The Impact of Struvite and Soil pH on Chilli Pepper Plant Growth and Nutrient Release

Birdsfoot trefoil (Lotus corniculatus L.) accessions G 31276 and G 31272 exhibit rhizomatous growth and were collected from alkaline soils (pH 8.0–8.5). Nothing is known about the adaptation of rhizomatous birdsfoot trefoil to more acid soil. Our objective was to determine the effects of soil pH on plant growth and mineral concentration of rhizomatous and domestic non-rhizomatous birdsfoot trefoil. Three entries, Norcen AU Dewey, and RBRC (a bulked reciprocal cross of G 31276 and G 31272), were grown at soil pH levels of 5.0, 6.0, 7.0 and 8.0 in a glasshouse. Dry-matter (DM) production and concentrations of Al, Ca, K, P, Mg, Mn and Zn in tissues were determined. No significant entry × soil pH interaction was found for either DM accumulation or mineral concentration, indicating the RBRC responded to acidic soil pH like the domestic entries Across entries, total DM was lower at soil pH 5.0 than at a higher pH. Concentration of Al and Zn in leaves and stems was greatest at soil pH 5.0 and declined with increasing PH. Calcium concentration in leaves and stems was highest at soil pH 8.0. Magneisum concentration was not affected by soil pH. Phosphorus concentration in leaves was lowest at soil pH 5.0 and tended to increase with increasing pH, whereas P concentration in stems was highest at pH 5.0 and not significantly different at pH 6 0 7 0 or 8 0. Leaf K concentration was not affected by soil pH, but K concentration in stems was highest at pH 5 0. Manganese concentrations in leaves and stems followed an irregular pattern. Similar responses to soil pH among entries suggest that birdsfoot trefoil populations derived from accessions G 31276 and G 31272 will not likely be limited by soil pH. Key words:Lotus corniculatus, nutrient concentration, rhizomatous growth, dry-matter distribution, pH tolerance

1. In order to find out suitable amount of nitrogen application to citrus plants in connection with soil reaction, an experiment which consisted of factorial combinations of three levels of nitrogen (low-6g, medium-12g, high-18g/pot) and four levels of soil pH, was carried out, using a mineral acid soil (red clay) taken at Mikkabi-cho, Shizuoka Prefecture.2. When soil pH was around 7.0, medium nitrogen application was most favorable for the growth of plant based on shoot growth, net increase of fresh weight and the content of various forms of nitrogen in the whole leaves. While the growth of plant at low soil pH level (4.37-4.50) was severely checked by medium or high nitrogen application.3. Regardless of the soil pH level, the electrical conductivity of the soil naturally increased with increasing the N-level. NH4-N increased with increasing the N-level and with increase in acidity. On the contrary K in the soil decreased with them, NO3-N decreased and P2O5 increased with lowering the soil pH level, regardless of the N-level.4. With few exceptions at higher soil pH levels, the accumulations of protein-N, soluble protein-N, amide-N, NH4-N and NO3-N in the leaves decreased with increasing the N-level, and with lowering the soil pH level, while only that of amino-N increased with increasing the N-level and with lowering the soil pH level. At any N-level the ratio of insoluble-N/soluble-N decreased with lowering the soil pH level.5. Therefore, medium or high nitrogen application to citrus plants may be permissible only when soil pH is as high as nearly 7.0, while it should severely check the growth of plant at the soil pH as low as nearly 4.5.

A novel gel-based slow/controlled release fertilizer (G-CRF) was developed, which was produced by combining various natural, seminatural, and/or synthetic organic macromolecule materials and natural inorganic mineral with conventional NPK fertilizers. Its nutrient release characteristics were studied to compare with conventional fertilizers through the soil column leaching method. The influences of soil factors, including temperature, pH, water, and nutrient contents in the G-CRF on nutrient release, were also investigated through soil-water incubation method. These results indicated that the G-CRF had better effect on controlling release of N, P, and K nutrients, and the effect was more efficient when soil-water content was lower than 45% (w/w), temperature was below 35°C, and soil pH was in the range from weak acid to neutral. In addition, considering the effect of controlling nutrient release and cost of the materials in the G-CRF, it is recommended that the most feasible NPK nutrient contents in the G-CRF ranged from 30 to 35%.

