Nutrient Deficiency in Cannabis Plants
Nutrient Deficiency in Cannabis Plants
The following is a republication of a peer-reviewed study from Applied Sciences (2019) providing scientifically rigorous descriptions and diagnostic images of nutrient disorders in Cannabis sativa. Use this guide to identify deficiency symptoms early and implement corrective nutrient applications before yield is impacted.
Custom Hydro stocks corrective fertilizers for all essential nutrients covered in this study, including Calcium Nitrate, Magnesium Nitrate, Iron Chelate, Manganese Chelate, Copper Chelate, Boron, Molybdenum, and Chelated Micronutrient Mixes. Contact us if you need help selecting the right corrective product for your program.
Originally published in Appl. Sci. 2019, 9(20), 4432. https://doi.org/10.3390/app9204432
Characterization of Nutrient Disorders of Cannabis sativa
by Paul Cockson 1, Hunter Landis 1,2, Turner Smith 1, Kristin Hicks 2, and Brian E. Whipker 1
1 — Department of Horticultural Science, North Carolina State University, Raleigh, NC 27695, USA
2 — North Carolina Department of Agriculture and Consumer Services, Raleigh, NC 27601, USA
Received: 23 September 2019 / Accepted: 9 October 2019 / Published: 18 October 2019
Abstract
Essential plant nutrients are needed at crop-specific concentrations to obtain optimum growth or yield. Plant tissue (foliar) analysis is the standard method for measuring those levels in crops. Symptoms of nutrient deficiency occur when tissue concentrations fall to a level where growth or yield is negatively impacted and can serve as a visual diagnostic tool for growers and researchers. Both nutrient deficiency symptoms and their corresponding plant tissue concentrations have not been established for cannabis. To establish nutrient concentrations when deficiency or toxicity symptoms are expressed, Cannabis sativa 'T1' plants were grown in silica sand culture. Control plants received a complete modified Hoagland's all-nitrate solution, whereas nutrient-deficient treatments were induced by withholding a single nutrient. Toxicity treatments were induced by increasing the element tenfold. Plants were monitored daily and, once symptoms manifested, plant tissue analysis was performed by most recent mature leaf (MRML) tissue analysis. Symptoms and progressions were tracked through initial, intermediate, and advanced stages. Information in this study can be used to diagnose nutrient disorders in Cannabis sativa.
Keywords: macronutrients; micronutrients; cannabis; deficiency; toxicity; fertility; symptomology; hemp; diagnostics; plant tissue analysis; CBD; THC; foliar
1. Introduction
Due to recent changes in legislation at the federal and state levels, there has been a surge of interest in growing, processing, selling, and using products containing cannabidiol (CBD), derived from hemp flowers. Hemp is legally defined as Cannabis sativa strains with a THC concentration no greater than 0.3% in any part of the plant. Cannabis sativa strains with THC greater than 0.3% are considered marijuana. Cannabis contains over 100 cannabinoids, including THC and CBD.
There is little published research investigating fertility requirements for floral hemp. This study provides an invaluable basis to identify nutrient deficiency in the field and to develop sufficiency ranges where corrective action can be made before visual symptoms are expressed.
2. Materials and Methods
Cuttings were taken from a hemp Cannabis sativa 'T1' on 3 July 2018 and stuck into 72-cell plug trays filled with an 80:20 (v:v) Canadian sphagnum peat moss and horticultural coarse perlite substrate amended with dolomitic lime and wetting agent. After three weeks of rooting, plugs were transplanted into 15.24-cm diameter plastic pots filled with acid-washed silica sand.
The experiment was conducted in a glass greenhouse in Raleigh, NC (35°N latitude), with 24°C/20°C (D/N) temperature setpoints. Control plants were grown with a complete modified Hoagland's all-nitrate solution:
Hoagland's control solution (ppm): 210 ppm NO₃-N, 31 ppm P, 235 ppm K, 200 ppm Ca, 49 ppm Mg, 64 ppm S, 4 ppm Fe, 0.989 ppm Mn, 0.019 ppm Cu, 0.019 ppm Zn, 0.486 ppm B, 0.01 ppm Mo
(Data added by Custom Hydro, 1-11-2020)
Nutrient deficiencies were induced by withholding a single nutrient from this solution. Boron and manganese toxicities were induced by increasing the concentration tenfold. The experiment was terminated 9 weeks after treatments began.
Figure 1. Sketch of a branch of Cannabis sativa 'T1' showing plant anatomy and terminology.
Table 1. Mean dry weights of Cannabis sativa 'T1' plants grown with a deficient macronutrient treatment compared to plants grown with a complete fertilizer.
3. Results
3.1. Macronutrient Disorders
3.1.1. Nitrogen
Symptoms of nitrogen (N) deficiency developed 6 weeks after treatment. Plants first displayed slight stunting and a slight overall yellowing of the lower foliage. As the deficiency progressed, yellowing became more intense and moved upward from the bottom leaves. In advanced symptoms, yellowing leaves became completely yellow and eventually turned necrotic and abscised.
