Stronger effect of maize rhizosphere than phosphorus fertilization on soil phosphatase activity and associated bacterial communities in acidic soil: distinct influences on phoC- and phoD-harboring bacteria

Aims The bacteria phoC and phoD genes encode acid and alkaline phosphatase (ACP and ALP), respectively, which mineralize organic phosphorus (P) to inorganic P. The relative importance of P fertilization and the plant rhizosphere on soil phosphatase activities and associated bacterial communities in acidic soils are poorly understood; whether phoC- and phoD-harboring bacterial communities display different responses remains undetermined. Methods Maize was grown in acidic soil supplemented with 0 (P0), 20 (P20), and 200 (P200) mg P2O5 kg− 1 for 42 days. Maize biomasses, plant nutrients, soil properties, phosphatase activities, and associated bacterial abundance and community composition were determined. Results Relative to bulk soils, rhizosphere showed increased ACP and ALP activities, phoC and phoD gene abundance, but these effects were reduced in strength with P200 treatment, except for phoC gene abundance. The rhizosphere effect increased α-diversity of phoC-harboring bacteria under P fertilization but reduced α-diversity of phoD-harboring bacteria under P0 and P20 treatments. The rhizosphere significantly influenced both phoC- and phoD-harboring bacterial community compositions, with stronger effect on phoD-harboring bacteria; while P fertilization affected phoD-harboring bacteria but not phoC-harboring bacteria. Immigrated and extinct species play important roles in reshaping phoC- and phoD-harboring bacterial communities, respectively, in response to the rhizosphere effect. Conclusions Compared with P fertilization, the maize rhizosphere more strongly influenced soil phosphatase activities and phoC- and phoD-harboring bacterial communities in acidic soils, with phoD-harboring bacteria responding more strongly to the rhizosphere effect and P fertilization. Notably, the strength of the rhizosphere effect heavily relied on P fertilization level.

Enhancement of Soil Phosphorus Bioavailability by Arbuscular Mycorrhizae and Earthworms Through Regulating Soil Bacterial Community and Plant Nutrient Balance Under Salt Stress

Aims Soil salinization is an important factor limiting plant phosphorus (P) uptake and crop production. This study aimed to investigate the effects of arbuscular mycorrhizal fungi (AMFs) and earthworms in enhancing soil P bioavailability by regulating soil salt ions and altering the soil bacterial community under salt stress. Methods Treatments with or without earthworms and with or without AMFs in a high-salinity soil were applied. Results The results showed that the maize biomass and plant P, Ca and Mg contents were significantly increased by earthworms and AMF inoculation, and the highest plant P, Ca and Mg contents were observed with earthworm application alone. Earthworms and AMFs significantly decreased the soil stable inorganic P (hydroxyapatite) proportion and increased the soil available dicalcium phosphate proportion. AMFs significantly increased soil phosphatase activity and inorganic P fraction contents. Earthworms and AMFs significantly increased soil bacterial Chao1 and phylogenetic diversity. Structural equation model analysis showed that the most important driver of soil P mineralization was soil bacterial diversity, followed by soil Ca2+ and total salt concentration. Network analysis suggested that the response of bacteria to soil Ca2+ but not salt concentration positively correlated with soil P availability. Earthworms and AMFs could stimulate certain bacteria harbouring the phoX alkaline phosphatase gene to increase soil phosphatase activity and soil P availability. Conclusions In conclusion, earthworms and AMFs could enhance soil P bioavailability by stimulating soil P-cycling bacteria to activate soil stable inorganic P and by improving the plant cation nutrient balance under salt stress.

Contrasting responses of soil phosphatase activity to nitrogen and phosphorus loadings: Implications for phosphorus management

<p>Human activity has caused imbalances in nitrogen (+N) and phosphorus (+P) loadings of ecosystems around the world, causing widespread P limitation of many biological processes. Soil phosphatases catalyze the hydrolysis of P from a range of organic compounds, representing an important P acquisition pathway. Therefore, a better understanding of soil phosphatase activity as well as the underlying mechanisms to individual and combined N and P loadings could provide fresh insights for wise P management. Here we show, using a meta-analysis of 188 published studies and 1277 observations that +N significantly increased soil phosphatase activity by 14%, +P significantly repressed it by 30%, and +N+P led to non-significant responses of soil phosphatase activity. Responses of soil phosphatase activity to +N were positively correlated with soil C and N content, whereas the reverse relationships were observed for +P and +N+P. Similarly, effects of +N on soil phosphatase activity were positively related to microbial biomass C, microbial biomass C:P, and microbial biomass N:P, whereas reverse relationships were observed for +P. Although we found no clear relationship between soil pH and soil phosphatase activity, +N-induced reductions in soil pH were positively correlated with soil phosphatase activity. Our results underscore the integrated control of soil and microbial C, N and P stoichiometry on the responses of soil phosphatase activity to +N, +P, and +N+P, which can be used to optimize future P management.</p>

Effects of Solanum nigrum, Crassocephalum crepidioides and Bidens pilosa straws on the nutrients content of soil and grape seedlings under cadmium stress

In order to improve the nutrients absorption of grape seedlings under cadmium (Cd) stress, the effects of Solanum nigrum, Crassocephalum crepidioides and Bidens pilosa straws on the nutrients content of soil and grape seedlings under Cd stress were studied by pot experiment. According to the results, the activity of soil phosphatase, soil catalase and soil sucrose by soil application of straws observed higher than CK to varying degrees. And soil application of straws increased the contents of soil alkaline nitrogen and available phosphorus in different degrees, while soil application of B. pilosa straws decreased the content of soil available potassium. In addition, the soil application of straws had a certain promoting effect on the total nitrogen content, total phosphorus content and total potassium content of grape seedlings compared with the CK. Among all treatments, C. crepidioides straws maximized the nutrients content in the shoots of grape seedlings, which could provide reference for grape cultivation in Cd-contaminated areas.