In the 1970s, the taxonomic classification of Cannabis took on added significance in North America. Laws prohibiting Cannabis in the United States and Canada specifically named products of C. sativa as prohibited materials. Enterprising attorneys for the defense in a few drug busts argued that the seized Cannabis material may not have been C. sativa, and was therefore not prohibited by law. Attorneys on both sides recruited botanists to provide expert testimony. Among those testifying for the prosecution was Dr. Ernest Small, while Dr. Richard E. Schultes and others testified for the defense. The botanists engaged in heated debate (outside of court), and both camps impugned the other's integrity. The defense attorneys were not often successful in winning their case, because the intent of the law was clear.
For profitable hemp farming, particularly deep, humus-rich, nutrient-rich soil with controlled water flow is preferable. Waterlogged acidic, compressed or extremely light (sandy) soils primarily affect the early development of plants. Steep and high altitudes of more than 400 m above sea level are best avoided. Hemp is relatively insensitive to cold temperatures and can withstand frost down to −5 °C. Seeds can germinate down to 1–3 °C. Hemp needs a lot of heat, so earlier varieties come to maturation. The water requirement is 300–500 l/kg dry matter. This is around 1/14th that of cotton, which takes between 7,000 and 29,000 l/kg, according to WWF. Roots can grow up to 3 feet into the soil and use water from deeper soil layers.
Textile expert Elizabeth Wayland Barber summarizes the historical evidence that Cannabis sativa, "grew and was known in the Neolithic period all across the northern latitudes, from Europe (Germany, Switzerland, Austria, Romania, Ukraine) to East Asia (Tibet and China)," but, "textile use of Cannabis sativa does not surface for certain in the West until relatively late, namely the Iron Age." "I strongly suspect, however, that what catapulted hemp to sudden fame and fortune as a cultigen and caused it to spread rapidly westwards in the first millennium B.C. was the spread of the habit of pot-smoking from somewhere in south-central Asia, where the drug-bearing variety of the plant originally occurred. The linguistic evidence strongly supports this theory, both as to time and direction of spread and as to cause."
A chief argument that has been advanced in favor of developing hemp as a paper and pulp source has been that as a non-wood or tree-free fiber source, it can reduce harvesting of primary forests and the threat to associated biodiversity. It has been claimed that hemp produces three to four times as much useable fiber per hectare per annum as forests. However, Wong (1998) notes evidence that in the southern US hemp would produce only twice as much pulp as does a pine plantation (but see discussion below on suitability of hemp as a potential lumber substitute in areas lacking trees).
Because C. sativa has been a neglected crop for so long in North America, there are only negligible genetic resources available on this continent. Most germplasm stocks of hemp are in Europe, and the largest and most important collection is the Vavilov Institute gene bank in Leningrad. Figure 11 shows THC concentrations in the Vavilov collection, as well as in our own collection, largely of European germplasm. A disturbingly high percentage of the collections have THC levels higher than 0.3%, making it difficult to incorporate these into breeding programs.
Medical marijuana in the U.S. is controlled at the state level. Per federal law, cannabis is illegal as noted in the Controlled Substances Act, but the federal government has stated they will not actively prosecute patients and caregivers complying with state medical marijuana laws. However, use of medical marijuana outside of the state laws for illegal use or trafficking will not be tolerated by state or federal government.
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