Foliar N concentrations were 62% lower in N-deficient plants (1.62% N) than in controls (4.28% N). N-deficient plants produced 50% less biomass than the control.
Figure 2. Nutritional disorders of nitrogen (N), phosphorus (P), and calcium (Ca) deficiency in Cannabis sativa 'T1'. Progression from initial, intermediate, through advanced.
3.1.2. Phosphorus
Symptoms of phosphorus (P) deficiency developed 7 weeks after treatment. Plants initially developed olive-green spots in an irregular pattern on lower and older leaves. As symptoms progressed, spots became larger, sunken, and almost wet in appearance with some marginal necrosis. In advanced symptoms, large necrotic portions developed.
Foliar P concentrations were 79% lower in P-deficient plants (0.09% P) than in controls (0.43% P). No statistically significant difference in biomass was observed.
3.1.3. Calcium
Symptoms of Ca deficiency developed 5 weeks after treatment. Growing tips and newly expanding leaves showed stunting and irregular growth. The basal portion of leaflets remained narrower with lighter green coloration. As symptoms progressed, interveinal chlorosis developed and new leaves showed severe stunting and marginal necrosis. In advanced symptoms, the death of the growing tip caused proliferation of axillary shoot development.
Foliar Ca concentrations were 90% lower in Ca-deficient plants (0.39% Ca) than in controls (3.73% Ca). No statistically significant difference in biomass was observed at the onset of symptoms.
3.1.4. Sulfur
Symptoms of sulfur (S) deficiency developed 7 weeks after treatment. Plants first displayed a slight overall yellowing, especially in the middle of the plant, with more pronounced yellowing at the base of the leaflets. In advanced symptoms, leaves became a very pale yellow, especially around the midrib and base of the leaflets.
Figure 3. Nutritional disorders of sulfur (S), magnesium (Mg), and potassium (K) deficiency in Cannabis sativa 'T1'. Progression from initial, intermediate, and advanced.
Foliar S concentrations were 73% lower in S-deficient plants (0.11% S) than in controls (0.41% S). No statistically significant difference in biomass was observed.
3.1.5. Magnesium
Symptoms of Mg deficiency developed 7 weeks after treatment. Initial symptoms were slight yellowing of the interveinal regions of lower and older foliage. As symptoms progressed, interveinal yellowing became more pronounced. In advanced symptoms, leaves showed a stark contrast between green veins and yellow interveinal regions, with some regions becoming necrotic.
Foliar Mg concentrations were 80% lower in Mg-deficient plants (0.12% Mg) than in controls (0.61% Mg). No statistically significant difference in biomass was observed.
3.1.6. Potassium
Symptoms of K deficiency developed 9 weeks after treatment. Initial symptoms were yellowing of the leaf margin, especially the saw-tooth of the leaflets, on lower and older foliage. As symptoms progressed, marginal yellowing became more pronounced and expanded inward toward the midrib. In advanced symptoms, tan necrosis developed along the saw-tooth margin.
Foliar K concentrations were 86% lower in K-deficient plants (0.41% K) than in controls (2.85% K). K-deficient plants weighed 27% less than the control.
3.2. Micronutrient Disorders
3.2.1. Manganese
Symptoms of Mn deficiency developed 6 weeks after treatment. Plants initially developed a bright yellow netted interveinal chlorosis on upper and central foliage, initiating at the midrib and spreading outward. In advanced symptoms, the interveinal netting became very distinct against green veinal regions, with small tan necrotic regions developing on the leaf surface.
Figure 4. Nutritional disorders of manganese (Mn), boron (B), and copper (Cu) deficiency in Cannabis sativa 'T1'. Progression from initial, intermediate, and advanced.
Foliar Mn concentrations were 74% lower in Mn-deficient plants (7.56 mg·kg⁻¹) than in controls (29.40 mg·kg⁻¹). No statistically significant difference in dry weights was observed.
3.2.2. Manganese Toxicity
Symptoms of Mn toxicity developed 7 weeks after treatment. Plants initially developed marginal yellowing of the lower leaves, which intensified and moved inward. In advanced symptoms, the leaf margin became necrotic and the leaf appeared severely chlorotic, with some symptomatic leaves abscising.
Figure 5. Nutritional disorders of manganese toxicity (Mn) and boron toxicity (B) in Cannabis sativa 'T1'. Progression from initial, intermediate, and advanced.
Foliar Mn concentrations were 53% higher in toxicity plants (47.88 mg·kg⁻¹) than in controls (31.13 mg·kg⁻¹). No statistically significant difference in dry weights was observed.
