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ARS Home » Plains Area » Bushland, Texas » Conservation and Production Research Laboratory » Soil and Water Management Research » Research » Publications at this Location » Publication #427603
Research Project: Dryland and Irrigated Crop Management Under Limited Water Availability and Drought

Location: Soil and Water Management Research

Title: Effect of early and late post emergence herbicides on weed suppression, crop injury, and biomass yield of industrial hemp in semiarid conditions

Author
item BAJWA, PREETMAN - Texas Tech University
item SAINI, RUPINDER - Texas Tech University
item SINGH, SUKHBIR - Texas Tech University
item MAKKAR, JASLEEN - Texas Tech University
item TROSTLE, CALVIN - Texas A&M Agrilife
item SINGH, HARDEEP - University Of Florida

Submitted to: Agrosystems, Geosciences & Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/17/2025
Publication Date: 3/18/2025
Citation: Bajwa, P., Saini, R., Singh, S., Makkar, J., Trostle, C., Singh, H. 2025. Effect of early and late post emergence herbicides on weed suppression, crop injury, and biomass yield of industrial hemp in semiarid conditions. Agrosystems, Geosciences & Environment. 8(1). Article e70078. https://doi.org/10.1002/agg2.70078.
DOI: https://doi.org/10.1002/agg2.70078

Interpretive Summary: Industrial hemp is receiving attention for its uses in the fiber industry and ability to produce with smaller irrigation needs, a plus in the Southern High Plains were water is increasing scarce. However, weed competition is a primary concern for hemp cultivation, causing reduced yields and inferior-quality fiber. Kansas State University researchers, working in a USDA ARS Ogallala Aquifer Program project, compared several chemicals used for weed control and found those best adapted for use with hemp. Early post S-metolachlor and ethalfluralin applications demonstrated potential as effective herbicides, yielding four-folds greater hemp biomass than untreated control at harvest. This provides key information to hemp growers for weed control needed to obtain high fiber yields.

Technical Abstract: Industrial hemp is receiving attention for its numerous benefits, particularly in the fiber industry. Weed competition is a primary concern for hemp cultivation, causing reduced yields and inferior-quality fiber. However, little is known about herbicide application in hemp since a limited range of herbicides are available for hemp production. During 2023, this study evaluated the effect of different post-emergence herbicides applied at early and late growth stages to optimize weed suppression and minimize crop injury in hemp under semiarid conditions. A randomized complete block design was used with six herbicide treatments, including early post (2 weeks after planting [WAP]) and late post (5 WAP) emergence applications of S-metolachlor, clopyralid, and ethalfluralin. Hemp plant stand showed no significant difference among treatments. Early post herbicide application reduced 86% of weed biomass compared to untreated control at 7 WAP. By 10 WAP, weed biomass became comparable across treatments. At harvest, untreated control recorded comparatively higher weed biomass than early post treatments and late post ethalfluralin. Plant height remained nonsignificant among treatments until 10 WAP. At harvest, control showed no variation with late post treatments but recorded an average of 63% lower plant height than early post applications. Hemp biomass was insignificantly affected by treatments at 10 WAP. However, on average, early post S-metolachlor and ethalfluralin applications demonstrated potential as effective herbicides, yielding four-folds greater hemp biomass than untreated control at harvest. In conclusion, early post Smetolachlor and ethalfluralin are promising tools for weed control, enhancing crop competitiveness and yield in hemp cultivation.