Relay crop/intercrop legumes in Hemp Grain Production
Hemp Genetics International
To assess the effects of legumes and other intercrops with hemp on hemp grain production and
determine legume regrowth parameters.
There were no significant differences observed among treatments in hemp plant density and plant height. Forage yield was significantly (P<0.001) high in hairy vetch + hemp relay (3041 kg ha-1) compared to other intercrop options. On the other hand, forage yields were not significantly different in sweet clover + hemp, alfalfa + hemp and red clover + hemp treatments (Table 15b). There were also no significant differences in hemp kernel weight regardless of the relay crop system involved. Hemp yield obtained from pea + hemp was significantly high (P=0.023) compared to other hemp relay systems but was not different from hemp check. The probable cause for higher yield in the pea + hemp intercrop could have been due to higher nitrogen fixing ability of pea compared to other legumes. Pea and hemp seemed to complement each other in an intercrop when considering the combined yield of 248 kg ha-1, which was significantly higher (P<0.001) than other treatments. Organic matter content measured was similar for the check, sweet clover + hemp, alfalfa + hemp, hairy vetch + hemp, and pea + hemp but was significantly higher than red clover + hemp treatment (P=0.021). Overall, the organic matter content ranged from 3.27 to 3.73 and had coefficient of variation of 4%.
Legume cover crops have many benefits that include; adding nitrogen to the soil, suppression of weeds, control soil erosion, reduce nitrogen leaching and reduce insect pests and disease incidences. Hemp relay cropping systems respond well to conditions where soil moisture is not limited (Canadian Hemp Trade Alliance, 2020). On the Canadian prairies, hemp growers have been investigating the merits of relay cropping legume cover crops in hemp stands. This trial explores the benefits of doing so by studying the effect on hemp grain production and assessing regrowth of relay crops. This is year 3 of performing the trial.
Clovers, hairy vetch, or alfalfa act as a post-harvest cover to compete against weeds, reduce compaction, increase water use and fix nitrogen. In order to achieve nitrogen benefits, legumes must be inoculated with the appropriate bacteria (Martens et al., 2001). The purpose of seeding pea with hemp was to try to increase grain production per acre, as is the case with some farmers who are not into livestock production but want to increase cash returns per unit area (Canadian Organic Growers, 1992). Use of fall rye was to compete with weeds (both physically and chemically through allelopathy) and then be terminated by a group 1 herbicide.