Allelopathy of Crop Residues Influences Corn Seed Germination and Early Growth

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Abstract
Crop residues produce alleochemicals that may inhibit corn [Zea mays (L.)] seed germination and early growth. Studies were conducted in which residues of corn, soybean [Glycine max (L.) Merr.], oat [Avena sativa (L.)], and mixed grass hay were extracted under N2 gas or air. Organic debris was removed and half of each extract was filter sterilized. Corn seeds were incubated in the extracts for 96 h at 25 °C. Percent germination, and lengths of coleoptile, radicle, and secondary roots were measured. Residues extracted under N2 gas or air did not differ significantly in their toxicity. Nonsterile residue extracts decreased germination to 74% for soybean and oat straw and 27% for corn and hay residues. Sterile extracts did not affect germination. Nonsterile soybean and oat extracts did not reduce coleoptile lengths but did reduce radicle and secondary root lengths by 34% compared to the water treatment. Sterilized extracts reduced radicle and secondary root lengths by 63%. Nonsterile corn and hay extracts reduced coleoptile lengths by 42% and radicle and secondary root lengths by 81%. A second extraction was performed by incubating the residues without aeration at 25 and 0.5 °C. Seed germination for treatments with nonsterile extracts obtained at 25 °C were similar to those for nonsterile extracts of Exp. 1. Extraction at 0.5 °C and filter sterilization also improved germination. Soybean and oat extracts did not strongly inhibit coleoptile lengths; however, a 61% reduction occurred in radicle and secondary root lengths for the sterilized, 0.5 °C extract. Corn and hay residues were generally more inhibitory to coleoptile, radicle and secondary root lengths; however, no consistent effects were observed from temperature and sterilization treatments.