Carbon variability in the soil of a rice field in Costa Rica

Knowledge of the soil carbon stock (SCS) is vital for appropriate farming practices management, ie. tillage and to monitor SCS changes as mitigation strategies of carbon footprint. This study aims to quantify the variability and spatial distribution of the SCS. In an area of 1 ha 45 micro-pit (1 x 0.8 x 1 m) were divided into four strata. Vertical distribution of soil carbon was quantified along with other chemical and physical soil properties that affect rice production in Parrita, Costa Rica. A map of spatial prediction of the distribution and goodness-of-prediction values were calculated to estimate the effectiveness of the SCS prediction when different numbers of sampling points were used 45, 27, 15 and 7 microplots. As accurate measurements, the Mean Absolute Error and the Mean Square Error were calculated. In this study, the SCS was 85.8 (±2.6) Mg C ha-1, into the total profile (0-100 cm), where the first 30 cm represented 46.2%. Prediction of the spatial distribution suggests that in annual agricultural crops, with tillage systems 15 sampling points ha-1 a can effectively estimate the SCS.