Mitigation of fluridone and pendimethalin residual phytotoxicity and yield-enhancing on wheat by Protaetia brevitarsis frass

This study aimed to evaluate the effects of Protaetia brevitarsis frass, biochar, and fly ash compounded with microbial inoculants or humic acid on mitigating residual phytotoxicity of commonly used cotton field herbicides fluridone and pendimethalin on wheat and on wheat yield enhancement.

A field plot experiment was conducted using three adsorbent materials: Protaetia brevitarsis frass (1500 kg/hm², L100), biochar (300 kg/hm², C40), and fly ash (6,000 kg/hm², F400). These materials were compounded with Shi'er Junyi (SEJ), Junlin Tianxia (JLT), and humic acid (FZS), respectively. An untreated control without soil amendment (CK) was included. Wheat plant height, stem diameter, chlorophyll content (SPAD value), phytotoxicity index, and yield were determined and compared among treatments.

At the jointing stage, the JLT treatment resulted in the greatest plant height, which was significantly higher than that of CK by 14.24%, while the L100 + SEJ treatment increased plant height by 11.78%. During the flowering stage, stem diameter was largest under the L100 treatment and was significantly increased by 8.63% compared with CK. Regarding chlorophyll content, the L100 treatment exhibited the highest SPAD value, which was 14.36% higher than that of CK, followed by the L100 + SEJ treatment with a significant increase of 12.00%. In terms of phytotoxicity mitigation, the phytotoxicity index under the L100 + SEJ treatment was significantly reduced by 81.95% at the seedling stage and by 89.52% at the jointing stage compared with CK, indicating a significant mitigation effect. Overall, Protaetia brevitarsis frass treatments were superior to biochar and fly ash in improving stem diameter, chlorophyll content, and phytotoxicity index. Yield analysis showed that the L100 + SEJ treatment achieved the highest grain yield, which was significantly increased by 31.20% compared with CK. In addition, the number of spikes, spike length, and grains per spike were increased by 18.16%, 16.76%, and 3.08%, respectively, with all yield components performing well.

Among the tested adsorbents, Protaetia brevitarsis frass demonstrated the most effective performance in promoting plant height, stem diameter, chlorophyll content, and yield compared to biochar and fly ash. Under the conditions of this study, the combined application of 1, 500 kg/hm² Protaetia brevitarsis frass with 150 kg/hm² Shi'er Junyi was identified as the optimal treatment combination for mitigating phytotoxicity in wheat.