Manganese requirement of sunflower (Helianthus annuus L.), tobacco (Nicotiana tabacum L.) and triticale (x Triticosecale W.) at early stage of growth

Manganese deficiency symptoms are more often observed in crops at early stages of growth since Mn²⁺ can be easily mobilized from the surface soil. The objectives of this study were to evaluate some of the popular rotation crops grown in Hungary for tolerance to low external Mn²⁺ levels and to determine the critical tissue concentration for Mn²⁺ deficiency during early stages of growth. Indicator plants of sunflower (Helianthus annuus L.) were grown with NPKCaMg-fertilization induced of 0.0425–0.0700 g kg⁻¹; of tobacco (Nicotiana tabacum L.) 0.0237–0.0337 g kg⁻¹; of triticale (x Triticosecale W.) 0.0103–0.0327 g NH₄-acetate + EDTA extractable soil Mn²⁺ kg⁻¹; and were grown for 73, 50, and 191 days. The minimum Mn²⁺ concentration required in soil nutrient contents was 0.0425 g kg⁻¹ for sunflower, 0.0243 g kg⁻¹ for tobacco, and 0.0103 g kg⁻¹ for triticale. Sunflower, tobacco and triticale achieved optimum growth from 0.048 to 0.065 g Mn²⁺ kg⁻¹, from 0.0249 to 0.0321 g Mn²⁺ kg⁻¹, and from 0.0287 to 0.0296 g Mn²⁺ kg⁻¹, respectively. Critical ABP's dry weight Mn²⁺ concentration at early stages of growth was 0.0536 g kg⁻¹ in sunflower, 0.458 g kg⁻¹ in tobacco, and 0.1938 g kg⁻¹ in triticale. Our results demonstrate that the tolerance to low external Mn²⁺ (triticale <0.0302 g kg⁻¹; sunflower <0.0562 g kg⁻¹; tobacco <0.0693 g kg⁻¹) and the critical tissue Mn²⁺ levels for deficiency varied significantly among crop species tested.     

Fertilisation of irrigated maize with pig slurry combined with mineral nitrogen

Maize (Zea mays L.) is a very important crop in many of the irrigated areas of the Ebro Valley (NE Spain). Intensive pig (Sus scrofa domesticus) production is also an important economic activity in these areas, and the use of pig slurry (PS) as a fertiliser for maize is a common practise. From 2002 to 2005, we conducted a field trial with maize in which we compared the application of 0, 30 and 60 m³ ha⁻¹ of PS combined with 0, 100 and 200 kg ha⁻¹ of mineral N at sidedress. Yield, biomass and other related yield parameters differed from year to year and all of them were greatly influenced by soil NO₃⁻-N content before planting and by N (organic and/or mineral) fertilisation. All years average grain yield and biomass at maturity ranged from 9.3 and 18.9 Mg ha⁻¹ (0 PS, 0 mineral N) to 14.4 and 29.6 Mg ha⁻¹ (60 m³ ha⁻¹ of PS, 200 kg ha⁻¹of mineral N), respectively. Grain and total N biomass uptake average of the studied period ranged from 101 and 155 kg ha⁻¹ (0 PS, 0 mineral N) to 180 and 308 kg ha⁻¹ (60 m³ ha⁻¹ of PS, 200 kg ha⁻¹of mineral N), respectively. All years average soil NO₃⁻-N content before planting and after harvest were very high, and ranged from 138 and 75 kg ha⁻¹ (0 PS, 0 mineral N) to 367 and 457 kg ha⁻¹ (60 m³ ha⁻¹ of PS, 200 kg ha⁻¹of mineral N), respectively. The optimal N (organic and/or mineral) rate varied depending on the year and was influenced by the soil NO₃⁻-N content before planting. For this reason, soil NO₃⁻-N content before planting should be taken into account in order to improve N fertilisation recommendations. Moreover, the annual optimal N rates also gave the lowest soil NO₃⁻-N contents after harvest and the lowest N losses, as a consequence they also could be considered as the most environmentally friendly N rates.     

