Kinetics of organosolv delignification of fibre crop Arundo donax L

Kinetics of ethanol–alkali delignification of fibre crop Arundo donax L. (giant reed) has been studied. The improved approach for determination of the reaction rate constants by accurate quantification of lignin fractions with different reactivity during standard procedure of graphical differentiation was applied. Following to a simplified model, the delignification process was considered as a complex of n-parallel irreversible first-order reactions with similar final product and analysed as a multi-component reaction system. Three kinetically distinguishable lignin fractions of A. donax were revealed and quantified in proportion of approximately 61, 23 and 16% (as initial, bulk and residual lignin, respectively) and their effective degradation rate constants were determined for different pulping conditions. The proportion of lignin fractions was different from that reported for wood, but close to another crop—wheat straw, where the initial lignin fraction was also found as a major fraction (about 90%). The values of apparent activation energy were estimated respectively as 64, 89 and 96 kJ mol⁻¹, and were generally within the range of those reported for wood kraft and organosolv pulping. The simulation of ethanol–alkali delignification using found kinetic parameters showed the high reproducibility of experimental data on lignin removal, providing thereby the adequate test on validation of the suggested kinetic approach. The data reproducibility was substantially higher in comparison with conventional consecutive kinetic model (sum of square residuals (SQR) 0.0036 versus 0.0856).     

Alkaline sulfite–anthraquinone (AS/AQ) pulping of wheat straw and totally chlorine free (TCF) bleaching of pulps

Alkaline sulfite–anthraquinone (AS/AQ) pulping of wheat straw and totally chlorine free (TCF) bleaching of resulting pulps was investigated. Wheat straw was supplied by the Ferdosii University Experimental Station in Northeastern Iran, cleaned and chopped into about 3–5 cm long pieces. In the AS/AQ pulping experiments, the active alkali charge on oven dry wheat straw, heating time to maximum cooking temperature, AQ dose and liquor to straw ratio were kept constant at 16%, 60 min, 0.1% and 4/1, respectively. The alkali ratio, Na₂SO₃/NaOH, calculated as NaOH, was varied from 20/80 to 80/20. Cooking time at maximum temperature was varied from 30 to 90 min and maximum cooking temperature was adjusted between 152 and 160 °C. Reference soda and soda/AQ pulps were produced.AS/AQ and soda/AQ pulps with kappa numbers below 15 were produced easily. Cooking of corresponding soda pulps under comparable conditions stopped at a kappa number of 25. The characteristics of unbleached AS/AQ, soda/AQ and soda pulps were compared. AS/AQ and soda/AQ pulps had similar tensile strength but tear was in favor to AS/AQ. The latter had much higher yield and brightness.TCF bleaching of AS/AQ pulp was performed in O Q (OP) or O Q (OP) P sequences. Oxygen delignification (O) resulted in a delignification degree of approximately one third. Followed by a chelating treatment (Q) and a subsequent (OP) stage under drastic conditions a brightness of 82.7% ISO was achieved in an O Q (OP) sequence. The sequence O Q (OP) P, with 2% H₂O₂ in the final P stage, improved brightness from 77.2% ISO after the OP stage to 83.6% ISO. Bleaching led to only small losses in tensile and burst strength but enhanced tear strength. Short beating in a Jokro mill was sufficient to attain good pulp strength. The results of this study indicate that AS/AQ pulping and TCF bleaching is a convincing alternative to produce high-quality pulp from wheat straw for writing and printing paper.     

Characterization of hairs and pappi from Cynara cardunculus capitula and their suitability for paper production

