Long-term evaluation of productivity,stability and sustainability for cropping systems in Mediterranean rainfed conditions

Mediterranean cropping systems in rainfed conditions are generally based on rotations with a very high frequency of winter wheat and, therefore, they are at risk of declining trends for yield and soil health in the long-term. In order to quantify this risk, a long-term experiment was set-up in 1971 in central Italy, which is still running at present (2016). This experiment is based on 13 rotations, i.e. three continuous winter wheat systems with different N fertilization rates (W150, W200 and W250), five maize/winter wheat rotations with increasing wheat frequency (maize preceded by 1–5 years of wheat: i.e., WM, 2WM, 3WM, 4WM and 5WM) and five two-year rotations of winter wheat with either pea (WP), faba bean (WFB), grain sorghum (WGS), sugar beet (WSB) or sunflower (WSU). All these rotations are managed either with the removal of crop residues after harvest (REM), or with their burial into the soil at ploughing (BUR). For each rotation, all phases are simultaneously grown in each year, according to a split-plot design (with REM and BUR randomised to main plots), with three replicates in complete blocks and plots of 24.5 m² each. The following data are considered: (1) total and marketable biomass yields from 1983 to 2012; (2) content of Organic carbon (OC) and total nitrogen (N) in soil, as determined in 2014. Considering the 30-year period, BUR resulted in an average positive effect on yield (+3.7%), increased OC (+13.8%) and total N content (+9.4%) in soil, while the C/N ratio was not significantly affected. Wheat in two-year rotations showed a significantly higher (+19.4%) average yield level than in continuous cropping or in 2WM, 3WM, 4WM and 5WM, mainly due to a drop in yield occurring in the first (−13%) and second (−19%) year of recropping. Increasing N fertilisation level from 150 to 250 kg N ha⁻¹ with continuous cropping resulted in an increase (+3.7%) in long-term average yield and in a decrease in yield stability. All rotations heavily based on wheat (continuous cropping and 5WM) produced the highest amount of buried biomass (>175 t ha⁻¹ in 30 years), with the highest increase in soil OC content (>16 t ha⁻¹). All the other rotations produced a lower amount of residues and were less efficient in terms of carbon sequestration in soil, apart from WFB, which gave a high increase in soil organic carbon content (+18.9 t ha⁻¹ in 30 years), in spite of a low amount of buried residues (158 t ha⁻¹).     

Effect of spring fertilization on ecosystem services of organic wheat and clover relay intercrops

Nitrogen (N) deficiency and weed infestation are main factors limiting yield and yield stability in organic wheat. Organic fertilizers may be used to improve crop performance but off-farm input costs tend to limit profitability. Instead, forage legumes may be inserted into the crop rotation to improve the N balance and to control weed infestation. In opposition to simultaneous cropping, relay intercropping of legumes in organic winter wheat limits resource competition for the legume cover crop, without decreasing the performance of the associated wheat.The aim of this study is to evaluate the effect of spring organic fertilization on the performance of intercropped legumes and wheat, and on services provided by the legume cover.Two species of forage legumes (Trifolium pratense L. and Trifolium repens L.) were undersown in winter wheat (Triticum aestivum L. cv Lona) in five organic fields during two consecutive crop seasons. Organic fertilizer was composed of feather meal and applied on wheat at legume sowing. The cover crop was maintained after the wheat harvest and destroyed just before sowing maize.Spring organic nitrogen fertilization increased wheat biomass (+35%), nitrogen (+49%), grain yield (+40%) and protein content (+7%) whatever the intercropping treatment. At wheat harvest, red clover biomass was significantly higher than white clover one (1.4 vs. 0.7 t ha⁻¹). Nitrogen fertilization decreased forage legume above-ground biomass at wheat harvest, at approximately 0.5 t ha⁻¹ whatever the specie. No significant difference in forage legume biomass production was observed at cover killing. Nitrogen accumulation in legume above-ground tissues was significantly higher for white clover than for red clover. Both red and white clover species significantly decreased weed infestation at this date. Nitrogen fertilization significantly increased weed biomass whatever the intercropping treatment and decreased nitrogen accumulation in both clover species (−12%).We demonstrated that nitrogen fertilization increased yield of wheat intercropped with forage legume while the performance of legumes was decreased. Legume growth was modified by spring fertilization whatever the species.     