Water relations, gas exchange and growth of cool-season grain legumes in a Mediterranean-type environment

The aim of this study was to identify the physiological characteristics which may affect the yield of six cool-season grain legume species grown in a water-limited Mediterranean-type climate in Western Australia. The rate of net photosynthesis, stomatal conductance and water relations were measured from flowering to complete leaf senescence in white lupin, chickpea, faba bean, field pea, grass pea and lentil. In irrigated plants, the midday leaf water potential was about −0.6 MPa in all species, while the maximum rate of leaf photosynthesis was 30 μmol m⁻² s⁻¹ for chickpea and white lupin, and below 20 μmol m⁻² s⁻¹ for the other species. With the development of water deficits, the leaf water potential in rain-fed plants decreased to about −3 MPa in chickpea and lentil and −2 MPa in the other species. Photosynthesis and stomatal conductance decreased markedly as the leaf water potential decreased below −0.9 MPa in all six species, including chickpea and lentil, which showed a high degree of osmotic adjustment. Despite the similarity in water use, restricted to the top 40 cm of soil, and water relations characteristics, yields varied markedly among species. Yields were strongly correlated with early biomass production and early pod development.     

Stomatal conductance and ozone exposure in relation to potato tuber yield—results from the European CHIP programme

Measurements of stomatal conductance on field-grown potato (Solanum tuberosum L.) cv. Bintje from the CHIP programme were combined to study the response to environmental factors. 3274 data points were used. Data were obtained from five sites: Jokioinen in Finland, Östad in Sweden, Giessen in Germany, Tervuren in Belgium and Sutton Bonnington in UK. Measurements were made in open-top chamber treatments with ozone and carbon dioxide exposure and in the ambient air. A typical light response curve was obtained with light saturation at approximately 400 μmol m⁻² s⁻¹ photosynthetically active radiation (PAR). The leaf temperature optimum for stomatal conductance was 29 °C. The stomatal conductance declined strongly at leaf-to-air vapour pressure differences >20 hPa. An elevated carbon dioxide concentration (680 μl l⁻¹) reduced the stomatal conductance by up to approximately 20%. Elevated ozone reduced the stomatal conductance towards the end of the growth period, in addition to the negative effect by ordinary senescence on stomatal conductance. A multiplicative model, based on the boundary line technique, was used to estimate the relationship between stomatal conductance and the environmental variables. Test with the data sets from two sites providing sufficient data, Östad and Giessen, showed that the multiplicative model had R²-values of 0.60 and 0.42, respectively, for the relationship between calculated and observed conductance. Test of the model with an independent data set from an open-top chamber experiment with the potato cultivar Kardal showed an R² of 0.59 between calculated and observed conductance. The conductance model was used to estimate the accumulated ozone uptake (CUO₃) by potato leaves from emergence to harvest. The relationship between CUO₃ and relative yield loss, using a threshold for the ozone uptake rate of 7 nmol m⁻² s⁻¹, provided a higher R²-value (0.45) than CUO₃ without any threshold and relationships based on the accumulated exposure over 40 nmol mol⁻¹ (AOT40) or the sum of all hourly average ozone concentrations exceeding 60 nmol mol⁻¹ (SUM06). All four relationships were however statistically significant.     

Nitrogen mineralization in sandy loam soils under an intensive double-cropping forage system with dairy-cattle slurry applications

