Spatial variation of soil carbon stability in sugarcane crops, central-south of Brazil

Abstract

The decay constant (k) of soil organic carbon can be used in the decision making of soil management practices and it is an indicative of the spatial variability of soil carbon stability, which depends on the interactions of physical, chemical and biological factors within agroecossystem. The aim of this work was to determine the spatial variability structure of soil carbon losses, expressed by the factor k, and its relationship with the soil attributes in sugarcane crops, in the central-south region of Brazil. The experiments were carried out in areas of commercial sugarcane plantations, in the cities of Motuca (MOT), Guariba (GUA) and Pradópolis - SP (PAD), in the State of São Paulo, and Aparecida do Taboado (APT), in Mato Grosso do Sul. The measurements of soil CO2 emission (FCO2) were recorded in the areas of study by the LI-COR system (LI-8100). The multivariate approach indicated that the two principal components (PC1 and PC2) explained around 55% to 68% of the total variability contained in the dataset in the areas studied, respectively. The soil physical attributes showed discriminatory power within PC1 and indicated a contrast between air-filled pore space and soil water content. In PC2, the chemical attributes indicated a joint action of the cations exchange capacity and available phosphorous content. PAD and APT areas presented negative and significant spatial patterns between factor k and PC1. For the spatial patterns between k and PC2 in GUA and APT, values with negative and significant correlations occurred. The results indicate that the soil carbon accumulation potential presented high spatial variability on a small scale; thus, in the same area, there were changes in the spatial patterns of factor k, presenting regions with potential accumulations or sources of carbon in the system of cultivation of raw cane, being able to be carried out the specific management in the same productive area.