Agriculture: Plant and Soil Science, Part 7

Question 1: Describe the value of manure and compost as nutrient sources.

Answer 1: Manure and compost are excellent sources of nutrients and organic matter for crops. Using soil organic matter helps increase the water retention of sandy soil. Drainage is also improved in fine soils, a wind and water erosion are diminished. Vegetable crops leave only scant crop residue behind. Organic matter, such as manure or compost, will maintain the organic matter levels of soil. Factors such as the type of animal manure, as well as whether the manure is fresh or composted, determine nutrient composition. Another determinant of nutrient content is whether the manure is heat dried. Heat drying manure and immature compost can make ammonia nitrate more volatile and reduce the nitrogen content of the compost. Residual effects can take place over two or three years after applying the manure or compost.

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Question 2: Discuss natural enemies in integrated pest control.

Answer 2: Natural enemies are organisms that can kill or limit the reproduction of other organisms. Common pests, such as insects and mites, have various natural enemies that reduce the need for pesticides. Predators are organisms that kill or attack other organisms. An example is the assassin bug. Some assassin bugs feed on other insects, such as caterpillars and aphids. Others feed on mammal blood. Insect parasites in larval stages parasitize other insects, killing their hosts as they mature. Some tachnid flies, for example, attack various moth species. Other natural enemies include plant pathogens, such as nematodes. Some nematodes, or roundworms, can be harmful to certain plants or animals, while others are extremely useful in pest control. Other examples of plant pathogens include insect-specific bacteria, such as those used in greenhouses to fight caterpillars and assorted fungi.

Question 3: Define integrated pest management.

Answer 3: Integrated pest management uses a variety of techniques to control pests. The emphasis is generally on doing the least harm to the pest or the environment. Such a strategy incorporates weather, cultural, biological, and genetic means of controlling pests, with pesticides being used only as a last resort. The use of integrated pest management has been gaining ground in recent years in various sectors of agriculture, business, and government. While elements of the grain industry have traditionally relied on chemical pesticides to manage pests, they now emphasize preventative measures, such as improved sanitation or grain aeration. Awareness of potential harm from pesticides has risen in recent years, so a movement toward less toxic methods is popular with the general public. Also, part of an integrated strategy is the use of native flora and fauna rather than imported species that may create unfavorable and unintended consequences for the environment.

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