Animal manure reduces aluminum toxicity in an acid soil

Manures are believed to be an effective treatment to reduce Al toxicity in acidic soils. A pot experiment was conducted to study the effect of feedlot manure (FM) and poultry litter (PL) on soil Al status and wheat growth. Custer, an acid susceptible wheat cultivar (Triticum aestivum L. var. Custer), was planted in a manure amended Teller (fine-loamy, mixed, thermic Udic Argiustoll) fine sandy loam soil and relationships between soil pH, organic carbon (OC), and Padded in the manure, 0.01 mol L-1 CaCl2 extractable Al(Al-CaCl2), 1.0 mol L-1 KCl exchangeable Al(Al-KCl), and wheat growth were investigated. An acidic surface soil was mixed with five levels of FM and PL and incubated for 30 d in an environmentally controlled growth chamber before wheat was planted. Wheat was grown for 35 d and harvested for aboveground dry matter. Both PL and FM increased soil pH, reduced Al-CaCl2 and Al-KCl, and increased wheat biomass. Wheat biomass was positively correlated with soil pH (r = 0.76), OC added (r = 0.63), and P2O5 added (r = 0.87) but was negatively correlated with Al-CaCl2 (r = -0.83) and Al-KCl (r = -0.87). Path analysis showed significant direct effects (p < 0.01) between wheat growth and OC added and P2O5 added. The direct effects of soil pH, Al-CaCl2, and Al-KCl were not significant (p > 0.05) but the indirect effects of OC added and P2O5 added were important contributors to the correlations between wheat biomass and soil pH, Al-CaCl2, and Al-KCl. These two animal manures have the potential to reduce Al toxicity in acidic soils but need to be further evaluated at a field scale.