Low oxygen levels and light exposure affect quality of fresh-cut Romaine lettuce

Modified atmosphere packaging (MAP) has the potential to extend the shelf-life of fresh-cut lettuce mainly by limiting the oxidation processes. However, exposure to light conditions has been described as causing browning and quality loss. The influence of O₂ partial pressures (pO₂) and light exposure during storage on the shelf-life of fresh-cut Romaine lettuce was studied. Fresh-cut lettuce was exposed daily during storage to different light conditions: light (24 h), darkness (24 h) and photoperiod (12 h light + 12 h darkness). Changes in respiration rate, headspace gas composition, sensory quality, colour, electrolyte leakage, stomatal opening, water loss, texture and compositional constituents related to browning such as vitamin C and individual and total phenolic compounds were evaluated. Different weight samples (75–275 g), packaged with an initial pO₂ of 0.5–2.0 kPa balanced with N₂, reached pO₂ from 0.1 to 1.5 at the steady-state. Atmospheres with low pO₂ (0.2–0.5) at the steady-state preserved lettuce quality by the control of browning and the prevention of off-odours and off-flavours. Light exposure during storage positively influenced the number of open stomata (74% in light vs 24% in darkness) which contributed slightly to weight loss. Consumption of O₂ in samples exposed to light differed significantly from those stored in photoperiod or darkness (10.6 ± 7.0, 18.3 ± 3.5 and 25.8 ± 8.6 nmol O₂ kg^?1 s^?1, respectively). Packages exposed to light showed higher pO₂ compared with packages stored in darkness while those exposed to photoperiod had intermediate values. Moreover, location of the packages in the shelves affected package headspace gas composition and thus, packages near the front of the shelves showed higher pO₂ than those at the back. The different light conditions did not influence the content of vitamin C or the individual and total phenolic compounds. This study shows that under light conditions respiration activity was compensated by photosynthesis resulting in a higher pO₂. Thus, browning of fresh-cut Romaine lettuce can be promoted by light exposure during storage as it increases headspace pO₂.     

Nitrogen uptake and utilisation efficiency of two-row and six-row winter barley cultivars grown at two N levels

In order to limit overproduction and pollution risks, low N fertiliser agricultural systems are likely to be advocated in Europe. An experiment was carried out in 1994 and 1995 to compare N uptake and N utilisation of two-rowed and six-rowed winter barley (Hordeum vulgare L.). Two sets of two-rows and six-rows, composed of 18 varieties each, were cultivated in northern France on a haplic luvisol without (N1) and with 100–110 kg/ha (N2) N fertiliser. Mean grain yield was 596 g/m² at N1 and 779 g/m² at N2. On average six-rows outyielded two-rows by 4% (34 g/m²) at N2 and 11% at N1 (70 g/m²). Ears/m² was the yield component which fell most sharply between N2 and N1 (718 and 510 ears/m² on average). Six-rows had fewer ears/m² at both N levels but they lost more ears than two-rows (−33% and −26%, respectively). While the number of grains/ear was approximately the same for two-rows at both N levels (21.9 grains/ear on average) in 1995, it was significantly higher at N1 than at N2 for six-rows (44.7 and 38.5, respectively). Thousand kernel weight was higher at N1 than at N2, the difference being higher for six-rows (+7%) than for two-rows (+4%). N uptake efficiency (total plant N/soil N supply) was identical at N2 and higher for six-rows at N1 in 1995. Total N utilisation efficiency (total above-ground dry weight/total plant N) was equal at both N levels. HI (grain yield/total above-ground dry weight) was higher at N1 in both years and at N2 in 1994 for six-rows. Six-rows outyielded two-rows at high and low N levels. This was therefore associated mainly with higher HI and not with better N uptake or utilisation efficiency.     

