Long-term effects of different arable cropping systems on surface erosion processes and C-factor in hilly Mediterranean environment

Soil erosion is an environmental threat strongly amplified by agricultural activity and, in the last decade, by climate change; it affects many European countries and in particular Italy. Water erosion is currently considered the most important cause of soil degradation. The vegetation cover represents a natural soil protection against water erosion phenomena as it reduces the rainfall impact energy, hinders surface runoff and promotes soil infiltration. For these reasons, identifying appropriate crop systems able to reduce soil loss is a key issue for proposing economical solutions in management planning. This work reports the results of a long-term study (12 years) aimed at determining the vegetation cover effectiveness, diversified by structure and duration of the crops in rotation, and the soil tillage impact on erosion and surface runoff. The C-factor determination, without resorting to very detailed measures, is provided by the indirect application of Universal Soil Loss Equation (USLE). Five different soil managements were included in this study. Four experimental plots were cultivated with different cropping systems and intensification tillage degree (CS), and a standard plot (SP) maintained in bare conditions by up and down slope tillage operations. The annual value of soil loss, calculated as mean for the five treatments, was 35.84 t ha-1, and ranged between 4.11 and 72.07 t ha-1. The results showed that CS4 and CS1 presented, on average, the lowest soil loss values of 9.38 and 13.93 t ha-1, respectively. The soil conservative management (minum tillage, strip tillage, shredded crop residues and grassy crops) allowed, in these two CS, to reach, on average, a soil cover degree (≥ 50 %) for 260 and 210 days and to obtain a C-factor of 0.12 and 0.14, respectively. In the CS3 (mixed conservative and conventional) with a soil cover degree ≥ 50 % for 182 days and a C-factor of 0.19, the soil loss was equal to 18.65 t ha-1. The conventional farming system (CS2) recorded an average value of soil loss of 55.04 t ha-1 with a maximum value of 138.20 t ha-1 in 2015/16; this CS also presented the lowest number of days (135) with a land cover level ≥ 50 % and the highest C value (0.50). The analysis allowed consolidating previous information and identifying strategies to be adopted in the Mediterranean hillside environment to significantly reduce soil losses due to water erosion.