Sewage sludge treated with bentonite,vermiculite or biochar can improve soil properties and enhance growth of grasses

Sewage sludge treated with 15% bentonite, vermiculite or biochar was evaluated as a soil amendment in comparison to limed and untreated sludge. Seven treatments were established to two soils, an acid and an alkaline, in three replications, i.e. 2% addition of sludge treated with bentonite, vermiculite, biochar and lime and application of 2% untreated sludge, inorganic fertilization and no sludge or inorganic fertilizers (control). Then, the soil treatments were used in a pot experiment with perennial ryegrass (Lolium perenne L.) as a test plant. Sludge treated with the clay minerals or biochar improved pH of the acid soil and significantly increased organic matter and available nutrients of both soils compared to control. Although no salinity or sodicity hazard was evidenced, the initial salinity of acid and alkaline soil increased by four-eight and two-three times, respectively, upon addition of all sludge treatments, especially that of untreated sludge. Moreover, soil available zinc (Zn) increased by four-eight times. Soil application of sludge treated with the clay minerals or biochar increased the total aboveground biomass yield of ryegrass in the acid and alkaline soil by 133%–171% and 72%–88%, respectively, compared to control and enhanced nutrient uptake by plants. Furthermore the microbial metabolic quotient indicated lack of low pH and heavy metal stress with addition of sludge to the acid soil. After three harvests of ryegrass, the residual effect of sludge on pH of acid soil and salinity, available phosphorus (P), Zn and boron (B) of both soils still persisted. Thus sewage sludge treated with 15% bentonite, vermiculite or biochar could be applied to soils at a rate of 2% (≈80 Mg ha⁻¹) to serve as soil amendment and fertilizer for grasses and pasture species; however, caution is needed regarding possible P build-up, Zn phytotoxicity and salinization risks.     

A study of mechanical behavior and morphology of carbon nanotube reinforced UHMWPE/Nylon 6 hybrid polymer nanocomposite fiber

We report a phenomenal increase in strength, modulus, and fracture strain of ultra high molecular weight polyethylene (UHMWPE) fiber by 103 %, 219 %, and 108 %, respectively through hybridizing this fiber with Nylon 6 as a minor phase and simultaneously reinforcing it with single-walled carbon nanotubes (SWCNTs). Loading of Nylon 6 and SWCNTs into UHMWPE was 20.0 wt% and 2.0 wt%, respectively. Hybridized fibers were processed using a solution spinning method coupled with melt mixing and extrusion. We claim that the enhancement in strain-to-failure of the nanocomposites is due to induced plasticity in the hybridized Nylon 6-UHMWPE polymers. The enhancement in strength and stiffness in the nanocomposites is attributed to the load sharing of the SWCNTs during deformation. Differential scanning calorimetry (DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) studies showed that changes in percent crystallinity, rate of crystallization, crystallite size, alignment of nanotubes, sliding of polymer interfaces and strong adhesion of CNT/polymer blends were responsible for such enhancements.     

Evaluation of certain Ni soil tests for an initial estimation of Ni sufficiency critical levels

Although Ni is officially recognized as an essential micronutrient for all higher plants, the majority of the published research on soil availability of Ni focuses on its hazardous role as a heavy metal. The objective of the study was to evaluate certain Ni soil tests in uncontaminated soils for an initial estimation of its sufficiency critical levels. Nickel was extracted from 30 cultivated soils employing the following extraction methods: DTPA, AB‐DTPA, AAAc‐EDTA, Mehlich‐3, 0.1 M HCl, and 0.1 M HNO₃. Ryegrass (Lolium perenne L.) was grown in pots containing the soils, harvested five times, certain plant parameters were determined, and the Cate–Nelson procedures were used for Ni critical levels determination. Among the six methods, HCl was the least reliable extractant for the evaluation of soil available Ni, whereas the most significant (p ≤ 5%) relationships between Ni concentration or Ni uptake by ryegrass and Ni soil tests were consistently obtained for AAAc‐EDTA or Mehlich‐3 extractable Ni. In many cases, > 80% of the variability of Ni concentration or uptake by ryegrass was explained by these two soil tests without the inclusion of other soil properties that affect Ni bioavailability. Sufficiency critical levels of Ni in soil were ≈ 2 mg kg^–1 for both methods. Consequently, as an initial approach, concentrations of AAAc‐EDTA or Mehlich‐3 extractable Ni < 2 mg kg^–1 are probably a good guide to indicate soils that will respond to Ni fertilization.     

Differential incorporation of conjugated linoleic acid isomers into egg yolk lipids

The incorporation pattern of conjugated linoleic acids (CLA) isomers into the egg yolk of hens in relation to that in the diet was studied. Silver-ion high-performance liquid chromatography (Ag-HPLC) was used to separate individual CLA isomers. It was found that the isomeric distribution pattern in the egg yolk lipids was different from that in the dietary fat. Total cis/trans isomers accounted for 81.2% of total CLA incorporated into the egg yolk, which was in contrast to the value of 92.0% of total CLA in the diet. Total cis/cis isomers accounted for 3.8% total CLA in the diet but they were 6.6% of the total CLA in the egg yolk lipids. In contrast, total trans/trans isomers were 12.2% of the total CLA isomers in the egg yolk lipids, whereas they were only 4.2% of total CLA in the diet. The results showed that total trans/trans-CLA was preferentially incorporated into the egg yolk, whereas the incorporation of total cis/trans-CLA isomers was partially discriminated. Within each group, the incorporation of individual isomers into the egg yolk lipids was also selective. cis-9,trans-11/trans-9,cis-11 and cis-10,trans-12/trans-10,cis-12 were the two major isomers in the diet. Ag-HPLC analysis showed that the former was preferentially transferred into the egg yolk compared with the latter. It was observed that supplementation of CLA in the diet of laying hens decreased the concentration of oleic acid (18:1n-9), arachidonic acid (20:4n-6), and docosahexaenoic acid (22:6n-3) but increased that of linolenic acid (18:3n-3), stearic acid (18:0), and palmitic acid (16:0) in the egg yolk, suggesting that CLA may inhibit Delta6 and Delta9 desaturases.     

