Soil Properties and Macro Cations Status impacted by Long-Term Applied Poultry Litter

Most ethnic populations worldwide consume poultry products. Whereas poultry litter (PL) is a traditionally inexpensive and effective fertilizer to improve soil quality and agricultural productivity, overapplication to soils has raised concerns because excess nutrients in runoff could accelerate the eutrophication of fresh bodies of water. A long-term field experiment of land application of PL to soils used for pasture growth has been maintained for nearly two decades in the Sand Mountain region of north Alabama, USA. In this work, several soil parameters impacted by the long-term applied litter were characterized. The findings clearly support previous general observations that long-term applied litter on pasture soils altered soil properties and macrocation levels. Unlike other studies, however, the effects of applied litter at multiple rates and years were examined, thus revealing the dynamic impacts on soil properties. Hay yields increased with the increase of years of PL application, regardless of the applied rate. This observation was consistent with previous observations that the labile phosphorus (P) portion in these soils increases with application years whereas total P increases with the cumulative applied PL amounts. Poultry litter application did not markedly affect soil electric conductivity, bulk density, or sodium (Na) or potassium (K) levels, especially at the soil surface (0–20 cm). Soil pH, carbon (C), C/nitrogen (N) ratio, calcium (Ca), and magnesium (Mg) were profoundly affected at all three soil depths (0–20, 20–40, and 40–60 cm). Most soil parameters analyzed in this study reached peak values with 10–15 years 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 macrocations were altered positively as a result of accumulative functions. Continuous litter application may negatively alter a soil’s capacity to retain macrocations, 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. Our observation suggested that best management practices for land application of PL should take into consideration the different effects of PL application history