Long‐Term Tillage and Cropping System Effects on Chemical and Biochemical Characteristics of Soil Organic Matter in a Mediterranean Semiarid Environment

Several studies have reported how tillage and cropping systems affect quantity, quality, and distribution of soil organic matter (SOM) alongthe profile. However, the effect of soil management on the chemical structure of SOM and on its hydrophobic and hydrophilic componentshas been little investigated. In this work, the long-term (19 years) effects of two cropping systems (wheat monoculture and wheat/faba beanrotation) and three tillage managements (conventional, reduced, and no tillage) on some chemical characteristics of SOM and theirrelationships with labile carbon (C) pools were evaluated. Soil samples were taken from the topsoil (0–15 cm) of a Chromic Haploxerert(central Sicily, Italy). After 19 years of different tillage and cropping systems management, total organic C significantly differed amongtreatments with the labile organic C pools showing the greater amount in no till and in wheat/faba bean plots. Hydrophobic and hydrophiliccomponents of SOM, determined by diffuse reflectance infrared Fourier transform spectroscopy, were mainly affected by cropping system,whereas aromatic components of SOM by tillage. Soil organic matter components and characteristics showed significant correlations with thesoil biochemical parameters, confirming the expected synergism between chemical and biochemical properties. This study demonstrated that(i) no tillage and crop rotation improve the chemical and biochemical properties of SOM of Vertisols under semiarid environment; and (ii)tillage management and cropping systems have affected, after 19 years, more the chemical and biochemical properties of SOM than itsquantity.