Soil Organic Carbon Storage Is Distinguished from Semiarid and Humid Climates Under Grain Cereals Cultivation.

The distribution of cereals crops in Chile cover a wide range of climate regions, from the semiarid climates in the NorthCentral region to the humid temperate climates in the South. These crops are of great importance in Chile, and cover most of the agricultural land. On the other hand, previous studies have demonstrated that the changes in soil organic carbon (SOC) stocks are mainly explained by the climate, land use and management, and soil type. Our previous research in the Chile's semiarid region have shown that SOC stock has decreased up to 50% in the last three decades. Interestingly, in the South region SOC contents have almost not been impacted. In this study, we analyzed a series of Andisols from the southern region, derived from volcanic ash with a low bulk density, high aggregate stability, and high SOC content (up to 13%). Therefore, the objective of this study was to evaluate the SOC changes between year 1980 and 2016 as a function of the climate condition and crops cultivation. With this purpose we used the Rothamsted Carbon model (RothC) with 36 years of actual climate, soil properties, management, and yield records. The RothC model performed well, but tends to underestimate the carbon stocks in areas with humid climate and in soils with higher carbon content. In order to overcome this limitation, a water aggregates stability (a soil physical property) was used to fit the modeled carbon data to the measured ones. In addition, our results showed that the cereal crops have a different impact soil carbon stocks depending on the climate conditions. These and other related findings are discussed in this paper as the increments in soil carbon stocks in cereal crops are highly limited in semiarid environments and in response to climate change scenarios.