The capitula of Cynara cardunculus contain hairs and pappi representing 7% of the total plant biomass. These low density biomass components could be mechanically separated without apparent losses using a whole-plant processing prototype. Hairs and pappi are filamentous structures made up of longitudinally aligned fibre cells, without intercellular voids or pitting, with the following dimensions regarding length, width and wall thickness: 1.35 mm, 19.8, and 4.8 μm for hairs and 1.78 mm, 10.4, and 2.9 μm for pappi. Chemically hairs and pappi have low content of ash (1.9% and 1.1%, respectively), extractives (5.4% and 6.0%) and lignin (10.6% and 17.8%), and high content of holocellulose (77.5% and 72.8%) and α-cellulose (55.2% and 46.8%).Pulps could be produced using a conventional kraft process with high yields and low residual lignin, e.g. 63% at Kappa 7 for hairs and 48% at Kappa 11 for pappi, low coarseness values (0.04 and 0.03 mg m^?1) and adequate pulp properties for paper (40 and 42 N mg^?1 tensile index; 3.6 and 3.4 kPa m² g^?1 burst index in unrefined pulps of hairs and pappi, respectively). The results also indicated that there is scope for improving pulp quality by optimising pulping conditions to this type of new raw materials. The differences between hairs and pappi may also be further exploited namely the lower lignin content of hairs and the higher slenderness and wall thickness of pappi fibres.The utilization of hairs and pappi may strengthen the differentiated use of biomass fractions of the Cynara plant and its potential as a bioenergy crop.     

Improving the use of kenaf for kraft pulping by using mixtures of bast and core fibers

Kenaf (Hibiscus cannabinus L.) is a herbaceous annual plant amenable to use as a papermaking raw material. Kraft and soda pulping of kenaf have so far been done exclusively on the bark fraction (about 34–38% of the stem) or whole stem of the plant. Using kenaf bark exploits the higher quality of its bast fibers but reduces the typically high crop yields of this plant. In any case, core kraft pulp has acceptable properties some of which (e.g. tensile index, burst index) can even surpass those of bark pulp. Pulp made from both fractions has been found to exhibit better bonding properties than bark pulp. However, too high a proportion of core fibers can result in difficult drainage, a low tear strength or poor air permeability. These problems restrict the proportion of core that can be mixed with bast fibers, hinders separation of the two fractions and raises operational costs.The primary purpose of this study was to examine the influence of the core–bark ratio on the properties of mixed kenaf pulp. We used unrefined core pulp and refined bark pulp. Based on the results for kraft sacks, obtaining kenaf paper from both fractions has some advantages. Because Gurley air porosity changed dramatically with the proportion of core pulp used, it was used to determine the maximum amount of core fibers to be added to bast fibers. A proportion of up to 34% was found to have no adverse effect on air permeability. Such a proportion allowed paper strength to be preserved with an acceptable tear index (19.8 mN m²/g) and excellent tensile index (72 N m/g). Also, energy consumption was reduced if only the bark fraction was refined. The proposed strategy thus provides increased fiber yields of kenaf per hectare per year and valorizes the core fraction.     

Paper from olive tree residues

An experimental design was performed to study the influence of process variables (135–175 °C for temperature, 60–120 min for pulping time and 15–25% for active alkali) on the properties of pulps (yield, Kappa index, viscosity, 1% NaOH solubles, alcohol–benzene extractives holocellulose, lignin and α-cellulose contents and brightness) and paper sheets (stretch index, burst index, and tear index) obtained from olive trimming residues. Obtaining pulps with acceptably high physical and chemical properties entails operating at a temperature of 175 °C for 90 min and 25% of active alkali. The paper sheets obtained from olive trimming residues pulps that were produced in different degrees of refining are characterised for their stretch index, burst index, and tear index. An increase in the different parameters for the paper sheet upon increasing the degree of refining is found. All pulps reached between 33 and 39 kN m/kg in the stretch index, between 1.5 and 2 kN/g for the burst index and 0.7–2.5 N m²/g for the tear index and not in excess of the refining degree (<45 °SR).     

Interactions between non-flooded mulching cultivation and varying nitrogen inputs in rice–wheat rotations

