Soil quality increases with long-term chabazite-zeolite tuff amendments in arable and perennial cropping systems.

The application of natural zeolites to improve soil quality and functioning has become highly popular, but we still miss information about the long-term effects on the soil due to its application. This study assesses the soil quality index (SQI) of three distinct agricultural soil systems 6-10 years after a single application of natural chabazite zeolite as a soil amendment. These soils exhibit different management practices: intensive arable (cereals), intensive perennial (pear) and organic perennial (olive). In the arable system, a zeolite application dosage of 5, 10 and 15 kg m-2 was tested and compared to unamended soil. In the two perennial systems, an application of 5 kg m-2 was tested against untreated reference sols. A set of 25 soil physical, chemical and biological parameters linked to soil health and quality were analysed at each experimental site. The dataset was investigated through Principal Component Analysis (PCA) to calculate the soil quality index (SQI) using linear scoring. In the arable-cereal field, the SQI doubled (0.3 to ca. 0.6 for all amendments) in chabazite-amended plots; a dose effect was not recognizable. In both perennial fields, the SQI was significantly higher in the chabazite-amended plots (5 kg m-2) with similar increases as compared to the arable-cereal field. At each site, the indicators selected by the PCA were different, indicating that chabazite addition impacted soil quality differently in each cropping system. Overall, the results highlighted a significant increase in soil quality with chabazite amendment, which confirms its potential for increasing soil health in the long-term.

Incidence of foliar treatments and geographical origin on the geochemical fingerprints of leaves and fruits in olive growing.

Recently, food quality and safety has become of great interest, with a consequent demand for geographical identification of agri-food products and eco-friendly agricultural practices. In this study geochemical analyses of soils, leaves and olives from two areas in the Emilia-Romagna Region (Italy), Montiano and San Lazzaro were performed aiming at identifying geochemical fingerprints able to (1) univocally determine the locality of provenance and (2) the effect of different foliar treatments (control, dimethoate, and alternating of natural zeolitite and dimethoate in MN; Spinosad + Spyntor fly, natural zeolitite and NH4+-enriched zeolitite in SL). PCA and PLS-DA (including VIP analysis) were used to discriminate between localities and different treatments. Bioaccumulation and Translocation Coefficients (BA and TC) were studied to evaluate differences in the uptake of trace elements by plants. The PCA performed on soil data highlighted a total variance of 88.81%, allowing a good distinction between the two sites. Leaves and olives PCA showed that using trace elements it is possible to discriminate different foliar treatments (total variance: 95.64% and 91.08% in MN; 71.31% and 85.33% in SL of leaves and olives, respectively) better than the identification of their geographical origin (87.46% of leaves and 83.50% of total variance of olives). PLS-DA of all samples gave the largest contribution to the discrimination of different treatments and geographical identification. Among all elements, only Lu and Hf were able to correlate soil, leaf, and olive for geographical identification through VIP analyses, but also Rb and Sr were significant in the plant uptake (BA and TC). For the discrimination of different foliar treatments, Sm and Dy were identified in MN site, whereas Rb, Zr, La and Th correlated leaves and olives from SL. Based on trace element analyses, it can be put forward that (1) the geographical origin could be discriminated and (2) different foliar treatments applied for crop protection can be recognized, which means, reversing the reasoning that each farmer can develop a method to pinpoint his own product.

Recycling nitrogen from liquid digestate via novel reactive struvite and zeolite minerals to mitigate agricultural pollution.

Recycling nutrients is of paramount importance. For this reason, struvite and nitrogen enriched zeolite fertilizers produced from wastewater treatments are receiving growing attention in European markets. However, their effects on agricultural soils are far from certain, especially struvite, which only recently was implemented in EU Fertilizing Product Regulations. In this paper, we investigate the effects of these materials in acid sandy arable soil, particularly focusing on N dynamics, evaluating potential losses, transformation pathways, and the effects of struvite and zeolitic tuffs on main soil biogeochemical parameters, in comparison to traditional fertilization with digestate. Liming effect (pH alkalinization) was observed in all treatments with varying intensities, affecting most of the soil processes. The struvite was quickly solubilized due to soil acidity, and the release of nutrients stimulated nitrifying and denitrifying microorganisms. Zeolitic tuff amendments decreased the NOx gas emissions, which are precursors to the powerful climate altering N2O gas, and the N enriched chabazite tuff also recorded smaller NH3 emissions compared to the digestate. However, a high dosage of zeolites in soil increased NH3 emissions after fertilization, due to pronounced pH shifts. Contrasting effects were observed between the two zeolitic tuffs when applied as soil amendments; while the chabazite tuff had a strong positive effect - increasing up to ∼90% the soil microbial N immobilization - the employed clinoptilolite tuff had immediate negative effects on the microbial biomass, likely due to the large quantities of sulphur released. However, when applied at lower dosages, the N enriched clinoptilolite also contributed to the increase of microbial N. From these outcomes, we confirm the potential of struvite and zeolites to mitigate the outfluxes of nutrients from agricultural systems. To gain the best results and significantly lower environmental impacts, extension practitioners could give recommendations based on the soils that are planned for zeolite application.

Distinct Particle Films Impacts on Olive Leaf Optical Properties and Plant Physiology.

