14 Feb 2013
sustainable soils

Sustainable soils Part 2 – How nutrients and soil biology work together to form sustainable soils and healthy plants

To understand how soils work in conjunction with plants, you really need to understand cellular biology; however, in this article, we are going to take a much simpler look at how soil nutrients, plant function and soil biology work together to form a sustainable environment.

As indicated in February’s article, most of us who are trying to “fix” or “maintain” our soils are concerned about the NPK numbers on fertilizer bags; however, knowing the nitrogen, phosphorus and potassium levels of a product is only the start to creating a sustainable soil. “Generations of gardeners have been brought up on 10-10-10 and 39-9-12, but nitrogen, phosphorus and potassium are just three of many nutrients that plants need to survive.”

Two additional nutrients to consider when evaluating soil’s sustainability are calcium (which stabilizes pH levels and biological activity, loosens soil, is a major component of plant cell walls and is a key indicator of weed growth) and magnesium (which holds soil particles together and is a major component that promotes plant growth). An equally important factor to consider is the relationship between calcium and magnesium. Evidence shows that soils low in calcium and high in magnesium tend to exhibit greater weed pressure and are prone to compaction. There are additional secondary nutrients and micronutrients to consider, but we’ll address that in future discussions.

A good soil test will provide you with nutrient levels currently in your soil. Here are a few suggestions to assist you:

  • Don’t use a cheap test. Inexpensive tests are likely to paint an inaccurate picture of your soil, which can result in over-fertilization and further damage to your soil.
  • Make sure your test is checking for soluble nutrient values. Our soils in the Midwest are typically heavy in clay, which binds up nutrients and makes them inaccessible to plants. Soluble values tell you the amount of that nutrient that is available for the plant.
  • Make sure your test checks for the pH, organic matter percentage, cation exchange capacity (CEC) and base saturation levels. Ideally you are looking for a pH value of 6-7, 5-15 percent organic matter, CEC of 10-15 and a calcium to magnesium ratio of 7:1. Anything above or below these numbers will likely require inputs to adjust and this could take months or years.

So, now that we have a basic understanding of nutrients, how do we get the nutrients into the plants? This is where biology plays such a critical role in soil sustainability.

Plants have a symbiotic relationship with their soils. Plants give up nearly 60 percent of their energy to their roots, which release exudates. Exudates are a food source for bacteria and the start of the nutrient cycling process within the soil food web as well as the start of sustainability.

If you are applying a dry fertilizer to your lawn, garden or farm, and you have insufficient biological activity in the soil, there is no way for your grass or other plants to take up those necessary nutrients and very little defense against pests and diseases. If possible, have a bioassay test done on your soil to get a basic understanding of your biological activity.

In an organic environment, soil organisms need to digest the organic material (nutrients) and smaller organisms (soil food web) before any plant can benefit from the micronutrients. This is why synthetic fertilizers are so harmful and why we have become so dependent on them. Once the synthetic nutrient is absorbed into the plant, the runoff leaches into the ground, thus killing off the microorganisms in the soil. Once the organisms are gone, you become dependent on the synthetic fertilizer.

To speed up the nutrient cycling process, many organic farmers and land care professionals create and use custom blended compost teas. By suspending the micronutrients of quality compost in a liquid form, the plants and soil organisms can access the benefits of the compost/nutrients far more quickly and, if the soil is lacking in biodiversity, we can inoculate the soils with the necessary biology to ensure all necessary components are available for a healthy, sustainable soil.

Diversity is important because every soil is different. Having a wide variety of bacteria and fungi handles a wide variety of deficiencies. In order for the bi-products of the microbiology to be of any value, however, the soil food web needs to continue its cycle with the help of arthropods, nematodes and protozoa (the shredders, predators and grazers found in the third trophic level of the soil food web). Backyard Organics provides the necessary predators by using good quality compost, naturally rich with nematodes and protozoa, and extracting them using an actively aerated brew process. We then add a variety of appropriate nutrients that help the microbiology live and prosper until your soil is able to sustain itself.

So, if you are considering taking a healthier, more sustainable approach to maintaining your yard and gardens, consider not only the nutrients the plants need, but also the biology and the whole ecology necessary to sustain that environment.