A 3-year field experiment examined the effects of non-flooded mulching cultivation and traditional flooding and four fertilizer N application rates (0, 75, 150 and 225 kg ha⁻¹ for rice and 0, 60,120, and 180 kg N ha⁻¹ for wheat) on grain yield, N uptake, residual soil N_min and the net N balance in a rice–wheat rotation on Chengdu flood plain, southwest China. There were significant grain yield responses to N fertilizer. Nitrogen applications of >150 kg ha⁻¹ for rice and >120 kg ha⁻¹ for wheat gave no increase in crop yield but increased crop N uptake and N balance surplus in both water regimes. Average rice grain yield increased by 14% with plastic film mulching and decreased by 16% with wheat straw mulching at lower N inputs compared with traditional flooding. Rice grain yields under SM were comparable to those under PM and TF at higher N inputs. Plastic film mulching of preceding rice did not affect the yield of succeeding wheat but straw mulching had a residual effect on succeeding wheat. As a result, there was 17–18% higher wheat yield under N0 in SM than those in PM and TF. Combined rice and wheat grain yields under plastic mulching was similar to that of flooding and higher than that of straw mulching across N treatments. Soil mineral N (top 60 cm) after the rice harvest ranged from 50 to 65 kg ha⁻¹ and was unaffected by non-flooded mulching cultivation and N rate. After the wheat harvest, soil N_min ranged from 66 to 88 kg N ha⁻¹ and increased with increasing fertilizer N rate. High N inputs led to a positive N balance (160–621 kg ha⁻¹), but low N inputs resulted in a negative balance (−85 to −360 kg ha⁻¹). Across N treatments, the net N balances of SM were highest among the three cultivations systems, resulting from additional applied wheat straw (79 kg ha⁻¹) as mulching materials. There was not clear trend found in net N balance between PM and TF. Results from this study indicate non-flooded mulching cultivation may be utilized as an alternative option for saving water, using efficiently straw and maintaining or improving crop yield in rice–wheat rotation systems. There is the need to evaluate the long-term environmental risks of non-flooded mulching cultivation and improve system productivity (especially with straw mulching) by integrated resource management.     

Surface chemical composition of some non-wood pulps

The surface lignin and extractives coverage of some non-wood pulps (wheat straw, reed, bagasse, bamboo and kenaf bark) were investigated by means of ESCA and compared with wood pulps. Strong enrichment of lignin and extractives on the pulp fiber surface was found for all of the pulps. At the same bulk lignin content level, the surface lignin coverage was found to be higher in the non-wood pulp than in the softwood pulp. The possible reasons for this were examined.     

Structural characterization of stalk lignin from banana plant

Dioxane lignins from two fractions of banana plant ‘Dwarf Cavendish’ stalk (floral stalk (DL_FS) and rachis (DL_R)) were structurally characterized by a set of spectroscopic (Ultraviolet (UV), FTIR, solid- and liquid-state NMR) and chemical degradation (permanganate (PO) and nitrobenzene oxidation (NO)) techniques. Despite both lignins are of HGS-type, strong structural differences were observed between them. Thus, DL_FS showed almost twice the abundance of H and G units and almost half of the abundance of S units when compared to DL_R. DL_R possessed significantly higher amount of β-O-4′ structures (0.32/C₆ against 0.12/C₆) and the molecular weight (5400 Da against 3750 Da) than those of DL_FS. About 72% of the condensed structures in DL_FS are of β-5 and 5–5′ types, whereas 4-O-5′-diaryl ether structures were the most abundant condensed structures in DL_R. Most of H units in both lignins are terminal phenolic coumarates linked to lignin substructures by ester bonds. Both lignins are structurally associated with suberin-like components in cell wall tissues. Structural features of stalk lignin were discussed in terms of possible restrictions for the kraft pulping of integral stem material.     

Rice straw mulching and nitrogen response of no-till wheat following rice in Bangladesh

Wheat (Triticum aestivum L.) cultivation in no-till soil of a postrice harvest field utilizes residual soil moisture and reduces the time period from rice harvest to wheat seeding in intensive rice-wheat cropping systems. Some of the major constraints in no-till wheat production are high weed infestation, poor stand establishment due to rapid drying of topsoil and low nitrogen use efficiency (NUE). A field experiment was conducted at the research farm of the Wheat Research Centre, Dinajpur, Bangladesh, for two consecutive years to overcome those constraints, to evaluate rice straw as mulch, and to determine the optimum application rate of nitrogen (N) for no-till wheat. The treatments included 12 factorial combinations of three levels of mulching: no mulch (M₀), surface application of rice straw mulch at 4.0 Mg ha⁻¹ that was withdrawn at 20 days after sowing (M₁), the same level of mulch as M₁ but allowed to be retained on the soil surface (M₂), and four nitrogen levels (control 80, 120 and 160 kg ha⁻¹). Rice straw mulching had a significant effect on conserving initial soil moisture and reducing weed growth. Root length density and root weight density of wheat were positively influenced both by straw mulching and N levels. N uptake and apparent nitrogen recovery of applied N fertilizer were higher in mulch treatments M₁ and M₂ as compared to M₀. Also mulch treatment of M₁ and M₂ were equally effective at conserving soil moisture, suppressing growth of weed flora, promoting root development and thereby improved grain yield of no-till wheat. N application of 120 kg ha⁻¹ with straw mulch was found to be suitable for no-till wheat in experimental field condition.     

