Soil organic carbon dynamics and microbial responses to intercropping sweet corn with legumes under different row arrangements in coastal Odisha

Abstract Intercropping of cereals and legumes can improve resource-use efficiency and soil fertility compared with monocropping. A field experiment was conducted during rabi , 2023–24 at OUAT, Bhubaneswar, India to evaluate the effects of sweet corn ( Zea mays L.) intercropped with cowpea ( Vigna unguiculata ) and black gram ( Vigna mungo ) under different row arrangements on soil organic carbon (SOC), biological properties and soil fertility. The experiment was conducted in a randomized block design comparing sole sweet corn with intercropping systems in 1:1, 1:2 and paired 2:2 row arrangements. Soil samples collected at 30 and 60 days after sowing (DAS) and at harvest were analysed for soil organic carbon (SOC), microbial populations, microbial biomass carbon (MBC), soil basal respiration (SBR), dehydrogenase activity (DHA), urease activity (UA) and available primary soil nutrients. Intercropping generally improved SOC and soil biological properties compared with sole sweet corn, with the paired 2:2 row arrangement showing the most pronounced response. At harvest, this treatment increased SOC by 5.9% and MBC by 67% over sole sweet corn and recorded the highest DHA (1.46 µg TPF g -1 soil h -1 ) and UA (67.0 µg NH 4 + -N g -1 soil h -1 ). It also recorded higher SBR and enhanced bacterial and actinomycete populations whereas fungal population remained unaffected. The paired 2:2 arrangement also enhanced available primary soil nutrients with the strongest response observed at harvest. These findings indicate that appropriate spatial arrangement in sweet corn-legume intercropping can improve soil organic carbon and microbial functioning within a cropping season. Paired-row intercropping therefore shows potential as a soil fertility management strategy for sustainable sweet corn production under the East and South Eastern Coastal Plain of Odisha.