Weed community in organic maize-legume intercropping system

Organic maize (Zea mays L.) production is particularly challenged by weeds competition. Therefore, weed management in organic systems demands an integrated approach, considering not only techniques, but also the design and occupation of agroecosystems in space and time. This work aims to evaluate the initial effects of maize-legume intercropping with different arrangement of species of legume on weeds community in an organic system. Treatments consisted of maize intercropped with: Crotalaria spectabilis Rhot. (Showy rattlebox); Cajanus cajan (L.) Millsp. (Pigeon pea); Crotalaria spectabilis + Cajanus cajan and one control, consisting of maize monocropping. Weed abundance data for each treatment and phenological stage of maize (14 and 18 BBCH scale) in the 2017/2018 and 2018/2019 growing seasons were used to calculate the Shannon–Wiener diversity index (H) and the Pielou index (J). Data was also analyzed by principal component analysis (PCoA), along with the Similarity Percentage. The relative importance (RI) of the weed species were determined in 2017/18 between harvests and after the maize harvest in 2018/19. Maize/Crotalaria spectabilis intercrop in the 2017/2018 harvest resulted in less weed diversity and greater similarity to the maize monocrop, indicating a population of specialized weeds, that are highly competitive with maize in the organic system. The relative importance of the major weed species was not influenced by the farming systems over the two growing seasons.