Studio su gli effetti sinergici tra compost e biochar nel miglioramento della qualità del suolo

La presenza della sostanza organica nel suolo ne garantisce la qualità ed è uno dei migliori indicatori di fertilità del terreno in quanto è l’unica componente legata sia alle caratteristiche fisiche che a quelle chimiche e biologiche, nonché al flusso potenziale di elementi all’interfaccia suolo-radice. Nel lungo tempo è fondamentale che il contenuto di sostanza organica del suolo sia mantenuto, anche con continui apporti di residui organici e ammendanti. Tra gli ammendanti più utilizzati negli ultimi anni, in questo studio sono stati presi in considerazione il compost verde e il vermicompost. Il primo deriva dalla decomposizione e stabilizzazione biologica della sostanza organica fresca derivata da piante, attraverso l’azione di diverse specie di microrganismi in condizioni aerobiche, il secondo deriva dalle interazioni tra lombrichi e microrganismi che si instaurano durante la degradazione della sostanza organica ed è composto, principalmente, dai residui fecali dei lombrichi che elaborano la matrice organica di partenza per i loro fabbisogni metabolici. Recentemente è stato valutato per l’utilizzazione agricola anche un materiale carbonioso (biochar), derivante dalla pirolisi di diverse biomasse di rifiuto, con lo scopo di mantenere e incrementare il contenuto in sostanza organica e contemporaneamente ridurre le emissioni di gas serra provenienti dal processo agricolo. In laboratorio sono stati creati dei microcosmi costituiti da un suolo agrario ammendato con compost verde, vermicompost e biochar, e altre due combinazioni tra biochar e gli altri due ammendanti (biochar + compost verde e biochar + vermicompost) per valutare un eventuale effetto sinergico. La prova è stata protratta per un anno con periodici campionamenti, a temperatura ambiente e mantenendo una umidità costante (50% della capacità idrica massima) ottimale per tutte le attività biologiche. Sono stati monitorati pH, carbonio organico e solubile, azoto totale, nitrico e ammoniacale, fosforo assimilabile, potassio scambiabile, respirazione basale, biomassa microbica, attività idrolitica totale, fosfatasi e deidrogenasi. L’aggiunta dei due compost al suolo ha provocato l’aumento di sostanza organica e di tutti gli elementi di fertilità. I risultati nel tempo dimostrano che i due compost generalmente migliorano la qualità del suolo, sia a livello chimico che biologico. Il biochar si presenta invece sostanzialmente poco attivo rispetto ai due compost e mostra valori simili a quelli del terreno di controllo. Per i parametri esaminati, non sono stati osservati incrementi oltre la soglia dell’additività nelle miscele tra biochar e gli altri due ammendanti. Non si registrano dunque particolari effetti sinergici positivi, anzi il biochar sembra in certi casi limitare l’espressione di alcune attività dei due compost nel suolo (come per esempio quella deidrogenasica). La minore attività generale del biochar, testimoniata anche dalla minore quantità di CO2 sviluppata nei test respirometrici, conferma la sua attitudine ad arricchire di carbonio il suolo diminuendo le emissioni di gas serra

New strategies for the application of biochar and wood distillate as soil improvers in agricultural systems

Lo scopo principale di questa tesi è quello di trovare una o più strategie per valorizzare i prodotti solidi (biochar) e liquidi (distillato di legno) del processo di pirolisi per scopi agricoli. La tesi è focalizzata sull'uso del biochar in agricoltura considerando molteplici aspetti: il suo arricchimento con composti organici (vermicompost e distillato di legno) e il suo utilizzo in particolari condizioni di irrigazione; l'utilizzo del biochar è stato testato su terreni poco fertili (uno sabbioso e povero di C organico, l'altro argilloso-limoso e privo di P disponibile) che sono stati fortemente irrigati o hanno subito stress idrico per valutare come il biochar possa migliorare alcuni aspetti relativi a queste criticità; terreni a bassa e media fertilità unitamente a biostimolanti tramite fertirrigazione per valutare se vi fossero effetti sinergici tra i due materiali organici sia sul suolo che sulla pianta. Unitamente all'analisi relativa alla fertilità e nutrizione delle piante, è stata effettuata l'analisi della qualità del suolo per monitorare la possibile influenza dei trattamenti sui microrganismi e sulle attività enzimatiche. L'obiettivo principale era il miglioramento del sistema suolo/pianta sia nei suoli a bassa e media fertilità. The main purpose of this thesis is to find one or more strategies to enhance the solid (biochar) and liquid (wood distillate) products of the pyrolysis process for agricultural purposes. The thesis is focused on the use of biochar in agriculture considering multiple aspects: its enrichment with organic compounds (vermicompost and wood distillate) and its use in particular conditions of irrigation. The use of biochar was tested on: low fertile soils (one sandy and poor in organic C, the other clayey-silty and lacking in available P) that have been either strongly irrigated or have undergone water stress for evaluating how biochar could improve some aspects related to these criticalities; low and medium fertile soils together with biostimulants via fertigation to assess whether there were synergistic effects between the two organic materials both on the soil and on the plant. Together with the analysis concerning the fertility and nutrition of the plants, soil quality analysis was carried out to monitor the possible influence of the treatments on microorganisms and enzymatic activities. The main focus was on enhancing the soil/plant system in both low and medium fertility soils

