The objective of this project was to demonstrate visual symptoms of common nutritional disorders of hydroponically grown hemp (Cannabis sativa L.) Four macronutrients (nitrogen, phosphorus, potassium, and magnesium) were selected. To generate the images used in this article, nutritionally deficient fertilizer was implemented in a deep water culture (DWC) hydroponic system in 1-gallon containers.
Hemp cultivar ‘TJ’s CBD’ was propagated vegetatively and rooted for 2 weeks before placement in the DWC system. There were two replicate plants per treatment. Table 1 lists the control fertilizer recipe; deficient nutrition solutions had 0 ppm for their respective N, P, K, or Mg deficiency. The plants were monitored, the DWC water was replaced, and data was collected weekly for 6 weeks. This article presents clear visual symptoms (leaf and whole plant) of nutrient disorders.
Once a plant is beginning to show visual symptoms of nutritional problems, there is likely already a negative change in overall plant health and productivity. If found early enough, growers can implement a change in fertilizer regimen. Identifying and tracking visual symptoms is very important for growers because various nutritional symptoms may look very similar, such as changes in appearance, location, etc. Correct diagnosis of a crop’s nutritional problems may pose a great challenge. Therefore, it is important to use laboratory tissue testing to definitively diagnose a disorder. Proactively monitoring crop fertility, including weekly substrate testing for pH and EC and periodic laboratory tissue analysis (Table 2), can help identify nutrient disorders before they present obvious visual symptoms.
This report focused on visual symptoms of N, P, K, and Mg deficiency. An excellent resource for a more comprehensive assessment of macronutrient and micronutrient disorders in hemp is presented by Cockson et al. (2019).
Read more at e-gro.org