Biological attributes of soil cultivated with corn intercropped with Urochloa brizantha in different plant arrangements with and without herbicide application

Abstract

Cultural techniques such as spatial distribution of plants and initial control of the growth rate of forage by applying herbicide sub-doses should be adopted for economic sustainability of intercropping between corn and forage. However, disturbances in the system can affect mycorrhizal colonization, metabolic quotient, microbial respiration, and the number and diversity of arbuscular mycorrhizal fungi (AMF). The objective of this study was to evaluate the effect of nicosulfuron spraying and the seeding density of Urochloa brizantha on soil microbiological attributes. The treatments were arranged in a 2 × 4 factorial design in randomized blocks. The first factor was nicosulfuron doses (0 and 1/5 of the recommended), and the second factor was the forage seeding densities (0, 2, 4 and 6 kg of seeds per hectare). Soil samples were collected 60 days after the emergence of corn plants. The respiratory rate, carbon associated with microbial biomass, metabolic quotient, diversity and number of mycorrhizal fungi spores and mycorrhizal colonization were determined in the soil samples. The seeding density of U. brizantha interfered with microbial respiration, metabolic quotient, mycorrhizal colonization and the population of AMFs. A planting density of 8 kg ha−1 associated with the application of nicosulfuron resulted in a lower metabolic quotient. The increase in forage seeding density linearly reduced corn yield when sub-doses of nicosulfuron were not applied. Management of the spatial distribution of plants and control of initial forage growth by spraying nicosulfuron provide economic and environmental sustainability to the production system.