Environmental management E363 lecture 4 soil

E363 – ENVIRONMENTAL MANAGEMENT LECTURE - SOIL Dr Nguyen Thi Hoang Lien nguyenthihoanglien@hus.edu.vn WHAT IS SOIL? • Soil is a mixture of minerals, air, water, and organic materials, such as roots, decaying plant parts, fungi, earthworms, bacteria, and microorganisms • An acre of healthy topsoil can contain 900 pounds of earthworms, 2,400 pounds of fungi, 1,500 pounds of bacteria, 133 pounds of protozoa, 890 pounds of arthropods and algae, and in some cases, small mammals (Sullivan, Preston “Sustainable Soil Management: Soil Systems Guide” ATTRA National Sustainable Agriculture Information Service National Center for Appropriate Technology (NCAT) May 2004) ORGANIC MATTER • Any part of a plant or animal, either living or dead - leaves, roots, sticks, fruit, seeds, worms, insects, manure, and food scraps are all examples of organic matter • The decomposition of organic matter provides soils with the nutrients required by plants to grow • Organic matter also improves soil structure, and helps the soil to retain more water THE ISSUES  “A  nation  that  destroys  its  soils  destroys  itself.” - Franklin D Roosevelt (Letter from President to Governors White House, Washington DC February 26, 1937) Healthy soils are essential for the production of crops used to feed humans and livestock In addition to providing a stable base to support plant roots, soils store water and nutrients required for plant growth INDUSTRIAL AGRICULTURE Industrial agriculture practices continue to damage and deplete this valuable natural resource While intensive plowing and monocrop agriculture systems have caused nutrient depletion and wide-scale soil erosion, over-application of fertilizers and pesticides have contaminated our soils and polluted our waterways SOIL EROSION • Erosion is the movement of soil by water, wind, or gravity • Although this process occurs naturally throughout the world, industrial farming practices have dramatically increased the speed at which agricultural soils are eroded • The rate of erosion is highest when soil is not covered by a protective layer of plants or decaying organic matter • Industrial farmland is particularly susceptible to erosion due to intensive tillage (plowing), which eliminates protective ground cover from the soil surface and destroys root systems that help hold soil together • Since soil formation is an extraordinarily slow process, erosion poses a serious problem; soil erosion can quickly cause fertile farmland to become unsuitable for agriculture In extreme cases, erosion can lead to desertification, a process which causes arid soil to become barren and incapable of sustaining plant growth for many years • Even low rates of soil erosion can severely damage agricultural land; not only does erosion reduce the water holding capacity of a given soil, it also strips away nutrients and organic matter In fact, soil removed by erosion contains about times more nutrients and 1.5 to times more organic matter than the soil that remains behind • In addition to removing valuable soil from farmland, erosion pollutes waterways with sediment • Runoff containing sediment degrades aquatic ecosystems by reducing stream depth and increasing turbidity (making water cloudier), causing the population of fish and other aquatic organisms to decline • Eroded sediment also affects humans by disrupting drainage systems, increasing the cost of water treatment, filling up reservoirs, and obstructing waterways • Furthermore, wind erosion damages buildings and covers roads, railways, and other structures with soil SOIL NUTRIENTS AND FERTILIZERS In order to grow, plants require a variety of different nutrients: Boron (B) Manganese (Mn) Calcium (Ca) Molybdenum (Mo) Carbon (C) Nitrogen (N) Chlorine (Cl) Oxygen (O) Copper (Cu) Phosphorus (P) Hydrogen (H) Potassium (K) Iron (Fe) Sulfur (S) Magnesium (Mg) Zinc (Zn) • In  natural  environments such as prairies and forests, plants obtain most necessary nutrients from minerals found within the soil When these plants die, they fall to the ground, decompose, and release nutrients back into the soil, making them available for new plants In this way, nutrients are "recycled" with each generation of plants • On  farms, since crops are continually harvested or eaten by grazing livestock, there is no steady supply of decaying plant material to replenish nutrient levels within the soil Instead, nutrients must be restored by adding fertilizers to the soil • Traditionally, agricultural soils were fertilized using livestock manure, which is rich in nutrients and organic matter Farmers also practiced crop rotation, regularly alternating the types of crop grown in various fields and periodically allowing fields to remain unplanted This process enables organic matter to accumulate and decompose, thus restoring nutrients to the soil • Industrial  agriculture has dramatically altered the nutrient management practices used on farms Modern industrial farms no longer