Does Well-Rotted Manure Acidify the Soil?

Manure

• When purchasing or acquiring manure, you are also purchasing animal bedding, leftover feed remnants and other animal refuse. Allowing manure to rot or mature before utilizing it in a garden eliminates these disease-causing materials. Manure should smell sweet and have a crumbly texture before use in the garden. Oftentimes, manure is part of a compost heap, where it is incorporated and aged in concert with kitchen scraps and yard debris. This mix of heavily organic matter aerates garden soil and supplies it with slow-release nutrients, such as nitrogen, phosphorous and potassium. Manure's mix of ingredients and slow decomposition rate eventually affects soil's acidity levels, but at a much lesser rate and degree than inorganic fertilizers.

pH Scale

• Soil is a mixture of mineral particles, air, water and organic matter, and even living matter like microorganisms, annelids and insects. All of these ingredients make up a soil's structure. Some soil is dense and compact, while others are loose and sandy. Soil structure influences nutrient availability, water retention and pH levels. The pH scale measures hydrogen's availability in soil. Hydrogen combines with oxygen and forms water. Water encourages chemical reactions that processes nutrient levels. Neutral soil measures 7.0 on the pH scale. Higher numbers indicate alkaline soils, while low numbers indicate acid soils.

Acid Soils

• Some plants, such as rhodendron, azalea and blueberries prefer acidic soils. Most garden plants thrive in slightly acidic conditions within a 6.0 to 6.5 pH range. However, extremely acid soils chemically bind nutrients, making them unavailable to plants. Balancing pH levels is essential to healthy soil and plants. Before adding any soil amendments, submit soil samples to your local university extension for analysis. Samples are usually submitted before starting a new garden and every 3 to 4 years after that, or when plants fail to thrive. Soil analysts provide gardeners with recommendations for their soil types and plants. Some soils are naturally more acidic than others. Knowing your soil's baseline helps determine whether or not to amend soil with high or low quantities of manure and fertilizer.

Alkaline Soils

• Extremely alkaline soils allow the build up of other nutrients, such as aluminum and magnesium, and can cause soil toxicity. Alkaline soils are usually light, highly porous and sandy. The soil's high porosity rapidly leaches essential nutrients. Nutrients travel through soil before plants have the opportunity to take in the food they require. Compost bulks soil and helps retain water, as well as nutrients. Manure application in alkaline soils helps raise pH levels. For extremely alkaline soils, however, gardeners should use inorganic fertilizers that rapidly elevate acid levels. This is especially helpful before planting a garden.