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Crops
Seeds are tested for various qualities to ensure a high quality harvest, and to limit or prevent the spread of undesirable and invasive species.
Crop
improvement
Domestication of plants is done in order to increase yield, improve disease
resistance and drought tolerance, ease harvest and to improve the taste and
nutritional value and many other characteristics. Centuries of careful assortment
and breeding have had enormous special effects on the characteristics of crop
plants. Plant breeders use greenhouses and other techniques to get as many as
three generations of plants per year so that they can make improvements all
the more quickly.
Plant assortment and breeding in the 1920s and 1930s improved pasture (grasses and clover) in New Zealand. Extensive radiation mutagenesis efforts (i.e. primitive genetic engineering) during the 1950s produced the modern commercial varieties of grains such as wheat, corn and barley.
For instance, average yields of corn (maize) in the USA have increased from around 2.5 tons per hectare (40 bushels per acre) in 1900 to about 9.4 t/ha (150 bushels per acre) in 2001, primarily due to improvements in genetics. Similarly, worldwide average wheat yields have increased from less than 1 t/ha in 1900 to more than 2.5 t/ha in 1990. South American average wheat yields are around 2 t/ha, African under 1 t/ha, Egypt and Arabia up to 3.5 to 4 t/ha with irrigation. In contrast, the average wheat yield in countries such as France is over 8 t/ha. Higher yields are due to improvements in genetics, as well as use of intensive farming techniques (use of fertilizers, chemical pest control, growth control to avoid lodging). [Conversion note: 1 bushel of wheat = 60 pounds (lb) ˜ 27.215 kg. 1 bushel of corn = 56 pounds ˜ 25.401 kg]
In industrialized agriculture, crop "improvement" has often reduced nutritional and other qualities of food plants to serve the interests of producers. After mechanical tomato-harvesters were developed in the early 1960s, agricultural scientists bred tomatoes that were harder and less nutritious (Friedland and Barton 1975). In fact, a major longitudinal study of nutrient levels in numerous vegetables showed significant declines in the last 50 years; garden vegetables in the U.S. today contain on average 38 percent less vitamin B2 and 15 percent less vitamin C (Davis and Riordan 2004).
Very recently, genetic engineering has begun to be employed in some parts of the world to speed up the selection and breeding process. The most widely used modification is a herbicide resistance gene that allows plants to tolerate exposure to glyphosate, which is used to control weeds in the crop. A less frequently used but more controversial modification causes the plant to produce a toxin to reduce damage from insects (c.f. Starlink).
There are specialty producers who raise less common types of livestock or plants. Aquaculture, the farming of fish, shrimp, and algae, is closely associated with agriculture.Apiculture, the culture of bees, usually for honey—increasingly for crop pollination.c
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