Found this website from 1999:
Hemp helps detoxify and regenerate the soil
Falling leaves and shrubs not used in processing fall to the ground and replenish the soil with nutrients, nitrogen, and oxygen. This rich organic mulch promotes the development of fertile grassland. Some of the carbon which is “breathed” in by the plant in the form of CO2 is left in the roots and crop residues in the field. The CO2 is broken down by photosynthesis into carbon and oxygen, with oxygen being aspirated back into the atmosphere. With each season more CO2 is reduced from the air and added to the soil.
Hemp roots absorb and dissipate the energy of rain and runoff, which protects fertilizer, soil, and keeps seeds in place. Hemp plants slow down the velocity of runoff by absorbing moisture. By creating shade, hemp plants moderate extreme variations in temperatures, which conserves moisture in the soil. Hemp plants reduce the loss of topsoil in windy conditions. Hemp plants also loosen the earth for subsequent crops
Hemp plants can even pull nuclear toxins from the soil. In fact hemp was planted near and around the Chernobyl nuclear disaster site to pull radioactive elements from the ground. The process is called phyto-remediation, which means using plants (phyto) to clean up polluted sites. Phyto-remediation can be used to remove nuclear elements, and to clean up metals, pesticides, solvents, crude oil, and other toxins from landfills. Hemp breaks down pollutants and stabilizes metal contaminants by acting as a filter. Hemp is proving to be one of the best phyto-remediative plants found.
The minimum benefit of a hemp crop is in its use as a rotation crop. Since hemp stabilizes and enriches the soil farmers grow crops on, and provides them with weed-free fields, without cost of herbicides, it has value even if no part of the plant is being harvested and used. Any industry or monetary benefit beyond this value is a bonus. Rotating hemp with soy reduces cyst nematodes, a soy-decimating soil parasite, without any chemical input. Hemp could be grown as a rotation crop and not compete with any other food crops for the most productive farmland. Marginal lands make fine soil for hemp, or hemp can be grown in between growing seasons.
Hemp and the Environment
All hemp products are completely biodegradable, recyclable, and hemp is a reusable resource in every aspect: pulp, fiber, protein, cellulose, oil, or biomass.
Hemp can grow in any agronomic system, in any climate, and requires no herbicides, pesticides, fungicides, or insecticides to grow well. Hemp is its own fertilizer, its own herbicide (it is a weed), and its own pesticide. Hemp plants only need 10-13 inches of water, 1/3 of the amount which cotton requires, to grow to 8-12 feet in 3-4 months.
Using hemp as biomass fuel would also reduce global warming because the hemp energy crop would pull carbon from the air and realease an equal amount when burned, instead of just releasing carbon as petrolium gasoline does now.
Using hemp biomass to make charcoal, could eliminate the need to burn petrolium coal. Hemp biomass burns with virtually no sulfur emissions or ash, which minimize acid rain caused by the burning of coal.
Deforestation is a big problem. Keeping trees alive and standing is necessary to our oxygen supply, and our well being. Trees provide the infrastructure which keeps microbes, insects, plants, fungi, etc. alive. The older and bigger the tree, the better for the environment it is. The more trees there are, the more oxygen is in the air, which helps reduce global warming.
Hemp growing could completely eradicate the necessity to use wood at all because anything made from wood can be made from hemp, especially paper. The paper demand is suppose to double in next 25 years, and we simply cannot meet this demand without clear-cutting all of our forest. Using hemp for paper could reduce deforestation by half. An acre of hemp equals at least 4 acres of trees annually. Hemp paper can be recycled 7 to 8 times, compared with only 3 times for wood pulp paper. Hemp paper also does not need to be bleached with poisonous dioxins, which poison waterways.
Carpets made from nylon, polyester, and polypropylene contaminate ground water. Hemp carpet is biodegradable and safe for the ground water when it is discarded. In 1993, carpet made up 1% of solid waste, and 2% of waste by volume.
Our garbage facilities are overfilling with plastics. Hemp can make plastics which are biodegradable.
Petrochemicals lubricants, paints, sealants, etc., poison the ground when they are discarded. Hemp can replace all of these petroleum-based products with non-toxic biodegradable organic oil-based products.
“Why use the forests which were centuries in the making and the mines which required ages to lay down, if we can get the equivalent of forest and mineral products in the annual growth of the fields?”