Comparison of Belowground Responses of Rhizoma Peanut-Bahiagrass Mixtures with Their Monocultures.

Growing legumes and grasses together is a management practice that might bring environmental and economical benefits by decreasing the utilization and manufacture of industrial N fertilizer. The mineralization of belowground biomass is one of the pathways which N can be transferred from legumes to grasses. The goal of this study was to evaluate belowground responses of rhizoma peanut (RP; Arachisglabrata Benth.) and bahiagrass (Paspalum notatum Flüggé) mixtures in contrast with their monocultures. The study was conducted in a randomized complete block design with eight treatments and three replications. Treatments were two bahiagrass entries (‘Argentine’ and ‘DF9’, receiving 90 kg N ha^-1 harvest^-1), two RP entries (‘Ecoturf’ and ‘Q6B’), and the combinations of each entry of bahiagrass with each entry of RP (Argentine-Ecoturf, Argentine-Q6B, DF9-Ecoturf, and DF9-Q6B). Two 0- to 20-cm depth x 10.8-cm diameter soil cores were sampled at the beginning (July 2015 and at the end (September 2016) of the study. Variables analyzed were root-rhizome biomass, N and C content, δ¹⁵N, δ¹³C, C:N ratio, and proportion of each component in the belowground biomass. There was a treatment × year interaction for root-rhizome biomass because in 2016 Argentine and DF9 monocultures had twice as much belowground biomass as they did in 2015.Total N and C content, did not differ from RP or bahiagrass monocultures (P>0.05), however they were greater in 2016 (P<0.05; 139 kg N ha^-1 and 5360 kg C ha^-1) than in 2015 (61 kg N ha^-1 and 3540 kg C ha^-1). In 2016, mixture C:N ratio in the belowground biomass were equivalent to N-fertilized bahiagrass monocultures. Bahiagrass and RP belowground proportion did not differ among the mixtures. There was a change (P<0.05) in the Argentine δ¹⁵N from -0.76 to 1.68‰ from 2015 to 2016. Mixtures of RP-bahiagrass can perform as good as N fertilized bahiagrass or RP pastures.