Agronomic characteristics and optimized sweet potato root production in monoculture under green manuring

One of the challenges of the scientific research on sweet potatoes in semi-arid environments is to increase biomass amounts of spontaneous species from the Caatinga biome, such as hairy woodrose (Merremia aegyptia L.) and roostertree (Calotropis procera Ait.), for use as green fertilizers during cultivation. Therefore, this study aimed to agronomically and economically optimize the agronomic characteristics of sweet potato root production in a monoculture, fertilized with equal amounts of biomass mixture of these spontaneous species, over two years of cultivation. The experimental design was complete randomized blocks with five treatments and five replications. The treatments consisted of equal amounts of hairy woodrose and roostertree biomass at 16, 29, 42, 55, and 68 t ha-1 on a dry basis. An additional sweet potato treatment was planted in each experiment, one without fertilizers (control) and another with mineral fertilizer, to compare with the treatment of maximum physical or economic efficiency. Sweet potato fertilization obtained the maximum optimized productive efficiency by incorporating 46.97 t ha-1 of dry biomass of M. aegyptia and C. procera into the soil. The maximum optimized agroeconomic efficiency (based on net income) of sweet potato cultivation occurred by adding 41.55 t ha-1 of dry biomass of M. aegyptia and C. procera to the soil. Using biomass from the green fertilizers M. aegyptia and C. procera is a viable technology for producers who practice sweet potato monocropping in semi-arid environments.