Acetosolv delignification of Miscanthus sinensis bark: Influence of process variables

Using a face-centred composite experimental design with three central point replicates, we investigated the effects of cooking time (60–180 min), acetic acid concentration (60–95% of liquor weight) and HCl concentration (0.05–0.15% of liquor weight) on the yield, residual Klason lignin content and total polysaccharide content of pulps obtained from Miscanthus sinensis bark by the acetosolv process. Response surfaces fitted satisfactorily to the experimental results showed the most influential of the independent variables to be acetic acid concentration; increasing acetic acid concentration reduced yield and lignin content, and increased total polysaccharide content (except at the highest concentrations of the acids). The response surface for lignin content was used to design a Box–Wilson steepest-descent optimisation procedure to determine the conditions minimising pulp lignin content; the minimum achieved, 0.5%, was obtained using a cooking time of 147 min, an acetic acid concentration of 93.25% and an HCl concentration of 0.122%, under which conditions pulp yield was 52.6%.     

Characterization and degradation of lignin from steam explosion of pine and corn stalk of lignin: The role of superoxide ion and ozone

Steam explosion of corn stalk in the presence of 3% sulphuric acid at 200 °C for 5 min gave the highest recovery of lignin. Lignin has M_w = 2640 and M_z = 93,994. In the UV spectrum absorptions at λ = 231 and 280 nm were recorded. ¹H NMR spectrum of lignin showed signals attributable to cinnamaldehyde units, guaiacyl units, and syringyl units. Syringyl and guaiacyl units are in 1:1 ratio. ¹³C NMR spectrum showed signals for guaiacyl, syringyl, and p-hydroxyphenyl units. The spectrum showed a prevalence of guaiacyl units. The ¹³C NMR spectrum is in agreement with the presence of cinnamic units. The same characterization was performed on lignin from pine. The irradiation of lignin from pine from steam explosion process in the presence of oxygen, in conditions described for the formation of superoxide ion, for different irradiation time was followed isolating the lignin and determining the average molecular weight. The experiments showed that, until 8 h irradiation, M_n decreases, while M_w and M_z increases. After 8 h irradiation an inverse behaviour was observed, with an increase of M_n and a decrease of M_w and M_z. These results are in agreement with an initial polymerization process followed by a photoinduced degradation. Ozonization was carried out in acetonitrile–methanol solution. The reaction showed a zero-order kinetics. After 50 min the average molecular weight of lignin is the half. The reaction mixture was analyzed by using GC–MS. Oxalic acid was determined.     

Lignin as a base material for materials applications: Chemistry,application and economics

Lignin has long laboured under the label of “waste material”. However, as part of the thematic network EUROLIGNIN, a survey and desk study was undertaken to assess the changes and patterns in the utilisation of lignin with respect to materials applications. This showed that over the last 10–15 years there has been an explosion of research into, and commercialisation of, lignin-based products and processes which add significant value to a material that was previously, and continues to be, used as a low-value fuel for pulping boilers. The innate chemistry of lignin, a phenolic heteropolymer, has allowed it to make inroads into the high value polymer industries whilst continuing to act as feedstock material for the binder industries. Indeed the replacement of phenolics by lignin in resins systems is economically attractive with the phenolic resins market utilising approximately 2.52 M tonnes in 2001. Currently lignin, predominantly as lignosulphates, is used as a binding and dispersing agent in different industries with approximately 1 M tonnes (on a 100% solids basis) used annually, for example, in concrete admixtures. These and other applications will be discussed and expanded upon here with emphasis on both the economics of the markets and what is still required for lignin to mature as a valuable resource in its own right.     

