Optimisation of Nitrogen, Phosphorus, and Potassium for Soilless Production of Cannabis sativa in the Flowering Stage Using Response Surface Analysis.

Lewys Bevan,Youbin Zheng,Max Jones

doi:10.3389/fpls.2021.764103

Abstract

Following legalisation, cannabis has quickly become an important horticultural crop in Canada and increasingly so in other parts of the world. However, due to previous legal restrictions on cannabis research there are limited scientific data on the relationship between nitrogen (N), phosphorus (P), and potassium (K) supply (collectively: NPK) and the crop yield and quality. This study examined the response of a high delta-9-tetrahydrocannabinol (THC) Cannabis sativa cultivar grown in deep-water culture with different nutrient solution treatments varying in their concentrations (mg L–1) of N (70, 120, 180, 250, 290), P (20, 40, 60, 80, 100), and K (60, 120, 200, 280, 340) according to a central composite design. Results demonstrated that inflorescence yield responded quadratically to N and P, with the optimal concentrations predicted to be 194 and 59 mg L–1, respectively. Inflorescence yield did not respond to K in the tested range. These results can provide guidance to cultivators when formulating nutrient solutions for soilless cannabis production and demonstrates the utility of surface response design for efficient multi-nutrient optimisation.

Highlights

Drug-type cannabis (Cannabis sativa) is an important horticultural crop grown for medicinal and recreational purposes
This study examined the response of a high delta-9tetrahydrocannabinol (THC) Cannabis sativa cultivar grown in deep-water culture with different nutrient solution treatments varying in their concentrations of N (70, 120, 180, 250, 290), P (20, 40, 60, 80, 100), and K (60, 120, 200, 280, 340) according to a central composite design
Inflorescence yield decreased markedly outside of the range of 160–230 mg L−1 N, and 40–80 mg L−1 P. These findings suggest that drug-type cannabis responds well to nitrogen and phosphorus during the flowering stage

Summary

Introduction

Drug-type cannabis (Cannabis sativa) is an important horticultural crop grown for medicinal and recreational purposes. Many countries have prohibited the cultivation of drug-type cannabis which provided a significant barrier to research on this crop. Following the 2018 repeal of cannabis prohibition in Canada, production of cannabis has quickly become an important part of the Canadian horticulture industry worth billions of dollars annually (Zheng, 2021). Cannabis cultivators still lack scientific information about optimal growing conditions, such as supply of mineral nutrients, to help maximise crop yields, quality, and profits while minimising environmental impacts. Among the most important nutrients for plants are nitrogen (N), phosphorus (P), Cannabis Fertilisation Optimisation solution, but this N concentration is fairly low compared to conventional hydroponic nutrient solutions and may have been a limiting factor for plant growth and yield (Yep et al, 2020b). More research is needed to determine the optimal nutrient solution K concentration during cannabis flowering in soilless production systems when other nutrient elements are not limiting

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