Exercise 4. Entitle each paragraph or find a phrase in the text that will serve as a title of the paragraph. Read and translate the text. Choose an abstract of ten lines and get ready to read it aloud.
The increasing amounts of fertilizers and other agricultural chemicals applied to soils since World War II ended in 1945, plus industrial and domestic waste-disposal practices, led by the mid-1960s to increasing concern over soil pollution. Soil pollution is the build-up in soils of persistent toxic compounds, chemicals, salts, radioactive materials, or disease-causing agents, which have adverse effects on plant growth and animal health.
The effectiveness of a pesticide as well as the hazards of harmful residues depends largely on how long the pesticide remains in the soil. For example, DDT, a chlorinated hydrocarbon, has a half-life of three years in cultivated soils, while organophosphorus insecticides persist for only days or months. Insecticides persist longer if worked into the soil than if left on the surface. Herbicides applied to soils may not persist at all or may persist up to two years or longer, depending on the compound. Eventually, all pesticides disappear because of evaporation and vaporization, leaching, plant uptake, chemical and microbial decomposition, and photodecomposition.
Maintenance of specific soil acidities is important in soil management because it controls the adaptation of various crops and native vegetation to different soils. The ordinary procedure for correcting excess soil acidity is the application of lime in the form of limestone, dolomitic limestone, or burnt lime. About 18.14 million metric tons of limestone are used annually on United States farms. When lime is added, the hydrogen of the complex soil colloid is exchanged for the calcium of lime.
The mechanical loss of fertile topsoil is one of the greatest problems of agriculture. Such loss is almost always caused by erosion resulting from the action of water or wind. According to the U.S. Department of Agriculture, more than half of all fertile U.S. topsoil has been damaged to some extent by erosion. Commonly implemented practices to slow soil transport include terraces and diversions. Terraces, diversions, and many other erosion "control" practices are largely unnecessary if the ground stays covered year-round.
Irrigation may be defined as the science of artificial application of water to the land or soil. It is used to assist in the growing of agricultural crops, maintenance of landscapes, and revegetation of disturbed soils in dry areas and during periods of inadequate rainfall. Additionally, irrigation also has a few other uses in crop production, which include protecting plants against frost, suppressing weed growing in grain fields and helping in preventing soil consolidation.
Various types of irrigation techniques differ in how the water obtained from the source is distributed within the field. In general, the goal is to supply the entire field uniformly with water, so that each plant has the amount of water it needs, neither too much nor too little. The modern methods are surface irrigation, localized irrigation, drip irrigation, sprinkler irrigation, center pivot irrigation, sub-irrigation.