Screening two biodegradable polymers in enhanced efficiency fertiliser formulations reveals the need to prioritise performance goals

Enhanced efficiency fertilisers (EEF) may reduce nitrogen (N) losses and improve uptake efficiency through synchronising N release with in-season plant requirements. We hypothesised that EEF formed via matrix encapsulation in biodegradable polymers will improve N use efficiency when compared to conventional urea fertiliser. This hypothesis was investigated for two biodegradable polymer matrices: polyhydroxyalkanoate (PHA), containing 11.6% urea (by mass), and polybutylene-adipate-co-terephthalate (PBAT), containing either 19.4 or 32.7% urea; and two contrasting soil types: sand and clay. Nitrogen availability and form was investigated under leaching conditions (water) with a growth accelerator pot experiment involving a horticultural crop and novel non-destructive three-dimensional scanning to measure in-season biomass development. The PBAT 32.7% formulation enabled greater above ground biomass production at both 50 and 100 kg N ha^-1 equivalent application rates compared to conventional urea. For the sandy soil, plant scanning indicated that improved uptake performance with PBAT 32.7% was probably the result of greater N availability after 25 days than for conventional urea. Two of the encapsulated formulations (PHA and PBAT 19.4%) tended to decrease nitrogen leaching losses relative to urea (P < 0.05 for the red clay soil). However, decreased N leaching loss was accompanied by poorer N uptake performance, indicative of N being less available in these biopolymer formulations. A snapshot of nitrous oxide emissions collected during peak nitrate concentration (prior to planting and leaching) suggested that the biopolymers promoted N loss via gaseous emission relative to urea in the sandy soil (P < 0.05), and carbon dioxide emissions data suggested that biopolymer-carbon increased microbial activity (P < 0.1). Controlled testing of N release in water was a poor predictor of biomass production and leaching losses. The diverse behaviours of the tested formulations present the potential to optimise biopolymers and their N loadings by taking into account soil and environmental factors that influence the efficient delivery of N to target crops. The greater N uptake efficiency demonstrated for the PBAT 32.7% formulation confirms our hypothesis that matrix encapsulation can enable better synchronisation of N release with crop requirements and decrease leaching losses.

Sorbents can tailor nitrogen release from organic wastes to match the uptake capacity of crops

Delivering nutrients from mineral or organic fertilizers out of synchrony with crop uptake causes inefficiencies and pollution. We explore methodologies for evaluating sorbents as additives to organic agricultural wastes to retain nitrogen in an exchangeable form and deliver at rates that approximate the uptake capacity of roots. Focussing on ammonium (NH₄⁺) as the main inorganic nitrogen form in the studied wastes (sugarcane mill mud, poultry litter), we tested geo-sorbents and biochar for their ability to retain NH₄⁺. Sorption capacity was ranked palagonite < bentonite, biochar, vermiculite < chabazite, clinoptilolite (5.7 to 24.3 mg NH₄⁺ g^-1 sorbent). Sorbent-waste formulations were analysed for sorption capacity, leaching and fluxes of NH₄⁺. Ammonium-sorption capacity broadly translated to sorbent-waste formulations with clinoptilolite conferring the strongest NH₄⁺ attenuation (80%), and palagonite the lowest (7%). A 1:1 ratio of sorbent:waste achieved stronger sorption than a 0.5:1 ratio, and similar sorption as a 1:1.5 ratio. In line with these results, clinoptilolite-amended wastes had the lowest in situ NH₄⁺ fluxes, which exceeded the NH₄⁺ uptake capacity (I_max) of sugarcane and sorghum roots 9 to 84-fold, respectively. Less efficient sorbent-waste formulations and un-amended wastes exceeded I_max of crop roots up to 274-fold. Roots preferentially colonized stronger sorbent-waste formulations and avoided weaker ones, suggesting that lower NH₄⁺ fluxes generate a more favourable growth environment. This study contributes methodologies to identify suitable sorbents to formulate organic wastes as next-generation fertilizers with view of a crop's nutrient physiology. Efficient re-purposing of wastes can improve nutrient use efficiency in agriculture and support the circular nutrient economy.

