Maintaining soil pH in the target range for crops is important to sustain crop yield and quality (especially in pH sensitive crops like alfalfa), foster beneficial soil microbial activity and nitrogen fixation, maintain the availability of essential nutrients, reduce aluminum and micronutrient toxicity, maintain herbicide effectiveness, and suppress disease-causing pathogens.
Lime applications, when based upon soil test recommendations, are often cost-effective, resulting in improvements in crop yield and quality. Adjusting soil pH is often the first step to correcting crop nutrient deficiencies but will not replace fertilizer applications to meet nutrient needs.
If agricultural or pelletized lime is not available, few cost-effective alternatives exist. Liming materials contain a basic cation, such as calcium, magnesium, or potassium, and react with the soil to neutralize acidity. Common agricultural limes in Wisconsin are often calcium and/or magnesium carbonate materials. While products such as calcium chloride and gypsum (calcium sulfate) contain calcium, they do not have an effect on soil pH and therefore, are not limes. Liquid lime products, which are often finely ground calcium oxide, hydroxide, or carbonates, do neutralize soil acidity, the amount required to effectively change soil pH is significant and often cost-prohibitive to utilize in row-crop agriculture.
In situations where soil pH cannot be adjusted, altering soil fertilizer application techniques, such as banding of phosphorus fertilizers in low and very low testing soils, in addition to broadcast applications, and foliar applying micronutrients when deficiencies are present, may help maintain nutrient solubility and increase nutrient uptake efficiency.
Target soil pH for Wisconsin Field Crops. Adapted from Table 4.2 in A2809
The target pH for Wisconsin crops is found in table 4.2, pages 30 to 32, of Nutrient Application Guidelines for Field, Vegetable and Fruit Crops in Wisconsin. The target soil pH for a crop rotation is determined by the most acid sensitive crop in the 4-year future rotation. For example, in a corn-soybean-wheat rotation, soybean has the highest target soil pH (6.3 vs 6.0 for corn and wheat). Therefore, the target pH for the rotation is 6.3.
Lime recommendations are based upon soil test results and reflect the amount of commercial lime required to reach the rotational target pH. The lime requirements when using 60-69 and 80-89 lime are typically listed on the soil test report. It should be noted, lime takes time to react. Lime’s effective neutralizing material rating is based upon the material that will effectively increase soil pH over a 3 year time period.