INTERRILL ERODIBILITY OF SOME OHIO SOILS BASED ON FIELD RAINFALL SIMULATION

Prediction of soil erodibility and an understanding of erosion processes are vital to sustained productive use of agricultural land. Interrill erodibilities (K(i)) of five Ohio soils were assessed and compared with predicted K(i) using the Water Erosion Prediction Project equation (WEPP-K). A portable rainfall simulator was used to apply almost-equal-to 70 mm h-1 intensity rain for 1 h on 0.75-m2 field plots representing crop row sideslopes. The soils studied included Miamian (fine, mixed, mesic Typic Hapludalf) and Riddles (fine-loamy, mixed, mesic Typic Hapludalf) silt loams, Crosby silt loam (fine, mixed, mesic Aeric Ochraqualf), Kokomo sility-clay loam (fine, mixed, mesic Typic Argiaquoll) and Mechanicsburg loam (fine-loamy, mixed, mesic Ultic Hapludalf). The value of K(i) determined for each soil was related to selected physical and chemical properties. Values of K(i) varied significantly between soils and ranged from 1.23 +/- 0.09 to 1.97 +/- 0.60 x 10(-6) kg s m-4. Interrill erodibility was negatively correlated with water-stable aggregates (WSA) > 0.25 mm (r2 = 0.50), WSA > 0.5 mm (r = 0.49), and organic C (r2 = 0.61), and positively correlated with Middleton's dispersion ratio (r2 = 0.84) and the ratio of water-dispersible clay to total clay (r2 = 0.70). The WEPP-K(i) differed from measured by almost-equal-to 10 to 40%, ranging from 1.1 to 2.0 kg s m-4. There was no correlation between WEPP-K(i) and measured K(i).