rate of 12 lbs. per thousand square feet.

    Take note that high readings (excessive amounts of phosphates) are indicative of soil that has a low pH level. The trapped phosphorus is released when the correct amount of lime is applied.

    Number Three: Potassium (K)

    Potassium is the "universal helper.” It stimulates rooting, photosynthesis, chlorophyll formation, starch formation, and sugar functions. Adequate levels of K reduce susceptibility to insect and disease outbreaks. Low soil test levels indicate the need for K fertilization, especially in soils with a low cation exchange capacity (CEC).

    If the CEC is low, I recommend increasing your soils OM level to help increase K availability.
    Soils which are predominately clay, have tight, lattice-like structures that keep potassium unavailable to the plant and typically test low. Conversion to organic gardening will naturally release unavailable K in the soil in the future.

    0-100 PPM Apply 20lbs. per 1,000 square feet for kelp meal, or Apply 15lbs. per 1,000 square feet for wood ash, or Apply 7lbs. per 1,000 square feet for sulfate of potash

    101-150 PPM Apply 13lbs. per 1,000 square feet for kelp meal, or Apply 10lbs. per 1,000 square feet for wood ash, or Apply 5lbs. per 1,000 square feet for sulfate of potash

    151- 250 PPM Apply 7lbs. per 1,000 square feet for kelp meal, Apply 5lbs. per 1,000 square feet for wood ash, Apply 3lbs. per 1,000 square feet for sulfate of potash. If soil test levels are over 250 no further K remediation is required other than regular organic fertilizer.

    Number Four: Magnesium (Mg)

    Magnesium is considered a secondary macro nutrient. The chlorophyll molecule is built around the atom on Mg, so this nutrient is essential to plant growth and viability. Clay soil often contains excessive amounts of Mg which can cause anaerobic (oxygen deprived) conditions due to soil density. Excessive Mg can also cause N, P & K deficiencies.
    The nitrification process becomes reversed and nitrate is formed in a process called denitrification.
    Under these circumstances Organic matter is processed into methanol which is toxic to the soil microbiology. The result is lifeless, sticky soil which becomes easily waterlogged during rainy periods and will not absorb water when it has become hard during dry times.

    Less than 150 PPM, Apply 50lbs. of dolomitic lime per 1,000 square feet

    151-300 PPM, Normal range, no other amending except for quality organic fertilizer which will naturally contain Mg

    301 PPM and higher, Apply 100 lbs. of Gypsum per 1,000 square feet and re test the following season.

    Number Five: Calcium (Ca)

    Calcium is considered a secondary macro nutrient but it is considered the most important element for the following reasons. Ca helps to form stable soil aggregates which give the soil structural capacity to hold nutrients and absorb water and air. Soil with these characteristics promote prolific microbial growth and earthworm activity. Ca helps to neutralize toxins, assists in root development and carbohydrate movement as well as being involved in protein synthesis and reproductive tissue.

    Number Six: Cation Exchange Capacity

    (CEC) is measurement of the capacity for holding cations (Ca, Mg, K, and Na). This capacity is influenced by the amount of clay and humus present. It is measured from 0 for pure sand to 100 for pure humus. High quality soils range from 18-25 the best getting as high as 35. If your have a high CEC value it is holding a lot of nutrients which can be released for plant and microbial growth.

    How Much Lime Do I Need?

    The amount of lime needed to raise your pH level is determined by your soil test report. First you must know what the pH level required by the plants you intend to grow. For lawns that is typically 6.5 to 7.0.

    With your soil test report in hand, find what the reading is for Cation Exchange Capacity (CEC).

  • Find that level on the list below.
  • Now find your Calcium (Ca) level from your test report
  • Compare your reading with the optimum Ca level listed below.
  • Subtract your level and multiply this figure by 4.
  • Now divide this number by 43.
  • This new figure tells you how many pounds of lime to apply per 1,000 square feet of growing area.

    For example, let's say that your CEC is 6.7 (round it up) Look at 7 on the chart below, the Optimal Ca level is 910. Now subtract the figure for Ca on your soil test report from 910. Take this number and multiply it by 4. Now, divide it by 43 to find how many pounds per 1,000 square feet. (so if you have 3,000 square feet of growing area, then you'll use 3 times the amount).

    Soil CEC/Optimal Ca Level (ppm) 30/3900 - 29/3770 - 28/3640 - 27/3510 - 26/3380 - 25/3250 - 24/3120 - 23/2990 - 22/2860 - 21/2730 - 20/2600 - 19/2470 - 18/2340 - 17/2210 - 16/2080 - 15/1950 - 14/1820 - 13/1690 - 12/1560 - 11/1430 - 10/1300 - 9/1170 - 8/1040 - 7/910 - 6/708 - 5/650 - 4/520

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