• Energy Research

Plant biostimulants have gained great interest from the agrochemical industry and farmers because of their ability to enhance nutrient use efficiency and increase abiotic stress tolerance in crop production. However, despite the considerable potential of biostimulants for the sustainable development of the agricultural sector, the environmental evaluation of the application of biostimulants is still missing. Hence, this is the first study that focuses on the environmental assessment of the biostimulant action of arbuscular mycorrhizal fungus Glomus intraradices and vegetal-derived protein hydrolysate on two greenhouse vegetable crops, spinach and zucchini squash, under different fertilization regimes. The life cycle assessment from a cradle to gate perspective, which covers all processes related to crop cultivation up to harvest, was carried out to calculate the carbon footprint of the production chain for these two crops. The results of the comparative analysis revealed that the CO2 equivalent emissions of both crops were reduced due to the biostimulant applications. In particular, the effect of the mycorrhization on the reduction of carbon emissions compared to the un-mycorrhized control was higher in zucchini plants under organic fertilization (12%) than under mineral fertilization (7%). In addition, organic fertilization increased the total carbon footprint of zucchini (52%) compared with mineral fertilization. The results also showed that an increase of nitrogen fertilization from 15 to 45 kg N ha−1 in spinach production enhanced the total CO2 emissions per ton of harvested leaves in comparison with treatments that involved the foliar applications of protein hydrolysate together with a lower nitrogen input; this increase was 4% compared to the unfertilized treatment with application of biostimulant. This study can support decision-making in terms of agronomic technique choices in line with sustainable development of vegetable crop production.

Sweet basil (Ocimum basilicum L.) is a highly versatile and globally popular culinary herb, and a rich source of aromatic and bioactive compounds. Particularly for leafy vegetables, nutrient management allows a more efficient and sustainable improvement of crop yield and quality. In this work, we investigated the effects of balanced modulation of the concentration of two antagonist anions (nitrate and chlorine) in basil. Specifically, we evaluated the changes in yield and leaf metabolic profiles in response to four different NO3−:Cl− ratios in two consecutive harvests, using a full factorial design. Our work indicated that the variation of the nitrate-chloride ratio exerts a large effect on both metabolomic profile and yield in basil, which cannot be fully explained only by an anion-anion antagonist outcome. The metabolomic reprogramming involved different biochemical classes of compounds, with distinctive traits as a function of the different nutrient ratios. Such changes involved not only a response to nutrients availability, but also to redox imbalance and oxidative stress. A network of signaling compounds, including NO and phytohormones, underlined the modeling of metabolomic signatures. Our work highlighted the potential and the magnitude of the effect of nutrient solution management in basil and provided an advancement towards understanding the metabolic response to anion antagonism in plants.

In response to tackling the environmental consequences of fertiliser production, biofertilisers from organic sources are strongly promoted in line with circular economy and maximising resource use. Despite the outstanding potential of bio-based fertilisers for the sustainable development of the agricultural sector, an environmental investigation of these fertilisers is required to replace synthesised fertilisers. Considering the importance of iron as a plant micronutrient and the scientific gap in the environmental assessment of relevant fertilisers, iron-based fertilisers produced in EU and US geographical zones are selected as a case study in this paper. Therefore, this study examines the environmental performance of two iron-based fertilisers (Fe-biochelate and Fe-EDDHA) by the life cycle assessment (LCA) methodology. The LCA model has been implemented in Simapro software by the ecoinvent database and ReCipe 2016 method considering 1 kg iron content as a functional unit. The results revealed that the Fe-biochelate reduced impacts (69–82%) on all relevant categories, including global warming (69%), terrestrial ecotoxicity (82%), and fossil resource scarcity (77%) in comparison with Fe-EDDHA. Soymeal and acetic acid were the main stressors identified in Fe-biochelate production, while phenol, ethylenediamine and glyoxal were the most significant contributors to the impact categories related to Fe-EDDHA. As a result, Fe-biochelate can be considered a more eco-friendly alternative to Fe-EDDHA.

