(Georgia Institute of Technology, 2007-03)
Gaskin, Julia W.; Speir, Adam; Morris, L. M.; Ogden, Lee; Harris, Keith; Lee, D.; Das, K. C.
Pyrolysis of biomass for hydrogen fuel and bio-oil produces a char byproduct. There is evidence that land application of char may increase soil water holding capacity and the ability of the soil to retain nutrients. Increases in these soil characteristics could be beneficial to plant growth as well as improving water quality. Chars produced under different conditions and from different feedstocks have different characteristics. Of the common feedstocks tested, peanut hull char contained higher nutrients and had a higher cation ex-change capacity than pine chip, pine bark, or hardwood chip chars. Preliminary moisture release curve data from a Tifton loamy sand indicated moisture holding capacity may be increased at very high rates of char addition. Soil moisture was periodically measured during the growing season in a field study of microplots amended with peanut hull and pine chip pellet char. Although the average soil water content of the plots amended at 22 Mg ha-1 was higher than the control, differences in volumetric water content were only significant on one date.
(Georgia Institute of Technology, 2005-04)
Gaskin, Julia W.; Harris, Keith; Cabrera, Miguel L.; Risse, L. Mark
The Georgia P Index was developed as a tool to evaluate the risk of bioavailable P loss in fields under various management practices. We compared the results of the P Index with four years of data from 1.5 m by 4.6 m bermudagrass plots fertilized with poultry litter at 8.9 Mg ha-1 (recommended rate); poultry litter at 17.9 Mg ha-1; composted poultry litter, poultry litter with alum, commercial fertilizer; and a control (no amendments). P Index ratings above 75 indicate high risk where management should be changed. The P Index indicated management changes would be needed for the 17.9 Mg ha-1 treatment during all 4 years, for composted PL during year 4, and for PL with alum during years 3 and 4. The P Index did not indicate management changes were necessary using the recommended rate of 8.9 Mg ha-1 after 4 years of application; however, volume-weighted P concentrations in the 8.9 Mg ha-1 treatment were double the control concentrations during years 3 and 4. The comparison indicates that the P Index does identify high risk management practices under the conditions of this study.