Hemp, because of its height, dense foliage and its high planting density as a crop, is a very effective and long used method of killing tough weeds in farming by minimizing the pool of weed seeds of the soil.Using hemp this way can help farmers avoid the use of herbicides, to help gain organic certification and to gain the benefits of crop rotation per se. Due to its rapid, dense growth characteristics, in some jurisdictions hemp is considered a prohibited noxious weed, much like Scotch Bloom. It has been used extensively to kill weeds in agriculture.
Hemp is very environmentall friendly as it requires few pestisided and no herbicides. It has been called a carbon-negative raw material. Results indicate that high yield of hemp may require high total nutrient levels (field plus fertilizer nutrients) similar to a high yielding wheat crop.
Hemp is one of the earliest domesticated plants known.
“…it is certain that hemp contributes more than any other crop towards repairing the damage done by its own growth through the return of the leaves to the soil, besides other matters while it is undergoing the process of retting. Hemp is an admirable weed killer and in flax countries is sometimes employed as a crop in rotation, to precede flax because it puts the soil in so good condition.” –Charles Dodge, Director, Office of Fiber Investigation, 1890
“Hemp prevents the growth of weeds and other vegetation which would be found on such soils in most other crops or after others are laid by, and its cultivation also seems to make the soil more uniform in character.” –Lyster Dewey, The Hemp Industry in the United States, USDA Yearbook of Agriculture, 1901
“Very few of the common weeds troublesome on the farm can survive the dense shade of a good crop of hemp…In one 4-acre field in Vernon County, Wis., where Canada thistles were very thick, fully 95 per cent of the thistles were killed….” –Lyster Dewey, Hemp. USDA Yearbook of Agriculture, 1913.
“Hemp has been demonstrated to be the best smother crop for assisting in the eradication of quack grass and Canada thistles….At Waupon in 1911 the hemp was grown on land badly infested with quack grass, and in spite of an unfavorable season a yield of 2,100 pounds of fiber to the acre was obtained and the quack grass was practically destroyed.” –Andrew Wright, Wisconsin’s Hemp Industry, 1918.
“Hemp has been recommended as a weed control crop. Its dense, tall growth helps to kill out many common weeds. The noxious bindweed, a member of the morning glory family is checked to some extent by hemp.” –B. B. Robinson, Hemp, USDA Agric Bull #1453, 1943
“Among the species studied, the hemp species proved itself to be the best in fiber production. This plant was all the more interesting owing to its low fertilization requirements, and its ability to grow without being irrigated and without chemicals, whether it be for weed or pest control.” –Barriere, et al. 1994 (1)
“Hemp grows quickly, soon covers the ground and chokes out the weeds. So weed control is not necessary.” –Eddy A. A. de Maeyer. 1994 (1)