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The dynamism of carbon pools and flows in landscapes requires special attention to the methods and tools for measuring all carbon-containing soil components. An important component of the carbon budget in carbonate geosystems is the dissolved inorganic carbon, part of which is carried out by surface and lateral flows into water bodies, which requires attention to assessing the total alkalinity (TA) of soils on calcareous rocks. Analysis of soils and parent rocks in the Polar Urals with a CaCO3 content of 0 to 100% revealed the factors that influence the value of their TA, namely, (a) the method used for preparing soil samples and water extraction (the ratio of soil weight to the volume of distilled water, ms : , and the quality of separation of solid and liquid phases); (b) the moment of recording the acid titration endpoint for extracts; and (c) the presence of organic acids with pKa < 4.4. The latter reduces the content of bicarbonate ion by converting it into carbonic acid, not measurable by titration. This mechanism is confirmed by (a) analysis of the model solutions of sodium bicarbonate and formic (pKa = 3.75), tartaric (pKa1 = 3.04 and pKa2 = 4.37), and malic (pKa1 = 3.46) acids; (b) cation–anion balance of soil water extracts; and (c) a negative shift in the titration TA values (the sum of carbonate and organic alkalinities) relative to the amount of equivalents of dissolved inorganic carbon determined by high-temperature catalytic oxidation at the same ms : ratios in both methods. It is possible to compare the TA of soils measured by different laboratories only strictly performing all experimental conditions. It is recommended to use a centrifuge to separate the solid and liquid phases of carbonate soils and a pH-meter or a titrator to record the endpoint of titration. [ABSTRACT FROM AUTHOR]

There is a growing interest in recovering and recycling phosphorus (P) from waste streams to reduce reliance on finite and non-renewable phosphate rock in agriculture. Struvite, derived from waste streams, has emerged as a potential alternative P fertilizer. However, its behaviour in soil remains unclear. This study aimed to investigate the behaviour and effectiveness of struvite as a P fertilizer in acidic Acrisol and calcareous Cambisol soils, focusing on the P dissolution from struvite, struvite P diffusion in soil and P availability. Our findings revealed that the P dissolution from struvite in solution is pH-dependent, with the most dissolution observed at pH 4.5 and significantly less at pH 7.0 and pH 8.5. Consequently, P dissolution from struvite was more rapid in the Acrisol compared with the Cambisol. This was supported by the increased accumulation of water-soluble P in the Acrisol and acid-extractable P in the Cambisol within the 0-1 cm concentric soil section surrounding the struvite application site, as demonstrated in the petri dish experiment. However, the Acrisol exhibited a gradual decrease in P diffusion over time, in contrast to the Cambisol, which showed an increasing trend. This can be attributed to the stronger P fixation observed in the Acrisol. The application of struvite resulted in increased soil P availability, as determined by the diffusive gradients in thin films (DGT) technique, particularly in the Acrisol where struvite was concentrated. Furthermore, the presence of organic acids enhanced struvite P availability in both Acrisol and Cambisol soils. These findings contribute to a better understanding of struvite behaviour in different soil environments and provide valuable insights for optimizing its use as a sustainable and efficient P fertilizer. [ABSTRACT FROM AUTHOR]

