Physical Effects of Organic Matter Amendment of a Southeastern US Coastal Loamy Sand

Abstract

We tested 12 organic sources as amendments for E horizon and a mixture of E and Bt horizons of a southeastern coastal loamy sand. Amendments were intended to increase carbon and improve soil physical properties. Amendments included biochar, cellulose, corn (Zea mays L.) stalk, corn starch, cotton (Gossypium hirsutum L.) hull, cotton meal, manure residual, peanut (Arachis hypogaea L.) hull, poultry litter, soybean (Glycine max L. Merr.) plant, wheat (Triticum aestivum L.) straw, and wood shavings. Amendments were added at a rate of ∼1% (wt wt−1) or ∼22 Mg ha−1 organic carbon content to 450 g soil and incubated in a laboratory for 60 days. Cellulose, corn stalk, and corn starch amendments had the most dry-sieved aggregation at 35% versus the control, peanut hull, poultry litter, wood shavings, and biochar, which had the least at 21%. Biochar, wood shavings, and corn starch–amended treatments had the highest penetration resistances at 0.25 to 0.38 MPa above the mean; cellulose and cotton meal had the lowest at 0.24 to 0.32 MPa below the mean. Poultry litter and manure residual–amended treatments needed the least amount of water added to maintain 0.1 (wt wt−1); cellulose, biochar, and soybean plant needed the most. All needed less than the control. Mixing Bt horizon into the E improved most physical properties. All amendments improved some physical properties—more carbon, more aggregation, or reduced soil penetration resistance. Biochar retained 26% of its carbon, more than other amendments that retained 13% to 23%.