Incorporated Sorghum Residues Reduce Emergence and Seedling Growth of Some Crops

Abstract

Allelochemicals from sorghum [Sorghum bicolor (L.) Moench] residues may inhibit the emergence and growth of other crops. We examined the effects of residues from two sorghum landraces, IS9456, a high sorgoleone producer, and IS22320, a zero sorgoleone producer. Residues were applied at 7.2 g, 14.4 g and 21.6 g kg-1 of soil. Emergence and the growth of maize (Zea mays L.), wheat (Triticum aestivum L.) and soybean [Glycine max (L.) Merr.] were tested in three glasshouse pot experiments at the University of Zimbabwe in 2017. The 2×3 factorial experiments were laid as a randomized complete block design with six replications. Residues from IS22320 significantly (P<0.05) reduced the emergence of maize by 22.2% compared to residues from IS9456. Sorghum variety as a source of residue did not significantly (P>0.05) reduce the emergence, height, chlorophyll content or dry weight of soybean. Increasing the residue rate significantly (P<0.05) reduced the percent emergence, height, chlorophyll content and dry weight of soybean. There was a significant sorghum variety × residue application rate interaction on the percent emergence (P<0.001) and chlorophyll content (P<0.05) of wheat. Increasing the IS9456 residue application rate from 7.2 to 14.4 g kg-1 soil increased the chlorophyll content of wheat. The timing of maize and wheat planting after sorghum residue incorporation may be critical.