The olive fruit fly is worldwide considered a major harmful pest of the olive agroecosystem. In Italy, the fruit fly infestation is traditionally countered by spraying chemical insecticides (e.g., dimethoate), but due to the recent ban of dimethoate by the Reg EU2019/1090 and the increasing awareness of consumers of food sustainability, the interest in developing chemical-free alternatives to pesticides, such as the use of particle-films, is rising. A field experiment was conducted to assess the effect of different particle films (kaolin-base and zeolitite-base) on leaf gas exchanges and leaf optical properties. Results showed that with the dust accumulation on the leaves' surface, photosynthesis, stomatal conductance, transpiration and water use efficiency were significantly lower in kaolin-treated olive trees compared to those treated with zeolitite and to the control, while olive trees treated with zeolitite showed physiological parameters similar to the untreated plants. Microstructural differences of different particle film on the leaf and olive surfaces emerged by ESEM observations also influenced leaf optical properties. Oils produced by zeolitite-treated plants show higher intensities of gustatory and olfactory secondary flavors compared to kaolin and test oils.

Phlogopite-pargasite coexistence in an oxygen reduced spinel-peridotite ambient.

The occurrence of phlogopite and amphibole in mantle ultramafic rocks is widely accepted as the modal effect of metasomatism in the upper mantle. However, their simultaneous formation during metasomatic events and the related sub-solidus equilibrium with the peridotite has not been extensively studied. In this work, we discuss the geochemical conditions at which the pargasite-phlogopite assemblage becomes stable, through the investigation of two mantle xenoliths from Mount Leura (Victoria State, Australia) that bear phlogopite and the phlogopite + amphibole (pargasite) pair disseminated in a harzburgite matrix. Combining a mineralogical study and thermodynamic modelling, we predict that the P-T locus of the equilibrium reaction pargasite + forsterite = Na-phlogopite + 2 diopside + spinel, over the range 1.3-3.0 GPa/540-1500 K, yields a negative Clapeyron slope of -0.003 GPa K-1 (on average). The intersection of the P-T locus of supposed equilibrium with the new mantle geotherm calculated in this work allowed us to state that the Mount Leura xenoliths achieved equilibrium at 2.3 GPa /1190 K, that represents a plausible depth of ~ 70 km. Metasomatic K-Na-OH rich fluids stabilize hydrous phases. This has been modelled by the following equilibrium equation: 2 (K,Na)-phlogopite + forsterite = 7/2 enstatite + spinel + fluid (components: Na2O,K2O,H2O). Using quantum-mechanics, semi-empirical potentials, lattice dynamics and observed thermo-elastic data, we concluded that K-Na-OH rich fluids are not effective metasomatic agents to convey alkali species across the upper mantle, as the fluids are highly reactive with the ultramafic system and favour the rapid formation of phlogopite and amphibole. In addition, oxygen fugacity estimates of the Mount Leura mantle xenoliths [Δ(FMQ) = -1.97 ± 0.35; -1.83 ± 0.36] indicate a more reducing mantle environment than what is expected from the occurrence of phlogopite and amphibole in spinel-bearing peridotites. This is accounted for by our model of full molecular dissociation of the fluid and incorporation of the O-H-K-Na species into (OH)-K-Na-bearing mineral phases (phlogopite and amphibole), that leads to a peridotite metasomatized ambient characterized by reduced oxygen fugacity.

Mitigation of sodium risk in a sandy agricultural soil by the use of natural zeolites.

Na+ contamination of irrigation waters represents a global environmental issue for soil structure and plant production. Notwithstanding several techniques for the reduction of Na+ have been proposed in recent years, they generally exhibit disadvantages, including low recyclability and relatively high operational/maintenance costs. In this paper, we propose a natural and eco-friendly solution for the reduction of Na+ risk in coastal agricultural sandy soil (SS), vulnerable to salinity stress. A series of column leaching experiments have been conducted to assess the influence of Italian zeolite-rich tuff (natural zeolites, NZ) addition to soil (NZSS) on Na+ removal, SAR, and CROSS index, under three different salinity scenario. Result showed that the Na+ removal efficiency varied between 46.4 and 54.3% in soil amended with NZ, and analogously SAR index was significantly reduced from 7 to up 13 points. SAR and CROSS indexes resulted better correlated in SS rather than NZSS due to the influence of K+ released by NZ. In conclusion, soil amendment with NZ represents a natural and eco-friendly solution for increasing sandy soil resilience to Na+ risk.

Effects of middle-term land reclamation on nickel soil-water interaction: a case study from reclaimed salt marshes of Po River Delta, Italy.

Reclaimed salt marshes are fragile environments where water salinization and accumulation of heavy metals can easily occur. This type of environment constitutes a large part of the Po River Delta (Italy), where intensive agricultural activities take place. Given the higher Ni background of Po River Delta soils and its water-soluble nature, the main aim of this contribution is to understand if reclamation can influence the Ni behavior over time. In this study, we investigated the geochemical features of 40 soils sampled in two different localities from the Po River Delta with different reclamation ages. Samples of salt marsh soils reclaimed in 1964 were taken from Valle del Mezzano while soils reclaimed in 1872 were taken nearby Codigoro town. Batch solubility tests and consecutive determination of Ni in pore-water were compared to bulk physicochemical compositions of soils. Bulk Ni content of the studied soils is naturally high, since these soils originated from Po River sediments derived from the erosion of ultramafic rocks. Moreover, it seems that Ni concentration increases during soil evolution, being probably related to the degradation of serpentine. Instead, the water-soluble Ni measured in the leaching tests is greater in soils recently reclaimed compared to the oldest soils. Soil properties of two soil profiles from a reclaimed wetland area were examined to determine soil evolution over one century. Following reclamation, pedogenic processes of the superficial horizons resulted in organic matter mineralization, pH buffer, and a decrease of Ni water solubility from recently to evolved reclaimed soil.