Salinity of nutrient solution influences the shelf-life of fresh-cut lettuce grown in floating system

Quality, microbiological and enzymatic characteristics of fresh-cut lettuce (Lactuca sativa var. longifolia, ‘Duende’), grown in floating system with three electrical conductivities of nutrient solutions (2.8, 3.8 and 4.8 mS cm^?1), were investigated in order to evaluate the effect of salinity on product shelf-life during cold storage (9 d at 4 °C). Pre-harvest salinity of 3.8 and 4.8 mS cm^?1 improved the properties of fresh-cut lettuce, since CO₂ production was reduced with a subsequent control of the decay process. Fresh-cut processing caused an activation of polyphenol oxidase and peroxidase; in all cases the product obtained by salinity treatments was less subject to oxidase activity and browning phenomena during storage. Increased salinity reduced the number of mesophilic bacteria and of moulds and yeasts, assessed by plate counts on different culture media; in contrast, Enterobacteriaceae levels were unaffected by pre-harvest treatments. The research demonstrated that an increase in nutrient solution electrical conductivity, through the use of floating system, affects fresh-cut lettuce characteristics, improving shelf-life of the product.     

Radiation use efficiency,chemical composition,and methane yield of biogas crops under rainfed and irrigated conditions

For biomethane production, the cup plant (Silphium perfoliatum L.) is considered a promising alternative substrate to silage maize (Zea mays L.) due to its high biomass potential and associated ecological and environmental benefits. It has also been suggested to grow cup plant on less productive soils because of its presumed drought tolerance, but robust information on the impact of water shortage on biomass growth and substrate quality of cup plant is rare. Therefore, this study assesses the effects of soil water availability on the chemical composition and specific methane yield (SMY) of cup plant. Furthermore above-ground dry matter yield (DMY) was analysed as a function of intercepted photosynthetic active radiation (PAR) and radiation use efficiency (RUE). Data were collected in a two-year field experiment under rainfed and irrigated conditions with cup plant, maize, and lucerne-grass (Medicago sativa L., Festuca pratensis Huds., Phleum pratense L.). The cup plant revealed a slight decrease of −6% in the SMY in response to water shortage (less than 50% of plant available water capacity). The average SMY of cup plant [306 l (kg volatile solids (VS))⁻¹] was lower than that of maize [362 l (kg VS)⁻¹] and lucerne-grass [334 l (kg VS)⁻¹]. The mean drought-related reduction of the methane hectare yield (MHY) was significantly greater for cup plant (−40%) than for maize (−17%) and lucerne-grass (−13%). The DMY reduction in rainfed cup plant was mainly attributed to a more severe decrease in RUE (−29%) than for maize (−16%) and lucerne-grass (−12%). Under water stress, the mean cup plant RUE (1.3 g MJ⁻¹) was significantly lower than that of maize (2.9 g MJ⁻¹) and lucerne-grass (1.4 g MJ⁻¹). Compared to RUE, the reduced PAR interception was less meaningful for DMY in rainfed crops. Hence, the cup plant is not suitable for growing on drought prone lands due to its high water demand required to produce reasonably high MHYs.     

Modelling photosynthetic efficiency (α) for the light-response curve of cocksfoot leaves grown under temperate field conditions

Net photosynthetic rate was measured from the youngest fully expanded leaves of field grown cocksfoot (Dactylis glomerata L.) in open pastures and under trees in the Lincoln University silvopastoral experiment (New Zealand). The photosynthetic efficiency (α) and convexity (θ) of the light-response curve were derived from 209 fitted non-rectangular hyperbola functions. There was no relationship between θ and any of the environmental or management variables with a stable mean value of 0.96. For α, individual functions were required for temperature (10–31 °C), nitrogen (N) concentration (1.5–5.9% N), water status (expressed as pre-dawn leaf water potential, ψ_lp) (−0.01 to −1.6 MPa), regrowth duration (20–60 days), and different times (up to 180 min) under moderate (850–950 μmol m⁻² s⁻¹ photon irradiance) and severe (85–95 μmol m⁻² s⁻¹ photon irradiance) shade. The highest α of 0.036 μmol CO₂/μmol photon irradiance was found in non-limiting conditions and defined as the standardised maximum (α_s=1). Values of α_s=1 were measured in optimum ranges of 10–24 °C, 4.0–5.9% N, −0.01 to −1.0 MPa and 20 days regrowth. In addition, values of α_s reached a steady-state asymptote of 0.74 after 60 min of severe shade and 0.92 after 40 min of moderate shade. Individual functions of α could not be integrated into a simple multiplicative model but a ‘law of the minimum factor’ model was appropriate. Predicted results from this model were then validated with 46 independent data points collected when at least two factors were outside their optimum range. The model accounted for 88% of the variation in observed α values. This research has derived functional relationships for α that can be used to assist predictions of leaf photosynthesis and ultimately pasture growth by their inclusion in canopy photosynthesis models.     

