Chapter 37 - Soil and plant nutrition. This chapter define soil texture and soil composition; explain why plants cannot extract all of the water in soil; define cation exchange and describe how plants can stimulate the process; discuss the problems of topsoil erosion and farm irrigation in arid regions; suggest actions that can help mitigate these problems;. | Chapter 37 Soil and Plant Nutrition Overview: “The Nation that Destroys Its Soil Destroys Itself” Farmland productivity often suffers from chemical contamination, mineral deficiencies, acidity, salinity, and poor drainage. Healthy soils improve plant growth by enhancing plant nutrition. Typically, plants obtain carbon dioxide from the air, and water and minerals from the soil. Dust Bowl ---> Could this Happen Again?? Figure Could this happen again? Soil is a living, finite resource Plants obtain most of their water and minerals from the upper layers of soil. Living organisms play an important role in these soil layers. This complex ecosystem is fragile. Soil Texture Soil particles are classified by size; from largest to smallest they are called sand, silt, and clay. Soil is stratified into layers = soil horizons. Topsoil consists of mineral particles, living organisms, and humus = the decaying organic material. Soil horizons A horizon B horizon C horizon Figure Soil horizons After a heavy rainfall, water drains from the larger spaces in the soil, but smaller spaces retain water because of its attraction to clay and other particles. The film of loosely bound water is usually available to plants. Loams are the most fertile topsoils and contain equal amounts of sand, silt, and clay. Soil Topsoil Composition A soil’s composition refers to: ** its inorganic (mineral) AND ** organic chemical components. Inorganic Components Cations (for example K+, Ca2+, Mg2+) adhere to negatively charged soil particles. This adhering of cations prevents them from leaching out of the soil through percolating groundwater. During cation exchange, cations are displaced from soil particles by other cations. Displaced cations enter the soil solution and can be taken up by plant roots. Negatively charged ions do not bind with soil particles and can be lost from the soil by leaching. Cation exchange in soil Soil particle – – – – – – – – – K+ K+ K+ Ca2+ Ca2+ Mg2+ H+ H+ H2O + CO2 . | Chapter 37 Soil and Plant Nutrition Overview: “The Nation that Destroys Its Soil Destroys Itself” Farmland productivity often suffers from chemical contamination, mineral deficiencies, acidity, salinity, and poor drainage. Healthy soils improve plant growth by enhancing plant nutrition. Typically, plants obtain carbon dioxide from the air, and water and minerals from the soil. Dust Bowl ---> Could this Happen Again?? Figure Could this happen again? Soil is a living, finite resource Plants obtain most of their water and minerals from the upper layers of soil. Living organisms play an important role in these soil layers. This complex ecosystem is fragile. Soil Texture Soil particles are classified by size; from largest to smallest they are called sand, silt, and clay. Soil is stratified into layers = soil horizons. Topsoil consists of mineral particles, living organisms, and humus = the decaying organic material. Soil horizons A horizon B horizon C horizon Figure Soil .
