Optimum Organic Environment Creation and MaintenanceThe following meticulously designed guiding principles and tools depict Synergy’s strategic plan for effective soil and fertility management on organic farms.
Soil Testing and the Sufficiency Level Approach to FertilityWhatever the approach a farmer takes to managing fertility, soil testing will help determine the proper application rates of lime to adjust soil pH and the current availability of nutrients in the root zone. Soil tests can help farmers avoid over-application of expensive nutrients. Over-application can cause pollution when nutrients leach from or run off farm fields into water supplies.
Figure 4- Essential Crop Nutrients
Source: Synergy European Consulting
Soil Test Index ValuesMany soil testing labs subscribe to the sufficiency level concept of fertilization. They use a rating scale or index to indicate whether or not a soil’s nutrient content is sufficient to meet yield expectations. A soil test report provides index values for most of the important crop nutrients. Although the sufficiency level approach can increase soil nutrient test values, its chief goal is not to build a nutrient bank account in the soil. The sufficiency system helps reduce leaching losses of mobile nutrients, such as potassium, in highly weathered soils with a low cation exchange capacity (CEC). The CEC measure on a soil test reflects a soil’s ability to hold mineral nutrients, such as calcium and potassium, as well as many important micronutrients, such as zinc and copper.
Soil Organic Matter ContentOne of the most common objectives of organic farming—increased soil organic matter content—is difficult to measure. Soil samples from the same area of a farm may differ widely, based on the site-specific nature and properties of soils, the variability of the organic matter source (such as bark, leaves, or green manure) in the soil sample, and the state of decomposition of the organic matter. Soil organic matter content can be measured directly or indirectly by measuring soil humic matter content. Different labs in different states may choose to measure and report one or the other. Humic matter, the most reactive component of soil organic matter, is a key component of nutrient retention in soil. Therefore, it is impossible to be 100 percent accurate in measuring the total soil organic matter content by determining the humic matter content. Humic matter values on soil tests are generally much lower than the actual soil organic matter content, particularly in soils high in organic matter. For example, some organic soils show less than 10 percent humic matter, although the soil organic matter content may be 50 percent or more. Organic farmers who want a ballpark estimate of soil organic matter content can use the following equation to convert humic matter (HM) to organic matter (OM):
Figure 5- Calculation 1
Source: Synergy European Consulting Increases in the humic matter index in a soil test may provide organic farmers with indicators of improvements to soil quality. A farmer may want to include humic matter as an evaluative parameter when preparing the soil improvement program for a certification application.