Analysis of soil carbon in Spanish agricultural soils. Relevant aspects in relation to the organic farming reconversion in the Mediterranean area

Abstract

Analysis of soil carbon in Spanish agricultural soils. Relevant aspects in relation to the organic farming reconversion in the Mediterranean area.

Organic carbon levels in agricultural soils are specially relevant in the management models based on the organic reserve of the soil. Losses of soil organic matter that occur associated to tillage practices can enhance, in some cases, soil degradation. This fact may be specially relevant in dry and semiarid climates. By analysing a soil data base of the Spanish forest and agricultural soils we discuss the distribution of C in the soil surface horizon across climates and land uses. In each climatic area, by comparing forest with agricultural soils we found that soils in semiarid climate show greater resistance to soil C losses and lower resilience than soils of wetter climates. This fact suggest that semiarid soils can be at or near soil degradation thresholds and thus its management should avoid any losses of soil organic matter.