Allelopathy effect of crop residues on seed germination and seedling growth of corn and soybean

Abstract

The aim of this study was to evaluate the allelopathic effects of aqueous extracts of grain sorghum (Sorghum bicolor (L.) Moench), canola (Brassica napus L.), ryegrass (Lolium multiflorum L.) and turnip (Raphanus sativus var. oleiferus L.) on seed germination and seedling growth of soybean (Glycine max (L.) Merrill) and corn (Zea mays L.). The experimental design was completely randomized with four replicates per treatment and an experimental unit consisting of 50 seeds. The soybean and corn seeds were placed on trays containing sheets of absorbent paper soaked in 15 ml of the extract, closed and incubated with a 12-hour photoperiod at 25°C for seven days. Seed germination, normal and abnormal seedlings, fresh and dry matter, length of the aerial part and roots, and electrical conductivity of the seeds exposed to the extracts for 24, 48 and 96 hours were evaluated. The aqueous extract of turnip reduced soybean seed germination by 27.3%, while ryegrass and turnip extracts reduced corn germination by more than 65%. Canola and ryegrass extracts reduced fresh and dry matter of shoots and seedling length of soybean and corn. Electrical conductivity did not vary between extracts and crops, but there was a difference with contact time, 96>48>24 hours. In soybean, turnip extract had the most pronounced effects, negatively impacting germination, root development, shoot length and total seedling mass. Ryegrass and turnip extracts had the greatest potential to reduce corn germination, growth, root development and seedling dry matter.