The effects of different sowing times on maturity rates, biomass, and plant growth of industrial fiber hemp

Hemp in the Northern hemisphere is planted in April–May under long-day conditions to prevent precocious flowering. In Queensland, Australia, where premature flowering is inevitable, it may be necessary to plant hemp closer to the summer solstice to optimize solar radiation and longer day-length. However, high temperature at that time may limit growth of hemp in the Burnett/Wide Bay region, Queensland, Australia. Field experiment where day length did not exceed 13 h and 40 min, we evaluated effect of five spring/summer sowing times on flowering time, plant growth and yield. Of the five planting dates (15 Sept–PD1, 25 Oct–PD2, 25 Nov–PD3, 16 Dec–PD4, and 23 Jan–PD5), (PD3) stood out as the optimal time of planting. Planting date 3 was significantly later to develop male buds and the first open male flowers. Plant height at harvest was the highest for PD3 (999 mm) compared to all other planting dates. Planting date 3 also yielded highest dry matter (7.8 t ha−1). Yields were well below what would be considered viable in Europe for fiber hemp, but the results of the experiment may be used to indicate potential of seed hemp crop for QLD.