Industrial hemp (Cannabis sativa L.) has a long history of human use. Early in the 20th century, some predicted hemp would be the first billion dollar crop given its multiple industrial applications. Government policy that restricted, then prohibited, hemp's use in the U.S. prevented that from happening. A reawakening to the versatility and usefulness of hemp for products ranging from engineering fibers and textiles to food and health products has developed over the last 30 years. Hemp-based products are thriving on the market for public demand. In Virginia, passage of legislation in 2017 made hemp a legal cash crop. Appropriate management decisions rely on information available from researchers. However, very few data on hemp production are available for this region. Hemp varieties may differ in part due to the broad range of latitude associated with their source of origin (e.g., from Italy to Finland in Europe) and thus the plant's differential responses to light and temperature regimes. Thus, a factor such as varietal response to soil temperature at germination could be an important variable for successful establishment, which is critical to crop productivity. Stand establishment, in turn, may be affected by factors such as germination temperature, which has implications for planting date. Along with establishment, few data have been published regarding hemp's tolerance to different herbicides. To date, the only published studies from the Southern region of the United States regarding hemp production in response to herbicide treatments were conducted in Kentucky. Generating basic information on hemp response to temperature for germination and tolerance to herbicides will be important step for developing a suite of useful agronomic practices that support the incorporation of hemp into Virginia cropping systems. The hemp industry's development in Virginia is still in its early stages, and the research described here focused on questions related to germination temperature and herbicide tolerance will help to improve our understanding of and determine suitable agronomic practices for the crop We thus designed experiments to test the following null hypotheses: Industrial hemp will not differ in germination response to temperatures, regardless of source of origin. Industrial hemp will not differ in measures of visible injury, yield, and growth in response to preemergent or postemergent herbicide treatments. / Master of Science / Industrial hemp (Cannabis sativa L.) has a long history of human use. Early in the 20th century, some predicted hemp would be the first billion dollar crop given its multiple industrial applications. Government policy that restricted, then prohibited, hemp’s use in the U.S. prevented that from happening. A reawakening to the versatility and usefulness of hemp for products ranging from engineering fibers and textiles to food and health products has developed over the last 30 years. Hemp-based products are thriving on the market for public demand. In Virginia, passage of legislation in 2017 made hemp a legal cash crop. Appropriate management decisions rely on information available from researchers. However, very few data on hemp production are available for this region. Hemp varieties may differ in part due to the broad range of latitude associated with their source of origin (e.g., from Italy to Finland in Europe) and thus the plant’s differential responses to light and temperature regimes. Thus, a factor such as varietal response to soil temperature at germination could be an important variable for successful establishment, which is critical to crop productivity. Stand establishment, in turn, may be affected by factors such as germination temperature, which has implications for planting date. Along with establishment, few data have been published regarding hemp’s tolerance to different herbicides. To date, the only published studies from the Southern region of the United States regarding hemp production in response to herbicide treatments were conducted in Kentucky. Generating basic information on hemp response to temperature for germination and tolerance to herbicides will be important step for developing a suite of useful agronomic practices that support the incorporation of hemp into Virginia cropping systems. The hemp industry’s development in Virginia is still in its early stages, and the research described here – focused on questions related to germination temperature and herbicide tolerance – will help to improve our understanding of and determine suitable agronomic practices for the crop We thus designed experiments to test the following null hypotheses: Industrial hemp will not differ in germination response to temperatures, regardless of source of origin. Industrial hemp will not differ in measures of visible injury, yield, and growth in response to preemergent or postemergent herbicide treatments.

The exploitation of metallic sulfide ores produces vast quantities of fine-grained wastes hosting potentially toxic elements (PTEs). There are concerns that, if improperly disposed of and managed, waste mineral particles can behave as vectors that disperse PTEs via aeolian and fluvial transport, subsequently contaminating soils and crops used to support human populations. The importance of these particles, as sources and influencers of PTE biogeochemistry in productive soils, has received limited research. Long-term (365 d) batch incubation experiments, field weathering experiments and phytoavailability trials, were performed to establish the rate, patterns and factors limiting PTE (Cd, As, Hg) release from grains of sphalerite (Zn(Fe,Cd)S), arsenopyrite (FeAsS) and cinnabar (HgS) into soil matrices (0.1 % mineral:soil m/m), and the bioavailability of the liberated PTEs to important food crops (Tricitum aestivum, wheat and Oryza sativa, rice). All three of the ores underwent chemical weathering in oxic agricultural soils of both temperate and sub-tropical provenance, during which nonessential PTEs (cadmium, mercury, arsenic) were released in bioavailable forms, at rates relevant to agricultural production. Sphalerite weathered at a rate of 0.6 to 1.2 % a-1 (Cd basis) in the experimental soils, releasing 0.5 to 1 μmol Cd g-1 ZnS a-1 into the soil matrix. Cinnabar weathering reached a maximum of 12.0 – 13.5 % (Hg basis) after 90 days exposure in oxic soils, whereas arsenopyrite weathering was rapid and extensive, reaching 56 to 66 % (S basis) after 180 days. The PTE concentrations accumulated in edible grains of wheat and rice grown in the sulfide-contaminated soils were higher than international food safety limits by factors of 8 (Cd in rice), 10 – 30 (Hg in wheat and rice) and 8 – 12 (As in wheat and rice). The primary geochemical factors controlling PTE release and bioavailability were solid-phase associations (i.e. PTEs complexed by clays, metal oxyhydroxides and organic matter) and the precipitation of secondary mineral phases. Weathering arsenopyrite grains were passivated from further oxidation by secondary iron-arsenate phases, which also co-precipitated arsenic liberated from the ore. Secondary phase formation was identified as the cause of decreasing extractable Hg (liberated from cinnabar) after mercury release from cinnabar peaked (≤ 90 days exposure). For sphalerite, the evidence indicates that secondary sulfide phases formed under flooded (sulfate-reducing) soil conditions (paddy rice), limited the bioavailability of cadmium previously liberated under oxic conditions. These key findings demonstrate a potential human health hazard relating to the dispersal of PTE-hosting sulfide ore particles produced by mining activities into soils supporting human populations via crop contamination. This work also highlights differences in ore geochemistry, showing the need for additional research on different ore minerals and their alteration products.