chemistry

In 1960 the US used 7,464 tons of fertilizer, 37% of it nitrogen, 34% phosphate, and 29% potash. By 1970 the total had more than doubled to 16,068 tons, and the nitrogen component had risen to 46%. By 1980, the total stood at 23,083 with 49% nitrogen, 24% phosphate and 27% potash. Since the 1980's use has been more or less steady at slightly over 21,000 tons, but the nitrogen component has gone up to as high as 57%, with the rest equally divided between phosphate and potash.

Fertilizer uses are heavily concentrated in states draining into the Mississippi watershed. Other high use areas include the Eastern seaboard, Florida, California's central valley and Eastern Washington state.

In 1995, about 4.5 billion pounds of chemicals were used as pesticides in the US every year. Half of that is chlorine and chlorine products used to treat water. A quarter are conventional pesticides, petroleum and sulfur. The majority of these are used in agriculture to produce food and fiber. That amounts to nearly 1 billion pounds. Another one billion pounds is in herbicides.

Pesticide uses have leveled off too, especially in agriculture. But in-home uses are skyrocketing and in-home uses are quickly making up for any losses. Surveys estimate that home owners use as much fertilizer and pesticide per acre for lawn care as agriculture does to grow food. 

Excess fertilizer and pesticide run off into rivers and streams and end up in the oceans. There the fertilizer can powerfully boost algae and micro-organism growth. These critters can grow so quickly that they choke off oxygen supplies and kill fish and shellfish. Algae blooms also produce toxins that find their way to people.

Pesticides accumulate in filter feeders that are eaten by fish and so these end up in the food supply as well.

Think about that when you look at your green lawn.