Soil Fertility Approaches and Grow Your Soil Recommendations
In general, there are four main approaches that have been developed for improving soil fertility with organic fertilizers over the last century.
- The first is the “Base Cation Saturation Ratio (BCSR)” which prioritizes achieving an ideal ratio of calcium, magnesium and potassium in the soil. This approach was developed in the 1930s by Dr. F. E. Bear and later expanded by Dr. William Albrecht in the early days of soil science. However, when the approach was tested thoroughly in the 1970s and 80s, the higher nutrient application rates required by this approach did not result in significantly higher yields, higher nutritional value of the crops, or any other potential benefits. Still, this approach is strongly encouraged by some and remains popular among some growers. To learn more about base saturation, click here.
- The second is the “Sufficient Level of Available Nutrients (SLAN)“ which focuses on ensuring a crop has sufficient levels of all nutrients needed to maximize its yield and quality. It can be summarized as feeding the crop and is the soil fertility approach widely adopted by U.S. land-grant universities. It adds the least amount of fertilizers to realize economic gain and generally requires annual fertilization.
- The third approach, called “Maintenance”, considers the amount of nutrients that will be removed by a crop and adds that amount back to the soil (typically assuming that nutrients are not returned to the soil through composting and/or safely and properly processed human waste). Fertilization with this approach is often based on the farmer’s estimated yields to estimate soil nutrient removal rather than soil testing post harvest. However, there are not strict rules or protocol’s and this approach can use soil testing (as is encouraged by GYS) as a more accurate way of maintaining soil nutrient levels.
- The fourth approach, called “Build‐Up” focuses on ensuring nutrient levels are above the minimum needed for the crops being grown, based on soil testing, to provide a buffer to the farmer if soil testing and fertilization become difficult in future years. Often this build-up approach is combined with the maintenance approach to achieve longer-term goals.
A Grow Your Soil (GYS) organic fertilizer recommendation for your soil is created by combining the best of SLAN, Build-Up and Maintenance. Base saturation levels are reviewed for sodium as well as for calcium to determine if a soil is sodic or possibly calcareous. With a GYS recommendation, you are ensured your soil has the nutrients needed for all the crops you are growing, as well as a buffer (the degree to which is determined by the farmer’s goals) to allow long-term soil and crop health. Often, a GYS recommendation is designed for organic farmers and gardeners growing a diversity of crops in a year, using sustainable soil management methods. While most recommendations are designed for a specific crop using SLAN, a typical GYS recommendation is designed to feed the soil and ensure that it has enough organic matter and nutrients to allow a wide variety of crops to thrive, although GYS recommendations can also be designed based on the SLAN approach. Many small‐scale farmers and gardeners grow a wide variety of crops and they do not want to have to deal with a different fertilizer recipe for each of their crops. Not only is working with many fertilizer recipes a very error‐prone approach for most small‐scale growers, but having a fertilizer recipe specialized for a particular crop can be non‐optimal for a grower rotating crops within a year. In addition, GYS ensures that the organic fertilizers we recommend are available to you and will amend our recommendations if you cannot access the recommended fertilizer(s). A recommendation is of little use if you can’t find the fertilizers or apply them at the rates recommended! Application rates in a GYS recommendation are designed to ensure sufficient nutrient availability for a wide range of crops as well as a buffer based on present soil nutrient levels, the farmer’s long term goals for the land, and the availability of soil testing and fertilization to the grower in the future. Improving soil fertility can be complicated, based on the varying goals and available resources of growers. Small‐scale growers are often faced with resource constraints that limit the amount of soil testing they are able to do, with some only able to test their soil every few years or less. Grow Your Soil takes all of these factors into consideration and aims to ensure that the soil not only has sufficient nutrients for that season for the crops being grown, but has some reserves that for the most part will be replenished through sustainable soil management practices such as GROW BIOINTENSIVE®. The goal of Grow Your Soil is to provide an organic fertilizer recommendation that helps you create a soil that can support a wide variety of crops, hold and store a maximum amount of water and nutrient, and minimize the loss of its nutrients, so that when you then recycle crop residues by adding compost, you are able to maintain and even improve your soil’s overall fertility now and into the future.
