How to manage soil pH

Published on Saturday, 3 May 2014 23:45 - Written by Chad Gulley Extension Agent

Soil pH is important when it comes to growing forages for pastures and hay production. Many soils in Texas have an acid soil pH meaning the pH is less than 7.0. Soil acidity is caused by several factors such as environment, climate and culture.

Factors such as the parent material from which the soil is derived, leaching by rainfall or irrigation removes basic elements from the soil profile leaving acidic elements, and cultural practices we apply or take away from the soil profile. Rainfall can cause elements such as calcium, magnesium and sodium to leach leaving elements such as hydrogen, aluminum, and manganese that are more acidic. Cultural practices such as nitrogen fertilization, removal of harvested crops, and soil erosion can also result in a lower soil pH value.

Soil test recommendations for lime applications are based on 100 ECCE (effective calcium carbonate equivalent) liming products. Lime applications can be made any time but planning ahead can allow the limestone time to break down in the soil when targeting a specific growing season. In other words, lime applications are not instantaneous and need some time to actually change the pH of the soil.

Optimum nutrient uptake by most crops occurs at soil pH between 6.0 and 7.0. Availability of fertilizer nutrients such as nitrogen (N), phosphorus (P), and potassium (K) generally is reduced as soil pH decreases. Phosphorus is sensitive to pH and can become a limiting nutrient in very acidic soils.

Soil pH also can affect the types, concentrations and activities of soil microorganisms. Soil microbes play important roles in the recycling of soil nutrients. Laboratories across Texas routinely monitor soil pH when analyzing soil testing to determine crop nutrient needs.

For warm season forages, target soil pH varies according to forage species. The target soil pH for bermudagrass is 5.5 to 8.0. Bahiagrass target pH is 5.5 to 6.5. Crabgrass target pH is 5.5 to 7.0. Crabgrass is a weed to many producers but managed properly it can be a high value forage in the right situation.

For cool season forages, the target soil pH for annual ryegrass is 6.0 to 7.0. The target soil pH for oats is 5.5 to 7.0. The target pH for rye is 5.0 to 7.0. Legumes such as clovers are sensitive to pH. For ball clover, the target soil pH ranges from 6.5 to 8.5. The target soil pH for Arrowleaf clover is 6.0 to 7.0. The target soil pH for crimson clover is 6.0 to 7.0.

Soil pH also is very important when looking to plant the home garden, flower beds or even many fruit tree varieties. Many plants are sensitive to the soil pH so it is important to have your soil sample analyzed.

While some plants like azaleas and blueberries like a more acidic soil, many other plants need a pH to be more neutral. Your soil may need some amending to alter the pH for the desired variety of plants you wish to grow.

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