In field non-invasive sensing of the nitrogen status in hybrid bermudagrass (Cynodon dactylon × C. transvaalensis Burtt Davy) by a fluorescence-based method

The level of N fertilization and the content of leaf N in Cynodon dactylon × C. transvaalensis Burtt Davy cv. ‘Tifway 419’ bermudagrass were evaluated non-destructively with a fluorescence-based method. It was applied directly into the field by using the Multiplex portable fluorimeter during two consecutive seasons (2010 and 2011). In the 2010 experiment, the nitrogen balance index (NBI₁) provided by the sensor was able to discriminate (at P < 0.05) six different N levels applied, up to 250 kg ha⁻¹, with a precision (root mean square error, RMSE) in the rate estimate of 3.29 kg ha⁻¹. In 2011, the index was insensitive to the N treatment between 150 kg ha⁻¹ and 250 kg ha⁻¹ N rates, and its precision was 39.98 kg ha⁻¹. Calibration of the sensor by using the destructive analysis of turf samplings showed a good linear regression between NBI₁ and the leaf N content for both 2010 (R² = 0.81) and 2011 (R² = 0.93) experiments. This allowed mapping of the leaf N spatial distribution acquired by the sensor in the field with a prediction error of 0.21%. Averaging the overall estimates of leaf N content per N treatment provided an upper limit of 200 kg ha⁻¹ for the required fertilization, corresponding to a critical level of leaf N of about 2.3%. Our results confirm the usefulness of the new fluorescence-based method and sensor for a precise management of fertilization in turfgrass.     

Postharvest quality of peeled prickly pear fruit treated with acetic acid and chitosan

White (Opuntia albicarpa) and red (Opuntia ficus-indica) prickly pears were peeled and submerged in chitosan solutions containing different concentrations of acetic acid (1.0 or 2.5%) to obtain ready-to-eat prickly pear products. Some physicochemical (pH, total soluble solids, color, weight loss, and firmness), antioxidant (phenolic compounds and antioxidant activity), microbiological (aerobic mesophile bacteria and yeasts plus molds), and sensory (color, firmness, aroma, flavor, and overall acceptance) characteristics were assessed during 16 d of storage at 4 ± 1 °C and 85 ± 5% of relative humidity. Chitosan coating containing 1.0% of acetic acid delayed weight loss, maintained firmness and color of white prickly pear during the storage time. Most of the sensory values for white prickly pear coated with chitosan containing 1.0 and 2.5% of acetic acid were higher than those obtained for uncoated fruit. Red prickly pear coated with chitosan with 2.5% acetic acid did not maintain its sensory quality throughout 16 d of storage. Chitosan coating with 1 and 2.5% acetic acid did not affect phenolics content and antioxidant activity in white prickly pears; however, an increase of these compounds was observed in red prickly pears. Microbe populations were unchanged in white prickly pears (<10 CFU g⁻¹) and slightly increased in red prickly pears (10–500 CFU g⁻¹) coated with chitosan during the entire storage time.     

Impact of a decontamination step with peroxyacetic acid on the shelf-life,sensory quality and nutrient content of grated carrots packed under equilibrium modified atmosphere and stored at 7 °C

