Soil processes as affected by replacement of natural mesquite ecosystem with maize crop

Abstract

Abstract In the central highlands of Mexico, the vege­ tation is dominated by mesquite (Prosopis spp.), a legu­ minous tree or shrub. An experiment was carried out to investigate how cultivating the land and the disappear­ ance of the natural ecosystem affected the biological functioning of the soil. Soil was sampled from under the canopy of isolated (MESO treatment) and densely growing mesquite trees (DENS treatment), from the surrounding soil not covered by the canopies of the trees (BARE treatment) and from adjacent land culti­ vated with maize (ARABLE treatment). Soil was char­ acterized and then incubated aerobically for 39 days at 22 ± 1oc and C02, N20 production , microbial biomass C and inorganic N concentrations were monitored. The organic C content was 2.3 times and 1.1 times greater in the MESO and the BARE treatments, respectively, than in the ARABLE treatment, while microbial bio­ mass C was 3.5 times and 1.3 times greater. The micro­ bial biomass activity as expressed by C02 production was 5.9 times and 3.9 times greater in the MESO and the BARE treatments, respectively, than in the ARA­ BLE treatment, while N mineralization, as witnessed by the increase in N03 - concentrations, was 3.4 times and 1.7 times greater. No significant amounts of N20 were produced in any of the treatments. It was found that cultivating land characterized by the presence of mesquite changed its characteristics profoundly, and even soil not covered by tree canopies had higher microbial biomass C, and C and N mineralization than soil culti­ vated with maize and beans.