# Characterization of Nutrient Disorders of _Camabis sativa_
## 4 Discussion  
While some anecdotal deficiency symptoms for cannabis are available in lay publications, scientifically rigorous symptomatology, particularly symptomological progression, is very limited or non-existent in the literature. In this study, most documented symptoms of deficiencies were consistent with descriptions from current literature for other plant species ([PERSON] et al., [9]; [PERSON], [16]; [PERSON], [17]; [PERSON] et al., [18]) with some exceptions. Concentrations of N, P, K, Ca, Mg, and S in the leaves when deficiency symptomatology first appeared were 1.62, 0.09, 0.41, 0.39, 0.12, and 0.11%, respectively. Concentrations of B, Cu, Fe, Mn, Mo, and Zn in the leaves when deficiency symptomatology first appeared were 2.46, 1.41, 60.1, 7.56, 0.06, and 10.7 mg\(\cdot\)kg\({}^{-1}\), respectively. Plants grown without Mo did not exhibit leaf symptomatology nor less dry matter production despite leaf tissue values being 96% lower than the complete controls. While visual symptoms of Cu deficiency displayed the interveinal chlorosis in younger leaves documented in other plants, the Cu-deficient cannabis also showed an odd wilting pattern (Figure 4). This wilting in Cu-deficient hemp plants is mentioned in fiber hemp ([PERSON], [19]). Copper is important in cell wall metabolism ([PERSON], [20]). The condition which [PERSON] [19] referred to as \"\"gummi'-hemp\" may indicate that Cu is needed in greater quantities in hemp than in other species, especially when grown for fiber. While these symptoms of wilting and lodging were in fiber hemp, which has a very vigorous vertical growth habit, the same process could be occurring in floral hemp cultivars. Additionally, B-deficient treated plants displayed similar wilting tendencies. Upon further inspection of the roots, it was shown that the terminal growing tip had died and turned necrotic, and there were many axillary roots due to the loss of apical dominance. Boron is important in cell wall development and elongation of plant cell walls, especially in the radicle and other root meristematic regions ([PERSON] and [PERSON], [21]; [PERSON], [22]). The wilting seen could have been due to a lack of root mass due to an underdeveloped root system. Given all plants were irrigated for the same amount of time, it is feasible to assume that the wilting was due to a lack of water uptake because root growth was impaired. Nutrients varied in how rapidly deficiency symptoms were visually apparent. In treatments where N, P, Ca, Mg, S, Mn, and B were withheld, deficiency symptoms were observed within 6 to 7 weeks. Conversely, where K, Zn, Cu, Fe were withheld, visual deficiencies only occurred after 9 weeks and, as previously noted, not at all in Mo. The use of visual symptomatology as a diagnostic tool may be more useful for the nutrients that demonstrate symptoms sooner rather than later. However, for field and greenhouse floral hemp production, visual symptoms may express early enough in the season where rescue nutrient applications can be made. Additionally, routine MRML tissue sampling during the season will identify if nutrients are getting near the concentrations that show symptoms, thus allowing a correcting nutrient application before symptoms are expressed. Some nutrient deficiencies had a significant suppressive effect on yield, as measured by whole plant dry weight, while withholding other nutrients did not affect total biomass. Deficiencies of N, K, B, and Cu produced significantly less crop biomass by 50, 27, 28, and 45%, respectively, as compared to the control. While all other nutrient deficiencies had less biomass, none suppressed yield at a significance level of \(P>0.05\). Above-ground biomass may not be the appropriate metric for testing critical levels in these nutrients, and other factors, such as secondary metabolite production, maybe a better indicator of the minimum nutrient concentrations for optimum production.