BSCI 124 Lecture Notes

Undergraduate Program in Plant Biology, University of Maryland


Introduction Example: Tomato Production Problems associated with Agricultural practices

I. The problem of declining genetic diversity [REQUIRED READING] in our food crops [REQUIRED READING] and agricultural animals.  Seed companies focus on providing seeds of certain new varieties of crops to growers. These varieties have been bred for combining favorable characteristics, such as high yield, ability to survive machine picking and packing, and resistance to certain diseases.  However, by providing only a few varieties, we lose the diversity provided by growing the wide range of varieties historically developed for that crop; Different varieties are adapted to different environmental factors (drought, different pests or diseases, flooding) that we may not forsee as a problem until they happen.  Focusing on one variety is similar to the old adage of "putting all our eggs in one basket".

II. Soil erosion: Loss of soil comes from tilling (plowing) the land and the effects of wind and watersoil erosion on farmland

Soil is a valuable resource.  The rich and deep soil of the Midwest US is what makes our country the breadbasket of the world and is important to our economy.  Soil is made of organic and inorganic matter.  The organic matter is important for giving texture to the soil, which allows root growth, and for feeding the microorganisms that live in the soil and the plant needs to grow.  The topsoil is the richest in organic matter.

III. Salinization of soil from irrigation: salt built-up in the soil to the point that crop plants can not grow. Water is necessary for plant growth. Irrigation is needed to farm areas that do not have sufficient rainfall to water crops.  Many areas of the US could not otherwise be used for the crops that consumers will buy. IV. Desertification: The expansion of desert at the expense of cropland or rangeland. V. Excessive use of commercial fertilizer: Fertilizers must be used because growing and harvesting plants depletes the soil of essential minerals (fertilizer mainly contains: N - nitrogen; P - phosphorous; K - potassium) that are taken up into the plant.  Some crops, such as tobacco, use up more of the minerals than others. VI. Widespread use of pesticides- chemicals used to control insects (pictures of examples), fungi, bacteria, nematodes which injure crop plants.  Overall, pests reduce the productivity by about 15-20%. At some times or in some places, pests and diseases will become much more of a problem and can effectively wipe out most of a crop. Pesticides can reduce this loss and so are valuable for producing crops.bollworm on cottono keep the plant upright. VII. Other examples Other Sites of Interest:
Web of Life
World Wildlife Fund
World Resources Institute: Index to topics
Agriculture Genome Information Center
AgriGator: An agricultural based search engine FAO: Food and Agriculture Organization of the United Nations
Union of International Associations: Links to all aspects of human effort
CIESIN: Information for a changing world
CGIAR: Consultative Group on International Agricultural Research
Review of soil erosion
Pesticide residues in food
Review of salinization and inadequate soil drainage
Review of drought
"Desertification of arid lands" by H.E. Dregne, a classical paper
Soil salinization problem- in Canada
A history of the Chesapeake Bay
Pesticides Consumer information
Report on Pesticide concerns- Consumer Reports web site
Pesticides in foods
Technical report on pesticides in food
National IPM Network
National Biological Control Institute
Some technical definitions relating to biodiversity
Growing Green: Executive Summary
IPM applications

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Last revised: Dec 7, 2000 - Straney