Peroxyacetic acid (PAA) is a strong oxidizer and exerts antimicrobial properties. The effect of a decontamination step with 80 and 250 mg L⁻¹ PAA on shelf-life of grated carrots stored under equilibrium modified atmospheric packaging at 7 °C was determined and compared with the shelf-life of unwashed and water-washed carrots. Microbial parameters, including total aerobic plate count, numbers of lactic acid bacteria, Lactobacillae and yeasts, and sensory quality were evaluated. Next to these parameters, atmospheric gas composition, pH and nutrient content were also monitored. The suggested packaging configuration prevented CO₂ accumulation, but at the end of the study anoxic conditions were reached for unwashed carrots and carrots washed with 80 mg L⁻¹ PAA. The microbial shelf-life of water-washed carrots was 4 d based on the yeast count, whereas the flavour was not acceptable after 5 d. The total aerobic plate count and the yeast count determined the shelf-life of carrots treated with 80 mg L⁻¹ PAA on 5 d, whereas the flavour was unacceptable after 7 d. None of the microbial parameters determined the shelf-life of carrots washed with 250 mg L⁻¹ PAA. However, this treatment had already a pronounced adverse effect on the initial sensory quality. Water washing already decreased the content of all individually studied nutrients (−16 to −28%), except for lutein content and the antioxidant capacity. Additional losses after adding PAA on day 0 were found for α-tocopherol and phenols. Regardless of the applied treatment, α- and β-carotene remained stable during storage, whereas ζ-carotene, lutein and α-tocopherol were unstable. The phenol content and the antioxidant capacity of unwashed, water-washed and 80 mg L⁻¹ PAA-treated carrots increased significantly at the end of the storage period, whereas no changes were found in carrots treated with 250 mg L⁻¹ PAA.On the condition that carrots were packed under an adequate EMA, the 80 mg L⁻¹ PAA treatment showed possibilities for extending shelf-life without pronounced effects on nutrient content.     

The combined effects of aqueous chlorine dioxide,fumaric acid,and ultraviolet-C with modified atmosphere packaging enriched in CO2 for inactivating preexisting microorganisms and Escherichia coli O157:H7 and Salmonella typhimurium inoculated on buckwheat sprouts

The combined effects of a sanitizer mixture, ultraviolet-C (UV-C), and modified atmosphere packaging (MAP) on the quality of non-inoculated and inoculated (Escherichia coli O157:H7 and Salmonella typhimurium) buckwheat sprouts were examined. Buckwheat sprouts were treated with a sanitizer mixture (comprising 100 mg L⁻¹ aqueous ClO₂ and 0.3% fumaric acid) and 2 kJ m⁻² UV-C, packaged under two different conditions (air and CO₂ gas) and storage for 8 d at 4 °C. The combination of the sanitizer mixture and UV-C treatment reduced the initial counts of preexisting microorganisms in the buckwheat sprouts by 1.9 log CFU g⁻¹ and reduced the initial inoculated counts of E. coli O157:H7 and S. typhimurium on buckwheat sprouts by 3.0 and 2.3 log CFU g⁻¹, respectively. The preexisting microorganisms and inoculated pathogens in buckwheat sprouts packaged under CO₂ gas were significantly reduced during storage following the combined treatment compared to those of the control by above 95%. Differences in Hunter L^*, a^*, and b^* values among the treatments were negligible. The combined sanitizer mixture and UV-C treatment increased the sprout rutin content by 147%, but there was no significant difference in 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity between treatments during storage. Therefore, the combination of sanitizer mixture made from aqueous ClO₂ and fumaric acid, UV-C irradiation, and MAP can improve the microbial safety and quality of buckwheat sprouts.     

Semi-commercial ultralow oxygen treatment for control of western flower thrips,Frankliniella occidentalis (Thysanoptera: Thripidae), on harvested iceberg lettuce

Pallet-scale ultralow oxygen (ULO) treatment was applied to iceberg lettuce after various lengths of postharvest storage to determine the effects of pre-treatment storage on lettuce tolerance to ULO treatment for control of western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae). Lettuce from seven cultivars was vacuum cooled and stored at 2 °C after harvest for 0, 2, 3, and 5 d before being subjected to 2-d ULO treatment with 0.003% oxygen at 10 °C ambient temperature. Complete control of thrips was achieved in all three tests. Temperature of lettuce increased from about 5 °C at the start of ULO treatment to 9.6 °C at the end of the treatment. Fresh vacuum-cooled lettuce from three of seven cultivars sustained injury to heartleaves by the ULO treatment. Lettuce that had been stored at the low temperature for 2, 3, or 5 d before the ULO treatment tolerated the ULO treatment and there was no significant quality reduction compared with untreated controls. Heavier heads were significantly more susceptible to heartleaf injury than lighter heads. This study demonstrated that 2-d postharvest refrigerated storage followed by 2-d ULO treatment was effective in controlling western flower thrips with minimal adverse effects on lettuce quality. The ULO treatment protocols developed in this study also have potential to be scaled-up for commercial ULO treatment applications.     

