Microbial consortium inoculant and rock mineral fertiliser differentially improved yield and nutrient uptake of industrial hemp (Cannabis sativa L.) varieties

Industrial hemp (Cannabis sativa L.) production is attracting widespread attention in agriculture but is facing cultivation challenges in nutrient-poor sandy soils. The crop has a fibrous deep taproot system known to have a good association with the rhizosphere soil microbiome. However, there are few reports on incorporating microbial inoculants with or without rock mineral fertilisers to facilitate nutrient mineralisation and stimulate growth of industrial hemp. To test whether microbial consortium inoculant with or without fertiliser improves the growth and yield of industrial hemp by increasing root biomass and nutrient uptake, we assessed the impact of microbial inoculant and rock mineral fertiliser in two hemp varieties (Morpeth and Han FNQ). The experiment was conducted in a randomised complete block design with four treatments: control (CTRL), consortium microbial inoculum (MI), rock mineral fertiliser (MF) and combined microbial inoculum and mineral fertiliser (MI+MF). Plants were grown in compost in a controlled-environment phytotron and harvested 30 and 70 days after sowing (DAS). Han FNQ had higher root dry weight, shoot length, leaf chlorophyll, Mn and Zn uptake than Morpeth at 30 DAS, and Han FNQ in the MI+MF treatment also had greater root volume than Morpeth in all treatments at 30 DAS. At 70 DAS, Morpeth had a higher seed yield than Han FNQ and Morpeth in the MI treatment had greater shoot and root dry weight, leaf chlorophyll, root length and volume, and higher uptake of all macro- and micronutrients in shoots and seeds than Han FNQ in all treatments. These findings suggest that the resource stoichiometry and trade-balance model in plant-microbes symbiosis govern the effectiveness of MI on industrial hemp. The application of MF and the initial nutrients abundance in the compost might suppressed MI activity at 30 DAS whereas, the nutrient limiting condition at 70 DAS might triggered MI activity and symbiotic trade of nutrients between plant and microbes which facilitated root growth and nutrient uptake particularly, in the variety Morpeth.