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 P added in the manure, 0.01 mol L −1 CaCl 2 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 P 2 O 5 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 P 2 O 5 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 P 2 O 5 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.