Monday, November 13, 2006

Impacts of Long-Term Land Applied Poultry Litter on Soil Properties and Macro Cations Status.

Zhongqi He, USDA-ARS, New England Plant, Soil, and Water Laboratory, Orono, ME 04469, Irenus Tazisong, Alabama A&M Univ, 4900 Meridian St, Box 1208, Normal, AL 35762-1208, Zachary Senwo, Alabama A&M University Accounts Payable, Alabama A&M University, Po Box 552, Normal, AL 35762-0552, and Donglin Zhang, Univ of Maine, Dept of Plant, Soil and Env. Sciences, Orono, ME 04469.

Poultry litter (PL) is a traditionally inexpensive and effective fertilizer to improve soil quality and agricultural productivity. However, over application to soils has raised concerns because excess nutrients in runoff could accelerate the eutrophication of fresh water bodies. A long-term field experiment of land application of PL to soils used for pasture growth has been maintained for nearly two decades at the Sand Mountain region of north Alabama, USA.  In this work, we characterized several soil parameters impacted by the long-term applied litter. Our findings clearly support previous observations that long-term applied litter on pasture soils altered soil properties and macro cations levels. Unlike other studies, we examined the effects of applied litter at multiple rates and years, thus revealing its dynamic impacts on soil properties. PL application did not markedly affect soil electric conductivity, bulk density, Na or K levels, especially at the soil surface (0-20 cm). Soil pH, Ca and Mg were profoundly affected at all the three soil depths (0-20, 20-40, and 40-60 cm) examined. Most soil parameters analyzed in this study reached peak values with 10 years of applied litter, which did not correspond to the highest rates or cumulative amounts of applied litter. This observation suggests that there was a turning point  of impact for applied litter around 10 years: prior to that the soil macro cations were altered positively due to accumulative functions. Continuous litter application may negatively alter a soil’s capacity to retain macro cations, leading to less impact observed in this study. In other words, pasture soils with more than 10 years of applied litter would have higher potential for leaching and runoff. Information obtained from this study will be helpful in developing best management practices for land application of PL.