Chemical composition and pulp characterization of Tunisian vine stems

In this study, the valorisation of Tunisian vine stem wastes was investigated. The chemical composition of the vine stems was studied, and it was found that when compared to non-wood plants, they contain greater amounts of extractives, lignin, and comparable holocellulose content. An elementary analysis of the ashes showed that the major constituents were mineral elements (K and Ca). Soda pulping of vine stems led to a yield of about 35% after the bleaching step. This amount is lower than that obtained for wood plants and similar to that observed for annual plants. The morphological properties, Kappa number, and degree of polymerization of the resulting pulp were determined. Finally, paper handsheets were prepared from the pulp, and their physical properties were investigated. The breaking length, Young's modulus, and burst index of the produced paper presents quite acceptable values. Further, the silica content of the stems is low, which is advantageous for the pulping process. Experimental results obtained for both the pulp and paper show that this agricultural residue has the potential to be used for papermaking applications.     

Studies on Hibiscus cannabinus and Hibiscus sabdariffa as an alternative pulp blend for softwood: An optimization of kraft delignification process

Hibiscus cannabinus and Hibiscus sabdariffa, agro-based residues consist of bast and wood fibers which resemble to those of softwood and hardwood, respectively. The runkel ratio of core fibers H. cannabinus and H. sabdariffa is comparable to that of Picca abies, whereas, it is much less than those of hardwood like Eucalyptus tereticornis. The slenderness ratio of H. cannabinus is much closer to P. abies in comparison to H. sabdariffa whereas, it is 7.7 and 13% less than E. tereticornis. The flexibility coefficient of H. cannabinus and H. sabdariffa are slightly lower than that of P. abies but it is 59.6 and 57.0% are more than that of E. tereticornis. It indicates that morphological characteristics of core fibers of H. cannabinus and H. sabdariffa closely resemble to that of softwood except fiber length which can be compensated by long bast fibers. Due to identical pulping conditions, H. cannabinus and H. sabdariffa can be delignified together by kraft pulping process. The optimum cooking conditions for H. cannabinus and H. sabdariffa were found to be as, active alkali 16%, sulfidity 20%, temperature 160 °C, time (at temperature) 120 min and wood to liquor ratio of 1:4.5. An anthraquinone (AQ) dose of 0.05% at an active alkali dose of 13% (as Na₂O) produces the screening rejects and kappa number similar to that obtained by using 15% active alkali (as Na₂O). The reaction kinetics study indicates that delignification is of first order. Low sulfidity AQ additive kraft pulping at constant H-factor produces better strength properties compared to non-additive kraft cooks.     

Comparative study of organosolv lignins from wheat straw

Dewaxed wheat straw was treated with acetic acid–H₂O (65/35, v/v), acetic acid–H₂O (80/20, v/v), acetic acid–H₂O (90/10, v/v), formic acid–acetic acid–H₂O (20/60/20, v/v/v), formic acid–acetic acid–H₂O (30/60/10, v/v/v), methanol–H₂O (60/40, v/v) and ethanol–H₂O (60/40, v/v) using 0.1% HCl as a catalyst at 85 °C for 4 h, in which 78.2, 80.0, 88.2, 89.4, 94.1, 23.5 and 37.4% of the original lignin, and 42.4, 58.7, 70.0, 65.1, 76.5, 14.2 and 22.2% of the original hemicelluloses was released, respectively. Lignins obtained were characterized by their content of hemicelluloses, composition of phenolic acids and aldehydes, molecular weight, thermal stability and by UV, Fourier transform infrared (FT-IR), ¹H and ¹³C nuclear magnetic resonance (NMR) spectroscopy. The results showed that aqueous organic acid was more effective than aqueous organic alcohol for extensive delignification and selective fractionation of cellulose, lignin and hemicelluloses from the straw. In particular, the addition of formic acid gave a significant effect on the dissolution of lignin. All the acid-insoluble lignin fractions contained small amounts of contaminated hemicelluloses as shown by their content of neutral sugars, 0.9–4.3%, and had weight-average molecular weight between 3960 and 4340 g mol⁻¹. An increase in concentration of acetic acid or formic acid in organosolv resulted in an increment in release of guaiacyl units and in lignin condensation. However, the lignin preparations released during the treatment with aqueous organic alcohol without organic acid contained almost equal amounts of non-condensed guaiacyl and syringyl units with fewer p-hydroxyphenyl units. The β-O-4 ether bonds together with β-β, β-5 and 5-5′ carbon–carbon linkages were identified to be present in lignin substructures.     

