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Soil acidification is an issue for agriculture that requires effective management, typically in the form of lime (calcium carbonate, CaCO3), application. Mid infrared (MIR) spectroscopy methods offer an alternative to conventional laboratory methods, that may enable cost-effective and improved measurement of soil acidity and responses to liming, including detection of small–scale heterogeneity through the profile. Properties of an acidic soil following lime application were measured using both MIR spectroscopy with Partial Least Squares Regression (MIR-PLSR) and laboratory measurements to (a) compare the ability of each method to detect lime treatment effects on acidic soil, and (b) assess effects of the different treatments on selected soil properties. Soil properties including soil pH (in H2O and CaCl2), Aluminium (Al, exchangeable and extractable), cation exchange capacity (CEC) and organic carbon (OC) were measured at a single field trial receiving lime treatments differing in rate, source and incorporation. Model performance of MIR-PLSR prediction of the soil properties ranged from R2 = 0.582, RMSE = 2.023, RPIQ = 2.921 for Al (extractable) to R2 = 0.881, RMSE = 0.192, RPIQ = 5.729 for OC. MIR-PLSR predictions for pH (in H2O and CaCl2) were R2 = 0.739, RMSE = 0.287, RPIQ = 2.230 and R2 = 0.788, RMSE = 0.311, RPIQ = 1.897 respectively, and could detect a similar treatment effect compared to laboratory measurements. Treatment effects were not detected for MIR-PLSR-predicted values of CEC and both exchangeable and extractable Al. Findings support MIR-PLSR as a method of measuring soil pH to monitor effects of liming treatments on acidic soil to help inform precision agricultural management strategies, but suggests that some nuance and important information about treatment effects of lime on CEC and Al may be lost. Improvements to prediction model performance should be made to realise the full potential of this approach. [ABSTRACT FROM AUTHOR]

The acidic soils of western Newfoundland require liming for successful production of most crops. Locally sourced paper mill waste wood ash (WA) and paper sludge (SL) have potential as cheaper alternatives to limestone (LIME). Two greenhouse experiments evaluated WA and SL as liming and soil conditioning amendments for annual ryegrass (Lolium multiflorum) production. At 55 days after seeding, soil pH in WA (6.2 and 6.3) and wood ash and paper sludge (WASL) (6.0 and 6.3) were not different from that in LIME (6.0 and 6.5) for Experiments 1 and 2, respectively. However, pH in SL was 0.4 and 0.3 points lower than in LIME. Compared to LIME, WA, SL, and WASL produced 31%–52% and 57%–74% greater biomass yield in Experiments 1 and 2, respectively. N uptake was greater in WA (60 and 129 kg N ha−1) and WASL (51 and 97 kg N ha−1) compared to LIME (40 and 85 kg N ha−1), in Experiments 1 and 2, respectively. SL did not differ from LIME in Experiment 1, but reduced N uptake by 57% in Experiment 2. The results show significant potential of WA as an alternative amendment for liming and yield improvement of annual ryegrass grown in NL podzolic soils. However, SL has limited potential due to the risk of increasing N immobilization and residual soil mineral N when growing conditions are limiting. Combining SL with WA or biochar seemed to alleviate these risks. Overall, the adoption of these amendments for field production systems warrants serious consideration, following supplemental field studies to determine optimal application rates and timing. Core Ideas: The podzolic soils of Newfoundland have low pH and fertility, hence require liming.Locally sourced wastes, such as paper mill wood ash (WA) and sludge (SL), could be used as liming and nutrient sources.WA was equivalent to limestone (LIME) in improving and sustaining optimal soil pH.WA produced 52% and 74% greater annual ryegrass yield than conventional LIME application in podzolic soils. [ABSTRACT FROM AUTHOR]

Tillage conservation practices (CA), traditional agriculture (TA), and liming influence soil properties and crop yield. However, it is essential to demonstrate which tillage and liming practices improve soil properties and forage corn yield. This study compared soil properties and forage corn production in two tillage systems with the addition of dolomite and lime, which formed four treatments. The tillage in the first three days surpassed the TA soil CO2 emission, with 64.8% more CO2 than in the CA soil, and the TA hydraulic conductivity and bulk density were more suitable than those in the CA soil. The CA soil had 233 earthworms m−2 more than in TA. The TA green forage corn yielded 6.45 t ha−1 more than in CA, with a higher P, Ca, and Mg foliar content than in CA, but in the CA, the foliar N and K were higher than in TA. The liming increased soil cations (except K), highlighting the lime on dolomite with—52% Al and + 4.85 t ha−1 of forage corn compared to the control. Soil CO2 emission was far lower in CA than in TA, with a slightly lower forage yield, and other soil properties were improved, meaning lower land preparation costs and time savings than in TA. Lime improved acidic soil faster than dolomite, generating higher forage yields. [ABSTRACT FROM AUTHOR]

