Influence of organic amendments on soil structure and soil loss under simulated rain

The influence on soil properties and soil loss under simulated rain, of four organic by-products (cotton gin crushed compost (CCGC), by-product obtained after the two-step olive oil extraction process (BOO), sewage sludge (SS) and organic municipal solid by-product (MSW) applied annually at 10,000 kg organic matter ha−1, was studied over 4 years on a Typic Xerofluvent under dryland conditions near Sevilla (Spain). All organic by-product treatments reduce bulk density, aggregate instability and soil loss. The CCGC and BOO treatments had similar effects and were more effective than SS and MSW treatments. Compared with the control (no organic amendment) treatment, CCGC and BOO treatments reduced bulk density by 20% and 19%, respectively, aggregate instability by 33% and 28%, respectively, and soil loss under simulated rain at 140 mm h−1 by 32% and 30%, respectively. Compared with the control treatment, the SS and MSW treatments reduced bulk density by 12% and 9%, respectively, aggregate instability by 16% and 14%, respectively, and soil loss under simulated rain at 140 mm h−1 by 23% and 19%, respectively. The stronger effects of CCGC and BOO might have been because they had humic acid contents than SS and MSW.