Quantifying Macro- and Micro-Pores to Assess the Influence of Forage Grass On Coastal Plains Soils through the Use of Computed Tomography (CT).

Quantifying Macro- and Micro- Pores to Assess the Influence of Forage Grass in a Sod-Based Rotation on Coastal Plains Soils through the Use of Computed Tomography (CT)

R.E. Prevatt, J.A. Howe, N.K. Twarakavi, and F.J. Arriaga

                The addition of forage grasses to the traditional cotton-peanut rotation has shown to improve water infiltration, but the cause is not well understood.  The objective of this study was to determine whether the addition of forage grasses to the cotton-peanut rotation affects pore size and distribution.   Sites in Headland, AL and Quincy, FL were established 8-10 years ago with 200 m² plots in a randomized complete block design with all combinations of sod-based (bahia-bahia-peanut-cotton) and traditional peanut-cotton (Headland site) or peanut-cotton-cotton (Quincy site) rotations replicated three times.  Soil cores Two fields in Headland, AL were sampled by taking soil cores 7.5 cm in diameterwide and approximately 60 to 90 cm in length and were taken in triplicate in each plotlong.  These fields were planted in Bahia grass, peanuts and cotton.  We have several different treatments on the two fields covering Plow vs. Strip-till and Grazed vs. Non-grazed for both a traditional peanut – cotton rotation and the Sod-Based Rotation.  The objective of our study is to see how the Bahia grass will affect the soil structure through the size and amount of macro and micro pores in the soil.  To determine the size, shape, and abundanceamount of these macro- and micro- pores, we will be using Ccomputed tTomography (CT) sScans were performed on 2 of the 3 cores within 3 weeks of collection.  and then running them through aA computer algorithm was used to program to quantify and analyze vertical the pores through gray scale analysis.  Following CT scans, cores from each plot were divided by depth (>>>) and homogenized into a composite sample representative of the entire plot.  Horizons were evaluated by color change and bulk density was also determined.  Permeability was determined in the field using a method by Amoozegar and Wilson (1999).  Size and quantity of pores was greater in soils that had bahiagrass in the rotation.  Distribution and quantity of pore sizes was related to permeabilityWith this information we will be able to determine water holding capacities and  in these soils and, in turn, be able to determine if the Bahia grass was beneficial or not in contributing to the overall soil quality..