Mechanisms of nitrite accumulation occurring in soilnitrification.

Ivermectin is a widely used antiparasitic medication essential for controlling parasitic infections in agricultural and veterinary applications. However, its environmental use is limited by its potential ecological impacts on non-target organisms. This study investigates the degradation kinetics of ivermectin under varying soil pH conditions to better understand its environmental persistence and bioavailability, particularly in tropical soils. The results demonstrate a strong dependence of ivermectin degradation rates on soil pH, with distinct trends observed in acidic and basic conditions. In alkaline soils (pH > 7), ivermectin undergoes accelerated degradation, driven by increased hydrolysis and oxidation reactions. This rapid breakdown is attributed to the enhanced chemical reactivity of ivermectin in high pH environments, where alkaline hydrolysis dominates. Conversely, in acidic soils (pH < 7), degradation rates are significantly reduced, as the chemical stability of ivermectin is preserved under low pH conditions. Acidic environments inhibit hydrolysis while stabilizing the molecular structure of ivermectin, leading to its prolonged persistence in the soil matrix. Furthermore, pH influences ivermectin solubility and microbial activity: in acidic soils, increased solubility enhances microbial access, promoting biotic degradation, although at a slower chemical degradation rate. In contrast, basic conditions decrease solubility, limiting microbial involvement and favoring abiotic pathways. The interplay between pH-dependent chemical and microbial degradation processes highlights the complex dynamics governing ivermectin’s environmental fate. These findings provide critical insights into the role of soil pH in shaping ivermectin’s persistence, bioavailability, and ecological impact. Understanding these trends is crucial for predicting the environmental behavior of ivermectin, especially in agricultural settings, where soil pH management can serve as a mitigation strategy. By optimizing soil pH, the ecological risks associated with ivermectin use can be minimized, reducing potential harm to non-target organisms and mitigating environmental contamination. This study underscores the need for integrating soil chemistry into sustainable agricultural practices to ensure the responsible use of ivermectin.

Acidification of soil due to forestation at the global scale

Hexavalent Chromium (Cr(VI)) contamination in soils poses significant ecological risks due to its mobility and toxicity, with retention mechanisms governed by interactions between soil properties and Cr(VI). However, the quantitative roles of key soil parameters in Cr(VI) retention remain poorly resolved, particularly across diverse soil types. This study investigated Cr(VI) retention behaviors in 16 Chinese soils (15 types) through batch experiments, isothermal adsorption model, correlation analysis and path analysis. The results showed that the retention of Cr(VI) in acidic soils was significantly higher than in alkaline soils. Acidic soils (pH < 5.4) with higher concentrations of exchangeable Fe(II) (Exch-Fe(II)) exhibited strong Cr(VI) holding capabilities,while Alkaline soils (pH > 7.3) with highest content of CaCO3 show negligible Cr(VI) reactions.Cr(VI) retention was high at soil pH values below approximately 5.5, but declined sharply at higher pH values. The Langmuir model was only suitable for describing acidic soils (pH < 5.4), while the Freundlich equation was applicable to all soils. Correlation analysis revealed that soil pH, the content of soil organic matters(SOM), Exch-Fe(II), complexed iron (Com-Fe), and clay were significantly related to the Cr(VI) retention (p < 0.01), whereas the CaCO3 content was negatively related to the Cr(VI) retention (p < 0.05).Path analysis revealed that soil pH was the most important direct factor, followed by Exch-Fe(II), Com-Fe, clay, in determining Cr(VI) retention in natural soil. CEC and CaCO3 content had only limited directly effects on the Cr(VI) retention. Additionally, The content of SOM, Amorphous iron oxides(Amo-Fe), and Easily reducible manganese(Er-Mn) content had little directly effect on Cr(VI) retention. To validate these findings, Cr(VI) retention was measured in all soils after adjusting their pH to 4.3, 6, and 8. The results highlighted soil pH and Exch-Fe(II) content were the most decisive factors for evaluating Cr(VI) retention in natrual soils,whereas SOM content was an unreliable parameter for assessing this process.

