Organic farming is the oldest form of agriculture. Chemical interventions in plant growth cycles are common to the last century. Chemical weed control products are called herbicides, and organic weed control methods are cultural. Cultural methods use cover crops, mulching, companion planting and farmscaping. Chemical weed control can prevent weed seed germination or kill growing plants. Health problems may arise from the use of chemical methods for weed suppression.
The most popular type of chemical weed suppression product uses glyphosate as its main ingredient. Glufosinate and diquat are two other common weed suppressant ingredients. These chemicals are non-selective contact herbicides that do not kill the underground portion of weeds. Systemic herbicides are absorbed into the plant vascular system. They are slower-acting and kill plants within several days. Some fertilizers are manufactured with weed-killing chemical additives.
Preventative weed control is the preferred method in sustainable gardening and large-scale agriculture. Cover cropping is recommended by the National Sustainable Agricultural Information Service. According to its report on organic fruit orchards, "Combined with a well-planned sequence of tillage, cover cropping is an effective pre-plant weed suppression strategy that also contributes to soil fertility and stable humus." Home gardeners suppress weed growth with a thick mulch cover.
Some chemical weed control products are applied before weed seeds germinate. They should be applied two to four weeks before the typical germination date in your area, according to Colorado State University Extension. Weed seeds fall from grasses in autumn and germinate from spring to mid-summer the following year. Apply the chemical weed control uniformly across the soil to prevent germination. Post-emergent weed control chemicals kill young weed plants but may not be effective on mature growth.
The Capitol District Community Gardens recommend prevention as the best medicine. "In the fight against weeds, the most important element is to provide the best conditions possible for the growth of desirable plants" and this includes organically amended soil and mulching. Black plastic and newspapers are good mulch materials. Corn gluten meal can prevent weed seed germination. Hand weed with tools specific to weed eradication.
Roundup is a well-known chemical weed killer. In studies at the University of Caen, France, Roundup was shown to cause human reproductive problems. Studies have also shown that farm workers exposed to Roundup have a higher incidence of wives who miscarry or have premature births, according to the National Institutes of Health. Glyphosate also kills earthworms in the soil.