Nitrogen (N) mineralization and soil mineral N contents were measured at 2-week intervals over a 2-year period (June 1994–May 1996) on two different sites in the North West region of Portugal. The experiment was established in fields, which had for many years been under a double-cropping forage system with maize from May to September and a winter crop (mixture of cereals and Italian ryegrass) during the rest of the year. In addition to N fertilizers, dairy-cattle slurry was applied regularly at the sowing of each crop. On this intensive forage system, quantification of N released from slurry, crop residues and soil organic matter becomes important when better N use efficiency and reduced environmental impact from agricultural practices are required. Net N mineralization rates of the 0–10 cm soil layer fluctuated considerably between consecutive incubation periods and ranged from −0.88 to 1.87 mg N kg⁻¹ day⁻¹ with annual average rates of between 0.41 and 0.65 mg N kg⁻¹ day⁻¹. The total N mineralized in the 10 cm depth soil layer reached values between 122 and 224 kg N ha⁻¹ year⁻¹, showing that mineralization was a very important N source for the crops. The amounts of N released during the cold season (November–February) were equivalent to 27–48% of the yearly total. Regression analysis indicated that seasonal variation in N mineralization was only poorly explained by soil moisture and temperature. The changing balance during the year between soil moisture and temperature will contribute to the relatively constant N mineralization rates. Soil mineral N contents during the maize crop were high and exceeded the nutrient requirements for the optimum yield of this crop. Under the climatic conditions of the region and due to the poor development of the winter crop plants at the time, the mineral N left in the soil after the maize crop and released by mineralization during the cold season is particularly vulnerable to nitrate leaching losses.     

Seed yield, oil and phytate concentration in the seeds of two oilseed rape cultivars as affected by different phosphorus supply

A greenhouse pot experiment was conducted for studying seed and oil yield, P uptake and phytate concentration in the seed of two oilseed rape cultivars (Brassica napus L. var. Oleifera, cv. Bristol and cv. Lirajet), grown on a soil substrate at different levels of plant available phosphorus (6, 19, 31 and 106 mg P-CAL kg⁻¹ soil, resp.). All other nutrients were maintained at a high level. At maturity, seed yield and seed quality were investigated. An increase in the phosphorus soil supply resulted in a significant (P<0.05) increase in seed and oil yield, oil and P concentration of the seeds, and P transported to the seeds. The phytate-phosphorus concentration ranged from 0.5 to 6.9 g kg⁻¹ in the seeds and from 0.9 to 12.8 g kg⁻¹ in rapeseed meal. Insufficient P supply resulted in a reduced concentration of phosphorus and phytate in the seeds. Significant interactions between the factors cultivar and P supply were found for the traits seed yield, oil yield, and P-harvest index.     

Effects of row spacing and liquid manure on directly drilled winter wheat in organic farming

In the optimisation of grain yield and quality of wheat, plant distribution is a key factor. In contrast to high yield levels, at moderate levels, widening the row space did not decrease grain yield. To gain information about changes in the quality and yield with changing in row spacings in organic farming systems, experiments were conducted at two locations in the Swiss midlands in 2001/2002. Winter wheat (Triticum aestivum L., cv. Titlis) was directly drilled in rows 0.1875 and 0.3750 m apart at the same seeding rate per area. An unfertilised treatment and the usual application of 60 m³ ha⁻¹ liquid farmyard manure were compared. While the grain yield was not decreased by the wider row spacing, the thousand kernel weight (TKW), and grain protein content were increased from 42.6 to 43.5 g and from 11.7 to 12.7%, respectively, compared to the narrow row spacing. Liquid manure, on average of both experimental sites, increased the yield (from 3.725 to 4.765 Mg ha⁻¹) and the grain protein content (from 12.0 to 12.5%). Doubling the space between the rows from 0.1875 to 0.3750 m seemed to be a suitable strategy for managing directly drilled winter wheat in organic farming systems.     

Pod photosynthesis and drought adaptation of field grown rape (Brassica napus L.)

In rape (Brassica napus L., cv. Global) seed growth mainly depends on husk CO₂ assimilation. In irrigated plants, the net photosynthetic rate (A_max) was 10–13 μmol CO₂ m⁻² s⁻¹ in non-maturing pods and correlated with nitrogen content. The stomatal conductance of water vapour (g_H2O) was 0.3 mol m⁻² s⁻¹ in non-maturing pods. The photosynthetic nitrogen use efficiency (NUE) was 8.3 μmol CO₂g⁻¹ N s⁻¹, about one-third of that in leaves. The photosynthetic water use efficiency (WUE; A_maxg_H2O⁻¹) was similar in pods and leaves. In severely droughted plants, the photosynthetic rate was reduced to 38%. The seed growth rate, however, was not influenced by intermittent periods of water stress, indicating translocation of assimilates to the seeds. The drought resistant character of the pods was due to low specific area, succulence, low stomatal conductance causing a small decrease of ΔΨ day⁻¹ during soil drying and maintenance of high relative water content during severe drought. A mathematical formulation of the pod water release curve was undertaken. © (1997) Elsevier Science B.V.     

