Comparative tolerance of Pinus radiata and microbial activity to copper and zinc in a soil treated with metal-amended biosolids

A study was conducted to evaluate the effects of elevated concentrations of copper (Cu) and zinc (Zn) in a soil treated with biosolids previously spiked with these metals on Pinus radiata during a 312-day glasshouse pot trial. The total soil metal concentrations in the treatments were 16, 48, 146 and 232 mg Cu/kg or 36, 141, 430 and 668 mg Zn/kg. Increased total soil Cu concentration increased the soil solution Cu concentration (0.03-0.54 mg/L) but had no effect on leaf and root dry matter production. Increased total soil Zn concentration also increased the soil solution Zn concentration (0.9-362 mg/L). Decreased leaf and root dry matter were recorded above the total soil Zn concentration of 141 mg/kg (soil solution Zn concentration, >4.4 mg/L). A lower percentage of Cu in the soil soluble + exchangeable fraction (5-12 %) and lower Cu2+ concentration in soil solution (0.001-0.06 μM) relative to Zn (soil soluble + exchangeable fraction, 12-66 %; soil solution Zn2+ concentration, 4.5-4,419 μM) indicated lower bioavailability of Cu. Soil dehydrogenase activity decreased with every successive level of Cu and Zn applied, but the reduction was higher for Zn than for Cu addition. Dehydrogenase activity was reduced by 40 % (EC40) at the total solution-phase and solid-phase soluble + exchangeable Cu concentrations of 0.5 mg/L and 14.5 mg/kg, respectively. For Zn the corresponding EC50 were 9 mg/L and 55 mg/kg, respectively. Based on our findings, we propose that current New Zealand soil guidelines values for Cu and Zn (100 mg/kg for Cu; 300 mg/kg for Zn) should be revised downwards based on apparent toxicity to soil biological activity (Cu and Zn) and radiata pine (Zn only) at the threshold concentration. © 2013 Springer-Verlag Berlin Heidelberg

Phytoextraction: Where's the action?

Many articles concerning phytoextraction of trace elements state that it is "an emerging technology that can be used for the low-cost clean-up of contaminated land. . .". Given the lack of commercial phytoextraction operations or even successful field trials, we sought to determine whether phytoextraction could ever compete with existing technologies to clean up soil within a realistic time-frame, say . 10 are required to reduce the total metal concentration in soil by 50% within 25. years, under conditions that are ideal for phytoextraction. Heterogeneity of both the target element, nutrients, and water in soil, as well as heterogeneity of plant roots has a large, but as-yet unquantified effect on remediation time. Variations in climatic conditions, including drought and flooding can also reduce metal extraction rates. Unlike phytoextraction for soil cleansing, phytomining could theoretically produce valuable crops of metal. However, phytomining suffers from a low efficiency of metal extracted per unit of land. Ironically, phytomining may have a larger ecological footprint than conventional mining. Currently, lack of infrastructure limits its implementation. While our review shows that phytoextraction for soil cleansing and phytomining is currently impractical, it is not our intention to discourage research in this area. The best rebuttal of our analyses would be full-scale field operations. However, investigations of new plants/soils/soil conditioner combinations should at least demonstrate how phytoextraction could work by providing convincing basic mass-balance calculations

Cadmium accumulation by forage species used in New Zealand livestock grazing systems

© 2015 Elsevier B.V. All rights reserved. Cadmium (Cd) accumulation in 12 forage plant species was investigated in a glasshouse trial. Potted soil (total Cd 0.43 mg kg- 1) was fertilised with varying rates of superphosphate to manipulate phosphorus availability, plant growth rate and soil Cd availability. Mean tissue Cd concentration decreased in the order chicory > plantain > turnip > lucerne > sheep's burnet > strawberry clover > kale > perennial ryegrass > haresfoot trefoil > red clover > crimson clover > white clover. Chicory and plantain had significantly greater mean tissue Cd concentrations (1.639 and 0.734 mg kg- 1 DM, respectively) than all other species. Rate of superphosphate and plant yield had little influence on plant tissue Cd concentration. The correlation between soil total Cd and plant tissue Cd concentration was generally poor (R2 = 0.006-0.428) and was only significant for perennial ryegrass and red clover. Modelling of lamb kidney Cd accumulation indicated that food standard maximum levels may be exceeded in animals younger than the current meat industry 30 month offal discard age. With increased use of chicory and plantain as specialist forage crops in New Zealand, this information will be important for improving livestock Cd accumulation risk assessment models

Nitrification rate in dairy cattle urine patches can be inhibited by changing soil bioavailable Cu concentration.

