Managing Soil pH: Four Facts You Should Know
When looking at soil test results, what’s the first thing you look at? If your answer isn’t soil pH it may be time to reconsider. Soil pH characterizes the soil as acidic (0-7), neutral (7), or alkaline (7-14) and if properly managed can optimize fertilizer use efficiency and crop yield. Soil pH governs many soil chemical and biological processes in the soil, including nutrient chemistry. When developing your nutrient management strategy, remember these four facts about soil pH:
- Adjusting soil pH could increase crop yield and fertilizer-use efficiency, so it should be the first factor considered when addressing nutrient deficiencies. It’s important to note that adjusting soil pH will not replace fertilizer applications but maximizes the efficiency of the fertilizer applied. 1
- The soil pH for optimum nutrient availability varies for different nutrients. A pH range of about 6-7 will usually optimize availability of all nutrients. With the exception of phosphorus, which is most available within a pH range of 6 to 7, macronutrients including nitrogen, potassium, calcium, magnesium and sulfur are more available within a pH range of 6.5 to 8. Most micronutrients become more available as the soil becomes more acid with an optimum pH range of about 5 to 7. 2
- Soil pH can be modified with the addition of fertilizers, tillage practices, soil organic matter, drainage, and soil amendments. Liming should be considered a regular practice on acid soils below a pH of about 6.0-6.5. Because crops vary in their sensitivity to pH, the crop rotation will be an important consideration in the pH desired. Lowering the pH of high-pH soils above about 7.5 is much more difficult and often not economical because the pH at these levels is usually dominated by the presence of lime in the soil. Elemental sulfur may be a good option for this process. Talk to your local agronomist/CCA for recommendations based on your specific soil.
- Soil test laboratories also measure what is called “buffer pH” in acid soils. Soil pH measures the active acidity in the solution (acidic < 7, alkaline > 7) and the buffer pH measures the residual/reserve soil acidity. Soil pH indicates if you need to apply lime, and buffer pH would determine how much lime is needed to change the pH to the desired level.3
Get the most out of your fertilizer investment
Having the right soil pH will help your crop maximize fertilizer use for a better yield and ROI. After reviewing your soil test information, get in touch with your local Smart Nutrition MAP+MST rep to discuss application rates and timing.
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