Key points are not available for this paper at this time.
Two agricultural soil microbial communities were analyzed using phospholipid fatty acid (PLFA) analysis to identify coarse differences between community compositions after a 3-year nitrogen (N) rate study on cotton followed by a rotational cereal crop. The soils studied were a Wasco sandy loam and Panoche clay loam. The study compared the influence of soil type, soil N levels, and how rotation crops affected soil microbial biomass. Principal component analysis of the PLFA signatures indicated that microbial communities were significantly different between the two soil types after 3 years of similar management and cotton residue inputs. The Panoche soil showed a greater total microbial biomass than the Wasco soil. Phospholipid fatty acid biomarker results showed that the Panoche soil was characterized by a fungal population, and the Wasco soil showed evidence of a bacterial composition. The observed microbial response to different soil N levels was negligible, but crop yields were highly responsive to N treatments. Cereal rotations after 3 years of cotton produced a substantial increase in microbial biomass, but did not alter the community composition of either soil. Results suggested that microbial communities found in the two soils responded to changes in residue inputs from subsequent crop rotations by increasing total microbial biomass, but community composition was not influenced by changes in crop type or N additions. Based on the results of this study, soil texture had a more decisive role in soil microbial composition and consequent microbial activity than N fertilization or different rotational crops after 3 years of similar management.
Roberts et al. (Tue,) studied this question.