ARS | Publication request: SOIL AMENDMENTS TO DECREASE HIGH STRENGTH IN SE COASTAL PLAIN HARDPANS

Submitted to: Southern Conservation Tillage for Sustainable Agriculture Proceedings
Publication Type: Proceedings
Publication Acceptance Date: June 1, 2006
Publication Date: June 24, 2006
Citation: Busscher, W.J., Novak, J.M., Caesar-Tonthat, T.C., Sojka, R.E. 2006. Soil amendments to decrease high strength in SE Coastal Plain hardpans. Southern Conservation Systems Conference Proceedings, June 26-28, 2006, Amarillo, Texas, p. 142-149.

Technical Abstract: Southeastern Coastal Plain loamy sands often contain cemented subsurface hard layers that restrict root development. Soil properties are usually improved by tillage but can also be improved by adding soil amendments. Wheat and polyacrylamide (PAM) amendments were mixed into a Norfolk soil, a mix of 90% hard layer soil and 10% Ap horizon to assure microbial activity. Our hypothesis was that incorporation of wheat and PAM would improve soil physical properties, making the soil more amenable to root growth. Treatments contained 1 lb of soil, 6.44 lbs lb-1 wheat stubble, and 30 or 120 PPM of PAM; duplicate sets of treatments were incubated for 30 d and 60 d at 10% (w/w) water content. Treatments were leached with 1.3 pore volumes of water. After leaching and equilibration to stable water contents, soil strengths were measured with a .12-in diameter flat-tipped bench-top penetrometer. PAM formulation of 2.64 x 104 lbs mole-1 molecules, anionic, and 35% charge density decreased bulk density when added at the higher rate of 120 PPM of soil. The higher PAM rate also decreased the amount of water that was needed to maintain treatments at 10%. Both PAM and wheat amendments decreased penetrometer resistances and increased aggregation. Amendments improved soil physical properties, especially when the higher rate of PAM was used and when treatments were allowed to incubate for a longer period of time.