Environmental Problems, Their Causes, and Sustainability 1

(a) Terracing(b) Contour planting and strip cropping(c) Alley cropping(d) WindbreaksFigure 14-14 Solutions: in addition to conservation tillage, soil conservation methods include (a) terracing,(b) contour planting and strip cropping, (c) alley cropping or agroforestry, and (d) windbreaks.Some farmers establish windbreaks, or shelterbelts,of trees (Figure 14-14d) to reduce wind erosion,help retain soil moisture, supply wood for fuel, andprovide habitats for birds, pest-eating and pollinatinginsects, and other animals.Some governments use land classification to identifyeasily erodible (marginal) land that should beneither planted in crops nor cleared of vegetation.In the United States, the Natural Resources ConservationService has set up a classification system toidentify types of land that are suitable or unsuitable forcultivation.How Can We Maintain and Restore SoilFertility? Conservation and FertilizersSoil conservation can reduce loss of soil nutrients,and applying inorganic and organic fertilizers canhelp restore lost nutrients.The best way to maintain soil fertility is through soilconservation. The next best thing to do is to restoresome of the plant nutrients that have been washed,blown, or leached out of soil or removed by repeatedcrop harvesting.Fertilizers can partially restore lost plant nutrients.Farmers can use organic fertilizer from plant andanimal materials or commercial inorganic fertilizerproduced from various minerals.There are several types of organic fertilizer. One isanimal manure: the dung and urine of cattle, horses,poultry, and other farm animals. It improves soil structure,adds organic nitrogen, and stimulates beneficialsoil bacteria and fungi.Manure use in the United States has decreased becausemost farmers no longer raise crops and livestockon the same farm and it costs too much to transport animalmanure from feedlots near urban areas to distantrural crop-growing areas. Also, tractors and other motorizedfarm machinery have largely replaced horsesand other draft animals that added manure to the soil.Burning poultry wastes to produce electricityleaves a phosphorus-rich ash. Researchers at the U.S.Department of Agriculture are evaluating its value asan organic fertilizer. Also, Canada-based Internationalhttp://biology.brookscole.com/miller14285