Effect of integrated weed management on weeds, soil microbes, yield and economics of pearl millet cultivated within the alleys of custard apple (Annona squamosa L.) plantation

A field experiment was conducted during the Kharif season of 2023 at the Rajiv Gandhi South Campus, Banaras Hindu University, Mirzapur, Uttar Pradesh, India, to identify effective weed management protocols for understory crop, pearl millet, without compromising the perennial tree component. Specifically, the study evaluated integrated weed management strategies for pearl millet (Pennisetum glaucum L.) cultivated within the alleys of a 15-year-old custard apple (Annona squamosa L.) plantation. Ten treatments, comprising combinations of pre- and post-emergence applications of herbicides along with hand weeding (HW), were tested in a randomized block design with three replications. The pre-emergence application (PE) of atrazine 1.0 kg/ha followed by (fb) HW once at 25 days after sowing (DAS) and atrazine 1.0 kg/ha fb post-emergence application (PoE) of tembotrione 100 g/ha at 25 DAS were the most effective treatments. These combinations significantly reduced weed density and biomass, thereby enhancing pearl millet growth parameters such as plant height, chlorophyll content (SPAD), leaf area index (LAI), and plant dry weight. Assessment of soil biological health at harvest indicated that while dehydrogenase activity remained stable across all treatments, alkaline phosphatase and soil microbial biomass carbon (SMBC) were significantly higher with pendimethalin 1.0 kg/ha PE fb 2,4-D 0.75 kg/ha PoE at 25 DAS, indicating strong microbial resilience following herbicide degradation. Agronomically, atrazine 1.0 kg/ha PE fb HW once at 25 DAS recorded the highest pearl millet grain yield. However, the sequential herbicide application of atrazine 1.0 kg/ha PE fb tembotrione 100 g/ha PoE at 25 DAS achieved maximum benefit-cost ratio (2.86) due to significantly lower labor costs. Importantly, visual assessments confirmed that the evaluated herbicidal treatments did not cause any adverse phytotoxic effects on the mature custard apple trees.