Fiber yield and quality of fiber nettle (Urtica dioica L.) cultivated in Italy

To evaluate the production potential of fiber nettle crops in Tuscany (Italy), a German clone of fiber nettle was cultivated during 2006–2007.Although a longer experimentation is essential, the two first years of trials showed that the German clone used also seems to give good results in term of growth and fiber yield in an environment like central Italy, with higher temperatures and generally lower rainfall. Indeed the stalk mean dry matter obtained was about 15.4 Mg ha^?1 with a mean fiber content of about 11% of stalk dry matter, and the resulting fiber yield was 1696 kg ha^?1, comparable to or higher than those reported in the literature.The differences in chemical, physical and mechanical characteristics of fibers extracted from different portions of stalks seemed to indicate an intrinsic heterogeneity of the fibers along the stem. Fiber mean diameter values ranged from 47 to 19 μm and fiber length from 43 to 58 mm moving from stalk bottom to top. Tensile strength of the bottom part of the stalk was much lower than that of the other parts, with mean values of about 24 and 60 cN tex^?1, respectively. More constant mean values along the stalk were found for the elongation parameter (2.3–2.6%). Lignin content decreased moving toward the stalk top from about 4.4% to 3.5%.These physical–mechanical characteristics confirmed the potential of the fibers of nettle cultivated in Tuscany to be used for textile purposes. Indeed they were similar to hemp fibers in diameter, lignin content and elongation, and similar to flax or cotton in tensile strength.     

Acetosolv delignification of depithed cardoon (Cynara cardunculus) stalks

Modelling of the Acetosolv treatment of the cardoon bark (Cynara cardunculus) was accomplished using a second-order face-centred factorial design. We considered as independent (experimental) variables: cooking time (60–180 min), acetic acid concentration in the cooking liquor (60–90%) and hydrochloric acid concentration in the cooking liquor (0.20–0.80%); as well as dependent variables: pulp yield, kappa number and viscosity.Empirical models were deduced to satisfactorily fit experimental data with the values of the independent variables and allow quantifying the effects of each variable.An optimisation with constraints led to the calculation of the region of the experimental domain (time = 180 min, acetic acid concentration ≥ 71.3% and HCl concentration > 0.41%) leading to pulps with kappa numbers < 25 at a maximal pulp yield and viscosity, giving us maximum possible values for pulp yield (46.3%) and viscosity (557 mL/g).     

Cynara cardunculus L. — a new fibre crop for pulp and paper production

The pulping potential of the thistle Cynara cardunculus L. was evaluated by studying anatomy and chemical composition of the stalks and Kraft pulp yields and properties. C. cardunculus is a perennial plant, with annual harvests, that can be grown in hot and dry climates with high productivities. The stalk of the plant has a central pith, ca. 45% in volume and 10% in weight, of small parenchyma cells, surrounded by a cortex where numerous fibre vascular bundles are imbedded. The fibres are on average 1.3 mm long, 18.8 μm wide and have a 4.8 μm wall thickness. The whole stalks have 7.7% ash, 14.6% extractives, 17.0% lignin and 53.0% polysaccharides, mainly cellulose and xylans. The pith has more lignin than the depithed stalk (20.3 vs. 13.6%). The Cynara stalks could be cooked by standard Kraft pulping to produce well delignified pulps with high yields (44–47% with Kappa 11–15), low rejects and very good strength properties, especially in relation to tensile strength. Depithing of the stalks has a positive impact on pulp yield, chemical consumption and on the pulp strength properties.     