• The potential of microorganisms in olive trees in southern Brazil is still a gap. • Beneficial microorganisms can improve seedling growth and resistance to stress. • Each species of microorganism had its beneficial potential affected by pH. • The inoculant species can be adjusted according to the soil condition. The benefits of plant growth-promoting microorganisms to increase productivity have been demonstrated in various crops. Little is known about their potential in olive orchards in southern Brazil, whose naturally acidic soils are intensively limed for olive production. The present study investigated the effect of four inoculations (no inoculation, inoculation of the bacterium Azospirillum brasilense , inoculation of the fungus Trichoderma harzianum and inoculation of the fungus Trichoderma virens) at different levels of soil liming on the development of olive seedlings. The results showed that the microorganisms T. virens, T harzianum, and A. brasilense, but especially T. virens , when applied to the soil, promoted increased growth in height, diameter, and total dry mass yield of young olive trees, especially in conditions of lower soil acidity, with increases of 92, 34 and 33 % respectively, compared to the soil without inoculation. Less acidic environments, more favorable for olive tree development, enhanced the positive effect of these microorganisms. The microorganisms also mitigated the effects in potentially more stressful conditions, as observed by the higher concentration of photosynthesizing pigments, the reduction in hydrogen peroxide content, and the reduction in antioxidant enzyme activities in leaves and roots, in soil pH below that recommended for olive cultivation. [ABSTRACT FROM AUTHOR]

[Display omitted] • In soil, adsorption of FA is limited by the binding to external surfaces of nano-aggregates. • The overall adsorption of FA is pH independent and has a relatively low affinity. • In acid soils, FA prefers direct interaction with soil oxide particles, releasing phosphate. • NOM-oxide interaction can be reduced by soil liming, decreasing the solubility of oxyanions. • A dual-phase model is developed to describe the release of PO 4 upon FA addition. For more insight into the interaction of natural organic matter (NOM) with metal (hydr)oxides and oxyanions, the adsorption of added fulvic acid (FA) and the corresponding release of phosphate (PO 4) were studied for a series of agricultural soils (∼0 – 25 cm), strongly varying in soil properties. Interpretation of the data with surface complexation modeling using the NOM-CD model applied in a dual-phase mode shows that the adsorption of added FA, in contrast to PO 4 , is restricted to the external surfaces of nano-aggregates. The adsorption is relatively weak and pH-independent, due to its competition with the native NOM of the organo-mineral phase. At low pH, the functional groups of both added FA and native NOM shift in the interface towards the soil oxide surfaces, making both a good competitor for adsorbed phosphate, resulting in a higher amount of phosphate being released. With an increase in pH, the competition becomes weaker. As a result, more phosphate is bound and less is released when FA is added. Our surface complexation modeling points to the existence of organo-mineral nano-aggregates with sizes of >∼10 – 270 nm, which depends on the total reactive surface area of the soil. Our findings imply that organic amendments containing FA equilibrate with only a portion of the total reactive surface area. In acidic soils, the addition of such organic amendments will be more effective in solubilizing phosphate, which is beneficial from a plant nutrition perspective, but simultaneously it may also contribute more to environmental eutrophication. [ABSTRACT FROM AUTHOR]

