Characteristics of Brown Earth Soils free essay sample

Describe and explain the characteristics of any one soil type you have studied. (2009 Q18, 80 marks) In this answer I will discuss the characteristics of the Brown Earth soil. Brown Earth soils are known as a zonal soil as they developed as a result of the Cool Temperate Oceanic climate and the natural, mixed, deciduous vegetation of this climatic region. This climatic region is located between 30o and 55o North of the Equator. Brown Earths are the most common soil type in Ireland. Brown Earth soils have a number of characteristics that make them different from other soil types. Characteristics of a soil include colour, texture, structure, and chemistry. These characteristics are determined by the immediate environment and by a combination of processes that are active in that environment. Colour As the name suggests, Brown Earth soils are brown in colour. Soil colour is determined by soil forming processes. Humification is responsible for the dark colour of the Brown Earth soils. We will write a custom essay sample on Characteristics of Brown Earth Soils or any similar topic specifically for you Do Not WasteYour Time HIRE WRITER Only 13.90 / page Humification occurs when the organic matter on the surface of the soil is broken down and decomposed to form a substance called humus. The leaves of deciduous trees fall and decay in Autumn forming a layer of dark humus. This humus is washed into the soil by rainfall. The presence of this layer of humus makes Brown Earth soils very fertile The Brown Earth soils have a uniform colour throughout and have no distinct horizons. The Cool Temperate climate is warm enough for the presence of earthworms. Earthworms and other burrowers mix the soil together resulting in no distinct boundary between the A and B horizons. Texture Brown Earth soils have equal amounts of silt, sand and clay particles giving them a loamy texture. The texture of a soil describes how fine or coarse the particles of a soil feel. The loamy texture of the Brown Earth soil means that there is space between the soil particles for air and water to pass through it. This means that Brown Earth soils are well drained making them very fertile and ideal for agricultural purposes, as most plants will grow in a loam soil. The loamy texture of the Brown Earth soils can be attributed to the temperate climate. Brown Earth soils develop on different types of parent rock such as limestone and sandstone. In Ireland the parent material for Brown Earth soils is, in most cases, boulder clay, which was deposited during the last ice age. The process of mechanical and chemical weathering supplies the mineral particles for the soil. Freeze thaw action in upland areas and chemical weathering of the parent rock supply nutrients and minerals for the soil. The clay particles result from the process of hydrolysis. Structure The structure of a soil describes how the particles of a soil cling together. When particles of soil bind together they form lumps called peds. Brown Earth soils have a crumb structure. This means that the particles of soil are small, round and loosely packed together. This structure provides space for water and air to pass through the soil and, therefore, Brown Earth soils are well drained. The crumby structure of Brown Earth soils can be attributed to a number of factors such as the rich, organic content of the soil and the presence of living organisms. The mild temperatures of the Cool Temperate Oceanic climate encourage the activity of micro-organisms. Earthworms, bacteria and fungi help break down dead organic matter to humus. Chemistry As mentioned previously, Brown Earth soils are rich in humus. Humus is formed by the process of humification. Moderate levels of rainfall wash the nutrients into the soil but do not leach it. Climate and relief control the amount of humus in a soil. The mild winters and warm summers of the Cool Temperate climate are ideal for the formation of humus. Organic material builds up in lowland areas and the activity of earthworms and other decomposers in the soil break it down to form humus. The pH value of a soil refers to how acidic or alkaline the soil is. Acidic soils have a low pH value while alkaline soils have a high pH value. Brown Earth soils vary from having a slightly acidic to a slightly alkaline pH. The parent rock in the region influences the pH of the soil. Acidic Brown Earth soils form on rocks such as sandstone while alkaline Brown Earth soils form on rocks such as Limestone. The pH values of Brown Earth soils encourage the activity of earthworms and bacteria. These micro-organisms increase the fertility of the soil. [pic]