Synergistic Effects of Biochar and NPK Fertilizer on Soybean Yield in an Alkaline Soil

Ageratina adenophora is an invasive weed species found in many countries. Methods to control the spread of this weed have been largely unsuccessful. Soil pH is the most important soil factor affecting the availability of nutrients for plant and impacting its growth. Understanding the mechanisms of the influence of soil pH on the growth of A. adenophora may help to develop effective control measures. In this study, we artificially changed the soil pH in pot experiments for A. adenophora. We studied the effects of acidic (pH 5.5), weakly acidic (pH 6.5), neutral (pH 7.2), and alkaline (pH 9.0) soils on the growth, availability of soil nutrients, activity of antioxidant enzymes, levels of redox markers in the leaves, and the structure and diversity of the rhizosphere microbiome. Soil with a pH 7.2 had a higher (47.8%) below-ground height versus soils of pH 5.5 at day 10; plant had a higher (11.3%) above-ground height in pH 7.2 soils than pH 9.0 soils at day 90; no differences in the fresh and dry weights of its above- and belowground parts, plant heights, and root lengths were observed in plants growing in acid, alkaline, or neutral pH soil were observed at day 180. Correspondingly, the antioxidant enzymes SOD (superoxide dismutase), POD (peroxidase), CAT (catalase) and redox markers GSH (glutathione) and MDA (malondialdehyde) were measured in the leaves. Significant differences existed in the activities of CAT and the levels of GSH between those growing in acidic and alkaline soils and those in neutral pH soil at day 90; however, only lower (36.8%) CAT activities in those grown at pH 5.5 than those grown at pH 7.2 were found at day 180. Similarly, significant differences in available P (16.89 vs 3.04 mg Kg−1) and total K (3.67 vs 0.96 mg Kg−1), total P (0.37 vs 0.25 g Kg−1) and total N (0.45 vs 1.09 g Kg−1) concentrations were found between the rhizosphere soils of A. adenophora grown at pH 9.0 and 7.2 at day 90; no such differences were seen at day 180. High throughput analyses of the 16S rRNA and ITS fragments showed that the rhizosphere microbiome diversity and composition under different soil pH conditions changed over 180 days. The rhizosphere microbiomes differed in diversity, phylum, and generic composition and population interactions under acid and alkaline conditions versus those grown in neutral soils. Soil pH had a greater impact on the diversity and composition of the prokaryotic rhizosphere communities than those of the fungal communities. A. adenophora responded successfully to pH stress by changing the diversity and composition of the rhizosphere microbiome to maintain a balanced nutrient supply to support its normal growth. The unusual pH tolerance of A. adenophora may be one crucial reason for its successful invasion. Our results suggest that attempts use soil pH to control its invasion by changing the soil pH (for example, using lime) will fail.

Links between potassium of soil aggregates and pH levels in acidic soils under long-term fertilization regimes

The effects of three soil pH's, three soil temperatures, and three soil moistures on [14C]isofenphos degradation were investigated. All three factors interacted strongly and significantly affected the persistence of isofenphos as well as the formation of the degradation products (p less than 1%). Isofenphos degradation was greatest at the higher temperatures 35 degrees C greater than 25 degrees C greater than 15 degrees C (except under alkaline pH's), medium moisture 25% greater than 30% greater than 15%, and in both alkaline (pH = 8) and acidic soils (pH = 6) compared with neutral soil (pH = 7). Isofenphos oxon formation was greatest at higher temperatures 35 degrees C compared with 25 degrees C and 15 degrees C, in acidic soil greater than neutral soil greater than alkaline soil, and under high moisture (30%) compared with the 15% and 22.5% moistures. The formation of soil-bound residues was greatest at higher temperatures 35 degrees C greater than 25 degrees C greater than 15 degrees C, higher moisture 30% compared with 15% and 22.5%, and in alkaline soil compared with neutral and acidic soils.