Evaluation of CropSyst for simulating the yield of flooded rice in northern Italy

Research on rice cropping systems carried out in Europe has to face the great variability of pedo-climatic conditions, and the linked abundance of cultivated varieties, characteristic of the high latitudes-temperate areas where rice is traditionally grown.

Dynamic simulation models can provide an useful tool for system analysis needed to improve the knowledge, the agronomic management and crop monitoring.

For calibrate and validate CropSyst (never used for rice), a process-based simulation model, for Indica-type and Japonica-type varieties, data obtained from five field experiments, carried out in Northern Italy between 1989 and 2002, were used.

Plants were sampled during the life cycle from rice plots of five cv Loto, Cripto, Ariete, Drago, Thaibonnet and Sillaro, maintained at potential production, to determine some important crop variables and parameters such as aboveground biomass (AGB), leaf area index, specific leaf area, harvest index, the date of the main phonological stages.

At the end of the calibration process to the parameters (the others were set to the default value, taken from the Literature or measured) optimum mean daily temperature for growth, specific leaf area (for Japonica varieties), stem/leaf partition coefficient (empirical), leaf duration, were assigned the following values: 28 and 27 °C respectively for Japonica and Indica varieties, 27 and 29.5 m² kg⁻¹ respectively for Japonica early and medium-late varieties, 4.5, 3, 1.5 for Japonica early, medium-late and Indica varieties, 700, 850, 950 °C-days for the three groups of varieties.

The assessment of model performances has shown average RRMSEs of 20 and 22% at the end of calibration and for the validation process; the modelling efficiency is always positive and the coefficient of determination always very close to 1. General improvements will be achieved by the model by considering the thermal profile (strongly influenced by flooding water at mid latitudes) evolving in and over the canopy.     

Influence of modified atmosphere packaging on sensory quality of shiitake mushrooms

Shiitake mushrooms (Lentinus edodes) were packaged under air in two macroperforated packages (A—9.0 × 10³ perforations/m², 0.1 mm² surface and B—17 perforations/m², 0.1 mm² surface) and under two gas mixtures (15% and 25% O₂) in polyethylene packages, and stored at 5 °C for 18 d. The sensory quality of the mushrooms was evaluated using a trained assessors panel.

Mushrooms packaged in macroperforated packages A showed the smallest deterioration rate. However, weight loss after 6 d of storage reached 15%, which is unacceptable. Besides, shelf life of shiitake mushrooms in active modified atmosphere was limited by off-odour development. Mushrooms in these packages developed off-odour after 12 d of storage due to the fact that O₂ concentrations fall bellow 5%.

On the other hand, the shelf life of mushrooms packaged in macroperforated packages B was limited by their sensory deterioration, particularly by changes in the colour and uniformity of their gills. In this film, mushrooms could be stored for approximately 10 d with a weight loss lower than 2%.

Results from the present work suggest that during the first 6 d of storage all the evaluated packaging conditions were useful for reducing mushroom deterioration rate.     