Blueberry leaf extracts incorporated chitosan coatings for preserving postharvest quality of fresh blueberries

The phenolic compounds in blueberry (Vaccinium spp.) fruit and leaf extracts (BLE) were determined based on HPLC analysis. Antimicrobial assays against Staphylococcus aureus, Listeria monocytogenes, Salmonella typhimurium and Escherichia coli, as well as fungi isolated from the rotting blueberry fruit were conducted. The effects of chitosan coating incorporating different concentrations of BLE on the quality of fresh fruit during postharvest storage at 2 ± 1 °C and 95 ± 2% relative humidity (RH) for 35 d and then at room conditions for 3 d were also investigated. Five different coating treatments were applied including 2% (w/v) chitosan coating (T1), 2% (w/v) chitosan coating containing 4% (w/v, T2), 8% (w/v, T3), or 12% (w/v, T4) BLE, and 2% (w/v) chitosan coating containing 12% BLE plus modified atmosphere packaging (MAP at 3 kPa O₂ + 12 kPa CO₂) (T5). A sample of blueberries dipped into distilled water was used as control (T0). BLE had a greater variety of phenolic compounds than fruit extracts with syringic acid the highest concentration (0.259 ± 0.003 g kg⁻¹), but the total phenolic content in BLE was lower (P < 0.05) than in fruit extracts. BLE showed good antimicrobial activity against all tested microorganisms, with a minimum inhibition concentration from 25 to 50 g L⁻¹. The 2% chitosan coating that incorporated 8% or 12% BLE showed some degree of decreasing decay rate of fruit compared with the control, and the coating with BLE plus MAP had more effective control of fruit decay. All treated samples maintained higher total phenolic content and radical scavenging activity than the control. This study suggested that chitosan coating incorporating BLE can be employed to extend shelf-life and maintain high nutritional value of fresh blueberries during postharvest storage.     

Light exposure reduced browning enzyme activity and accumulated total phenols in cauliflower heads during cool storage

Effects of continuous light exposure (24 μmol m⁻² s⁻¹) on browning enzyme activity and total phenol (TP) content in fresh cauliflower heads were investigated during 7 d storage at 7 °C using darkness as the control. Results showed that light exposure inhibited polyphenol oxidase activity (PPO) by 26% and peroxidase (POD) by 16%, as well as lowering the browning index (BI) by 33%, compared to darkness, at the end of storage. Light exposure also induced 43%, 35%, and 20% increases in phenylalanine ammonia lyase (PAL) activity at 1, 3, and 5 d storage, respectively, thus accumulating 41% more de novo TP content than in darkness after 7 d storage. In addition, vitamin C content deteriorated during storage under both light and dark conditions, with light exposure preserving vitamin C content 30% more than in darkness. However, light exposure accelerated fresh weight loss, with the largest value of 1.8% at the end of storage.     

Effects of composite chemical pretreatment on maintaining quality in button mushrooms (Agaricus bisporus) during postharvest storage

This study evaluated the effects of composite chemical pretreatment on the quality of postharvest button mushrooms. Three different treatments, including (T1) control (water), (T2) 1 mmol L⁻¹ Na₂EDTA + 10 mmol L⁻¹ CaCl₂ and (T3) 1 mmol L⁻¹ Na₂EDTA + 2.5% CaCl₂ + 0.5% citric acid + 2.5% sorbitol were used for pretreatments. The results showed that T3-treated samples maintained good firmness and color and had less weight loss during the postharvest storage. Lower levels of H₂O₂, ⁻OH and low malondialdehyde content (MDA) were observed in T3 compared with T1 and T2 samples. Significantly higher soluble protein contents and higher activities in the antioxidant enzymes, i.e., superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), peroxidase (POD) were observed in T3 compared with T1 and T2 at the end of the storage period (P < 0.05). These results suggest that the T3 treatment could be useful in preserving button mushrooms.     

