Allelopathic Effect of Cover Crops on Germination and Early Seedling Growth of Cotton (Gossypium hirsutum)

Negative allelopathic impacts have been documented in row crops planted into cover crop residue. However, little is known about the actual allelopathic impacts of cover crops on germination and seedling growth of cotton. During the summer of 2018, a series of laboratory experiments was conducted at the West Tennessee Research and Education Center (WTREC) in Jackson, TN to study the allelopathic effects of cover crop extracts on germination and early seedling growth of cotton. Extracts from above-ground biomass of five single-species cover-crops (oats, winter pea, rye, vetch, and wheat) and a multi-species blend of cover crop from 4 different termination timings (planting, 6 wks. prior to planting, 3 wks. prior to planting, and furrow termination 6 wks. prior to planting with the remainder terminated at planting) were tested at 0, 25, and 50 v/v on ‘PHY 490 W3FE’ (Dow AgroSciences, Indianapolis, IN) seeds. Germination rate, germination percentage, root length, and fresh weight of seedlings were affected by cover crop extracts. Root length and germination percentage were more sensitive to allelopathic extracts than other parameters. Among the five tested cover crop species, the 50 v/v extract treatment from winterpea inhibited germination of cotton seeds the most (55%). Wheat and vetch showed the lowest allelopathic impact on cotton germination, but all cover crop extracts inhibited root elongation. Among the termination timings, the 50 v/v extract treatment from termination at planting reduced germination percentage the most (62%). Results suggest that cover crop species and cover crop termination timing will play an important role in reducing allelopathic impacts on cotton germination percentage and root length.

Key words; allelopathy, cover crops, termination timings, cotton, germination percentage, root length