Interactive effects of elevated atmospheric CO2 concentrations and plant available soil water content on canopy evapotranspiration and conductance of spring wheat

The present study was conducted to investigate the possible interactive effects of rising atmospheric CO₂ concentration [CO₂] and drought stress on water use of wheat. Spring wheat (Triticum aestivum cv. “Minaret”) was grown either in 1 m diameter lysimeters with 0.4 m soil depth (1998) or in the field (1999) in open-top chambers under two CO₂-concentrations (ambient, ambient + 280 ppm) and two watering regimes (well-watered = WW with a plant available water content PAW > 40 mm and drought stressed = DS, 10 mm < PAW < 30 mm) beginning after first node stage. Canopy evapotranspiration (E_C) was measured continuously from first the node stage until the beginning of flag leaf senescence using four open-system canopy chambers (0.78 m³). Seasonal changes of the absorption of photosynthetically active radiation (APAR) of the canopy and root growth (1999) were also measured.

In both growing seasons leaf area index increased in response to elevated [CO₂] in both water treatments. The related effects of [CO₂] on canopy radiation absorption (APAR) were, however, smaller. E_C was linearily related to APAR in both growing seasons. While elevated [CO₂] reduced the slope of this relation under WW conditions by ca. 20% in both growing seasons, it was not reduced (1998) and even increased (1999) under drought. Canopy conductance (G_C) calculated as E_C divided by vapour pressure deficit of air, showed a non-linear relationship to APAR that was best explained by saturation curves. Under WW conditions, elevated [CO₂] reduced the initial slope of G_C versus APAR as well as G_C at saturating light conditions (ca. −30%), while under DS conditions no effect of elevated [CO₂] could be detected. Under high light conditions (PAR > 400 μmol m⁻² s⁻¹) a critical “threshold value” of PAW (T_PAW, ca. 40 mm) could be identified above which G_C did not respond to PAW. While in 1998 G_C did not respond to elevated [CO₂] at PAW < T_PAW, it was slightly increased at low PAW values in the field experiments of 1999. The reduction of T_PAW by elevated [CO₂] may be explained by enhanced root growth (1999) that would have given the plants better access to soil water resources. The present results suggest that below a critical soil water content elevated [CO₂] will not reduce canopy water loss of wheat or may even enhance it.     

Productivity and water use efficiency of sweet sorghum as affected by soil water deficit occurring at different vegetative growth stages

The growth and production of sweet sorghum [Sorghum bicolor (L.) Moench] crops under semi-arid conditions in the Mediterranean environment of southern Italy are constrained by water stress. The effects of temporary water stress on growth and productivity of sweet sorghum were studied during three seasons at Rutigliano (Bari, Italy). The aim of this research was to evaluate the sensitivity of phenological stages subjected to the same water deficit. In a preliminary study it was observed that stomata closed when pre-dawn leaf water potential (Ψ_b) became lower than −0.4 MPa. This criterion was used in monitoring plant water status in three different plots: one never stressed and two stressed at different phenological stages (‘leaf’ and ‘stem’) when mainly leaves or stems were growing, respectively. An evaluation of the sensitivity of phenological stages subjected to identical water stress was obtained by comparing the above-ground biomass and WUE of drought crops with those of the well-irrigated crop (up to 32.5 t ha⁻¹ of dry matter and 5.7 g kg⁻¹). The sensitivity was greatest at the early stage (‘leaf’), when a temporary soil water stress reduced the biomass production by up to 30% with respect to the control and WUE was 4.8 g kg⁻¹ (average of three seasons). These results help quantify the effects of water constraints on sweet sorghum productivity. An irrigation strategy based on phenological stage sensitivity is suggested.     

Influence of aqueous 1-methylcyclopropene concentration, immersion duration, and solution longevity on the postharvest ripening of breaker-turning tomato (Solanum lycopersicum L.) fruit

