Hybrid brachiariagrass (Urochloa spp.) establishment with annual sorghum sudangrass (Sorghum bicolor (L.) Moench) and sunn hemp (Crotalaria juncea L.) mixtures at half and full recommended seeding rates

Abstract

The slow initial growth of hybrid brachiariagrass (Urochloa spp.) can require some months to achieve complete ground cover of a newly seeded area, leading to decreased forage production and increased weed infestation in the establishment year. To solve these problems, we attempted to sow seeds by mixing warm-season annual forages with brachiariagrass at a brachiariagrass pasture establishment (University of Florida, USA, 2017 and 2018). Treatments were single seeding of ‘Cayman’ brachiariagrass solo (BR), sorghum sudangrass solo (Sorghum bicolor (L.) Moench; SD), and sunn hemp solo (Crotalaria juncea L.; SH) and two mixtures of these three forages at half (HSR) or full (FSR) of the recommended seeding rate. The seeding rates of FSR were, respectively, 10, 20, and 25 kg/ha for brachiariagrass, sudangrass, and sunn hemp. The treatments were distributed in a randomized complete block design with four replicates. Plots were harvested at 6, 12, 18, and 24 weeks after seeding. The number of brachiariagrass seedlings in the HSR and FSR treatments was less than half that in the BR (P < .05). The BR treatment had greater brachiariagrass herbage accumulation (HA) at all harvests than HSR (4%–75% of BR) or FSR (7%–66% of BR). This difference between the BR and mixture treatments became narrower in later harvests. In addition to the decreased number of brachiariagrass seedlings, light and nutrient competition between annual forages are considered to be the causes of lower brachiariagrass HA in the mixture treatments. Sunn hemp increased forage HA and crude protein concentrations at 6 weeks. Sudangrass provided overyielding forage until 18 weeks after seeding, with a similar nutritive value as brachiariagrass. Mixing warm-season annual forages with brachiariagrass at the establishment, especially half of the seeding rates of sunn hemp and sudangrass, is a feasible management practice to increase HA during the first 12 weeks after seeding.