Soil-carbon sequestration and soil-carbon fractions, comparison between poplar plantations and corn crops in south-eastern Spain

The potential of soils as a sink of atmospheric carbon and the implications related to mitigate greenhouse-gas emissions are well recognized. The raising of tree crops on agricultural soils can augment soil-carbon sequestration more than do other agricultural uses such as corn crops. Thus, 6 plots with different durations of use as poplar plantation (5, 10, 20, 30, 50, and 100 years) were studied in comparison with 6 adjacent plots with corn crop. The carbon pool in poplar-plantation soils was positively correlated to the time of use at the three soil depths studied (0–20, 20–50, and 50–100 cm), the mean annual increase being 1.16 Mg C ha−1 year−1. Poplar-plantation soils also increased the total carbon content in a more effective way because the duration of use was also correlated with the most recalcitrant carbon forms. Therefore, land-use change from corn crops to poplar-plantation soils is economically profitable as well as positive both for the total organic-carbon pool as well as for the efficiency of carbon sequestration by the increase of non-oxidizable forms in the soil.

► Poplar crops on agricultural soils can augment soil-carbon sequestration more than do other row crops.
► Carbon pool in cultivated poplar soils was positively correlated to the time of use.
► Total carbon content increased in a more effective way (recalcitrant carbon forms).
► This use constitutes a profitable alternative both economically as well as environmentally.