Protein hydrolysates are largely used as plant biostimulants for boosting crop growth, and improving crop tolerance to abiotic stresses and fruit quality. Protein hydrolysate-based biostimulants are mostly produced by chemical hydrolysis starting from animal wastes. However, an innovative process of enzymatic hydrolysis of legume-derived proteins has been recently introduced by few companies. The objective of this study was to evaluate the energy use and environmental impact of the production processes of enzymatically-produced protein hydrolysate starting from lupine seeds and protein hydrolysate obtained from chemical hydrolysis of leather wastes through the application of life cycle assessment (LCA). The LCA method was applied through the software GEMIS “Global Emission Model for Integrated Systems”, elaborated at L’Oko-Institute in Germany, and the parameters taken into account were: CO2 emissions in g per kg of protein hydrolysate; the consumption of fossil energy expressed in MJ per kg of protein hydrolysate; and water consumption reported in kg per kg of protein hydrolysate. In the case of legume-derived protein hydrolysate, the evaluation of the energy use and the environmental impact started from field production of lupine grains and ended with the industrial production of protein hydrolysate. In the case of animal-derived protein hydrolysate, the LCA method was applied only in the industrial production process, because the collagen is considered a waste product of the leather industry. The type of hydrolysis is the step that most affects the energy use and environmental impact on the entire industrial production process. The results obtained in terms of CO2 emissions, fossil energy consumption and water use through the application of LCA showed that the production process of the animal-derived protein hydrolysate was characterized by a higher energy use (+26%) and environmental impact (+57% of CO2 emissions) in comparison with the enzymatic production process of lupine-derived protein hydrolysate. In conclusion, the production of legume-derived protein hydrolysate by enzymatic hydrolysis is more environmentally friendly than the production of animal-derived protein hydrolysate through chemical hydrolysis.

In Mediterranean climates, high temperatures and vapour pressure deficits are currently observed in greenhouses during summer. These conditions are responsible for a high transpiration rate leading to greater water consumption. Measuring and modelling transpiration can be useful for efficient irrigation management by allowing prediction of short-term water demand. The rate of transpiration of zucchini crops (Cucurbita pepo L.) grown in soilless culture was measured in a greenhouse located at Viterbo, central Italy, during spring–summer 2002. The Penman-Monteith equation was used to predict the potential transpiration of the plants averaged over 30-min intervals using different approaches in the calculation of aerodynamic resistance. The values obtained were compared with transpiration measured by a gravimetric method by weighing plants on an electronic balance. Leaf temperature was lower (up to 5°C) than air temperature on clear summer days owing to high transpiration rates. Stomatal resistance was computed and found to be exponentially related to solar radiation. The best fit in transpiration between the Penman-Monteith calculated and those measured was achieved when the heat transfer in the former was obtained as a process of mixed convection, where the slope of the regression was 1, and there was improvement of the coefficient of determination (R2 = 0.96). A simplified model of daytime transpiration based on easily measured variables (solar radiation and vapour pressure deficit) was developed and produced strong agreement with the gravimetric method (R2 = 0.93).

The effect of cultivar and nutrient solution macrocation proportions (SK, SCa, SMg) on the bioactive content of hydroponically cultivated lettuce was evaluated on two lettuce cultivars (red and green-pigmented Salanova®) grown in a fully controlled Fitotron® chamber. Fresh weight and color attributes were superior in green Salanova and in SK-treated plants, while elevated macrocation proportions (SK, SCa, and SMg) affected the corresponding minerals, P and Na content. SCa and SMg treatments raised ascorbate concentration and reduced nitrate levels in treated plants. Chicoric and chlorogenic acids were higher in red over green Salanova. Chlorogenic acid was higher in SCa and SMg plants and chicoric acid levels were SMg > SCa > SK. The SMg-treated red Salanova contained higher concentrations of target carotenoids. In conclusion, nutrient solution management constitutes an effective cultural practice to increase bioactive properties and functional quality of hydroponically grown lettuce.