Fiber hemp (Cannabis sativa L.) yield and its response to fertilization and planting density in China

Interest is growing worldwide to grow fiber hemp for innovative biomaterials while little information is available on the yield performance and agronomy of hemp. In the present study, the productivity of fiber hemp in response to fertilization and planting density was assessed at three sites in the main hemp-producing areas in China with locally bred cultivars in 2016 and 2017. The sites were Daqing in the north-east, Lu’an in the central-east, and Menghai in the south-west. At each site, the treatments were a factorial combination of three fertilization rates (300, 600, and 900 kg (N + P2O5 + K2O) per hectare), two NPK ratios (N:P2O5:K2O at the ratio of 3:1:2 and 4:1:2), and two planting densities (45 and 67.5 plants m−2). The harvested stem yield ranges were 9.0–12.2 Mg ha−1 in Daqing, 9.8–16.5 Mg ha−1 in Lu’an, and 5.2–15.1 Mg ha−1 in Menghai. Increasing the fertilization rate from 300 kg ha−1 to 900 kg ha−1 had little effect on the yields of stem, leaf and bark while it caused a decrease in the stem bark content in all sites. NPK ratio had a considerable effect on hemp stem yield, higher yield was achieved at 3:1:2 than 4:1:2. The effect of planting density on hemp yields varied among sites. Between the tested densities, the yields of biomass, stem and bark were higher at 45 plant m−2 in Menghai, at 67.5 plants m−2 in Lu’an while no significant difference was detected at Daqing. These results highlight the need to optimize fertilization and planting density according to environmental conditions. •The yields of fiber hemp was assessed in three main producing areas in China.•Fertilization rate over 300 kg ha−1 resulted in a decrease in the stem bark content.•Higher stem yield was achieved with N:P:K ratio at 3:1:2 than 4:1:2.•Stem yield was higher at 45 plants m−2 than 67.5 plants m−2 in south-western China