The influence of aqueous 1-methylcyclopropene (1-MCP) concentration, immersion duration, and solution longevity on the ripening of early ripening-stage tomato (Solanum lycopersicum L.) has been investigated. Tomato fruit at the breaker-turning stage were fully immersed in aqueous 1-MCP at 50, 200, 400 and 600 μg L⁻¹ for 1 min, quickly dried, and then stored at 20 °C. Ethylene production, respiration, surface color development, and rate of accumulation of lycopene and polygalacturonase (PG) activity were suppressed and/or delayed in fruit exposed to aqueous 1-MCP. Suppression of ripening was concentration dependent, with maximum inhibition in response to 1 min immersion occurring at concentrations of 400 and 600 μg L⁻¹. Climacteric ethylene peaks were delayed approximately 6, 7, and 9 d and respiration was strongly suppressed in fruit treated with aqueous 1-MCP at 200, 400, and 600 μg L⁻¹, respectively, compared with control fruit. Fruit firmness, lycopene content, PG activity, and surface hue of fruit treated at the three higher levels remained strongly suppressed compared with control. Skin hue values and pericarp lycopene content in response to treatment at the subthreshold 50 μg L⁻¹ provided evidence for differential ripening suppression in external versus internal tissues. Maximum delay of softening and surface color development in response to 50 μg L⁻¹ aqueous 1-MCP occurred following immersion periods of between 6 and 12 min. Factors affecting fruit penetration by aqueous 1-MCP and mechanisms contributing to recovery from 1-MCP-induced ripening inhibition are discussed.     

Growth and development of bambara groundnut (Vigna subterranea) in response to soil moisture: 2. Resource capture and conversion

A study was conducted in controlled environment glasshouses to investigate the effects of soil moisture on resource capture and conversion of three landraces (DipC, S19-3 and UN from Botswana, Namibia and Swaziland, respectively) of bambara groundnut (Vigna subterranea (L.) Verdc.). The study was conducted under two soil moisture treatments: an irrigated control and a drought treatment where irrigation was withheld from approximately flowering to final harvest. Drought reduced the mean fractional intercepted radiation (f) from 0.8 to less than 0.7 across landraces. The mean light extinction coefficient (=0.46) was not affected either by landrace or watering regime, while cumulative intercepted radiation (S_ci) reduced under drought because of the reduction in f. Drought reduced total transpiration (E_c) only in DipC while it had no effect on the other two landraces. Crops under irrigation extracted most of the water from the top 50 cm of the profile while those under drought extracted water down to 90 cm. The conversion coefficient for intercepted radiation (_s; g MJ⁻¹) was reduced by 32%, from 1.51 to 1.02 g MJ⁻¹. Similarly, drought reduced the dry matter/transpired water ratio (ε_w; g kg⁻¹) by 20% from 2.05 to 1.65 g kg⁻¹.     

The dynamics of lucerne (Medicago sativa L.) yield components in response to defoliation frequency

The productive life of lucerne (Medicago sativa L.) stands depends on the rate of mortality of individual plants. However, self-thinning of plant populations may be compensated for by increases in other yield components, namely shoots/plant and individual shoot mass. Frequent defoliation reduces lucerne yield but it is unclear whether this is caused by an acceleration of plant mortality or changes in these other yield components. To investigate this, crops with contrasting shoot yields were created using constant 28 or 42-day regrowth cycles applied to a ‘Kaituna’ lucerne crop in Canterbury, New Zealand during the 2002/2003 and 2003/2004 growth seasons. Two further treatments switched from 28 to 42 or 42 to 28 days grazing frequency in mid-summer (4th February) of each year. The annual yield of shoot dry matter (DM) ranged from 12 to 23 t/ha for the treatments defoliated consistently each 28 or 42 days, respectively. Plant population was unaffected by treatments and declined exponentially from 130 plants/m² in June 2002 to 60 plants/m² in September 2004. The dynamics of plant and shoot population were associated with the light environment at the base of the canopy. The slope of the size/density compensation (SDC) of plants was −1.67 for the treatment defoliated each 42 days, near the expected self-thinning slope of −1.5 for stands at constant leaf area index (LAI). Self-thinning of shoots resumed after each defoliation when the LAI reached 2.1 and the transmission of photosynthetically active radiation (PAR_t) was 0.20. At this point the proportion of aerial DM in the tallest (dominant) shoots increased non-linearly from 30 to >80%, due to the mortality of intermediary and suppressed shoots. The average maximum shoot population in each rotation was 780 shoots/m² and unaffected by the decline in plant population due to a compensatory increase from 6 to 13 shoots/plant as the stand thinned. A lower asymptote of 43 plants/m² was estimated as the minimum plant population at which yield component compensation would maintain the productive potential of these ‘Kaituna’ stands. Differences in shoot yield were explained (R² = 0.97) by changes in the individual shoot mass (ISM) that were consistently lowered by frequent defoliation treatments. Frequent defoliations reduced crop productivity by limiting the assimilation of biomass into each individual shoot with negligible impact on shoot appearance rate, the number of shoots per plant at an LAI of 2.1 or the rate of plant population decay. Inter-specific competition for light was proposed as the main factor controlling self-thinning of plants and shoots regardless of their individual C:N status.     

