A Four-Year Study of Biomass Production of Eastern Gamagrass Grown on an Acid Compact Soil

Abstract

A field study was conducted from 1997 to 2000 to determine the biomass production of ‘Pete’ eastern gamagrass [Tripsacum dactyloides (L.) L.] grown on a restrictive (acid compact) soil on six unlimed sites located on the North Farm at the Beltsville Agricultural Research Center in Beltsville, MD. Total biomass from two cuttings in 1997, 1998, and 2000 averaged 4261, 4995, and 6611 kg ha−1, respectively, despite deficits in moisture during those years. A single cutting in July 1999 averaged 2288 kg ha−1. Overall biomass varied more than two-fold for the six sites. Significant differences in biomass were found among sites, years, and harvests. In general, biomass varied with position on the slope, bulk density, and depth of the topsoil, but not with pH. The average biomass was generally lowest at the top of the slope where the thickness of the Ap horizon was relatively thin and the soil was extremely acidic (pH 4.3–4.4) (1:1 soil–water). High silt content and low bulk density of the soil were associated with highest biomass; rainfall distribution also appeared to be important. Eastern gamagrass at Sites 4 to 6 at the top of the slope generally had a low pH (4.3–4.4), high penetrometer resistance, and high bulk density. Penetrometer readings were lower between rows than within rows at the 5 cm depth. There was no significant relationship between bulk density and penetrometer readings, but biomass appeared to be related to bulk density. Dry weight of roots was reduced by increasing bulk density (r2=0.57) and also reduced at depths below 15 cm. Despite adverse stress imposed by shallow top soil, low pH, high bulk density, and moisture deficits, eastern gamagrass produce relatively high biomass. These results demonstrate the resilience of eastern gamagrass to an acid compact soil and indicate that this species is suited for reclamation of acid compact soils and for producing high quality forage on marginal lands, when supplied with adequate NPK.