Location: Southeast Watershed ResearchTitle: Liming potential of poultry litter in a long-term tillage comparison
Submitted to: Soil & Tillage Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/8/2019
Publication Date: 10/30/2019
Citation: Mower, J., Endale, D.M., Schomberg, H.H., Norris, S.E., Woodroof, R.H. 2019. Liming potential of poultry litter in a long-term tillage comparison. Soil & Tillage Research. https://doi.org/10.1016/j.still.2019.104446.
Interpretive Summary: Soil pH, a measure of the concentration of hydrogen ions in soil water, is used as measure of relative acidity or alkalinity with pH 7 being neutral. Soil pH is measured on a logarithmic scale thus a change in pH of one unit indicates a 10-fold increase in the hydrogen ion concentration. Soil pH influences availability of plant nutrients as well as other ions that can negatively impact plants. Globally 40 to 50% of potentially arable land is acidic (pH less than 5.5) which impairs crop productivity potential. Most agricultural crops grow best in soil where the pH is above 5.5 and are negatively impacted below this pH. Soil pH buffering capacity is an indication of how resistant a soil is to pH changes due to external influences such as cropping system management. An indication of soil pH buffering capacity is determined from the amount of lime needed to raise soil pH by one unit and is called the Lime buffer capacity (LBC). ARS and Texas A&M researchers studied how long-term application of poultry litter (PL) influences soil pH buffer capacity. In a Georgia Cecil sandy loam soil, researchers grew cotton with winter wheat cover crop (6 years), corn with winter rye (5 years), and millet with winter rye (4 years) using conventional and no tillage (CT and NT) management. Fertilizer was either mineral inorganic (CF) or organic (PL). Changes in pH and LBC were compared among the four treatments CTCF, CTPL, NTCF, and NTPL. The CTPL treatments resulted in a 0.6 unit pH increase in the top 15 cm. All treatments resulted in some increase in pH in the subsoil. The cropping system affected soil pH and LBC more than tillage or fertilizer management. The researchers concluded that the effect of poultry litter on soil pH was dependent on the soil type as well as the cropping system.
Technical Abstract: Soil acidity is a constraint to global food security and access to limestone to correct this problem is limited in many parts of the world. Animal manures have been shown to have a liming effect on acidified soils but the effect may be moderated by tillage management. This study evaluated the effect on soil pH of conventional tillage (CT) vs no-till (NT) under chemical (CF) or poultry litter (PL) fertilizer sources on a Cecil sandy loam (1:1 kaolinitic) over a 15 yr period. Fertility management changed during this period based on crops grown: 6 yr cotton with a winter wheat cover crop, 5 yr corn with rye, and 4 yr millet with rye. Changes in soil pH, soil organic carbon (SOC), and lime buffer capacity (LBC) were compared among the CTCF, CTPL, NTCF, and NTPL systems. The CTPL management resulted in a 0.6 unit pH increase in the top 15 cm, however, cropping system had a greater effect on both soil pH and LBC than tillage or fertilizer management. All systems resulted in increases in subsoil pH. Lime buffer capacity remained unchanged at all but the 76-91 cm depth, where decreases ranged from 27 to 43 kg CaCO3 eq ha-1 pH unit-1 year-1. In contrast to previous findings, our results indicate liming effects of animal manures should be investigated in the context of soil type and cropping system to better understand the true mechanism(s) of soil acidity amelioration.