Uptake and partitioning of sludge-borne copper in field-grown maize (Zea mays L.)

Accumulation of sludge-borne copper (Cu) by field-grown maize and its distribution between the different plant organs was studied in detail in a long-term sewage sludge field trial. Since 1974, field plots on a coarse sandy soil have been amended each year with farmyard manure (FYM) at a rate of 10 t dry matter (DM) ha⁻¹ year⁻¹ and with sewage sludge at the two levels of 10 t DM ha⁻¹ year⁻¹ (SS 10) and 100 t DM ha⁻¹ per 2 years (SS 100). All field plots have been cropped annually with maize. In 1993, five replicate plants per treatment were examined at six different growth stages from seedling to grain maturity. Each plant was separated into at least 12 different parts and the Cu content of each was determined. Regarding growth parameters, no visible deleterious effects on plant development due to the different soil treatments could be observed, although the dry matter yield of roots and stalks of SS 100-treated plants was significantly reduced. Significantly increased Cu concentrations of up to 60 mg Cu kg⁻¹ DM in the roots of young SS 100-grown maize plants and of up to 20 mg Cu kg⁻¹ DM in the upper leaves at silage stage were found. No critical Cu amounts were reached in the grains until harvest.     

Combined effects of 1-methylcyclopropene, calcium chloride dip, and/or atmospheric modification on quality changes in fresh-cut strawberries

The aim of this study was to determine the effects of 1-methylcyclopropene, 1-MCP (1 μL L⁻¹ for 24 h at 5 °C) on quality attributes and shelf life of fresh-cut strawberries. The 1-MCP was applied before (whole product) and/or after cutting (wedges), followed by storage in a continuous flow of air or air +1 μL L⁻¹ C₂H₄. The combined effects of 1-MCP and CaCl₂ dips (1% for 2 min) and/or CA (3 kPa O₂ + 10 kPa CO₂) were also examined. The application of only 1-MCP before and/or after cutting did not have a significant effect on firmness and appearance quality during storage for up to 12 days at 5 °C. The exposure to a continuous flow of 1 μL L⁻¹ C₂H₄ in air during storage did not increase the softening rate. 1-MCP applied before cutting or both before and after cutting of the strawberries increased respiration rates but reduced C₂H₄ production rates. Exposure to 1-MCP had a synergistic effect when combined with CaCl₂ plus CA. The combined treatment of 1-MCP + CaCl₂ + CA slowed down softening, deterioration rates, TA and microbial growth. Compared to the control, which had a 6-day shelf life, the shelf life of fresh-cut strawberries subjected to the combination treatment was extended to 9 days at 5 °C.     

Biomass yield and energy balance of giant reed (Arundo donax L.) cropped in central Italy as related to different management practices

In order to evaluate the possibility of reducing energy input in giant reed (Arundo donax L.) as a perennial biomass crop, a field experiment was carried out from 1996 to 2001 in central Italy. Crop yield response to fertilisation (200–80–200 kg ha⁻¹ N–P–K), harvest time (autumn and winter) and plant density (20,000 and 40,000 plants per ha) was evaluated. The energy balance was assessed considering the energy costs of production inputs and the energy output obtained by the transformation of the final product. The crop yield increased by +50% from the establishment period to the 2nd year of growth when it achieved the highest dry matter yield. The mature crop displayed on average annual production rates of 3 kg dry matter m⁻², with maximum values obtained in fertilised plot and during winter harvest time.