UV-C light inactivation kinetics of Penicillium expansum on pear surfaces: Influence on physicochemical and sensory quality during storage

UV-C inactivation kinetic data of Penicillium expansum on intact and wounded pear disks were determined. P. expansum conidia (0.5 mL, 1.6 × 10⁷ CFU/mL) were spot inoculated onto intact and wounded pear tissue with skin (excised disks), treated with UV-C doses ranging 0.101–3.06 kJ/m² at 23 °C and surviving conidia were enumerated. Changes in selected physicochemical parameters and sensory quality following UV-C treatment of whole pears were determined immediately after treatment, and 4 and 8 weeks of storage at 4 °C. A greater UV-C intensity was required for similar inactivation levels of P. expansum populations on wounded pear disks (3.1 kJ/m² for 2.7 log reduction) compared to intact pear disks (1.7 kJ/m² for 2.8 log reduction). No significant difference in % weight loss, or soluble solids content and texture was observed between UV-C treated and untreated pears. However, browning was observed on UV-C treated pear surfaces after 4 and 8 weeks along with changes in flavor and texture. An increase in consumer preference was noticed for the untreated control pears after 4 weeks storage.     

Response of climacteric-type guava (Psidium guajava L.) to postharvest treatment with 1-MCP

Guava (Psidium guajava L. cv. ‘Allahabad Safeda’) fruit harvested at the mature light-green stage were exposed to 300 and 600 nL L⁻¹ 1-methylcyclopropene (1-MCP) for 6, 12 and 24 h at 20 ± 1 °C, and held in either cold storage (10 °C) for 25 days or ambient conditions (25–29 °C) for 9 days. Most of the physiological and biochemical changes during storage and ripening were affected by 1-MCP in a dose dependent manner. Ethylene production and respiratory rates were significantly suppressed during storage as well as ripening under both the storage conditions depending upon 1-MCP concentration and exposure duration. 1-MCP treatment had a pronounced effect on fruit firmness changes during storage under both the conditions. The reduced changes in the soluble solids contents (SSC), titratable acidity (TA) and vitamin C content showed the effectiveness of 1-MCP in retarding fruit ripening. Vitamin C content in 1-MCP-treated fruit was significantly higher than in non-treated fruit, and those treated with 300 nL L⁻¹ 1-MCP for 6 h. The development of chilling injury symptoms was ameliorated to a greater extent in 1-MCP-treated fruit during cold storage and ripening. A significant reduction in the decay incidence of 1-MCP-treated fruit was observed under both the storage conditions. 1-MCP at 600 nL L⁻¹ for 12 h, in combination with cold storage (10 °C) seems a promising way to extend the storage life of guava cv. ‘Allahabad Safeda’ while 1-MCP at 300 nL L⁻¹ for 12 and 24 h or 600 nL L⁻¹ for 6 h, may be used to provide 4–5 days extended marketability of fruit under ambient conditions.     

Effects of varying nitrogen fertilization on crop yield and grain quality of emmer grown in a typical Mediterranean environment in central Italy

Experiments were carried out to study the effects of N fertilizer rates and timing of application on the yield and grain quality of a rainfed emmer crop (Triticum dicoccum Shübler) under Mediterranean conditions. The following parameters were analyzed: hulled and net grain yield, hulled index, spikes m^?2, spikelets per spike, kernels m^?2, thousand-kernel weight, biomass, plant height, lodging, grain protein and ash content. In the first experiment, different N rates (30, 60 and 90 kg N ha^?1 plus a control not fertilized) were split at three phenological stages (seeding 20%, tillering 40% and stem elongation 40%). In the second experiment, three N doses (30, 60 and 90 kg N ha^?1) were applied to three crop stages (seeding, tillering and stem elongation). In the third experiment, the rate of 90 kg N ha^?1 was distributed in different amounts (90-0-0, 0-90-0, 0-0-90, 45-45-0, 45-0-45, 0-45-45, 30-30-30) at the three mentioned crop stages. Increasing N rates resulted in higher hulled and net grain yield, as well as protein content. Fertilization (from 60 to 90 kg N ha^?1) applied to tillering maximized hulled and net grain yield. Fertilization (90 kg N ha^?1) applied to stem elongation gave the highest grain protein content (%) while splitting application (30 kg N ha^?1 each) at three phenological stages maximized protein yield per hectare. Application of half or one-third of 90 kg N ha^?1 to stem elongation improved grain protein content in comparison with applications at sowing, or at both sowing and tillering. The main factor determining higher yields with increasing N rates in this emmer crop was the number of kernels m^?2. None of the yield components accounted for differences in grain yield when timing and splitting application were varied.     

