EFFECTS OF SURFACE-TREATMENT ON SURFACE SEALING, RUNOFF, AND INTERRILL EROSION

Surface treatment influences the nature and extent of seal/crust forma tion, which affects runoff and erasion. This study evaluated the effec ts and longevity of soil amendments, tillage, and screen cover on runo ff and interrill erosion on a Cecil sandy loam (clayey, kaolinitic, th ermic Typic Kanhapludult) under natural rainfall conditions. Six field plots (3.5 x 0.9 m) with a slope of 0.06-m m(-1) were used in the stu dy. Three treatments (control, screen covet; crust-breaking shallow ti llage) were studied in duplicate in the first two-month period, and an other three (control, anionic polyacrylamide (PAM), and phosphogypsum) in a subsequent five-month period. Total runoff and soil loss were 69 , 61, and 47 mm and 5.3, 1.6, and 4.3 Mg ha(-1) for the control, scree n cover, and tillage treatments, respectively. Compared with control, screen cover reduced soil loss significantly but not runoff while till age reduced runoff more than sail loss. Total runoff and soil loss for the control, gypsum, and PAM treatments were 146, 48, and 81 mm and 3 .1, 2.6, and 2.5 Mg ha(-1), respectively. Runoff was reduced by 67% an d 44% for the gypsum and PAM relative to control and soil loss by 16% and 19%, showing gypsum and PAM were more effective in reducing runoff than soil loss. Runoff was significantly reduced in the gypsum and PA M treatments in the five months following surface application. Results showed screen cover and tillage temporally reduced or delayed seal/cr ust formation, while the effects of gypsum and PAM were more persisten t Combined with earlier findings, it appears that a combination of phy sical and chemical treatments is the best practice for controlling sur face sealing and reducing runoff and erosion on this soil.