S. De Pascale

Effects of soil salinity from long-term irrigation with saline-sodic water on yield and quality of winter vegetable crops

Abstract From 1988 onwards a study was carried out to evaluate the long-term effects of increasing water salinity (0%, 0.125%, 0.25%, 0.5% and 1% of commercial NaCl) on some vegetable crops growing in a clay-loam soil. In 1992 and 1993 the effects of the residual soil salinity on yield and some aspects of yield quality were studied in lettuce, endive and fennel grown during irrigation-free seasons on a field which had undergone the same irrigation treatment since 1988. Within the range of electrical conductivity of the saturated-soil extract (ECe) between 2.0 dS m −1 (treatment 0%) and 6.0 dS m −1 (treatment 1%) the marketable yield decreased by about 60% in endive and fennel and by about 15% in lettuce which proved more tolerant than the other crops. Gas exchange rates and stomatal conductance were reduced by salinity in lettuce. Soil salinity affected product quality: lettuce and endive appeared to be more sensitive to tipburn and necrotic symptoms occurring in the crop under saline-sodic conditions; fennel heart length, width, and thickness were also significantly reduced and the heart shape tended to be modified in plants grown on salt-affected plots. The results, obtained by analyzing the salt tolerance model of Maas-Hoffman and its descriptive parameters, place lettuce, endive and fennel in the moderately sensitive category. In terms of ECe, the threshold ranged from 1.8 dS m −1 (fennel) to 2.7 dS m −1 (lettuce) while the slope varied between 5.8% per dS m −1 (lettuce) and 15.7% per dS m −1 (endive).

Effects of soil salinity and top removal on growth and yield of broadbean as a green vegetable

Abstract In 1994 the effects of soil salinity and top removal were studied on faba bean for green consumption, grown during the irrigation-free season on a clay-loam soil which since 1988 had undergone the same irrigation treatments of increasing water salinity (0%; 0.125%; 0.25%; 0.5% and 1% of commercial NaCl). The response to salt tolerance was evaluated by using two models: The Maas and Hoffman model Yr = 100 − S(ECe) − T) and the van Genuchten model Yr = 100/[1 + ( EC e EC e50 ) p ]. Within the range of electrical conductivity of the saturated soil extract (ECe) between 2 dS m−1 and 6 dS m−1, soil salinity reduced plant height by 60%, leaf area by 70%, total above ground dry matter by 45%, mean pod weight by 15% and the number of pods per plant (48%). Leaf dry matter and specific leaf weight (SLW) were positively related to salinity. Higher salinity stress decreased the seed yield by 67% due to a reduction in weight and number of seeds, and also affected product quality. The results obtained by analysing the salt tolerance model of Maas-Hoffman and its descriptive parameters, place broadbean for green consumption in the moderately salt-sensitive category. In terms of relative yield per surface unit, from the Maas and Hoffman model the threshold value was 1.7 dS m−1 and yield was reduced at the rate of 15% (dS m−1)−1: the salinity level at 50% yield reduction (ECe50) was 5 dS m−1, compared to 4.7 dS m−1 of the van Genuchten model. With regard to pod yield per plant, the values of parameters were 1.8 dS m−1 (threshold) and 13% (dS m−1)−1 (slope) and the salinity level at 50% yield reduction (ECe50) was 5.6 dS m−1, compared to 5.4 dS m−1 of the van Genuchten model. Top removal at the beginning of pod set was ineffective. At low soil salinity the only effect of top removal was higher early production, indicating a more efficient partition of assimilates to growing pods and, therefore, rapid pod enlargement and higher yield at the first harvest.

Sulphur fertilisation affects yield and quality in friarielli (Brassica rapa L. subsp. sylvestris L. Janch. var. esculenta Hort.) grown in a floating system