Soil biochemical activities after the application of pyroligneous acid to soil

Pyroligneous acid (PA) is produced during the combustion of woody biomass and is a complex aqueous fraction resulting from the thermochemical rupture of the components of vegetable biomass.We evaluated the effect of PA on the soil microbial community and activity in order to assess the applicability of this acid in soil and to gather further information on the mechanisms of its toxicity or stimulation. Five concentrations of PA solution (0, 0.5, 1, 2 and 5%) were selected to monitor the biochemical parameters of the soil. The respirometric test showed that the increase in the evolved carbon dioxide-carbon (C) was not due to a release of the native organic C from the soil, but only from the organic compounds of PA. The highest values of microbial biomass content were found in the soil treated with the lowest PA doses, but decreased with increased doses. At higher application doses (2 and 5%), there was a decrease in most enzymatic activities and a loss of soil quality. When PA was applied in doses of up to 1%, our results indicated no negative effects on soil biology and that there was even an improvement

Soil and Foliar Applications of Wood Distillate Differently Affect Soil Properties and Field Bean Traits in Preliminary Field Tests

Natural products such as wood distillate (WD) are promising alternatives to xenobiotic products in conventional agriculture and are necessary in organic farming. A field study gave insight into the effectiveness of WD applied as foliar spray (F-WD), soil irrigation (S-WD), and their combination as growth promoters for field beans. The soil fertility and quality parameters, plant growth, nutrient uptake, and resource partitioning within plants were evaluated. In a pot trial, we tested the effect of S-WD on root nodule initiation and growth. S-WD increased DOC and microbial biomass by approximately 10%, prompted enzyme activities, and increased nitrate and available phosphorus in soil, without affecting the number and growth of nodules in field beans. In contrast, the F-WD slightly reduced the DOC, exerted a lower stimulation on soil enzymes, and lowered the soil effect in the combined distribution. In field beans, the F-WD reduced the stem height but increased the number of pods per stem; S-WD increased the N and P concentrations of leaves and the N concentration of the pods. Moreover, all WD treatments retarded plant senescence. The WD revealed itself to be promising as a growth promoter for grain legumes, but further research is needed to understand the interference between the combined soil and foliar applications

Wood distillate, a review over past application and future perspective on soil and plant research

Wood distillate (WD), also known as wood vinegar or pyroligneous acid, is traditionally applied as a pesticide in Asian countries. Recently, its efficacy as a corroborant for crops has been reported, but little is known about its mode of action, nor a molecular biology-based approach is hardly ever applied to investigate it. In this mini review we analyze the literature on the topic, trying to suggest how the molecular biology may help us to understand how WD influence that the plants development

Effect of Biochar, Green Compost, and Vermicompost on the Quality of a Calcareous Soil: A 1-Year Laboratory Experiment

Changes in the chemical and biological characteristics of a calcareous soil by the addition of green compost (GC), vermicompost (VC), biochar, biochar + GC, and biochar + VC were evaluated during a 360-day laboratory incubation. The GC and the VC treatments lowered the soil pH and increased the total and dissolved organic C, microbial biomass C, microbial quotient, alkaline phosphatase (AP-ase) and specific AP-ase, dehydrogenase (DH-ase) and specific DH-ase, and metabolic potential. The improvement in the biological activity of the soil was more notable and permanent with VC than GC. The biochar treatment temporarily increased the pH of the calcareous soil (pH 8.2) up to a maximum of 8.57, showed the greatest increase of total organic C, did not change dissolved organic C and microbial biomass C, and induced small effects on soil biological activities. When mixed with biochar (biochar + GC and biochar + VC), composts led to higher organic C mineralization; dissolved organic C, biomass C, and DH-ase activity; and did not change the metabolic quotient, specific AP-ase, and specific DH-ase activities. The AP-ase activity of biochar was enhanced only by the addition of VC, although in a nonadditive way. Metabolic potential was more than halved by the GC and was not changed by the VC. Overall, our study shows that the incorporation of both composts, particularly VC, into calcareous soils may improve soil quality, whereas biochar could have benefits for C sequestration. In addition, the mixing of GC, and especially VC with biochar, increased some soil quality parameters compared with the biochar-only treatment

