Abstract:The wheat (Triticum aestivum L.) and maize (Zea mays L.) straws are often returned to the field directly in the typical fluvo-aquic soils of the Huanghuaihai Plain, however, it is unclear whether the microorganisms that drive the straw decomposition in fluvo-aquic soils of different textures are related to the nutrient contents in the residual straws. In this study, a 10-month field decomposition experiment of wheat and maize straws with nylon bag method was conducted in fluvo-aquic soils of sandy, loam and clayey textures, the decomposition ratios of straws, the nutrient contents and the microbial community compositions in the residual straws were measured and their differences were compared and analyzed. The results showed that both the decomposition ratios of wheat and maize straws were increased with increasing clay content. The decomposition ratios of wheat and maize straws were 73.66% and 75.43%, 74.19% and 76.63%, 77.68% and 78.05% in soils of sandy, loam and clayey textures (P<0.05), respectively. The average nitrogen (N), phosphorus (P) and potassium (K) contents in wheat straws were 12.0%, 34.4% and 16.7% lower than those in maize straws (P<0.05), respectively, but there was no significant difference in carbon (C) contents between wheat and maize straws. The contents of C, N and K in wheat and maize straws were not influenced significantly by soil texture, but P content significantly increased with increasing clay content. The phospholipid fatty acid (PLFA) analysis showed that no significant differences in the populations of bacteria, fungi and actinomycetes were observed between wheat and maize straws. The population of gram-positive bacteria (G+) in wheat straws was 20.26% lower than that in maize straws, while the population of gram-negative bacteria (G-) in wheat straws was 16.35% higher than that in maize straws (P<0.05). Meanwhile, G+/G-, fungi/bacteria, monounsaturated fatty acids/saturated branched fatty acids were significantly different between wheat and maize straws. The average populations of bacteria, fungi and total PLFA in wheat and maize straws in the clayey fluvo-aquic soil was 25.1%, 30.3% and 22.9% lower than those in the sandy one (P<0.05), but the population of actinomycetes in the former was 93.8% higher than that in the latter (P<0.05). Redundancy analysis (RDA) showed significantly difference was existed in microbial community compositions between wheat and maize straws, which may be attributed to the differences in G+ and Gpopulations, among of which, the microbial community composition in wheat straws were mainly influenced by the ratios of C/N, C/P and C/K, while that in maize straws were mainly influenced by N, P, K content and decomposition ratio, suggesting different nutrient parameters that affected the microbial community compositions in wheat and maize straws.