|REDDY, K. CHANDRA|
Submitted to: CSA News
Publication Type: Popular Publication
Publication Acceptance Date: 5/15/2008
Publication Date: 6/19/2008
Citation: Sainju, U.M., Senwo, Z., Nyakatawa, E., Tazisong, I., Reddy, K. 2008. Poultry litter application increases carbon sequestration and soil quality. CSA News. 53(7): 4.
Technical Abstract: Poultry litter, a cheap source of nutrients, is widely available in the southeastern U.S. because of a large-scale poultry industry. Disposal of poultry litter is causing an increasing environmental concern because of groundwater contamination of nitrogen and phosphorus through leaching and surface runoff. Application of poultry litter in croplands can increase carbon sequestration and soil quality, which can offset agricultural carbon dioxide emission and sustain crop yields. Scientists from USDA-ARS, Sidney, MT and Alabama A & M University have compared the influence of poultry litter application with inorganic nitrogen fertilization on soil carbon sequestration and labile carbon fractions under various tillage and cropping systems in northern Alabama in a 10-year study funded by Evans-Allen Project. Results from the study were published in the May-June issue of Journal of Environmental Quality and presented in 2007 Annual Meeting of American Society of Agronomy in New Orleans, LA. Carbon from residues of cotton and corn was returned to the soil after harvest in the fall and from rye cover crop in the spring every year from 1996 to 2005. The experiment was conducted in high and low rates of poultry litter application and inorganic nitrogen fertilization in conservational- and conventional-tilled crops with and without cover crops. A bare fallow treatment without tillage, cropping, and fertilization was also included to evaluate the effects of cropping and fertilization on carbon sequestration. In 2006, soil carbon fractions that included soil organic carbon (SOC), particulate organic carbon (POC), microbial biomass carbon (MBC), and potential carbon mineralization (PCM) were measured. Although crop residue carbon was greater in the cropping system with than without cover crop, tillage and cropping system did not influence soil carbon sequestration and fractions. Residue carbon was lower with poultry litter than with inorganic nitrogen fertilization. When applied at 100 kilogram nitrogen per hectare, poultry litter, however, increased SOC by 8% compared with inorganic nitrogen fertilizer at 0- to 20-cm depth, thereby resulting in soil carbon sequestration rate at 510 kilogram carbon per hectare per year, regardless of tillage and cropping systems. Similarly, cropping and fertilization sequestered carbon at 730 kilogram carbon per hectare per year compared with bare fallow. Both poultry litter application and cropping also increased POC, MBC, and PCM compared with inorganic nitrogen fertilization and bare fallow, respectively. Increasing poultry litter application rate from 100 to 200 kilogram nitrogen per hectare, however, did not increase soil carbon fractions. Upendra, the lead scientist of the study, states that increased carbon sequestration with poultry litter was probably due to conversion of recalcitrant poultry carbon into SOC, since poultry litter also supplied carbon at 1.7 Megagram carbon per hectare per year when nitrogen was applied at 100 kg nitrogen per hectare per year. No such carbon was supplied when inorganic nitrogen fertilizer was applied to crops. The team concluded that long-term poultry litter application and continuous cropping can increase soil carbon sequestration and labile carbon fractions, thereby offsetting atmospheric carbon dioxide emission and improving soil and environmental quality. They suggest that poultry litter, instead of disposing it as a waste material that can contaminate surface and ground water, should be applied in croplands to increase carbon sequestration, improve soil quality, and supply nutrients to sustain crop production, especially in the humid subtropical regions of the southeastern U.S. where soil carbon level is lower than in the northern regions. Further research would be needed to examine to what extent poultry litter carbon is converted to SOC using radio isotop