Mr. Carter et al., SIMULATION OF SOIL ORGANIC-CARBON AND NITROGEN CHANGES IN CEREAL AND PASTURE SYSTEMS OF SOUTHERN AUSTRALIA, Australian Journal of Soil Research, 31(4), 1993, pp. 481-491
Maintenance and improvement of soil organic matter levels is an import
ant concern in dryland farming systems of temperate regions. The Centu
ry soil organic matter model was used to simulate changes in soil orga
nic C and total N under long-term wheat (Triticum aestivum L.) and pas
ture rotations at five sites in southern Australia. Average declines i
n soil organic C and total N of 14 and 10%, respectively, in continuou
s and wheat-fallow systems over a 10 to 20 year period were closely si
mulated by the model at each site. Additions of N fertilizer (80 kg N
ha-1), which prevented soil organic matter decline in continuous wheat
systems, was also well represented by the model. Trends in soil organ
ic matter under long-term legume pasture were not adequately simulated
by the model, probably due to the 'annual' nature of subterranean clo
ver (Trifolium subterranean L.) in dry seasons and subsequent changes
in the ratio of live to dead plant biomass and shoot to root ratios. O
verall, the study emphasizes the importance of adequate total plant C
production to prevent a decline in soil organic C.