[Display omitted] • 5 RDs neutralise 500 up to 10 000 mmol H+/kg, variation in mineralogy and target pH. • Automatic titration (pH stat) estimates pH-dependent dissolution rates and slopes. • Novel soil-RD suspension estimates fast/slow pools of acid neutralising capacity. • Low and high doses (12 Mg/ha, 340 Mg/ha) for validation in 2 year soil-RD mesocosm. • Mechanistic model using pH stat and soil-RD suspension predicts mesocosm soil pH. The ongoing acidification of soil poses a significant threat to the proper functioning of various ecosystems worldwide. Silicate rock dusts (RD) are increasingly amended to acid soils to restore their pH, but the acid neutralising capacity (ANC) and dissolution rate of these products are highly variable and lack proper assessment protocols. It is expected that pH-dependent RD ANCs and dissolution rates dictate the pH increase in soils depending on the initial pH and pH buffer power of the soil. This study addressed these questions by comparing and validating three accelerated weathering tests for their capacity to predict the gradual liming effects in a two-year outdoor mesocosm. Five commercial RDs (two basalts, phonolite, foidite, and trachy-andesite) were tested in four acidified forest soils varying in initial pH, in texture and associated pH buffer power. First, RD dissolution was measured in aqueous batch renewal systems during one year at various starting pH (3.5, 4.5, and 5.5) and constant temperatures (20 °C, 37 °C, and 65 °C). These showed that the ANCs of RDs exhibit a fast fraction (half-life < 1 day) followed by a slower fraction. Second, titration tests of RDs at fixed solution pH, i.e., pH stat , performed between pH 3.5 and 4.5 revealed surface normalised dissolution rates that decreased factors 10–100 per unit pH increase, the slope depending on the RD's mineralogy. Indeed, the rate ranking of observed surface area normalised dissolution rates confirmed that of literature-based values, weighed by the XRD-derived mineralogical fractions. Third, lime-calibrated agitated soil-RD suspension tests were conducted for two months, illustrating the dependency of RD ANC on soil context, and yielding ANCs that were factor 2–5 times larger than in the batch renewal test because of pH buffering effects of soil particulates. Finally, an outdoor soil mesocosm on the four acid soils amended with RDs at 12 Mg/ha and 340 Mg/ha was established and soil pH was monitored for 2 years. The observed pH trends corresponded well for both the low dose (R2 a = 0.67) and the high dose (R2 a = 0.93) with model predictions made using the pH- and temperature-dependent RD dissolution rates (pH stat test) and the soil pH buffer power and RD slow ANC-fraction (soil-RD suspension test). This model predicts half-lives of RD dissolution ranging between <1 month to >100 years depending on the starting pH of the soil, its pH buffer power, the RD mineralogy (XRD based) and its specific surface area. This study shows that the dissolution and ANC of RD can be most pragmatically predicted with a series of lime-calibrated soil-RD suspension tests of maximally two months. [ABSTRACT FROM AUTHOR]

The solubility of cadmium (Cd) in soil and its transfer to plants are influenced by soil pH. While increasing soil pH reduces Cd solubility and accumulation in rice plants grown in acidic soils, its effect on Cd accumulation in vegetables remains inconclusive. Here, we investigated the impact of soil pH on Cd accumulation in dicotyledonous vegetables and elucidated the underlying molecular mechanisms. Soils collected from various locations were supplemented with varying quantities of lime to achieve soil pH values of around 5.0, 6.0, 7.0, and 8.0. Raising soil pH from around 5.0 to 8.0 markedly decreased extractable Cd. However, increasing soil pH tended to promote shoot Cd accumulation in dicotyledonous vegetable species including lettuce, pakchoi, and Chinese cabbage, and the model dicotyledonous plant Arabidopsis thaliana. Conversely, soil pH increase resulted in a monotonic decrease in rice Cd accumulation. In our hydroponic experiments, we discovered that iron (Fe) deficiency substantially increased Cd uptake and accumulation in dicotyledonous plants but not in rice. Increasing soil pH reduced soil Fe availability and induced the Fe transporter gene IRT1 expression in dicotyledonous vegetables roots, which led to an increase in IRT1-mediated Cd uptake and subsequently increased Cd accumulation as soil pH increases. A comprehensive model incorporating extractable Cd and root IRT1 expression better explained Cd accumulation in vegetable shoots. The application of 50 mg/kg of Fe fertilizer in neutral or alkaline soils resulted in a significant reduction in Cd accumulation by 34–58% in dicotyledonous vegetables. These findings reveal that increasing soil pH has two opposite effects, decreasing soil Cd availability while promoting Cd uptake through IRT1 upregulation, reconciling the inconsistency in its effect on Cd accumulation in dicotyledonous plants. Our findings provide important insights for understanding the factors affecting Cd uptake in plants and offer a practical solution to mitigate Cd contamination in vegetables. [Display omitted] • Elevating soil pH increases Cd accumulation in lettuce, pakchoi, and cabbage. • Fe-deficiency increases IRT1-mediated Cd uptake by dicotyledonous vegetables. • Fe-transporter gene IRT1 is responsible for Cd uptake in dicotyledonous vegetables. • Applying Fe fertilizer can decrease Cd accumulation in dicotyledonous vegetables. [ABSTRACT FROM AUTHOR]