raise animals and crops together; instead, livestock are raised on enormous CAFOs, and crops are mass-produced on separate farms Although CAFOs generate tremendous amounts of manure, it is too costly to transport this manure to other cropland for use as fertilizer In order to avoid the expense of treating or transporting this animal manure, CAFO's typically store the waste in huge open-air pits, or "lagoons," and eventually spray the untreated liquid manure onto surrounding land • Instead, today's large-scale industrial farms depend on synthetic (manmade) chemical fertilizers to support high-intensity monocrop systems Unfortunately, synthetic fertilizers are often over-applied to cropland In fact, it is estimated that only about half of all fertilizers are actually absorbed by plants; the remaining chemicals pollute the atmosphere, soils, and waterways (Tilman, David “The Greening of the Green Revolution.” Nature Vol 396 November 19, 1998.) • The over-application of synthetic fertilizers and manure both contribute to the growing problem of nutrient pollution NUTRIENT POLLUTION • Nutrient pollution damages aquatic ecosystems by stimulating the rapid growth of algae This reduces the aesthetic and recreational values of waterways, and harms many other living organisms When the algae die, the process of decomposition uses oxygen dissolved within the water - this oxygen depletion eventually kills fish and other aquatic organisms • Nutrient pollutants washed from agricultural soils also degrade coastal environments • Excess nutrients degrade coral reefs and seagrass beds, reduce aquatic biodiversity, induce algal blooms, and cause tremendous fish kills • Nutrient pollution is also thought to induce outbreaks of Pfiesteria This toxic dinoflagelate (type of algae) emits a toxin that breaks down the skin tissue of fish, causing bleeding sores or legions Pfiesteria outbreaks have caused major fish kills and are thought to cause memory loss, confusion, respiratory problems, and skin problems in humans NUTRIENT POLLUTION AND HUMAN HEALTH • Nutrient pollution also affects human health by contaminating local water supplies • Nitrogen-contaminated groundwater is harmful to humans, particularly to vulnerable populations such as children, the elderly, and people who have suppressed immune systems • Infants who drink water contaminated with nitrates can suffer from methemoglobinemia, or blue baby syndrome, a condition that can cause brain damage or death LAW AND REGULATIONS • QCVN 03:2008/BTNMT: National technical regulation on the allowable limits of heavy metals in the soils • QCVN 15:2008/BTNMT: National technical regulation on the pesticide residues in the soils [...]... within the soil When these plants die, they fall to the ground, decompose, and release nutrients back into the soil, making them available for new plants In this way, nutrients are "recycled" with each generation of plants • On  farms, since crops are continually harvested or eaten by grazing livestock, there is no steady supply of decaying plant material to replenish nutrient levels within the soil Instead,... fertilizers to the soil • Traditionally, agricultural soils were fertilized using livestock manure, which is rich in nutrients and organic matter Farmers also practiced crop rotation, regularly alternating the types of crop grown in various fields and periodically allowing fields to remain unplanted This process enables organic matter to accumulate and decompose, thus restoring nutrients to the soil • Industrial ... that can cause brain damage or death LAW AND REGULATIONS • QCVN 03:2008/BTNMT: National technical regulation on the allowable limits of heavy metals in the soils • QCVN 15:2008/BTNMT: National technical regulation on the pesticide residues in the soils ... synthetic fertilizers are often over-applied to cropland In fact, it is estimated that only about half of all fertilizers are actually absorbed by plants; the remaining chemicals pollute the atmosphere, soils, and waterways (Tilman, David “The Greening of the Green Revolution.” Nature Vol 396 November 19, 1998.) • The over-application of synthetic fertilizers and manure both contribute to the growing... algae die, the process of decomposition uses oxygen dissolved within the water - this oxygen depletion eventually kills fish and other aquatic organisms • Nutrient pollutants washed from agricultural soils also degrade coastal environments • Excess nutrients degrade coral reefs and seagrass beds, reduce aquatic biodiversity, induce algal blooms, and cause tremendous fish kills • Nutrient pollution... allowing fields to remain unplanted This process enables organic matter to accumulate and decompose, thus restoring nutrients to the soil • Industrial  agriculture has dramatically altered the nutrient management practices used on farms Modern industrial farms no longer raise animals and crops together; instead, livestock are raised on enormous CAFOs, and crops are mass-produced on separate farms Although