Organic and inorganic amendments did not affect microbial community composition in the bulk soil differently but did change the relative abundance of selected taxa

Abstract

Deep placement of organic amendments such as poultry litter and legume residues has been developed as a technique to ameliorate sodic clay subsoils in the south‐east Australian cropping region. It has been suggested that the soil microbial community plays a key role in this process of subsoil amelioration. A controlled environment experiment using repacked soil units was conducted to investigate changes in the microbial communities of subsoil treated with organic and inorganic amendments. Poultry litter, inorganic nutrients and wheat straw plus inorganic nutrients with equivalent total nutrient content (460 kg N ha−1, 210 kg P ha−1 and 330 kg K ha−1) were mixed into a central band and incubated for 21 days, followed by 126 days with wheat plants. Changes to bacterial and fungal communities in the bulk subsoil, 2–7 cm from the amended band, were assessed using next‐generation amplicon sequencing of the 16S and ITS rRNA genes. There were small but significant (p < 0.05) changes in bacterial and fungal community structure of the amended treatments, relative to the unamended control, which were linked to the movement of solutes away from the amended band. The three amendments did not affect microbial community composition differently in the bulk soil, although there were changes in the relative abundance of selected taxa. Our results suggest that changes in soil microbial communities in the bulk subsoil in this experimental system largely depended on movement of the soil solution through the profile. Highlights We characterized effect of amendments on microbial communities in the soil beyond the detritusphere. Microbial community of bulk soil was different in amended treatments from the unamended control. Amendments did not affect community composition differently but did change relative abundances of certain taxa. Changes in microbial community structure were due to movement of soil solution away from the amendment.

Combined application of soluble organic and chemical fertilizers in drip fertigation improves nitrogen use efficiency and enhances tomato yield and quality

“…The reason may be that SOSC had the advantages of organic and inorganic fertilizers simultaneously. Plants can use the inorganic nutrients in liquid form instantly 41 . Nitrogen, however, is not able to be immediately available for plant uptake until mineralization in organic cropping system, although organic fertilizers can increase soil particle and soil aggregates and improve N fixation ability of soils 42 .…”

“…Plants can use the inorganic nutrients in liquid form instantly. 41 Nitrogen, however, is not able to be immediately available for plant uptake until mineralization in organic cropping system, although organic fertilizers can increase soil particle and soil aggregates and improve N fixation ability of soils. 42 This phenomenon indicated that it had a positive impact on reducing soil nutrient losses and increasing plant nutrients utilization to substitute the mineral fertilizers partially or completely with organic fertilizers.…”

Bacterial community shifts occur primarily through rhizosphere expansion in response to subsoil amendments

“…Studies have determined that the use of DBAs facilitate increases in bacterial abundance as well as changes in community‐level composition (Celestina, Sale, Hunt, et al, 2019; Celestina, Sale, Tang, & Franks, 2019; Celestina, Wood, Manson, et al, 2019; Wang et al, 2020). However, when the plant growth response is considered, soil bacteria likely respond to DBAs via direct and indirect mechanisms.…”

“…The direct response is primarily governed by bacteria responding to DBA increased nutrient availability, altered C and N source availability and decreased soil pH (Leff et al, 2015; Wang et al, 2020). However, as the amendment source is deep banded, and not mixed within the subsoil, a significant distance‐dependent effect is likely, with a greater bacterial response expected within the DBAs detritusphere compared to the bulk soil (Celestina, Sale, Tang, & Franks, 2019; Kuzyakov & Blagodatskaya, 2015). This is hypothesised to be driven by higher nutrient concentration and more pronounced soil physicochemical modifications immediately surrounding the DBAs.…”

Editorial for soil organic matter 2019 special issue

“…Xiao et al () used a pulse‐labelling approach to reveal that N fertilization increased belowground C in paddy rice systems that was confined to the root biomass and rhizosphere, particularly in the early growth stages. The paper by Celestina, Sale, Tang, and Franks () reports how organic and inorganic amendments, applied principally to ameliorate sodic soils, can affect the microbial community in the surrounding bulk soil, suggesting the migration of nutrients away from their source. Lee, Hwang, Park, Kim, and Lee () report that the use of film mulching, used to increase crop yields by improving soil moisture and temperature condition, increased the respiration of C and hence potential loss of SOM.…”