The Use of Commercial Bacterial Soil Inoculant Regime in an Urban Prairie Restoration

For successful grassland restoration, commercial soil inoculants are often recommended to increase establishment success. In spring 2009, a 0.94-ha tract was targeted for restoration at Phil Hardberger Park, a 126-ha park in the heart of San Antonio, Texas. Woody species, mainly Texas persimmon (Diospyros texana Scheele), and Ashe juniper (Juniperus asheii Buchholz), were removed and the area was divided into 10 subplots measuring 911 m2 on average. In September 2009, over 40,000 plugs of seven native grass species were planted. In addition, native prairie seed mixes, including various grass and forb seeds, were sown into the site at a rate of 11.26 kg/ha. Half of the native grass plants were treated with a soil bacteria inoculant plus additional nutrients (IN) (BioGensis IIITM DS Tainio Technology and Technique Inc.), and half were left as controls (C). Soil samples from the plots were taken in February 2010 and 2011 and analyzed for soil nutrients, bacteria, protozoa, and fungi. Vegetation data were collected October 2010 and May and October 2011 to assess differences in percent cover between the treatments. The IN treatment resulted in significantly higher percent cover in the second growing season of three native grasses, Eriochloa sericea (Scheele) Munro ex Vasey, Bouteloua gracilis (Willd. ex Kunth) Lag. ex Griffiths, and B. curtipendula (Michx.) Torr; however, no significant differences were found between the IN and C plots for measures of overall native species abundance, soil resources, or the presence of soil microbes. We concluded that commercial soil inoculants may not have been necessary for the successful establishment of a native grassland community.