Nitrogen application and cultivar effects on industrial hemp yield dynamics

Abstract

AbstractRenewed interest in hemp (Cannabis sativa L., <0.3% delta‐9‐tetrahydrocannabinol) production has motivated investigations into crop management and fertilizer application. Due to fertilizer regulations, soil characteristics, and unique climatic conditions in Florida, researching nutrient management for region‐specific hemp cultivation is essential. A study conducted in central Florida during 2021 and 2022 used six nitrogen (N) rates (0, 56, 112, 168, 224, and 280 kg ha−1) and five cultivars (NWG‐2730, X‐59, Bialobrzeskie, IH Williams, and Yuma) as a first effort to develop producer‐oriented fertilizer guidelines. The field experiments employed a randomized complete block design across N rates and varieties, with N applied in three split applications. The results indicated an interaction between cultivars and N rates, as expected due to their diverse genetic and geographic origins. Challenges in genetic and germination quality resulted in grain and biomass yield of two cultivars, X‐59 and Bialobrzeskie, that did not respond to the N application. Conversely, NWG‐2730, IH Williams, and Yuma cultivars demonstrated significantly higher yields within the 168–280 kg ha−1 N range. Moreover, cultivars demonstrated differing emergence counts (field count), and findings indicated a correlation between emergence and plant count at harvest (r = 0.68 and p = 0). The study also found a difference in germination count versus field count (after adjusting the seed rate depending on germination percentage). Enhanced plant count at harvest substantially elevated grain and biomass yield. The N application positively influenced plant height across all cultivars except Bialobrzeskie. Optimal plant height was achieved within the 168–280 kg N ha−1 range. Therefore, optimizing N rates and selecting cultivars (with higher emergence rates in the field) could help achieve higher biomass and grain yields.