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Straw return is an effective strategy to alleviate soil-borne diseases. Though watermelon Fusarium wilt is a severe soil-borne disease, the effect of wheat straw on the disease remains unclear. Thus, we investigated the effects of wheat straw on soil bacterial and fungal communities by adding wheat straw to consecutive watermelon soil in the greenhouse condition. The microbiome changes were further investigated using network analysis based on 16S rDNA and internal transcribed spacer deep sequencing. Wheat straw addition increased the fungal community diversity, whereas the bacterial diversity was not affected. Compared to the control group, the relative abundance of some bacteria, including Actinobacteria , Chloroflexi , and Saccharibacteria , was increased with wheat straw addition. For fungi, the relative abundance of Fusarium was decreased with wheat straw addition. Microbial network analysis demonstrated that the fungal community has a more complex connection than the bacterial community. In addition, redundancy analysis indicated that the Fusarium genera were significantly related to the disease index. Taken together, the addition of wheat straw might affect the microbial community through increasing the relative abundance of phylum Actinobacteria , decreasing the relative abundance of Fusarium, and increasing the fungal network complexity to enhance the defense of watermelon against Fusarium wilt disease.

Soil C‐N‐P stoichiometry offers an effective way to explore the balance, limitation, cycling, and distribution of chemical elements in Chinese fir plantations. This research aimed to explore how soil organic C (Corg), total N (Ntot), and total P (Ptot) contents and stocks, together with their stoichiometric ratios vary with stand age (3, 9, 17, and 26 years) as well as soil layer (0–10, 10–20, 20–30, and 30–40 cm) at aggregate scales in Chinese fir plantations from Guangxi, China. For Chinese fir plantations of diverse ages, soil aggregate stability, Corg, Ntot, and Ptot contents and stocks, together with C/N, C/P, and N/P ratios, remarkably declined when soil depth increased. Stand age could influence C‐N‐P stoichiometric characteristics in soil, but such effect was more obvious in soil depth of 0–30 cm in comparison to that of 30–40 cm. In 0–30 cm soil layer, Corg and Ntot contents and stocks, together with C/P and N/P ratios, first rose and then reduced during Chinese fir planting; meanwhile, the highest levels could be observed in the 17‐year‐old Chinese fir plantations. However, Ptot content and stock, together with C/N ratio, were not related to the stand age. Overall, the present research helped to understand soil C, N, and P dynamics within a chronosequence of Chinese fir plantations. Also, it provided supplementary information for soil ecological stoichiometry in global terrestrial ecosystems.

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