Summary The influence of nitrogen and sulphur fertilisation on yield and quality was studied in two ecotypes of friarielli (Brassica rapa L. subsp. sylvestris L. Janch. var. esculenta Hort.) grown in a floating system. In the first experiment, we assessed the effects of different levels of N fertilisation on friarielli yield. In a second experiment, we tested three concentrations of S in the nutrient solution [2.6 mM, 4.0 mM, and 8.5 mM; corresponding to N:S concentration ratios of 10:1, 6.5:1, and 3:1, respectively] with the objective of fine-tuning the nutritional requirements for N and S to optimise both friarielli yield and quality. The main findings can be summarised as follows: (i) friarielli can be grown efficiently in a hydroponic system; (ii) both yield and quality in friarielli are strongly dependent on the N:S ratio of the nutrient solution; (iii) S may affect shoot nitrate accumulation in response to N availability; (iv) the response to S fertilisation is genotype-specific; (v) the anti-oxidant capacity of shoots increases with increasing S concentrations in the nutrient solution; and (vi) 26 mM N and an N:S concentration ratio of 10:1 in the nutrient solution are suggested for the best performance of hydroponically-grown friarielli.

Leaf Anatomy and Photochemical Behaviour of Solanum lycopersicum L. Plants from Seeds Irradiated with Low-LET Ionising Radiation

Plants can be exposed to ionising radiation not only in Space but also on Earth, due to specific technological applications or after nuclear disasters. The response of plants to ionising radiation depends on radiation quality/quantity and/or plant characteristics. In this paper, we analyse some growth traits, leaf anatomy, and ecophysiological features of plants of Solanum lycopersicum L. “Microtom” grown from seeds irradiated with increasing doses of X-rays (0.3, 10, 20, 50, and 100 Gy). Both juvenile and compound leaves from plants developed from irradiated and control seeds were analysed through light and epifluorescence microscopy. Digital image analysis allowed quantifying anatomical parameters to detect the occurrence of signs of structural damage. Fluorescence parameters and total photosynthetic pigment content were analysed to evaluate the functioning of the photosynthetic machinery. Radiation did not affect percentage and rate of seed germination. Plants from irradiated seeds accomplished the crop cycle and showed a more compact habitus. Dose-depended tendencies of variations occurred in phenolic content, while other leaf anatomical parameters did not show distinct trends after irradiation. The sporadic perturbations of leaf structure, observed during the vegetative phase, after high levels of radiation were not so severe as to induce any significant alterations in photosynthetic efficiency.

Monitoring nitrogen forms in soil/plant systems under different fertilizer managements. A preliminary investigation

Abstract A field experiment was carried out on maize ( Zea mays , L.) to study the effects of different fertilizer management on nitrogen status in soil and plant response. Three different fertilizers, mineral (MN), mineral plus buffalo manure (MN + BM) and organo-mineral with peat (OMP), were added at the usual (140, 61 and 116 kg ha −1 ) and the reduced (70, 31 and 58 kg ha −1 ) rates of N, P and K. respectively. Soil samples were analyzed for N by both the Kjeldahl method and the electro-ultrafiltration technique (EUF). The soil Kjeldahl-N concentrations were scarcely affected by the different fertilizer treatments, while the EUF-N concentrations were closely correlated with the amounts of N added. The EUF also discriminated between the NO 3 -N and the sum of the ammonium and the easily extractable organic N forms (EUF-N org + NH 4 ). The largest proportions of EUF-Norg + NH 4 were found in the untreated plots and in the plots treated with buffalo manure. The different fertilizer treatments significantly affected grain yield, which ranged from a minimum of 6.3 t ha −1 from the untreated plots, to a maximum of 11.9 t ha −1 from those supplied with 140 kg N, 61 kg P and 116 kg K ha −1 by OMP fertilizer. The highest agronomic efficiency index for N was exhibited in the OMP treatment at the reduced rate. The grain yield was closely correlated with the total extractable EUF-N, but different relationships were found between the rate of N added, the level of EUF-NO,-N in soil and grain yield for the different fertilizer treatments.

Effects of high salinity and the exogenous application of an osmolyte on growth, photosynthesis, and mineral composition in two ornamental shrubs

ABSTRACT A greenhouse experiment was carried out to determine the growth, photosynthetic activity, and mineral composition in two ornamental shrubs [Viburnum lucidum L. (arrow-wood) and Callistemon citrinus (Curtis) Stapf. (red bottlebrush)] that had been treated or not treated with 2.5 mM glycine betaine (GB) or 5.0 mM proline (Pro). Plants were supplied with a non-salinised or salinised nutrient solution containing 200 mM NaCl. Salinity caused reductions in plant growth parameters, shoot biomass production, and net CO2 assimilation in both species. Neither Pro nor GB were able to mitigate the adverse effects of salinity in bottlebrush, whereas GB reduced the deleterious effects of salt stress on arrow-wood, indicating a differential species-specific response to these osmolytes. The application of GB to salt-stressed arrow-wood increased apical and lateral shoot lengths, the number of leaves per plant, and shoot dry biomass by 222%, 113%, 238%, and 49%, respectively, compared to untreated or Pro-treated plants. The improved performance of salt-stressed arrow-wood plants whose roots were treated with 2.5 mM GB was attributed to partial suppression of Na uptake, higher chlorophyll concentrations, and the better nutritional status (higher K) of shoots.

