Amending poultry litter with aluminum sulfate
(alum) reduces phosphorous (P) runoff and ammonia volatilization but its
effects on soil pH are not completely researched. Greenhouse pot experiments
with cotton (Gossypium hirsutum L.)
and soybean (Glycine max. L. Merr)
as test crops were conducted with a sandy loam (Fine-loamy, siliceous, semiactive, thermic Typic Paleudults) soil, that was adjusted to pH's of 4.5, 5.0,
5.5 and 6.5 using fine Ca(OH)2. The
objective was to determine if poultry litter amended with aluminum sulfate
(alum) or ferrous sulfate at 0, 10% and 20% by weight affected soil pH, soil
exchangeable aluminum and plant aluminum concentration when applied to meet N
requirement of the crop. Application of non-amended litter and litter amended
with 10% alum increased soil pH on all treatments. Application of litter
amended with alum or ferrous sulfate at 20% reduced soil pH and increased soil exchangeable
Al extracted with 0.01M CaCl2. The increase in soil exchangeable Al
and reduction in soil pH were greater for soils with pH of 4.5 and 5.0 than for
soils with higher pH. Amendments significantly increased shoot Al concentration
for plants grown in soil with pH of 4.5 and 5.0. The application of alum or
ferrous sulfate at higher rates to soils with pH less than 5.5 has detrimental
effects on the soil and plant and is of environmental concern.