Predicting vegetative phase nutrient uptake in Cannabis sativa L. via transpiration-driven mass-balance

TL;DR

This study uses transpiration data to predict nutrient uptake in cannabis plants, helping optimize fertilization and reduce waste.

Contribution

A transpiration-driven mass-balance framework for cultivar-specific nutrient uptake prediction in Cannabis sativa L.

Findings

Cultivar-specific nutrient uptake patterns were identified for nitrogen, phosphorus, and potassium.

Water use efficiency was similar between the two cultivars, but nutrient uptake varied over time.

Calcium and magnesium uptake increased steadily, while nitrogen and potassium uptake declined after week 1.

Abstract

The rapid expansion of Cannabis sativa L. cultivation necessitates fertilization strategies that optimize nutrient delivery and resource use. A transpiration-driven mass balance framework quantified nutrient removal from solution relative to whole-plant water use in two Cannabis sativa L. cultivars, CJ2 and First Light. Uptake measured via the pour-through method was compared against total and organ-specific tissue concentrations, verifying cultivar-specific mass balance nutrient uptake estimates. The objective was to formulate a nutrient replenishment strategy proportional to water uptake, enabling continuous, cultivar-specific fertilization optimization. Results revealed cultivar-specific uptake patterns: nitrogen ranged from 97–155 mg L-1 (First Light) and 78–145 mg L-1 (CJ2); phosphorus from 14–48 mg L-1 and 13–49 mg L-1; and potassium from 112–216 mg L-1 and 111–205 mg L-1, respectively. Water use efficiency (WUE) was similar across cultivars (CJ2: 4.71 g L-1 H2O; First Light: 4.59 g L-1 H2O). Temporal analysis normalized to transpired water showed peak nitrogen and potassium uptake during week 1, with significant declines by week 2 (p < 0.001), while calcium and magnesium uptake increased steadily (p < 0.0001). These findings support a scalable nutrient forecasting method based on nutrient uptake from solution that is proportional to whole-plant water use. Integrating transpiration data with tissue nutrient profiles enables cultivar-specific fertigation strategies that minimize waste and enhance sustainability in cannabis production.

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