The aim of this work was to address the issue of processed vs. non-processed biowastes for agriculture, by comparing materials widely differing for the amount of process energy consumption. Thus, residual post harvest tomato plants (TP), the TP hydrolysates obtained at pH 13 and 60 °C, and two known biochar products obtained by 650 °C pyrolysis were prepared. All products were characterized and used in a cultivation of radish plants. The chemical composition and molecular nature of the materials was investigated by solid state ¹³C NMR spectrometry, elemental analysis and potentiometric titration. The plants were analysed for growth and content of chlorophyll, carotenoids and soluble proteins. The results show that the TP and the alkaline hydrolysates contain lignin, hemicellulose, protein, peptide and/or amino acids moieties, and several mineral elements. The biochar samples contain also similar mineral elements, but the organic fraction is characterized mainly by fused aromatic rings. All materials had a positive effect on radish growth, mainly on the diameter of roots. The best performances in terms of plant growth were given by miscanthus originated biochar and TP. The most significant effect was the enhancement of soluble protein content in the plants treated with the lowest energy consumption non processed TP. The significance of these findings for agriculture and the environment is discussed.

Ambrosia artemisiifolia L. (common ragweed) is an invasive plant whose allelopathic properties have been suggested by its field behaviour and demonstrated through phytotoxicity bioassays. However, the nature of the molecules responsible for the allelopathic activity of common ragweed has not been explored. The main objective of this study was to identify the phytotoxic molecules produced by A. artemisiifolia. A preliminary investigation has indicated that a methanol extract of A. artemisiifolia completely inhibited the germination of cress and radish. Semi-preparative fractionation of the methanol extract allowed separating of phytotoxic fraction which contained a single compound. The structure of this compound was elucidated by liquid chromatography–mass spectrometry (LC-MS)/MS, high-resolution mass spectral, nuclear magnetic resonance, and Fourier transform infrared spectra as sesquiterpene lactone isabelin (C₁₅H₁₆O₄). The effect of pure isabelin was tested on four different weed species, confirming the inhibitory activity of molecule. The results indicate directions for the future studies about herbicidal specific activity of isabelin, as pure molecule or in the crude extract, as a potential candidate for biological weed control.

Adsorption isotherms of prosulfocarb were determined on soils with different physicochemical properties. The extent of adsorption increased with the organic carbon content, but the results also suggested the involvement of some inorganic soil surfaces. In order better to understand the role of each soil surface, adsorption–desorption isotherms were determined on model soil colloids consisting of a soil humic acid, a montmorillonite, a synthetic aluminium hydroxide and their associations. The highest adsorption was observed on the humic acid, but it was also confirmed that the montmorillonite interacted with prosulfocarb. In contrast, the aluminium hydroxide was not active and its association with montmorillonite provoked a decrease in adsorption compared with montmorillonite alone. Except for humic acid, the highest adsorption took place on the ternary association montmorillonite–aluminium hydroxide–humic acid. On each surface tested, the adsorption was largely reversible and decreased at increasing pH. The herbicidal activity of prosulfocarb was tested by the determination of the germination and growth of a typical weed, Lolium multiflorum Lam, in contact with prosulfocarb solutions at different concentrations. The herbicide did not prevent the germination of the seeds but inhibited the growth of the roots and leaves. The same test was performed in the presence of the ternary system to evaluate the influence of adsorption on the plant bioavailability. It was concluded that the presence of an adsorptive surface reduced the herbicidal activity and that the simple bioassay proposed could be useful in predicting the extent of adsorption in a given soil. Copyright © 2006 Society of Chemical Industry

Controlled-release fertilizers (CRF) are needed under current agriculture practice to decrease the environmental impact caused by fertilizer doses applied in excess of plants’ uptake rate. Commercial CRF are available. They are manufactured from mineral fertilizers encapsulated into a synthetic polymer matrix or coated by a polymer layer. However, substitution of fossil sourced organic polymers with biopolymers is a major environmental concern. In the present paper, we describe the manufacture by a continuous twin-screw extrusion process, and the mechanical and chemical properties of injection-molded composite pellets containing 90% sunflower protein concentrate (SPC) matrix, and 5–10% of a biopolymer (BP) obtained from municipal biowastes (MBW), and/or urea (U). The reported results show that SPC-BP-U behaves as an efficient eco-friendly CRF. BP contributes to several benefits to the performance of the composite pellets, upon increasing surface hardness, and controlling the formation of ammonia from urea hydrolysis and the release of organic nitrogen. The SPC-BP-U appears a powerful eco-friendly CRF to supply organic C and the three major N, P, and K nutrients to soil and plants. It offers worthwhile scope for being tested in the cultivation of specific plants under the real operational conditions of agriculture practices.

Inorganic (a montmorillonite; a complex of montmorillonite and aluminium hydroxide) and organo-mineral model soil colloids (a complex of montmorillonite, aluminium hydroxide and humic acid) were tested for their capacity to adsorb and desorb phenanthrene. The adsorption-desorption isotherms demonstrated that the inorganic surfaces were able to bind the pollutant, although to a lesser extent than the organo-mineral complex. The capacity of different aqueous solutions to desorb phenanthrene after 1, 7, and 30 days' contact with the model colloids was tested in order to assess their efficacy with respect to the aging effect. The solutions used were 0.01 N CaCl₂, dissolved soil organic matter (DOM), a model root exudates solution (aqueous solution of saccharose, fructose, glucose, fumaric acid, ferrulic acid, and leucine), and three commercial surfactants (sodium dodecyl sulfate, Tween 20, and didecyldimethylammonium bromide). The desorptive capacity of these solutions were compared with that of organic solutions (water-ethanol and n-hexane–ethanol). More than 85% phenanthrene was desorbed after 30 days aging by organic solutions. Among the aqueous solutions, the best results were obtained with dissolved soil organic matter solution and the model root exudates solution which were able to desorb up to 50% phenanthrene after 30 days aging. Such naturally occurring aqueous solutions should be preferred to synthetic compounds to mobilize phenanthrene in contaminated sites without further contaminating the environment.

This study reports a pilot experiment of composting of anaerobically digested sewage sludges deriving from the production of biogas in a wastewater treatment plant. Two composting piles (about 15 m³ each) were prepared by mixing 50% and 30% (v/v) sludges with lignocellulosic material. The composting process was monitored through determination of the main physicochemical properties. The stability of the composts was assessed by determination of the respiration index and dehydrogenase activity. The collected data indicated that, at both sludges concentrations, the process produced a compost suitable for agricultural applications as far as the physicochemical properties were concerned. On the other hand, in the pile containing 50% sludges, the maximum temperature of the thermophilic phase was lower than the temperature required (55°C) to ensure the sanitization of the compost. The germination and growth indexes of Lepidium sativum indicated the lack of phytotoxicity of the final materials. The suitability of the composts as field improvers and horticultural substrates has been attested through plant bioassays conducted on maize and chrysanthemum.