CAUL read and publish agreement 2023Ammonia oxidation to hydroxylamine is catalyzed by the ammonia monooxygenase enzyme and copper (Cu) is a key element for this process. We investigated the effect of soil bioavailable Cu changes induced through the application of Cu-complexing compounds on nitrification rate, ammonia-oxidizing bacteria (AOB) and archaea (AOA) amoA gene abundance, and mineral nitrogen (N) leaching in urine patches using the Manawatu Recent soil. Further, evaluated the combination of organic compound calcium lignosulphonate (LS) with a growth stimulant Gibberellic acid (GA). Treatments were applied in May 2021 as late-autumn treatments: control (no urine), urine-only at 600 kg N ha-1, urine + dicyandiamide (DCD), urine + co-poly-acrylic-maleic acid (PA-MA), urine + LS, urine + split-application of LS (2LS), and urine + combination of GA plus LS (GA + LS). In addition, another four treatments were applied in July 2021 as mid-winter treatments: control, urine-only at 600 kg N ha-1, urine + GA, and urine + GA + LS. Soil bioavailable Cu and mineral N leaching were examined during the experimental period. The AOB/AOA amoA genes were quantified using quantitative polymerase chain reaction. Changes in soil bioavailable Cu across treatments correlated with nitrification rate and AOB amoA abundance in late-autumn while the AOA amoA abundance did not change. The reduction in soil bioavailable Cu induced by the PA-MA and 2LS was linked to significant (P < 0.05) reduction in mineral N leaching of 16 and 30%, respectively, relative to the urine-only. The LS did not induce a significant effect on either bioavailable Cu or mineral N leaching relative to urine-only. The GA + LS reduced mineral N leaching by 10% relative to LS in late-autumn, however, there was no significant effect in mid-winter. This study demonstrated that reducing soil bioavailable Cu can be a potential strategy to reduce N leaching from urine patches.Published onlin

Response of Pinus radiata D. Don to Boron Fertilization in a Glasshouse Study

Limited information is available on the effect of slow-release boron (B) fertilizer on Pinus radiata growth and physiological properties and soil microbiological activities. A 7-month-long pot experiment was carried out under glasshouse conditions to investigate the response of Pinus radiata to different rates (0.0222, 0.0446, 0.089, and 0.178 mg B g-1 soil), equivalent to 0, 4, 8 16, and 32 kg B ha-1 of ulexite, a slow-release B fertilizer. Hot 0.02 M calcium chloride (CaCl2)-extractable soil B, soil dehydrogenase activity, plant B concentration, growth, and photosynthesis were measured at the time of harvest. The B concentrations in the soil and plant organs (needles, stem, and roots) significantly increased with increasing rates of B fertilizer. The optimum B fertilizer rates of 4-8 kg B ha-1 produced the greatest plant growth and net photosynthetic rate. However, the B rates of 16 and 32 kg B ha-1 significantly reduced net photosynthetic rate, and the rate of 32 kg B ha-1 significantly reduced stem diameter growth when compared to the optimum B rates. Soil dehydrogenase activity, an indicator of soil microbiological activities, was significantly reduced by B application at the rates of 16 and 32 kg ha-1. This study confirms the narrow range between B deficiency and toxicity in a tree crop and stresses the need for selection of the optimum rate of B fertilizer application. © 2012 Copyright Taylor and Francis Group, LLC

Processing of bio-ore to products

Hyperaccumulator plants may contain valuable metals at concentrations comparable to those of conventional metal ore and can be significantly upgraded by incineration. There is an incentive to recover these metals as products to partially counter-balance the cost of disposing the contaminated biomass from contaminated soils, mine tailings, and processing wastes. Metal recovery is included in the agromining chain, which has been developed over the past two decades for Ni and Au. More than 450 Ni-hyperaccumulator species are currently known and some grow quickly providing a high farming yield. Nickel recovery involves an extraction step, ashing and/or leaching of the dry biomass, followed by a refining step using pyro- or hydrometallurgy. The final products are ferronickel, Ni metal, Ni salts or Ni catalysts, all being widely used in various industrial sectors and in everyday life. Gold can be recovered from mine tailings using a number of plant species, typically aided by a timed addition of an Au-chelating extractant to the soil. Dry biomass is ashed and smelted. This approach enables the treatment of resources that could not be effectively processed using conventional methods. In addition to nickel and gold, the recovery of other metals or elements (e.g. Cd, Zn, Mn, REEs) has been investigated. Further effort is required to improve process efficiency and to discover new options tailored to the unique characteristics of hyperaccumulator plant biomass