• A multi-site (6), multi-year (3) field experiment was conducted. • Vine-growing areas differing in grape quality also differed in some soil properties. • Must quality related to soil limestone and nutrient content in premium-grade areas. • High tartaric acid content in must in the premium-grade area of Moriles Altos. • Standard-grade area (Ruedos) related to higher soil sand contents and larger grapes. There is a growing interest among consumers in some world regions in high-quality products including wine. In this work, we examined the unique quality wines obtained in the Montilla − Moriles wine Protected Designation of Origin (PDO) (Córdoba, southern Spain). Specifically, we assessed the influence of soil properties on the production and quality of Pedro Ximénez grapes in the Montilla − Moriles PDO terroir in six vineyards typical of three different production areas, namely: Sierra de Montilla and Moriles Altos (two premium-grade areas), on soils known as "albariza", characterized by their parent material (mainly marls and limestones), with a high calcium carbonate content and low organic matter content; and one standard-grade area (Ruedos), with soils developed on varied materials including Miocene marls, which are steeply and highly eroded. Representative soil profiles were evaluated and a field experiment to conducted to obtain data on grape production and quality over a period of three years in the six vineyards. Wine quality in the premium-grade areas was strongly influenced by physical characteristics of the vineyards (altitude and age), and also by some soil properties (limestone, poorly crystalline Fe oxides, and available P, Zn and Cu), production-related characteristics (leaf surface area exposed to solar radiation) and oenological variables (tartaric acid content). By contrast, quality in the standard-grade area was more closely related to soil sand and available Mn, and also to scarcely available P and Zn; however, grape bunches were more abundant and grapes larger (100-berry weight) in this area, and the must produced was richer in malic acid. These results suggest that soil properties in each premium-grade area of the Montilla-Moriles PDO (viz., Sierra de Montilla and Moriles Altos) set them apart from each other and distinguish them from the standard-grade area (Ruedos). Such soil properties are associated to consumer-appreciated quality-related parameters. [ABSTRACT FROM AUTHOR]

• Using in-situ measurements, size fractionation from soil to sediment was investigated for numerous calcareous soils. • The 0.2 mm was suggested as the boundary between high and low erodible fractions of calcareous soils. • Size range of 0.063–0.2 mm was found as the most susceptible fraction to wind erosion. • Soil fraction of 0.063–0.1 mm intensified calcareous soil potential for suspension-size sediment generation. • Critical values of various soil PSD criteria for wind erosion rate of calcareous soils were suggested. Soil texture and soil surface aggregate size distribution (ASD) are key factors to study soil erodibility by wind and sediment size distribution (SSD) in arid and semi-arid areas. However, less research has studied the effect of soil fractions on soil erodibility and wind-blown sediment size of calcareous soils. In the present study, we focused on the size fractionation and particle size distribution (PSD) of 60 calcareous soil samples collected from 20 semi-arid and arid areas in Fars province, southern Iran. Extensive in-situ wind tunnel experiments were conducted under controlled high wind speed to measure wind erosion rate (WER) and SSD. The results showed that the calcareous soils had different erodibility based on their PSD. Generally, the most erodible soils to the wind force were those with less than 10 % of clay and higher frequency of the 0.1–0.2 mm size class. However, when the soil clay content exceeds 20 %, ASD got dominated with the fraction of 0.4–0.8 mm and WER of the calcareous soils got limited. Besides, size range of 0.063–0.2 mm was suggested as the most wind erodible fraction of the calcareous soils. Furthermore, the mean weight diameter (MWD) of sediment particles averagely reduced 1.3 times as compared to that of the soil samples and WER got inhibited for regions in which the difference of soil and sediment MWD exceeded 0.05 mm. The SSD was significantly controlled by soil PSD and suspension-size sediments < 0.1 mm (SSS) were negatively proportional to soil clay, MWD, geometric mean diameter of soil particles (GMD), dry stable aggregates > 0.25 mm (DSA), and organic carbon as logarithmic equations. Moreover, the presence of the size fractions > 0.2 mm restricted the potential of calcareous soils to generate SSS, which would be quite beneficial for wind erosion combat and dust control of calcareous soils. [ABSTRACT FROM AUTHOR]

