The role of hydraulic lift and subsoil P placement in P uptake of cotton ('Gossypium hirsutum' L.)

Hydraulic lift can be a desirable characteristic for cotton growing in areas that experience frequent drying of the topsoil. This study employed specialized soil columns to test if cotton can hydraulically lift water and whether this hydraulically lifted water can facilitate P acquisition from the dry topsoil of a clay and a sandy soil. The role of subsoil P placement on cotton growth was also tested. By using a Theta probe, hydraulic lift was detected in the clay soil for 7 days after water was withheld from the topsoil. However, in the sandy soil, a significant overnight increase in soil water was only detected for one day for the treatment with subsoil P application. Where P was applied to the topsoil, and water was withheld, cotton roots showed significant root P uptake from the sandy soil, but negligible P uptake from the clay soil. Irrespective of topsoil watering, the higher root length density in the subsoil of the clay soil accounted for the pronounced response to deep P placement. This study demonstrated that soil texture affects the amount and longevity of hydraulic lift from cotton roots. Hydraulic lift detected in the clay soil did not aid P acquisition from dry surface soil by cotton plants

Australian native plant species Carpobrotus rossii (Haw.) Schwantes shows the potential of cadmium phytoremediation

Many polluted sites are typically characterized by contamination with multiple heavy metals, drought, salinity, and nutrient deficiencies. Here, an Australian native succulent halophytic plant species, Carpobrotus rossii (Haw.) Schwantes (Aizoaceae) was investigated to assess its tolerance and phytoextraction potential of Cd, Zn, and the combination of Cd and Zn, when plants were grown in soils spiked with various concentrations of Cd (20-320 mg kg(-1) Cd), Zn (150-2,400 mg kg(-1) Zn) or Cd + Zn (20 + 150, 40 + 300, 80 + 600 mg kg(-1)). The concentration of Cd in plant parts followed the order of roots > stems > leaves, resulting in Cd translocation factor (TF, concentration ratio of shoots to roots) less than one. In contrast, the concentration of Zn was in order of leaves > stems > roots, with a Zn TF greater than one. However, the amount of Cd and Zn were distributed more in leaves than in stems or roots, which was attributed to higher biomass of leaves than stems or roots. The critical value that causes 10% shoot biomass reduction was 115 μg g(-1) for Cd and 1,300 μg g(-1) for Zn. The shoot Cd uptake per plant increased with increasing Cd addition while shoot Zn uptake peaked at 600 mg kg(-1) Zn addition. The combined addition of Cd and Zn reduced biomass production more than Cd or Zn alone and significantly increased Cd concentration, but did not affect Zn concentration in plant parts. The results suggest that C. rossii is able to hyperaccumulate Cd and can be a promising candidate for phytoextraction of Cd from polluted soils

Modified fungal diversity in dense clay subsoils after deep-banding organic substrate

Context. Deep-banded nutrient rich amendments can overcome crop productivity constraints of Australian dense clay subsoils. However, knowledge on essential microbial community in field trials is limited. Methods. We examined subsoils that had been deep-ripped 2 years earlier with various types of amendments (organic, a blend of organic and inorganic, and purely inorganic). Subsoil samples (15–25 cm) were collected encompassing the amendment band (0 cm), as well as at increasing distances from it (14 and 28 cm). Bacterial 16S rRNA, fungal ITS amplicon sequencing, and SOM/TOC measurements on amendment band samples were done to assess microbial communities. Key results. While no variations were detected in bacterial communities across treatments, soils enriched with organic substrates diverged significantly in fungal diversity compared to the control, concentrated primarily within the amendment bands. Fungal response to these organic amendments was primarily dominated by an enrichment of filamentous saprotrophic fungi. Conclusion. Changes in fungal diversity and the enrichment of saprotrophic fungi is primarily attributed to the introduction of organic substrates into the subsoil. However, despite the absence of SOM/TOC differences between treatments, SOM/TOC levels were initially expected to rise in response to organic amendments. Consequently, variations in fungal communities may have initially arisen from heightened SOM/TOC levels but persisted even as these levels returned to baseline, suggesting a lasting legacy effect. Implications. A single application of deep-banded organic amendments was effective in enriching agriculturally significant fungi within dense clay subsoils after 2 years. This can further aid crop productivity by fostering soil structural improvements and optimising nutrient cycling, even after the organic amendments are undetectable