Integrating intercropping, nitrogen fertilization and Azospirillum spp. to enhance growth, yield, and quality of sweet corn-sweet potato systems in sandy land

Abstract A two-year field study was conducted to study the possibility of partially replacing the nitrogenous fertilizer with the inoculum in a sandy land without affecting the growth, yield, and quality characteristics of sweet potato-sweet corn intercropping systems. The first factor was nitrogen fertilizer: Azospirillum brasilense (Ab, T1), 100 kg N ha − 1 (half-dose of nitrogen, T2), 200 kg N ha − 1 (full dose of nitrogen, T3), Ab + 100 kg N ha − 1 (T4), Ab + 200 kg ha − 1 (T5). The second factor was the intercropping systems (IS): (1) 100%IS =sole sweet corn or sole sweet potato, (2) 75%IS = 3 rows of sweet corn + one row of sweet potato, (3) 50%IS = two rows of each crop, (4) 25%IS = one row of sweet corn + 3 rows of sweet potato. The interaction showed that all intercropping systems within T5 surpassed other treatment combinations in all the studied traits, but it was comparable to the intercropping systems within T4. The lowest results were observed in all traits within the bacteria treatment (T1). The highest significant fat percentage and total solids were found in T5 + IS in sweet potato. Land equivalent ratio was greater than one in all treatment combinations, but the highest values were observed in T5 + 50%IS and T1 + 50%IS. As inoculating intercropped plants with Azospirillum spp. with either full- or half-dose of nitrogenous fertilizer under sandy land conditions had comparable growth and yield for both crops, we conclude that integrating intercropping (50%IS) with microbial inoculation and a reduced (half) nitrogen fertilizer dose can effectively lessen the reliance on synthetic nitrogen inputs. The best return was achieved by intercropping sweet potato with sweet corn at a ratio of 50% for each, combined with Azospirillum spp. + 200 N ha − 1 .