• 28 years of sewage sludge application at low to moderate doses had a low effect on organic C concentration. • Soil organic C storage increased only at the highest dose (80 tons ha−1 y−1) • Exogenous C increased the concentration of labile fractions but accumulated mostly in mineral-associated fractions. • Rock-Eval® pyrolysis coupled to PARTY SOC model is more sensitive to the amount of sewage sludge added than other fractionations. • The response of SOC fractions did not directly correspond to that of yield of a cereal-based rotation. Soil organic matter (SOM) is a recognized carbon reservoir and paramount in soil functioning and agrosystems productivity. Different management strategies have been established to enhance SOM in arable soils, and one is the application of exogenous organic matter (EOM). Despite significant efforts in recent years, the consequences of EOM addition on increasing soil organic C (SOC) storage and stability in different pedoclimatic contexts remain incompletely understood. In this study, we evaluated the effect of long-term (28 y) sewage sludge (SS) addition to a calcareous soil supporting rainfed extensive crops in a Mediterranean sub-humid area in terms of SOC stabilization and distribution among functional fractions. To that end, we studied total SOM storage and soil fractions in a long-term experiment comparing 4 different doses of SS with mineral fertilization and no-fertilization controls. We compared the concentration, storage and distribution of C using two different fractionation methods (particulate vs. mineral-associated, defined by granulodensimetric fractionation, and active C vs. stable C defined by Rock-Eval® thermal analysis coupled to the machine learning PARTYsoc v2.0 model) on the tilled layer (0–30 cm). Three soil functioning indicators (crops yield, soil microbial biomass C and aggregate stability) were also quantified. We found that SS application, which slightly increased SOC concentration when SS was added, resulted in a net SOC stock gain only with the highest dose used (80 tons/ha), compared to mineral fertilization, suggesting that most of the C added was mineralized. An uneven response of soil fractions was however detected. The coarsest heavy physical fractions > 250 μm and 50–250 μm in size were the most enriched in their C concentration with SS addition, whereas SOC was mostly accumulated as mineral-associated C in the silt-size (2–50 μm) and the 50–250 μm fractions. Regarding thermal fractionation, SS treatments showed C gains between 57 % and 35 % in the active C pool, compared to mineral fertilization. This can be explained considering that the accumulated SOM in mineral-associated fractions corresponded to mean-residence times in the order of 20–40 years. The consequences on soil functioning indicators were not directly related to the amount of SOC stored in the soil, as the highest SOC gains corresponded to the highest dose, but not the highest yields, and some negative correlations were observed between SOC fractions and soil structural stability and microbial biomass. This can be related to some deleterious effects of excessive SS application reducing yields, the soil biological activity and soil structure, and represents an example of the need to decouple the assessment of soil health from that of SOC storage for certain soil management practices. The overall evaluation of the net consequences of long-term SS application indicated that low doses (10 tons/ha) seem a better choice, as they resulted in the highest efficiency in C incorporation, and in a slightly greater increase in SOC concentration than intermediate doses, and equal yields than mineral fertilization, but did not have the negative effects observed in soil functioning with higher doses. [ABSTRACT FROM AUTHOR]

Invasions of the aquatic weed Crassula helmsii pose a serious threat to native vegetation of soft water lakes, which increases the need for understanding the factors that regulate the success or failure of C. helmsii. Creating favorable conditions for native species seems promising to control C. helmsii , as previous research indicated that C. helmsii is a poor (root) competitor. We studied the development of C. helmsii growing together with the native Littorella uniflora (biomass, cover, tissue nutrient composition) at two different calcareous poor soil types (organic/acid, mineral/buffered) and under two different water tables (not inundated, submerged) in a greenhouse experiment. We found that when growing under submerged conditions, C. helmsii coexisted with L. uniflora and other native species without becoming dominant due to carbon limitation in the water layer. In contrast, we found that C. helmsii can easily become dominant over L. uniflora when growing on desiccated buffered fen soils with moderate nutrient availability. On the acidic/organic soils, C. helmsii development was poor and die-off was observed under both water level treatments, probably induced due to aluminum toxicity under a low acidity. These results indicate that creating oligotrophic and carbon-poor conditions are required for controlling C. helmsii. Restoration measures can preferably be taken before the onset of the rainy season and/or be followed by maintenance of a temporal artificial high water table to stimulate carbon limitation. Liming more or less organic shores could alleviate aluminum toxicity under acidic conditions which can potentially stimulate the development of C. helmsii. • Unraveling drivers Crassula helmsii invasions is essential for effective control. • C. helmsii easily becomes dominant on not inundated, mesotrophic soils. • C. helmsii development is restricted under submerged carbon limited conditions. [ABSTRACT FROM AUTHOR]