Fertilisation mainly enhanced dry matter yield in the initial period (+0.7 kg dry matter m⁻² as years 1–6 mean value). The biomass water content was affected by harvest time, decreasing by about 10% from autumn to winter. With regard to plant density, higher dry matter yields were achieved with 20,000 plants per ha (+0.3 kg dry matter m⁻² as years 1–6 mean value).

The total energy input decreased from fertilised (18 GJ ha⁻¹) to not fertilised crops (4 GJ ha⁻¹). The higher energetic input was represented by fertilisation which involved 14 GJ ha⁻¹ (fertilisers plus their distribution) of total energy costs. This value represents 78% of total energy inputs for fertilised crops.

Giant reed biomass calorific mean value (i.e., the calorific value obtained from combustion of biomass sample in an adiabatic system) was about 17 MJ kg⁻¹ dry matter and it was not affected by fertilisation, or by plant density or harvest time. Fertilisation enhanced crop biomass yield from 23 to 27 dry tonnes per ha (years 1–6 mean value). This 15% increase was possible with an energy consumption of 70% of the overall energy cost. Maximum energy yield output was 496 GJ ha⁻¹, obtained with 20,000 plants per ha and fertilisation. From the establishment period to 2nd–6th year of growth the energy production efficiency (as ratio between energy output and energy input per ha) and the net energy yield (as difference between energy output and energy input per ha) increased due to the low crop dry biomass yield and the high energy costs for crop planting. The energy production efficiency and net energy yield were also affected by fertilisation and plant density. In the mature crop the energy efficiency was highest without fertilisation both with 20,000 (131 GJ ha⁻¹) and 40,000 plants per ha (119 GJ ha⁻¹).     

Combustion quality of biomass: practical relevance and experiments to modify the biomass quality of Miscanthus x giganteus

A catalogue is set up describing the quality characteristics relevant for the combustion of biomass to be used as solid fuel. The practical relevance of these characteristics is discussed. The main characteristics are water concentration, the concentration of chloride and ash, the heating value and the concentration of volatiles and remaining coke. Further quality criteria are the concentrations of nitrogen, sulphur, potassium and calcium.

In multifactorial field trials at three locations, the influence of location, fertilizer application and harvest date on the quality of Miscanthus biomass from 3- and 4-year-old plantations was tested. The concentrations of water, minerals and ash, all three of which should be as low as possible, were higher in biomass from the cool and humid than in biomass from the warm location. The application of potassium fertilizer led to increases in the ash and potassium concentrations. Harvesting Miscanthus in February instead of December led to an improved biomass quality because the concentrations of ash, minerals and especially of water had declined.

Compared to other lignocellulose plants Miscanthus biomass has a very good combustion quality. In February the stems of Miscanthus had a water concentration of only 16–33%. The mineral concentrations were also low, with 0.3–2.1 g kg⁻¹ for chloride, 0.9–3.4 g kg⁻¹ for nitrogen and 3.7–11.2 g kg⁻¹ for potassium. © 1997 Elsevier Science B.V.     

Studying airflow and heat transfer characteristics of a horticultural produce packaging system using a 3-D CFD model. Part I: Model development and validation

A 3-D computational fluid dynamics (CFD) model of airflow and heat transfer processes within packed horticultural produce was developed. The model included explicit geometries of the product and package. Model results showed that airflow and temperature inside produce bulk were heterogeneous. The regions near the package vents showed relatively higher cooling air velocity and turbulence intensity. The coldest region was located behind the entrance vents. Pressure drops through entrance and exit vents were 51.1% and 45.2%, respectively. As the cooling air passed through the package vents and produce bulk, there was an increase in turbulence intensity. Validation of the model was conducted using experimental results. There was a good agreement between the predicted and measured results, average relative errors of predicted pressure drop and produce temperature were 13.80% and 16.27%, respectively.