Abstract

HELFRICH, M., FLESSA, H., LUDWIG, B.

J. Plant Nutr. Soil Sci., 173: 671-677 (2010)

Soil C dynamics below the plow layer have been little studied, despite a suspected large C-stabilization potential of subsurface horizons. The objective of this study was to test two simple models (model A. single compartment for C(3)- and for C(4)-derived C, model B: division of C(3)- and C(4)-derived C into active and passive compartments) in their ability to simulate the C dynamics in subsoil horizons of a Haplic Phaeozem after conversion from C(3) (rye) to C(4) cropping (maize). The models were calibrated on an unfertilized maize soil and then validated on a maize soil with NPK fertilization. Both models simulated well C(3)-C and C(4)-C dynamics in the investigated soil depths (20-40 cm and 40-60 cm) In all cases, the model efficiency EF was > 0, which indicated that the simulated values described the trend in the measured data better than the mean of the observations. However, we observed some inconsistency in the obtained parameter set (e.g., a higher proportion of passive C for C(4)-derived than for C(3)-derived C or a very low decomposition rate constant for passive C(4)-C in 40-60 cm), which we assume to result from data restrictions on the investigated soils. More detailed data on SOC pools and turnover rates in subsoils which are generally not yet available for most experimental plots is vitally needed-especially for applying more sophisticated C-dynamics models.