Do you manage your pH levels consistently?

Monitoring and managing the pH levels in your soils may be one of the easiest and most cost-effective practices any farmer can incorporate into their farm management program. Plant productivity, nutrient uptake efficiency and soil microbial activity can all be increased by simply maintaining soil pH in an optimal range.

One thing that most people do not understand about pH levels is that the difference between a pH level of 5.0 and 6.0 is not simply just a factor of 1. The pH scale is a logarithmic scale, meaning that the difference between say 5.0 and 6.0 is not a difference of 1 – it is difference of 10. Said another way, a pH of 5.0 is 10X more acidic than a pH of 6.0.

Why does this matter? Nutrients in the soil, whether they are already present or if they have been recently applied, are held in place by chemical bonds, either to clay particles, soil organic matter or other nutrients. Breaking these bonds and making the nutrients available to the plants requires various chemical reactions caused by water, organic acids secreted by plant roots or interaction with microorganisms in the soil. The speed and efficiency of chemical reactions are affected by pH – so pH has a major effect on nutrient availability.

The chart below shows the relative availability of different nutrients at various pH levels.

As can be seen, the ideal pH for nutrient release is 6.4 – this is the point where the major plant macronutrients (N-P-K and sulfur, calcium, and magnesium) are available and it is towards the upper end of the range for the most important micronutrients such as manganese, boron, copper, and zinc. These trace nutrients are essential to healthy, fully productive crops that have greater resistance to pests and diseases.

The majority of the 1450+ soil tests conducted by CaluSolv average a soil pH of around 5.5. At this level, phosphorus uptake is severely limited. In lower pH soils, phosphorus ties up very quickly with iron and aluminum. This is a very strong chemical bond. Looking at the chart above, it can be seen that phosphorus uptake is severely limited at a pH level of 5.5, so in soils with a low pH, the majority of phosphorus applications never reach the plant. Potassium, magnesium, calcium, and sulfur uptake are also affected. From a biological perspective, beneficial bacteria are more active at pH levels of 6.0 and above, they prefer a range of 6.4 to 6.8. When pH levels are low, nitrogen fixing bacteria (both in legumes and free-living nitrogen fixing bacteria) as well as phosphorus solubilizing bacteria are not as active, limiting nutrient availability even further.

The chart below shows the effect of pH levels on a typical N-P-K application. At a pH level of 5.5 – only 77% of applied N is available to the crop, 48% of P is available and 77% of K. Assuming an application of 200 units N, 100 units P and 100 units K – one-third of the fertilizer application is not available to the crop for which it is applied. Note that this calculation does not include nitrogen or phosphorus that is lost due to erosion or leaching due to compacted soils. That will lower the fertilizer efficiency even more. With the cost of all fertilizers increasing, it does not make sense to only receive the benefit of 2/3 of what you are purchasing.

CaluSolv’s blend of materials includes ingredients that help raise pH levels on acidic fields. CaluSolv’s Accelerated Regenerative Agriculture program also emphasizes monitoring pH levels on an annual basis and applying other soil amendments if necessary to move pH levels into optimal ranges, whether they are acidic or alkaline.