Long-term effect of tillage, nitrogen fertilization and cover crops on soil organic carbon and total nitrogen content
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No-till practices, in conjunction with cover crops and nitrogen fertilization, have been shown to augment soil organic carbon content and total nitrogen content. However, interactions between these components in a no-till system are not well-known. This study offers a long-term (1993-2008) comparative analysis of conventional versus no-till practices as well as a some insight regarding the synergies between no-till, nitrogen fertilization, and cover crops. Maize, wheat, and sunflower comprised the crops studied. Treatments varied according to nitrogen fertilization rate, cover crop utilized, and the type of tillage. This study revealed that in a Mediterranean climate, conventional tillage requires higher nitrogen fertilization rates than no-till to conserve or increase soil organic carbon and total nitrogen. No-till practices were able to conserve soil organic carbon even without nitrogen fertilization and cover crops, while increases in soil organic carbon and total nitrogen were seen with use of fertilizers and low and high nitrogen supply legume cover crops. It was concluded that conventional tillage could only achieve these outcomes with elevated fertilization levels and highly productive cover crops, presenting issues for low-input smallholder farmers running integrated operations with grazing animals.