Field application of PAM as an amendment in deep-tilled US southeastern coastal plain soils

In sandy soils of the southeastern USA coastal plains, crop production is limited by low water holding capacity and compacted soil layers that reduce root growth and productivity. Polyacrylamide (PAM) was added to sandy coastal plain soils to improve physical properties and yield. Soils were amended with linear and cross-linked PAMs. Treatments and controls included the following: (1) spraying a 600 mg kg−1 solution of linear PAM behind a subsoil shank at a rate of 3.93 kg ha−1, (2) spraying a 100 mg kg−1 solution at 0.66 kg ha−1, (3) spraying only water at 13.1 m3 ha−1, (4) dropping a dry PAM powder formulation (3005 KB) behind a subsoil shank at 300 kg ha−1, (5) dropping another dry PAM powder formulation (3005 K2) at 230 kg ha−1, (6) dropping a dry PAM powder formulation 3005 K2 at a lower rate of 55 kg ha−1, (7) applying nothing behind a subsoil shank, and (8) not subsoiling. In each of the 3 years of the experiment, new sets of treatments were set up while the old ones were maintained to look at longevity of the PAM effect. Though treatment effects were dominated by the tillage, the cross-linked PAMs were the only treatments more effective than tillage alone. The cross-linked PAMs may have been more effective because we could add more in dry form than in the spray form. The effect diminished with time similar to or faster than the results seen in tillage only. Though some PAM applications may have reduced cone indices, yields were not affected.