Comparison on the total phenol contents and the color of fresh and infrared dried olive leaves

The color (L*, a*, b* parameters), the total phenols content and the global chemical composition (moisture, protein, fat, carbohydrates and ash) of four fresh varieties of olive leaves (Chemlali, Chemchali, Zarrazi and Chetoui) were determined. Fresh olive leaves are characterized by a green color (greenness parameter, a*, varying from ?5.01 ± 0.26 to ?9.14 ± 1.21), an intermediate moisture content (0.85 to 1.00 g/g dry matter, i.e. 46 to 50 g/100 g fresh matter) and a variable amount of total phenols according to the olive leaf variety (from ≈2.32 to ≈1.40 g caffeic acid/100 g dry matter).Fresh leaves were submitted to blanching and/or infrared drying at 40, 50, 60 and 70 °C in order to be stabilized by reducing their moisture contents. The impact of IR drying temperature on some quality attributes (color, total phenols and moisture rate removal) was evaluated. Nevertheless, the effect of prior blanching treatment on the quality attributes of dried leaves is less significant and it depends on the olive leaf variety. The infrared drying induces a considerable moisture removal from the fresh leaves (more than 85%) and short drying durations (varying from ≈162 at 40 °C to 15 min at 70 °C). IR drying temperature showed a significant effect of on total phenols content and the color of the leaves whatever the leaf variety. In fact, total phenols content of dried olive leaves increased if compared to fresh ones. For example, total phenols of Chemlali leaves increased from 1.38 ± 0.02 (fresh leaves) to 2.13 ± 0.29 (dried at 40 °C) and to 5.14 ± 0.60 g caffeic acid/100 g dry matter (dried at 70 °C). IR drying allows preserving the greenness color of fresh leaves and enhancing their luminosity. It could be suggested for preserving olives leaves before their use in food or cosmetic applications.     

Does undersowing winter wheat with a cover crop increase competition for resources and is it compatible with high yield?

The sustainability of cropping systems can be increased by introducing a cover crop, provided that the cover crop does not reduce the cash crop yield through competition. The cover crop may be sown at the same time as a cash crop in the crop rotation. We carried out an experiment in 1999–2000 and 2000–2001 in the Paris Basin, to analyze the effects of simultaneously sowing winter wheat (Triticum aestivum L.) and red fescue (Festuca rubra L.), a turf grass. Competition between wheat and fescue was analyzed with one variety of red fescue, Sunset, and two varieties of wheat, Isengrain and Scipion, each sown at a density of 150 plants m^?2. In this study, we evaluated the effect of undersown fescue on wheat yield and analyzed the competition between the two species in detail. The undersown red fescue decreased wheat yield by about 12% for Isengrain (8.7 t ha^?1 for undersown Isengrain versus 9.8 t ha^?1 for Isengrain alone) and 7% for Scipion (7.4 t ha^?1 for undersown Scipion versus 8.0 t ha^?1 for Scipion alone). During the early stages of wheat growth (up to the ‘1 cm ear’ stage, corresponding to stage 30 on Zadoks’ scale), undersown fescue and fescue sown alone grew similarly. However, fescue biomass levels were much lower (5.6 and 4.7 g m^?2 for fescue grown alone and undersown fescue) than wheat biomass levels on the undersown plots (120 g m^?2 for Isengrain and 111 g m^?2 for Scipion). From the e1 stage onwards, the wheat canopy rapidly extended, whereas that of red fescue remained sparse. The time lag between the beginning of the rapid increase in LAI and PAR interception by wheat grown alone and that for fescue grown alone was 590 dd in the second year. This resulted in much slower growth rates for undersown fescue than for undersown wheat. Biomass production rate was therefore low for undersown fescue (12% those of fescue grown alone, on average, at the time of wheat harvest), as were levels of water and nitrogen use. Neither the water deficit that occurred during the second experiment nor the nitrogen nutrition status of the wheat on plots with undersown fescue significantly affected wheat biomass production after anthesis.The global interception efficiency index IG?_i indicated that the fraction of the PAR_o intercepted by the wheat during its growth (255 days) was 0.35.