Reliability analysis and duration-of-load strength adjustment factor of the rolling shear strength of cross laminated timber

In this study, the duration-of-load effect on the rolling shear strength of cross laminated timber (CLT), with different cross-sectional layups (five-layer and three-layer), was evaluated. A stress-based damage accumulation model is chosen to evaluate the duration-of-load strength adjustment factor of the rolling shear strength of CLT. This model incorporates the established short-term rolling shear strength of material and predicts the time to failure under arbitrary loading history. The model has been calibrated and verified based on the test data from low cycle trapezoidal fatigue tests (damage accumulation tests) in the previous study. The long-term rolling shear behaviour of CLT can then be evaluated from this verified model. As the developed damage accumulation model is a probabilistic model, it can be incorporated into a time based reliability assessment of the CLT products, considering short-term, snow, and dead load only loading cases. The reliability analysis results and factors reflecting the duration-of-load effect on the rolling shear strength of CLT are compared and discussed. The characteristic of this modeling theory lies in that the verified model is also able to predict the duration-of-load behaviour of CLT products under arbitrary loading history, such as long-term dead load case; then, these predictions of time to failure from the damage accumulation model can elucidate duration of load by the stress ratio evaluation approach. The results suggest that the duration-of-load rolling shear strength adjustment factor for CLT is more severe than the general duration-of-load adjustment factor for lumber; this difference should be considered in the introduction of CLT into the building codes for engineered wood design.     

Ectopic expression of GmPAP3 enhances salt tolerance in rice by alleviating oxidative damage

GmPAP3, a purple acid phosphatase from soybean (Glycine max), was previously shown to alleviate salt stress in BY‐2 cells and Arabidopsis thaliana by reducing oxidative damage. To make use of GmPAP3 for crop improvement, we investigated whether the protective function of GmPAP3 is persistent in rice. Compared with the untransformed wild type, the transgenic rice plants exhibited enhanced germination rate, longer shoots and roots, and higher survival rate under salt stress, when compared to the untransformed control. In addition, the transgenic plants also showed increased activity of superoxide dismutase (SOD) and catalase (CAT), proline content, water content and chlorophyll content, but decreased electrolyte leakage and malondialdehyde content in leaves. These results indicate that the expression of GmPAP3 could be used to enhance salt tolerance in rice.     

Modeling top height growth of red alder plantations

Height growth equations for dominant trees are needed for growth and yield projections, to determine appropriate silvicultural regimes, and to estimate site index. Red alder [Alnus rubra Bong.] is a fast-growing hardwood species that is widely planted in the Pacific Northwest, USA. However, red alder dominant height growth equations used currently have been determined using stem analysis trees from natural stands rather than repeated measurements of stand-level top height from plantations, which may cause them to be biased. A regional dataset of red alder plantations was complied and used to construct a dynamic base-age invariant top height growth equation. Ten anamorphic and polymorphic Generalized Algebraic Difference Approach (GADA) forms were fit using the forward difference approach. The Chapman–Richards anamorphic and Schumacher anamorphic model forms were the only ones with statistically significant parameters that yielded biologically reasonable predictions across a full range of the available data. The Schumacher model form performed better on three independent datasets and, therefore, was selected as the final model. The resulting top height growth equations differed appreciably from tree-level dominant height growth equations developed using data from natural stands, particularly at the younger ages and on lower site indices. Both the rate and shape parameters of the Schumacher function were not influenced by initial planting density. However, this analysis indicates that the asymptote, which is related to site index, may be reduced for plantations with initial planting density below 500 trees ha⁻¹. The final equation can be used for predictions of top height (and thus) site index for red alder plantations across a range of different growing conditions.     

Assessment of the adaptive capacity of plant species in copper mine tailings in arid and semiarid environments

Purpose

The objective of this work was to identify hyperaccumulator plants and evaluate their capacity on copper mine tailings in the Antofagasta Region (Chile), considered one of the most arid in the world.

Materials and methods

Two native plant species, Gazania rigens and Pelargonium hortorum, were grown during 11 weeks on mine tailings. The physico-chemical characterization of the mine tailings under study indicated that the substrate required conditioning to support a phytoremediation system. In this respect, organic and inorganic amendments and mycorrizhal fungi were added to the substrate. Three treatments were designed to assess the effects of the amendments through an analysis of variance.

Results and discussion

Indicators of plant growth and development were measured weekly, and concentrations of Cd, Cu, Fe, Mn, Pb, Al, and Zn in roots of tailing-grown plants and substrate were measured at the end of the experiment.

Conclusions

The results were used to determine the bioconcentration factor (BCF), which demonstrated that both species act as excluders of Fe, Mn, Pb, Al, and Zn. In addition, it was found that both species present characteristics of potential accumulators of Cu.