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This article in AJ

  1. Vol. 69 No. 5, p. 832-836
    Received: Aug 6, 1976

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Responses of Greenhouse-grown Cannabis sativa L. to Nitrogen, Phosphorus, and Potassium1

  1. C. B. Coffman and
  2. W. A. Gentner2



Growers of illegal Cannabis sativa L. use various cultural practices to maximize crop production. The objective of this study was to evaluate the morphological and biochemical responses of greenhouse grown C. sativa to soil incorporated N, P, and K as they reflect the geographical origin of Cannabis derivatives. Fertilizers were blended with Ap horizon soil from a Gilpin silt loam before placement in 12-cm pots. NH4NO3-N was applied at 0, 25, and 125 ppm. Phosphorus and K from super-phosphate and KCI, respectively, were applied at 0, 50, and 150 ppm. Forty-five-day-old anthesic Cannabis plants were harvested and combined leaf and flower tissues were analyzed for cannabidiol (CBD) and Δg-tetrahydrocanna-binol (Δ9THC). Nine essential elements were also measured in plant tissue. Plant growth, tissue yield, and concentration of CBD and Δ9THC were positively correlated with extractable P2O5 (p < 0.01). Phosphorus concentrations in tissue were similarly related to yield of dry matter and cannabinoid concentrations. Uptake of K was positively correlated with extractable K.2O across all treatment levels (r=0.40**), but was negatively correlated with tissue yield (r=--0.36"*). Growth and tissue yields were negatively related to total plant N (p< 0.01). Levels of extractable P2O5, Mn, B, and Mg were associated with specific concentration ranges for several plant elements plus Δ9THC. Thus, it was possible to partially characterize a soil by tissue analysis. For example, all of the plants grown on soil with less than 100 ppm of extractable P2O5 contained less than 8,000 ppm Δ9THC. Usefulness of such relationships will be dependent upon extensive evaluation of Cannabis on different soils under various cultural conditions. At this time, the reliability required for determination of origin of Canabis derivatives via chemical analysis does not exist when only essential elements and cannabinoids are considered.

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