3.2.3. Boron
Symptoms of B deficiency developed 6 weeks after treatment. Growing tips and newer foliage displayed distorted growth patterns. New and expanding leaflets were smaller and narrower at the base. In advanced symptoms, leaflet margins became necrotic and leaves distorted severely, curling inward and down. In the most advanced stages, growing tips died and the whole plant showed severe wilting due to death of root tips.
Foliar B concentrations were 96% lower in B-deficient plants (2.46 mg·kg⁻¹) than in controls (58.58 mg·kg⁻¹). B-deficient plants produced 28% less biomass than the control.
3.2.4. Boron Toxicity
Symptoms of B toxicity appeared 7 weeks after treatment. Plants initially developed marginal yellowing of the lower leaves, which intensified along the leaf margin and moved inward. In advanced symptoms, the leaf margin turned brown and eventually became necrotic.
Foliar B concentrations were >10-fold higher in toxicity plants (671.75 mg·kg⁻¹) than in controls (64.60 mg·kg⁻¹). No statistically significant difference in dry weights was observed.
3.2.5. Copper
Copper deficiency manifested after 9 weeks. Plants initially displayed slight stunting and distortion of newer and expanding leaves, especially at the leaflet base. In advanced symptoms, leaves displayed fine interveinal chlorosis and the leaf margin distorted, curling in and downward.
Foliar Cu concentrations were 70% lower in Cu-deficient plants (1.41 mg·kg⁻¹) than in controls (4.65 mg·kg⁻¹). Cu-deficient plants produced 45% less biomass than the control.
3.2.6. Iron
Symptoms of upper leaf interveinal chlorosis developed on Fe-deficient plants after 9 weeks. Leaves were lighter in appearance, with symptoms spreading throughout the upper half of the foliage, especially around the growing tip and newly expanding leaves.
Figure 6. Nutritional disorders of iron (Fe) and zinc (Zn) deficiencies in Cannabis sativa 'T1'. Progression from initial, intermediate, and advanced.
Foliar Fe concentrations were 46% lower in Fe-deficient plants (60.08 mg·kg⁻¹) than in controls (111.75 mg·kg⁻¹). No statistically significant difference in biomass was observed.
3.2.7. Molybdenum
Visual symptoms did not develop on Mo-deficient plants after 9 weeks. Despite a lack of visual symptoms, foliar Mo concentrations were 96% lower in Mo-deficient plants (0.06 mg·kg⁻¹) than in controls (1.46 mg·kg⁻¹). No statistical difference in dry weights was observed.
3.2.8. Zinc
Zinc deficiency manifested after 9 weeks. Deficiency symptoms first appeared as marginal yellowing on newer foliage and expanding leaves, concentrated along the toothed portions of the leaflets. As symptoms progressed, yellow marginal regions developed into tan, irregularly shaped necrotic regions along the leaf margin.
Foliar Zn concentrations were 58% lower in Zn-deficient plants (10.70 mg·kg⁻¹) than in controls (25.33 mg·kg⁻¹). No statistically significant difference in biomass was observed.
4. Discussion
Most documented symptoms of deficiencies were consistent with descriptions from current literature for other plant species, with some exceptions. Concentrations in the leaves when deficiency symptomology first appeared were: N 1.62%, P 0.09%, K 0.41%, Ca 0.39%, Mg 0.12%, S 0.11%; and B 2.46, Cu 1.41, Fe 60.1, Mn 7.56, Mo 0.06, Zn 10.7 mg·kg⁻¹.
Nutrients varied in how rapidly deficiency symptoms became visually apparent. N, P, Ca, Mg, S, Mn, and B showed symptoms within 6–7 weeks. K, Zn, Cu, and Fe only showed visual deficiencies after 9 weeks, and Mo showed no visual symptoms at all. Deficiencies of N, K, B, and Cu produced significantly less crop biomass by 50, 27, 28, and 45%, respectively, compared to the control.
5. Conclusions
This work serves as a baseline for nutritive values in the Cannabis sativa 'T1' cultivar. The nutrient disorders described provide hemp growers and researchers with detailed descriptions and high-quality diagnostic images to better identify nutrient disorders. With the exception of N, K, B, and Cu, most disorders had no significant effect on overall plant dry weight at the onset of symptoms. These data illustrate the importance of recognizing nutritional disorders at an early stage to implement corrective procedures in order to optimize yield and produce a successful crop.
Author Contributions
Conceptualization: B.E.W. and P.C.; Methodology: B.E.W., P.C., H.L., and T.S.; Formal analysis: P.C., H.L., and K.H.; Writing—original draft: P.C., B.E.W., and K.H.; Writing—review and editing: K.H., H.L., T.S. and B.E.W.; Supervision: B.E.W.
Funding
This research received no external funding.
Acknowledgments
We would like to thank the North Carolina Department of Agriculture and Consumer Services and Ryes Greenhouses for assistance with this research.
Conflicts of Interest
The authors declare no conflict of interest.
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