Relationships between antioxidant capacity and microbial activity in a soil amended with biochar, green compost and vermicompost

The aim of the study was to evaluate the relationships between the antioxidant capacity and the microbial activity in a soil amended with different organic materials. In a 1-year laboratory incubation, biochar, green compost and vermicompost were added to soil at the dose of 2.5% w/w. Antioxidant capacity (TEAC), dissolved organic carbon (DOC), water- and alkali-soluble phenols and microbial activity, as measured by the fluorescein diacetate hydrolysis (FDA), were monitored during incubation. Greater TEAC was in green compost and vermicompost than in biochar treated soil and it was directly related on the TEAC values of the added materials. The application of organic materials caused a marked increase of DOC and water- and alkali-soluble phenols, with values reflecting the amount of these compounds present in the amendments. The relationships between values of TEAC and phenols in the treatments suggest that these substances may be involved in determining the antioxidant capacity of soil. Compared to control, FDA was not influenced by B at each sampling time, probably because the inhibiting activity of TEAC of the material. The two types of compost, particularly vermicompost, stimulated FDA throughout the whole experimental period. Any possible inhibition of the microbial activity induced by TEAC of vermicompost and green compost could have been masked by the considerable supply of organic soluble compounds of composts, that may have stimulated strongly the microorganisms. These results suggest that the soil microbial activity can be defined by the balance between the stimulating activity of DOC and antioxidant activity of the phenols

Biofertilization with Liquid Vermicompost-Activated Biochar Enhances Microbial Activity and Soil Properties

Biochar (Bc) and liquid vermicompost extracts (LVEs) are increasingly being used as biofertilizers in agriculture to promote soil-microbe-crop interactions. However, although both these products can potentially act synergistically due to their complementary characteristics, their coapplication in different soils has not yet been investigated. Therefore, firstly, an LVE-activated biochar (BLVE) was experimentally formulated and the persistence of LVE bacteria over a 60-day storage period was determined. The total number of LVE bacteria increased by 10-fold after 7 days and was stable throughout the entire biochar storage period. In addition, changes in the composition of the bacterial community were observed after 30 days of storage, indicating that taxa less represented in pure LVE may be advantaged upon biochar colonization. Secondly, a microcosm experiment was performed to evaluate whether the biological fertility and enzyme activities of two soils, differing in organic matter content, could be enhanced by the addition of LVE-activated biochar. In this experiment, three different doses of Bc, LVE, and BLVE against the carbon-related biological fertility index (i.e., biological fertility index, BFI) and three enzyme activities over a 21-day incubation period were tested. The BLVE treatment yielded the best results (i.e., BFI +32%, enzyme activities +38%). This indicates that Bc and LVEs can act synergistically to promote soil fertility, quality, and microbial activity. By integrating LVE-activated biochar into their soil management practices, farmers could achieve higher crop yields and healthier products

Integrative Effect of UV-B and Some Organic Amendments on Growth, Phenolic and Flavonoid Compounds, and Antioxidant Activity of Basil (<i>Ocimum basilicum</i> L.) Plants

The application of organic amendments, biochar, and wood distillate (WD), as well as the exposure to UV-B radiation, are two sustainable ways to enhance soil fertility and increase plant nutraceutical quality, respectively. However, they have always been studied separately, without testing the eventual synergistic or antagonistic effect when applied together. The present study investigated the effects of biochar (2% w/w), WD (1:100), and their combination (BWD) on some biometric and biochemical parameters of basil plants (Ocimum basilicum L.) exposed to different doses of UV-B radiation (0, 1, 2 h d−1; UV-B irradiance of 1.36 W m−2) in controlled conditions. Root and stem length and weight were not affected by soil amendments, while 1 h d−1 UV-B increased the length (+28%) and weight (+62%) of the aerial part. When combining the above- and below-ground factors, a decrease in root length was observed in the 2 h d−1 UV-B-treated plants in both WD (−36%) and BWD (−39%) treatments. The co-application of below- and above-ground treatments generally decreased phenolic and flavonoid concentration in both fully expanded leaves and vegetative shoot apices. This preliminary study highlights an antagonistic action of the combination of the investigated factors, at these doses, on the plant growth and metabolism that should be considered