Effects of naturally and microbially decomposed cotton stalks on cotton seedling growth

Cotton stalk directly returning to cotton field has impeded the cotton growth to a large extent in Xinjiang province, China. The allelopathic effects of products from naturally and microbially decomposed cotton stalks on the cotton seedling growth were studied. The results showed that when the seedlings were treated with the 30-day microbially decomposed cotton stalks, they displayed better growth and physiological characteristics than those treated with the products of 30-day naturally decomposed cotton stalks. When treated with the microbially decomposed cotton stalks at a low concentration of 5 g kg^?1, the seedling dry weight and plant height even increased significantly compared to the untreated control (P < 0.05). The gas chromatography–mass spectrometry analysis showed that two compounds, dibutyl phthalate (DBP) and diisobutyl phthalate (DIBP), were detected with higher concentrations in the naturally decomposed cotton stalk extracts, which strongly inhibited the cotton seedling growth in bioassay, suggesting the two compounds might be the responsible allelochemicals inducing autotoxicity to cotton growth.