Assessment of plant growth promoting activities and abiotic stress tolerance of Azotobacter chroococcum strains for a potential use in sustainable agriculture

This study aimed to select and characterize bacterial strains with multiple plant growth promotion properties able to tolerate drought and salinity stress in order to improve plant growth performance under abiotic stresses. Plant growth promoting activities were evaluated in 106 bacterial strains isolated by soil, compost, lignocellulosic biomasses and food matrices. Two strains A. chroococcum 67B and 76A were selected for their multiple plant growth promotion activities (N2-fixing activity, synthesis of siderophores and indole-3-acetic acid) as well as antimicrobial activity against Sclerotinia minor. Moreover, the selected strains were tested for their tolerance to drought and salinity stress in in vitro experiments evaluating their growth, production of SOD, CAT, proline and ACC deaminase. The two Azotobacter chroococcum strains exhibited high tolerance to salt and drought stresses and could alleviate the negative effects exerted by abiotic stress on tomato plants. Overall results showed that the strains Azotobacter chroococcum 67B and Azotobacter chroococcum 76A could be interesting candidates to be employed as bio-effector in sustainable agricultural systems also under stressful conditions leading to improved economic and environmental benefits.

Microbial Community Dynamics and Response to Plant Growth-Promoting Microorganisms in the Rhizosphere of Four Common Food Crops Cultivated in Hydroponics.

Plant growth promoting microorganisms (PGPMs) of the plant root zone microbiome have received limited attention in hydroponic cultivation systems. In the framework of a project aimed at the development of a biological life support system for manned missions in space, we investigated the effects of PGPMs on four common food crops (durum and bread wheat, potato and soybean) cultivated in recirculating hydroponic systems for a whole life cycle. Each crop was inoculated with a commercial PGPM mixture and the composition of the microbial communities associated with their root rhizosphere, rhizoplane/endosphere and with the recirculating nutrient solution was characterised through 16S- and ITS-targeted Illumina MiSeq sequencing. PGPM addition was shown to induce changes in the composition of these communities, though these changes varied both between crops and over time. Microbial communities of PGPM-treated plants were shown to be more stable over time. Though additional development is required, this study highlights the potential benefits that PGPMs may confer to plants grown in hydroponic systems, particularly when cultivated in extreme environments such as space.

EFFECTS OF SOIL TYPE AND NITROGEN FERTILIZATION RATE ON THE NUTRITIONAL VALUE OF ORGANICALLY AND CONVENTIONALLY GROWN ENDIVE

The aim of this work was to investigate the influence of soil type and fertilization management on crop yield and antioxidant activity of organically and conventionally grown endive. Two different soil types (sandy and clay) and three levels of total nitrogen fertilization (0, 100, 200 kg N ha-1) were compared under conventional and organic farming systems. Quantitative (total yield, bunch mean weight, leaf area, dry matter) and qualitative parameters (total soluble solid (°Brix), titratable acidity, reducing sugars, colorimetric parameters, nitrates and nitrites content and antioxidant activity (DMPD method for the hydrophilic phase and the ABTS method for the lipophilic phase)) were determined. The yield was 24% lower in organic farming compared to conventional farming whereas higher bunch mean fresh weight and larger leaf area were generally found. Organically grown endive had a higher dry matter content. Increasing nitrogen application from 0 to 200 kg N ha-1 resulted in increased yield in both organic and conventional farming. The bunch mean weight and leaf area were higher in clay soils vs. sandy soils. The leaf nitrate content was not affected by the farming system (conventional or organic farming), yet it increased in the clay soil and at increasing nitrogen fertilization. Differences in antioxidant activity were associated to a general stress response of organically grown plants rather than to the cultivation regime itself.