Agro-environmental sustainability of using digestate fertilizer for solanaceous and leafy vegetables cultivation: Insights on fertilizer efficiency and risk assessment

Recent innovations in fertilization with treated digestate from food waste to recover nutrients for arid agricultural fields

This study aims to explore the development of sustainable fertilizers from waste materials of a biogas plant and a brewery. These wastes, rich in organic carbon and nitrogen, were processed with sulfuric(VI) and phosphoric(V) acid mixture, facilitating the production of free amino acids and achieving waste sanitization. This treatment produced by-products, which extended the range of possible applications. The highest concentration of free amino acids (360 mg/l) was achieved through hydrolyzing with a 40% concentration medium over 24 h. In this case, the maximum levels were recorded for beta-alanine (69.3 mg/l), glycine (46.8 mg/l), isoleucine (43.5 mg/l), proline (36.2 mg/l), and valine (31.5 mg/l). The study presents two fertilizer technologies, with and without micronutrients, that satisfy European Parliament Regulation 2019/1009 (Ntot > 2%, Norg > 0.5%, Corg > 3%). Bioavailability of nutrients in the formulations ranged from 60 to 100%. The efficacies of these fertilizers were evaluated in 30-day pot trials with various plant species, with both single application and fertigation tested. Multielement analysis confirmed high nutrient transfer in the soil-plant system, and the inclusion of micronutrients led to biofortification of plant biomass in Cu (48.3 ± 7.2 mg/kg), Mn (249 ± 37 mg/kg), Zn (164 ± 25 mg/kg), and Fe (211 ± 32 mg/kg). These sustainable fertilizers present an alternative to traditional, non-renewable fertilizers and offer promising solutions for precision agriculture and environmentally conscious production.

Environmental regulations and agricultural carbon emissions efficiency: Evidence from rural China

Reducing carbon emissions while maintaining simultaneous economic growth has been the focus of agricultural and environmental management research in recent times. To examine the influence of agricultural environmental regulations and related factors on agricultural carbon emissions efficiency, the entropy method was utilized to weigh each index and develop an index system for evaluating agricultural environmental regulations. This study utilizes the Super Slacked-Based Measure model that takes into account undesirable outputs. The research data used spans the years 2010-2019 and covers 31 provinces in China to calculate the efficiency of agricultural carbon emissions. A spatial Durbin model was employed to investigate the influence of environmental regulations and other influential factors on the efficiency of agricultural carbon emissions. The efficiency levels in the eastern region of China have consistently exceeded the national average, whereas the central region has demonstrated the lowest efficiency levels across the nation. Both the efficiency of agricultural carbon emissions and the intensity of agri-environmental regulations measured in this paper are strongly spatially autocorrelated between provinces. The environmental regulations index on local agricultural carbon emissions efficiency is significantly positive, while the effect on the agricultural carbon emissions efficiency in adjacent areas is not significant. Overall, agricultural environmental regulations effectively enhance agricultural carbon emissions efficiency, which in turn promotes technological innovation and economic growth. At the same time, local governments should actively adopt targeted strategies based on the actual situation of different regions in terms of their resource endowments and differences in the production characteristics of different crops.

Enhancing sustainable crop cultivation: The impact of renewable soil amendments and digestate fertilizer on crop growth and nutrient composition

