No abstract

No abstract

Biochar amendment to soil has the potential to improve soil quality and increase crop yield. Arbuscular mycorrhizal fungi (AMF) provide beneficial plant services of stress alleviation with respect to phosphorus (P) deficiency and drought. The aim of this study was to explore interactive effects of biochar with AMF, P fertilization levels and irrigation strategies on growth of potato plants. Potato plants were amended with wood biochar of 0.74 % w/w (B+) or not (BÀ), fertilized with phosphorus of 0.11 mg P g À1 soil (P1) or not (P0), irrigated with full irrigation (FI) or partial root-zone drying irrigation (PRD) and inoculated with AMF of Rhizophagus irregularis (M+) or not (MÀ) in split-root pots in a sandy loam soil. Plants were analysed for growth performance, P and nitrogen (N) uptake and water use efficiency (WUE). Biochar adsorption of mineral P and N in aqueous solution was tested in subexperiment. B+ significantly decreased plant biomass production except under P0 FI MÀ, where B+ increased plant biomass. This growth stimulation was counteracted by treatments of P1, PRD and M+. B+ significantly decreased plant leaf area, P and N uptake and WUE, but had no significant effect on root biomass and soil pH. The positive plant growth response to AMF was substantially reduced by biochar amendment. The wood biochar had no adsorption for mineral N, and it had 0.96 % adsorption for mineral P in aqueous solution. The results suggested that the negative effect of wood biochar application on plant growth may due to the reduced plant uptake of P and N and the possibility of phytotoxic effects of wood biochar on potato growth. It was concluded that the wood biochar used in current study had negative impact on plant growth and P/N uptake and it is not recommendable to apply this wood biochar to mycorrhizal agro-system, to soil fertilized with high rate of P or to soil suffering water deficiency.

a b s t r a c t a r t i c l e i n f oNine units in new-born intertidal zone of the Yellow River estuary, China were examined for concentrations of heavy metals (Pb, Cr, Cu, Zn and Ni) in sediments and plants. Heavy metal levels in surface sediments were in the order of Zn N Pb ≈ Cr N Cu ≈ Ni and generally increased in a seaward direction except for Z6 (Tamarix chinensis-Suaeda salsa zone) and Z7 (S. salsa-T. chinensis zone) units. Significant differences in metal concentrations of the 9 units were observed in the profiles (p b 0.01). Heavy metal levels in the shoots or roots of different plants decreased in the order of Zn N Cu N Pb N Ni N Cr and differed among plants or tissues. The roots at Z2 (Calamagrostis pseudophragmites zone), Z3 (Imperata cylindrical zone) and Z4 (Phramites australis zone) units accumulated greater metals than shoots [TFs (translocation factors) b 1], while the shoots at Z1 (Sparganium minimum-Potentilla supina zone), Z7 and Z8 (S. salsa zone) units accumulated greater metals than roots (TFs N 1), implying that intertidal plants showed different pathways in metal accumulation and internal transportation. Except for Pb, the concentrations of Cr, Cu, Zn and Ni in sediments were lower than the criteria of Class I recommended by the Environmental Quality Standard for Soils of China. Although heavy metal levels in intertidal zone were generally the lowest (Cr, Cu, Zn and Ni) or relatively moderate (Pb) compared with other estuaries or bays in Asia and Europe, high eco-toxic risk of Pb and Ni exposure still could be observed at Z4, Z6 and Z9 (mudflat zone) units. S. salsa was more suitable for the potential biomonitor or phytoremediation of all five heavy metals if intertidal sediments was seriously contaminated with increasing of pollutants loading in the Yellow River estuary.