RESUMEN
Increasing soil organic matter (SOM) is one purpose of applying manures to soils, but soil-applied manures decompose and disappear in a short time, leaving very little trace as SOM. The objective of this study was to test and identify agricultural and industrial products and by-products (PBPs) that reduce the speed of manure decomposition and, potentially, increase SOM. Raw poultry litter (PL) was amended with selected PBPs (15% fresh weight) and incubated for 1-3 mo. Unamended PL lost an average of 19% of its dry weight after 1 mo incubation and 24% of its dry weight after 3 mo. Monitoring the CO2 release during a 1-mo incubation revealed that decomposition and weight loss of unamended PL is greatest in the first 2 d. Amending PL with Al2 (SO4 )3 · 18H2 O and CaO reduced cumulative CO2 release and final dry biomass loss during the incubation period of 1-3 mo. Amending PL with Al2 (SO4 )3 · 18H2 O reduced PL temperature by up to 14 °C and pH by â¼4.0, whereas CaO elevated its temperature by up to 24 °C and pH by â¼4.0. Both products suppressed total culturable bacteria and reduced dehydrogenase activity soon after mixing. Amending PL with flue gas desulfurization gypsum, CaCO3 , cement kiln dust, or biochar either enhanced or had no effect on suppressing litter decomposition. Our results overall show that the decomposition of PL and possibly other manures may be slowed and that the soil-residence life of manure C may be increased using PBPs that raise or lower manure pH and temperature.