Outcomes assessment and minimally invasive surgery: historical perspective and future directions

BACKGROUND

Outcomes assessment is being used increasingly to shape practice patterns in all areas of medicine. Although outcomes assessment is not a new concept, the widespread application of outcomes measurement for modifying practice is novel. Instead of focusing on results of interventions in highly controlled environments, outcomes studies usually report results as they occur in uncontrolled, real-world environments. Recently, the Society of American Gastrointestinal Endoscopic Surgeons (SAGES) has initiated a society-wide initiative to monitor outcomes in patients undergoing various laparoscopic operations.

METHODS

Pertinent literature is reviewed as it relates to outcomes assessment. The historical background underpinning the modern interest in outcomes is outlined. Definitions of terms useful for understanding outcomes research are given. The impact of outcomes assessment on minimally invasive surgery, both positive and negative, are examined. The SAGES outcome initiative is introduced.

CONCLUSIONS

Although outcomes studies usually do not provide information on the causes of observations made, they have gained in popularity because they provide information about patient perceptions of disease, disability, and treatment. Minimally invasive surgical procedures often are reported in terms of outcomes assessment because a controlled clinical trial was rendered impossible by early and widespread application of laparoscopic surgery. The SAGES outcomes initiative will provide the necessary tools for the participation of surgeons in the process of practice profiling.

Hydrogel lens monomer constituents modulate protein sorption

PURPOSE

To examine the effect of hydrogel lens monomer constituents on protein sorption.

METHODS

A series of hydroxyethylmethacrylate (HEMA)-based hydrogels with various amounts of methacrylic acid (MAA) or N-vinyl pyrrolidone (NVP) were synthesized. A radiolabel tracer technique was used to measure the amount of protein adsorbed on or penetrating into the hydrogels. Penetration of fluorescence-labeled proteins in the hydrogels was studied by laser scanning confocal microscopy. Single-protein solutions of human serum albumin (HSA) and hen egg lysozyme were studied.

RESULTS

Inclusion of the comonomers MAA or NVP in hydrogels resulted in an increase in water content and also had a strong impact on protein sorption. An increase in the amount of MAA in the poly(HEMA-co-MAA) hydrogels increased lysozyme adsorption and penetration but reduced HSA adsorption. However, the amount of protein adsorbed for both HSA and lysozyme increased with the amount of NVP in the poly(HEMA-co-NVP) hydrogels. In contrast to the marked effect of MAA on protein sorption, in particular, on lysozyme sorption, NVP had little influence on protein sorption. When a hydrogel contains both MAA and NVP, MAA has the dominant effect on protein sorption-in particular, on lysozyme sorption. Furthermore, a large difference was observed in the amount of lysozyme adsorbed on the hydrogels that had similar water contents but little variation in adsorption of HSA.

CONCLUSIONS

Negatively charged carboxyl groups of the MAA constituent may influence lysozyme sorption in two ways: by electrostatic attraction and by increasing the possibility for the small lysozyme molecule to penetrate the hydrogels. Interactions of the surface lactam groups of NVP with proteins may be attributable to the attraction of proteins to NVP. Water content is not a primary factor in determining protein adsorption. It appears that the monomer constituents, such as MAA or NVP, control protein adsorption.

Silylcuprate Routes to Cyclohex-2-enylsilanes

The efficacy of the dimethyl(phenyl)silylcuprate and (to a lesser extent) the methyl-diphenylsilylcuprate reagents in converting cyclohex-2-enyl chlorides into the corresponding allylsilanes has been investigated. The presence of copper(I) greatly suppresses formation of the coupled hydrocarbon, and promotes stereo- and regio-selective carbon-silicon bond formation, in a predominantly anti-SN2′ manner. Spectroscopic characterization of the diastereomeric silanes is presented. Grignard routes to some of these silanes are described.