What happens when organic matter is added to the soil and does decomposition make soil acidic?
When organic matter is added to the soil, several processes occur that influence soil properties and nutrient cycling:
Now, regarding soil acidity, decomposition of organic matter can have an impact on soil pH. As organic matter decomposes, it releases organic acids as by-products. These organic acids can lower the soil's pH, making it more acidic. The process is often referred to as "soil acidification."
However, the impact of organic matter decomposition on soil pH depends on several factors:
- Type of Organic Matter: Different types of organic matter can have varying effects on soil pH. For example, organic materials like peat and some crop residues are more acidic, while others like wood ash or lime can be alkaline.
- Soil Buffering Capacity: The ability of the soil to resist changes in pH is known as buffering capacity. Soils with high buffering capacity are less affected by the acidifying effect of organic matter decomposition.
- Microbial Activity: Soil microorganisms can also influence pH by releasing acids during their metabolic processes.
Overall, while decomposition of organic matter can lead to soil acidification, the extent of this effect is influenced by multiple factors, and it is not always the case that organic matter addition will result in a significant decrease in soil pH. Farmers and gardeners often monitor soil pH and adjust it as needed to maintain optimal conditions for plant growth. Lime application is a common practice to counteract soil acidity and raise the pH when necessary.
Decaying organic matter produces H+ which is responsible for acidity. The carbon dioxide (CO2) produced by decaying organic matter reacts with water in the soil to form a weak acid called carbonic acid. This is the same acid that develops when CO2 in the atmosphere reacts with rain to form acid rain naturally. Organic matter causes soil particles to bind and form stable soil aggregates, which improves soil structure. With better soil structure, water infiltration through the soil increases and improves the soil's ability to absorb and hold water as well as reduces the potential for surface crusting of the soil.Highly acidic or alkaline soil is not good for plant growth. If the soil is too acidic then lime is added to soil to increase its pH and to reduce it acidity. If the soil is too basic then the organic matter is added to soil to decrease its pH and reduces its alkalinity. With increase in organic matter of the soil the particle density decreases. Typical particle densities for soils range from 2.60 to 2.75 g/cm3 for mineral particles. However, they can be as high as 3.0 g/cm3 for very dense particles and as low as 0.9 g/ cm3 for organic particles. Here are some of the things that soil organic matter does for your soil: Provides essential nutrients for plants as it is decomposed by microbes. Feeds and provides habitats for diverse soil organisms, including those that help fight plant pests and diseases. Generally, the higher the organic matter the lower the bulk density. Estimates of bulk density on specific soils have been made from organic matter concentrations using regression equations.More soil organic matter means more soil pores and lower bulk density. Some of those pores are large, which is great for infiltration, but won't increase plant-available water capacity. Base-forming cations are leached from soils, carbonic acid is formed from carbon dioxide, plant roots excrete organic acids, and decomposition produces acidic products. Well, decomposition releases nutrients in the soil and makes them available for plant uptake. The more nutrients there are for plants, the more the plants can grow. As the plants grow, they take in carbon dioxide from the atmosphere and store this carbon as biomass. Decomposition is a complex process. Organic matter is broken down into carbon dioxide and the mineral forms of nutrients like nitrogen. It is also converted into fungi and bacteria through these organisms feeding on the organic material and reproducing.
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