Todd and Tara Rockweit are owners of Backyard Organics, LLC, Wisconsin’s first organic land care business accredited by NOFA, one of two organizations in the country that accredit Organic Land Care Professionals (AOLCPs). Since 2004, Backyard Organics has been supplying natural and organic products and services for people, pets and property, including a complete do-it-yourself program. To read more about our products and services, or if you would like to submit a question, please visit us at www.backyardorganics.net, email info@backyardorganics.net or call 920.730.3253/888.200.0446.

06 Jan 2013
Complete Soil Analysis

Sustainable Soils – Part 1 Soil Basics

In a series of articles that will be written throughout this years growing season, I will try to walk you through the process of converting a non-productive and/or chemical dependent lawn, garden, and/or farm into a safe, sustainable environment that requires less time, money and effort to achieve fantastic results.  This month, however, we are going to focus on the basics of soil and help you understand how sustainability starts.

Soil is typically made up of 45% clay, silt, and sand; 25%  air; 25% water; and 5% organic matter (if you’re lucky).  Understanding your soil profile is the start to achieving sustainability but we are not done yet.

The conventional view of the soil looks at three “independent” factors which make up soil and they are structural, chemical and biological.  The emerging view of soil and soil health is looking at the same three factors; however, rather than looking at each component independently, soil health is achieved when all three are working together, not autonomously.  Lets consider the three factors independently and then how they should work together.

Soil Structure tells us the size and portion of the particles within a sample, in other words the percentage of sand, silt, and clay found in the soil sample.  Understanding soil structure is the start to better understanding the soil’s ability to retain nutrients, its holding capacity for water retention, and its tendency to become compacted.  For a quick and easy way to test soil structure, try the ribbon test.  Here is a link to the ribbon test instructions, http://backyardorganics.net/faq/

Understanding the chemical make up of soils is the typical benchmark used by most land care providers.  This will give you a better understanding of the macro (Nitrogen (N), phosphorus (P), potassium (K)) and micro nutrients found in the soil.  Chemical testing will also uncover the “blood count” and “blood pressure” of the soil, in other words the pH of the soil.  This pH is a critical factor in determining nutrient availability, especially if the soil is lacking biology, but we’ll get into that in later articles.  Depending on the test, a chemical test should also give you the holding capacity of nutrients (C.E.C.), organic matter percentage, and soluble values of macro and micro nutrients, which are the nutrients actually available to the plants.  Again, the chemical component to soils is certainly a key factor and one that should be understood but by itself will not achieve a healthy, sustainable soil.

The biological component to a healthy soil is probably the least discussed and perhaps the most influential factor in achieving sustainability.  The biological component is made of bacteria, fungi, protozoa and nematodes in addition to a variety of other insects.  Why is it important to understand the biological make up of your soil?  Because without good soil biology, pH alone will determine nutrient availability to your plants and manual inputs will then be required to retain the appropriate nutrient levels to feed those plants.

Here is a closer look at the microbes found in healthy soils;  Bacteria are mostly decomposers which feed on plant exudates and fresh organic matter.  They immobilize and retain nutrients in their bodies and are very nitrogen dense.  Bacteria have six times the nitrogen than the microbe which feeds on them.  Think of them as little bags of fertilizer!  Fungi are also decomposers, feeding on more complex organic matter.  Fungi  thread-like growth habit improves soil texture, transports water, and nutrients, and protects against pathogens.  Protozoa, nematodes and other insects are the preditors to bacteria and fungi and the carrier of the value which comes in the form of natural, slow releasing fertilizer.  The biological component to soil is the difference between “dirt” and “soil”.  Without biology, over time you would simply have sterile “dirt”.

 

“The nation that destroys its soil, destroys itself”, President Franklin D. Roosevelt.

Soils require a balance between structural, chemical and biological components to be sustainable.  If you are lacking one component, your soil will require manual inputs in the form of fertilizers (either organic or chemical based) or mechanical soil manipulation.  The greater the balance, the more sustainable the soil.

This article will also appear in the February, 2013 edition of Nature’s Pathways

In the months ahead we will talk more about how soil components should work together and how to build and maintain soil fertility.