Biological nitrogen fixation in three long-term organic and conventional arable crop rotation experiments in Denmark

Biological nitrogen (N) fixation (BNF) by legumes in organic cropping systems has been perceived as a strategy to substitute N import from conventional sources. However, the N contribution by legumes varies considerably depending on legumes species, as well as local soil and climatic conditions. There is a lack of knowledge on whether the N contribution of legumes estimated using short-term experiments reflects the long-term effects in organic systems varying in fertility building measures. There is also limited information on how fertilizer management practices in organic crop rotations affect BNF of legumes. Therefore, this study aimed to estimate BNF in long-term experiments with a range of organic and conventional arable crop rotations at three sites in Denmark varying in climate and soils (coarse sand, loamy sand and sandy loam) and to identify possible causes of differences in the amount of BNF. The experiment included 4-year crop rotations with three treatment factors in a factorial design: (i) rotations, i.e. organic with a year of grass-clover (OGC), organic with a year of grain legumes (OGL), and conventional with a year of grain legumes (CGL), (ii) with (+CC) and without (−CC) cover crops, and (iii) with (+M) and without (−M) animal manure in OGC and OGL, and with (+F) mineral fertilizer in CGL. Cover crops consisted of a mixture of perennial ryegrass and clover (at the sites with coarse sand and sandy loam soils) or winter rye, fodder radish and vetch (at the site with loamy sand soil) in OGC and OGL, and only perennial ryegrass in CGL at all sites. The BNF was measured using the N difference method. The proportion of N derived from the atmosphere (%Ndfa) in aboveground biomass of clover grown for an entire year in a mixture with perennial ryegrass and harvested three times during the growing season in OGC was close to 100% at all three sites. The Ndfa of grain legumes in both OGL and CGL rotations ranged between 61% and 95% depending on location with mostly no significant difference in Ndfa between treatments. Cover crops had more than 92% Ndfa at all sites. The total BNF per rotation cycle was higher in OGC than in OGL and CGL, mostly irrespective of manure/fertilizer or cover crop treatments. There was no significant difference in total BNF between OGL and CGL rotations, but large differences were observed between sites. The lowest cumulated BNF by all the legume species over the 4-year rotation cycle was obtained at the location with sandy loam soil, i.e. 224–244, 96–128, and 144–156 kg N ha⁻¹ in OGC, OGL and CGL, respectively, whereas it was higher at the locations with coarse sand and loamy sand soil, i.e. 320–376, 168–264, and 200–220 kg N ha⁻¹ in OGC, OGL and CGL, respectively. The study shows that legumes in organic crop rotations can maintain N₂ fixation without being significantly affected by long-term fertilizer regimes or fertility building measures.     

Determination of the critical nitrogen concentration of white cabbage

A measure of a crop's nitrogen (N) status can be obtained by relating the actual N concentration of the crop to the critical plant nitrogen concentration (PNC_c), the minimum N concentration required for maximum growth. In annual crops, PNC_c declines as plant size increases. Describing this decline is one of the main challenges for the implementation of the PNC_c concept in fertilizer management strategies. From two field experiments with repeated harvests of Dutch white cabbage and with N supply ranging from limitation to excess, the relation between PNC_c and weight per unit ground area of plant dry matter exclusive of roots (W) was estimated as: PNC_c = 5.1W^−0.33% for the linear growth phase (W > 1.5 t ha⁻¹; LAI > 1.4). From a third field experiment, a value of 4.5% N was estimated for PNC_c for the pre-linear growth phase. Also a power function: LAR = 0.011W^−0.33 described the relationship between leaf area ratio and weight. The exponent of the power function determines the rate of the decline. Therefore, having the same value of the exponent: −0.33, LAR and PNC_c declined at the same rates. The proportional decline in LAR and PNC_c corresponded to a constant nitrogen content on a leaf area basis of 4.7 g N m⁻² until onset of head formation.