Utilizing digestate as a fertilizer enhances soil nutrient content, improves fertility, and minimizes nutrient runoff, mitigating water pollution risks. This alternative approach replaces commercial fertilizers, thereby reducing their environmental impact and lowering greenhouse gas emissions associated with fertilizer production and landfilling. Herein, this study aimed to evaluate the impact of various soil amendments, including carbon fractions from waste materials (biochar, compost, and cocopeat), and food waste anaerobic digestate application methods on tomato plant growth (Solanum lycopersicum) and soil fertility. The results suggested that incorporating soil amendments (biochar, compost, and cocopeat) into the potting mix alongside digestate application significantly enhances crop yields, with increases ranging from 12.8 to 17.3% compared to treatments without digestate. Moreover, the combination of soil-biochar amendment and digestate application suggested notable improvements in nitrogen levels by 20.3% and phosphorus levels by 14%, surpassing the performance of the those without digestate. Microbial analysis revealed that the soil-biochar amendment significantly enhanced biological nitrification processes, leading to higher nitrogen levels compared to soil-compost and soil-cocopeat amendments, suggesting potential nitrogen availability enhancement within the rhizosphere's ecological system. Chlorophyll content analysis suggested a significant 6.91% increase with biochar and digestate inclusion in the soil, compared to the treatments without digestate. These findings underscore the substantial potential of crop cultivation using soil-biochar amendments in conjunction with organic fertilization through food waste anaerobic digestate, establishing a waste-to-food recycling system.

CmoNAC1 in pumpkin rootstocks improves salt tolerance of grafted cucumbers by binding to the promoters of CmoRBOHD1, CmoNCED6, CmoAKT1;2 and CmoHKT1;1 to regulate H2O2, ABA signaling and K+/Na+ homeostasis

The NAC transcription factor is a type of plant-specific transcription factor that can regulate plant salt tolerance, but the underlying mechanism is unclear in grafted vegetables. H2O2 and ABA in pumpkin rootstocks can be transported to cucumber scion leaves, promoting stomatal closure to improve salt tolerance of grafted cucumbers. Despite these observations, the regulatory mechanism is unknown. Here, our research revealed that CmoNAC1 is a key transcription factor that regulates H2O2 and ABA signaling in pumpkin roots under salt stress. The function of CmoNAC1 was analyzed using root transformation and RNA-seq, and we found that pumpkin CmoNAC1 promoted the production of H2O2 and ABA via CmoRBOHD1 and CmoNCED6, respectively, and regulated K+/Na+ homeostasis via CmoAKT1;2, CmoHKT1;1, and CmoSOS1 to improve salt tolerance of grafted cucumbers. Root knockout of CmoNAC1 resulted in a significant decrease in H2O2 (52.9% and 32.1%) and ABA (21.8% and 42.7%) content and K+/Na+ ratio (81.5% and 56.3%) in leaf and roots of grafted cucumber, respectively, while overexpression showed the opposite effect. The root transformation experiment showed that CmoNCED6 could improve salt tolerance of grafted cucumbers by regulating ABA production and K+/Na+ homeostasis under salt stress. Finally, we found that CmoNAC1 bound to the promoters of CmoRBOHD1, CmoNCED6, CmoAKT1;2, and CmoHKT1;1 using yeast one-hybrid, luciferase, and electrophoretic mobility shift assays. In conclusion, pumpkin CmoNAC1 not only binds to the promoters of CmoRBOHD1 and CmoNCED6 to regulate the production of H2O2 and ABA signals in roots, but also binds to the promoters of CmoAKT1;2 and CmoHKT1;1 to increase the K+/Na+ ratio, thus improving salt tolerance of grafted cucumbers.

Variability of Micro- and Macro-Elements in Anaerobic Co-Digestion of Municipal Sewage Sludge and Food Industrial By-Products

The main aim of this study was to evaluate the effect of the addition of selected industrial food wastes on the fate of micro- and macro-elements within an anaerobic digestion process (AD), as well as define the relationship between their content and AD efficiency. Orange peels, (OP), orange pulp (PL) and brewery spent grain (BSG) were used as co-substrates, while municipal sewage sludge (SS) was applied as the main component. The introduction of co-substrates resulted in improvements in feedstock composition in terms of macro-elements, with a simultaneous decrease in the content of HMs (heavy metals). Such beneficial effects led to enhanced methane production, and improved process performance at the highest doses of PL and BSG. In turn, reduced biogas and methane production was found in the three-component digestion mixtures in the presence of OP and BSG; therein, the highest accumulation of most HMs within the process was also revealed. Considering the agricultural application of all digestates, exceedances for Cu, Zn and Hg were recorded, thereby excluding their further use for that purpose.