N, P, and S fertilization effects on industrial hemp in Saskatchewan

Industrial hemp (Cannabis sativa L.) has become a well-known crop in western Canada in recent years, but insufficient information is available on its nutrient requirements for optimum yield. Our objective was to confirm the response of two hemp cultivars to increasing levels of nitrogen (N), phosphorus (P) and sulphur (S) in various sites in the province of Saskatchewan, during 2006-2008. Increasing N rates significantly increased plant height, biomass, and seed yield, when data were averaged across all sites (location-years), reaching maximum values at about 150 kg N ha -1 of applied N fertilizer. The cultivar Crag was taller and produced greater biomass than the cultivar Finola over all levels of N fertilizer rate. The minimum rate of N fertilizer to achieve maximum height/biomass for Crag, relative to Finola, was 5 kg N ha -1 lower for height (Finola: 163 kg N ha -1 ) but 9 kg N ha -1 higher for biomass (Finola: 180 kg N ha -1 ). Finola seed yield was more responsive to progressively greater rates of N fertilizer. Consequently, maximum seed yield (plateau) was 27% greater for Finola than for Crag, but 198 kg N ha -1 of fertilizer was required to achieve this maximum yield vs. 175 kg N ha -1 for Crag. There was generally little or no response to P fertilizer, on soils with adequate available P, or to S fertilizer on an S-deficient soil. Results from this study indicate that N fertilizer rate and cultivar choice are important management parameters to consider for industrial hemp production.Key words: Fertilizer, hemp cultivars, nitrogen, phosphorus, sulphur, soil extractable P, soil nitrate-N