soil+chemistry

Soil chemistry deals with the nutrient and mineral composition of the earth, and with the micro- and macro-organisms that dwell in soil.

Soil health has a big impact on what can grow or live in the soil. Some of the healthiest soils exist where volcanic ash fell, or where forest fires or brush fires once burned. The American Indians were known for burning vast tracts of midwestern plains in the spring, so that the grasses that would grow there would be greener and healthier (primarily to attract or support large herds of buffalo). Other naturally healthy soil regions include river deltas and flood plains.

Farmland would appear to be healthy soil. However, after decades of farming, these soils are nutrient-deficient and thus need human intervention to produce crops. These interventions include:
 * use of animal waste or plant compost as fertilizers
 * use of chemical fertilizers including phosphates and nitrates
 * use of herbicides and pesticides to eliminate pest plants or insects
 * crop rotation to prevent nutrient degradation
 * introduction of genetically modified crops that are resistant to disease, drought, insects, etc.

Of all these interventions, only one is truly ecologically safe. Can you identify it?

The use of animal waste or animal parts can pose a problem with the foods grown in them. One such problem is [|mad cow disease]. The use of diseased animal parts as a supplement and fertilizer is believed to have caused and helped spread mad cow disease, and any infected cow cannot be safe to consume. Another problem is [|salmonella] bacteria, which can come from animal waste products and from unclean foods.

Chemical fertilizers are utilized to help plants grow in nutrient-deficient soils. Any [|unused fertilizers]will then leach into the water table or run off into streams, rivers, lakes and oceans. Here, they can cause nitrate-enrichment and thus overgrowth of algae and eutrofication of fish. Phosphate fertilizers can contain elevated levels of cadmium, uranium, and polonium, all which are toxic (the last two are radioactive), which will make their way into the plants and their crop.

One of the most widely used [|pesticides] from its invention in 1939, to its partial ban in the US in 1972, to its complete ban in 2004, was DDT ([|dichlorodiphenyltrichloroethane]). It was used to combat malaria after World War II, and then as an agricultural insecticide. At its peak, the US was producing 82,000 tons per year, and used 600,000 tons throughout the years it was used. In 1962, a book titled "Silent Spring" was published by Rachel Carson, describing the environmental impacts of DDT - specifically, how it was threatening bird populations and was carcinogenic. Thus began an environmental movement to study and remove dangerous chemicals that were being used without any background research into their safety. Today, millions of farm workers get ill from pesticide exposure and as many as 18,000 die each year globally from pesticide exposure. Long-term, low-dose exposure to pesticides in consumers (we the people) is a big concern and has not been thoroughly researched. It has been found that pesticide exposure in children can lead to brain cancer, leukemia, and birth defects. Herbicides, used for weed control, have [|similar environmental and health issues], and have also not been thoroughly studied.

[|Genetically modified crops] have become a topic of debate over the past few years. Around 40% of corn grown in the United States is genetically modified. These crops are modified by inserting genes from other plants or animals into the genome of the crop, thus giving it a better resistance to disease or pests. There are a number of problems with genetically modified foods:
 * There have been few if any studies on these mutant breeds, and how they could affect the consumer; side effects could include more severe allergic reactions, damage to kidneys or liver, or even cancer from unknown mutagens in the foods.
 * These crops are difficult to keep isolated from natural breeds. The term used for cross-pollination of mutant crops with non-modified crops is "drifting"