Soil chemistry

Soil is made of many things.

Tiny rocks make up most of it. Small bits of sand and clay are also there. Water and air fill the tiny spaces in the dirt. Living things like bugs and plants live in the soil too. They help the soil stay healthy for new plants. It is a busy place under our feet!

Soil chemistry is the study of how soil works. It looks at how minerals and living things change the dirt. A scientist named J. Thomas Way is a father of this study. He did many tests on how soil moves tiny parts.

Soil is made of different parts. Minerals make up about 90% of its weight. The texture of soil depends on its parts. Sand has the largest pieces. It lets water drain away easily. Silt has medium pieces. It feels like flour. Clay has the smallest pieces. It is sticky when wet. Loam is a mix of all three.

Tiny spaces in the soil are very important. We call these pores. Large pores help move things in and out. Small pores stay inside soil clusters. Water and air fill these spaces. Air helps break down rocks into minerals.

Living things, or biota, also help. Plants, animals, and microbes live there. They use organic matter for power. This matter comes from dead plants or manure. When it breaks down, it makes humus. Humus helps soil hold water and stay healthy.

Soil chemistry is the study of the chemical parts of soil. It helps us understand how minerals and organic matter work together. This study is very important for protecting our environment. Scientists look at how pollution moves through the ground. They also study how chemicals change when they touch the soil. This knowledge helps us find ways to clean up contaminated land. By understanding these reactions, we can create better plans to fix the earth.

Soil is made of many different parts that work in a specific way. Minerals make up about 90% of the total weight of the soil. These minerals come from rocks or regolith. Tiny spaces called pores also exist within the soil. Large pores, or macropores, help move water and gases in and out. Small pores, or micropores, stay inside clusters of soil particles. Water moves through these spaces using forces like gravity and capillarity. Air in the soil provides oxygen to help break down rocks into minerals.

People have studied soil chemistry for a long time. In the early 1870s, a man named J. Thomas Way began his work. He was a chemist for the Royal Agricultural Society in England. He is often called the father of soil chemistry because of his experiments. Other important scientists like Edmund Ruffin and Linus Pauling also helped this field grow. Until the late 1960s, most experts focused on how soil helps plants grow. Now, many scientists focus on environmental soil science to study pollution.

Different types of soil particles change how the ground feels and works. Sand has large particles that drain water very easily. Silt has medium particles that feel like flour and hold moisture well. Clay has the smallest particles and can feel sticky when it is wet. A mix of all three is called loam. You can use a soil texture triangle to find the exact percentages of these particles.

This chart helps scientists see the balance of sand, silt, and clay. The shape of soil clusters also matters for how the ground stays together.

Living things, called biota, are a huge part of the soil system. This includes plants, animals, and tiny microbes. Microbes are very small but can weigh up to 10,000 kg per hectare. They help break down organic matter into something called humus. Humus is full of carbon, hydrogen, oxygen, sulphur, and nitrogen. This material comes from things like plant remains or manure. Living things use this organic matter for energy and nutrients. In return, they help keep the soil healthy and stable.

Soil chemistry is the study of the chemical characteristics within soil. It examines how mineral composition, organic matter, and environmental factors interact. This field is vital for understanding how nutrients move and how contaminants behave. Scientists use this knowledge to predict the fate of pollutants in the ground. They also study the processes that release these chemicals into the environment. By understanding these reactions, experts can develop cost-effective ways to clean up contaminated land. This science helps protect both ecological and environmental health.

When chemicals enter the soil, many complex reactions occur. These reactions can change how toxic a substance is to living things. Processes include adsorption and desorption, which involve particles sticking to or releasing from surfaces. Other reactions include precipitation, polymerization, dissolution, and hydrolysis. Scientists also look at hydration, complexation, and oxidation-reduction reactions. These steps determine if a contaminant stays in one place or moves through the soil. Understanding these specific mechanisms is essential for successful environmental remediation.

Soil structure describes how individual particles group into clusters called aggregates. The way these particles form depends on soil texture and parent material. Natural aggregation creates soil peds, which are soft clusters of particles. However, heavy equipment or tillage can cause compaction. This creates hard dirt clods instead of healthy, soft peds. Microbial activity also plays a role in forming these structures. Scientists classify these shapes based on their physical appearance. Spheroidal structures are rounded, while crumb structures are small and porous like bread. Granular structures are more durable than crumb types. Plate-like structures are thin and often found near plant areas. Block-like structures, which can be angular or sub-angular, are common in subsoils. Prismatic and columnar structures are longer than they are wide and often appear in deeper soil layers.

Minerals make up about 90% of the total weight of the soil. These minerals come from parental rocks or regolith. They exist in compound states involving elements like oxygen, iron, and silicon. Other common elements include aluminium, nitrogen, phosphorus, potassium, calcium, magnesium, carbon, and hydrogen. The formation of primary and secondary minerals helps define the rock composition. Soil also contains pores, which are tiny spaces between particles. Macropores help transport molecules and substances in and out of the soil. Micropores are found within the aggregates themselves. These pores allow water and gases to reach the surrounding atmosphere.

Water and air are essential components of the soil system. Water moves through macropores due to gravity and capillarity. Capillarity occurs because water adheres to soil surfaces and sticks to itself through cohesion. As water moves, it can cause leaching. This process carries ions deeper into lower soil horizons. The atmosphere in the soil contains oxygen, nitrogen, and carbon dioxide. While the atmosphere is 79% nitrogen and 20% oxygen, soil gases differ. Carbon dioxide levels increase with soil depth due to plant roots and organic matter decomposition. Oxygen is necessary to break down rocky mass into soluble minerals. If oxygen is lacking, microbial activity slows down or stops.

Soil texture is determined by the size of the particles present. Scientists use a soil texture triangle to calculate the percentages of different particle types. Sand is the coarsest particle, ranging from 0.05 to 2 mm. Sand has the largest pores and drains the most easily. Silt particles are medium-sized, between 0.002 and 0.5 mm, and feel like flour. Silt retains moisture well and contains many nutrients. Clay has the smallest particles, measuring less than 0.002 mm. Clay has small pores, which gives it high porosity, but it does not drain well. It can also shrink and swell. Loam is a combination of sand, silt, and clay.

Biota, or living organisms, are a major part of the soil's biological system. This includes plants, animals, and microorganisms. Plants create concentration gradients and influence water movement. Animals, such as detritivores like millipedes and decomposers like earthworms, regulate nutrient cycling. Microbes are especially important and can make up 1,000 to 10,000 kg of biomass per hectare. They are responsible for much of the respiration in soil. This respiration can release gases like methane and nitrous oxide, which relates to climate change. Microbes also form symbiotic relationships, such as mycorrhizae, where they exchange carbon for nitrogen with plant roots.

Organic matter is the largest source of energy and nutrients in the soil. When it decomposes, it forms humus. Humus contains elements like carbon, hydrogen, oxygen, sulphur, and nitrogen. It is a dynamic material that changes through oxidation and hydrolysis. Plant growers apply organic matter to improve soil structure and water retention. It also helps manage pH and regulate soil temperature. Without enough organic matter, soil can suffer from degradation and drying. This leads to lower fertility and makes the soil easier to erode.