Intensification of sodic soil due to increasing pH is an emerging environmental issue. The present study aimed to isolate and characterise alkaline stress-tolerant and plant growth-promoting bacterial strains from moderately alkaline soil (pH 8-9), strongly alkaline soil (pH 9-10), and very strongly alkaline soil (> 10). Total 68 bacteria were isolated, and screened for multiple plant growth promoting (PGP) attributes. Out of total, 42 isolates demonstrating at least three plant growth promoting PGP traits selected for further assays. Then out of 42, 15 bacterial isolates were selected based on enhanced maize plant growth under greenhouse experiment, and 16S rRNA gene sequencing revealed Bacillus spp. as a dominant genus. Furthermore, based on improved seed germination percentage and biomass of maize (Zea mays L.) under alkaline stress conditions Alcaligenes sp. NBRI NB2.5, Bacillus sp. NBRI YE1.3, and Bacillus sp. NBRI YN4.4 bacterial strains were selected, and evaluated for growth-promotion and alkaline stress amelioration under greenhouse condition. Amongst the selected 3 plant growth promoting rhizobacterial (PGPR) strains, Bacillus sp. NBRI YN4.4 significantly improved the photosynthetic pigments and soluble sugar content, and decreased proline level in inoculated maize plants as compared to uninoculated control under stress conditions. Moreover, significantly enhanced soil enzymes such as dehydrogenase, alkaline phosphatase and betaglucosidase due to inoculation of Bacillus sp. NBRI YN4.4 in maize plants grown in alkaline soil attributes to its role in improving the soil health. Therefore, alkaline stress-tolerant PGPR NBRI YN4.4 can be useful for developing strategies for the reclamation of saline/sodic soils and improving the plant growth and soil health in sustainable manner.

Biochar produced from pyrolysis of biomass such as wood, canopy, animal manure, and agricultural waste is recognized for its stability and for being a benefactor of soil health and plant growth. Its application in forestry is an area with growing research interest due to its ability to enhance soil physicochemical properties, including structure, water retention, and nutrient availability, thereby boosting plant growth, drought tolerance, and resistance to pests and diseases. However, the effectiveness of biochar varies based on factors like biochar type, application rate, soil type, and tree species. Potential risks associated with biochar use include nutrient immobilization, increased pH in alkaline soils, and enhanced leaching of toxic elements. Despite its promise, challenges such as knowledge gaps, lack of site-specific studies, and concerns of economic viability hinder widespread adoption of biochar in forestry. This qualitative review compiles over 150 published works from the past two decades on biochar application in forestry. It assesses the impacts of biochar on soil health and tree crops, highlighting its potential to improve soil fertility and promote tree growth. The review identifies significant findings, such as the positive influence of biochar on soil and plant health and outlines existing knowledge gaps that need addressing. By synthesizing current research, the review proposes future directions to optimize biochar use in sustainable forestry management, emphasizing the need for tailored approaches and economic assessments to facilitate broader adoption. The findings underscore the potential role of biochar in enhancing forestry practices while calling for further studies to resolve uncertainties and improve its practical implementation.Graphical

As most New Zealand pastoral soils are acidic, aluminium (Al) can be present at high concentrations and restrict plant root growth and shoot yield. In field trials, Al toxicity in white clover has been associated with CaCl2-extractable soil Al levels of 3-5 ppm or exchangeable soil KCl-extractable levels of 1-2 me/100g, when soil pH levels were below 5.5-5.7 in the top 75 mm. Lucerne is less tolerant of Al toxicity than white clover and ryegrass, which in turn are less tolerant than Lotus spp., arrow leaf, subterranean, Caucasian, Persian and gland clovers, and naturalised adventive annuals such as cluster, haresfoot, striated and suckling clovers. Soil Al toxicity generally increases with soil depth. Soil pH is a reliable indicator of soil Al and, on average, can be increased by 0.1 units/tonne/ha of applied lime to reduce soil Al to below the toxic range. Lime application is the most effective strategy where it can be ground-applied. A key limitation of ground-applied lime to reduce Al toxicity is that its movement down the soil only occurs slowly except in high rainfall areas. Soil Al and pH levels and legume content in hill soils varies according to slope and aspect and there is an opportunity to differentially apply lime by air to areas with low soil pH and more legume, for the best economic return.

Controlling factors of environmental flooding, soil pH and Diaprepes abbreviatus (L.) root weevil feeding in citrus: Larval survival and larval growth