Reclamation performance of vermicompost and trichocompost on chemical and microbiological properties of acidic and alkaline soil

The present study evaluates the effects of two different types of biofertilizers on the growth of okra (Abelmoschus esculentus) following completely randomized design with three treatments (control, vermicompost, trichocompost) and three replications using acid soil (pH 4.77) and alkaline soil (pH 7.87) The results showed partial (pH 5.9) and complete (pH 6.4) neutralization of soil acidity by trichocompost and vermicompost whereas pH increased in alkaline soil but EC decreased significantly by both treatments. Besides, total OC, total N, total P, total K, total S all increased significantly (P <0.05) in both soils (except S in alkaline soil) by both biofertilizer application but total Ca, Mg, Fe, Mn decreased in acid soil while results were mixed in alkaline soil. Results of plant height and root length were increased significantly (p <0.01) in both acidic and alkaline soil by vermicompost and trichocompost application. For nutrient uptake, Vermicompost appeared equally useful for acidic and alkaline soil and trichocompost appeared more useful in acidic soil than alkaline soil. The application of the two biofertilizers in both the soils had significant positive effects on the growth of okra. J. Asiat. Soc. Bangladesh, Sci. 51(1): 103-114, June 2025

Application of chemical fertilizer or manure can affect soil microorganisms directly by supplying nutrients and indirectly by altering soil pH. However, it remains uncertain which effect mostly shapes microbial community structure. We determined soil bacterial diversity and community structure by 454 pyrosequencing the V1-V3 regions of 16S rRNA genes after 7-years (2007–2014) of applying chemical nitrogen, phosphorus and potassium (NPK) fertilizers, composted manure or their combination to acidic (pH 5.8), near-neutral (pH 6.8) or alkaline (pH 8.4) Eutric Regosol soil in a maize-vegetable rotation in southwest China. In alkaline soil, nutrient sources did not affect bacterial Operational Taxonomic Unit (OTU) richness or Shannon diversity index, despite higher available N, P, K, and soil organic carbon in fertilized than in unfertilized soil. In contrast, bacterial OTU richness and Shannon diversity index were significantly lower in acidic and near-neutral soils under NPK than under manure or their combination, which corresponded with changes in soil pH. Permutational multivariate analysis of variance showed that bacterial community structure was significantly affected across these three soils, but the PCoA ordination patterns indicated the effect was less distinct among nutrient sources in alkaline than in acidic and near-neural soils. Distance-based redundancy analysis showed that bacterial community structures were significantly altered by soil pH in acidic and near-neutral soils, but not by any soil chemical properties in alkaline soil. The relative abundance (%) of most bacterial phyla was higher in near-neutral than in acidic or alkaline soils. The most dominant phyla were Proteobacteria (24.6%), Actinobacteria (19.7%), Chloroflexi (15.3%) and Acidobacteria (12.6%); the medium dominant phyla were Bacterioidetes (5.3%), Planctomycetes (4.8%), Gemmatimonadetes (4.5%), Firmicutes (3.4%), Cyanobacteria (2.1%), Nitrospirae (1.8%), and candidate division TM7 (1.0%); the least abundant phyla were Verrucomicrobia (0.7%), Armatimonadetes (0.6%), candidate division WS3 (0.4%) and Fibrobacteres (0.3%). In addition, Cyanobacteria and candidate division TM7 were more abundant in acidic soil, whereas Gemmatimonadetes, Nitrospirae and candidate division WS3 were more abundant in alkaline soil. We conclude that after 7-years of fertilization, soil bacterial diversity and community structure were shaped more by changes in soil pH rather than the direct effect of nutrient addition.

<p>Changes in agricultural management practices to enhance soil carbon (C) sequestration while maintaining crop productivity are a key opportunity to reduce the impact of humans on the environment, reducing greenhouse gas (GHG) fluxes to the atmosphere and nutrient leaching to aquatic ecosystems without compromising food and soil security. Amongst them, enhanced weathering (EW) of silicate minerals is a promising negative emission technology that can be associated with multiple co-benefits for crop production by spreading silicate minerals on arable soils (i.e. increase in crop yields, restoration of soil base cations and micro- and macronutrient stocks). A growing number of EW studies are focused on soil C sequestration and the effects on crop production. Yet, little is known about the impact of such management practices on GHG sink/source behaviour of agricultural soils and the soil bacterial communities involved.</p><p>In this context, winter wheat (<em>Triticum aestivum</em>) was grown in 20 mesocosms undergoing 4 different treatments: acid soil (pH ~5) with or without basalt addition (50 tones ha<sup>-1</sup>) and alkaline soil (pH ~7) with or without basalt addition. Soil GHG emissions (CO<sub>2</sub>, CH<sub>4</sub> and N<sub>2</sub>O) were measured at six different time points spread over the growing season (from March to June). Measurements included anaerobic conditions (i.e. immediately after irrigation events) and aerobic condition (i.e. in-between events). Simultaneously, soil was sampled for the study of the soil bacterial community.</p><p>We found that basalt application led to an increase in crop yield in acid soils, while it decreased the yield in alkaline soils. GHG emissions were not reduced by the basalt amendment. Soil CO<sub>2 </sub>fluxes peaked in-between irrigation events and were mainly influenced by the soil pH, being 2-fold higher in alkaline soils than in acid ones. Irrigation events increased both CH<sub>4</sub> and N<sub>2</sub>O fluxes. Soils acted as CH<sub>4 </sub>sink in-between irrigation events, but became sources shortly after those (up to 5-fold higher). While it was hypothesised that higher pH would result in an improved denitrification completion, the increase in pH induced by basalt application did not reduce soil N<sub>2</sub>O fluxes. Higher N<sub>2</sub>O fluxes were observed during irrigation events and in basalt-enriched mesocosms, as a result of combined enhanced nitrification and denitrification processes. Despite the modest effects of EW on soil GHG emissions, soil bacterial communities were very different for acid and alkaline soils, and varied significantly with basalt amendment and throughout time.</p><p>Overall, this study showed that EW resulted in an improved wheat yield and altered soil bacterial community in acid soils. However, the general effect of EW on soil GHG emissions was modest and complex.</p>

We evaluated the effect of elemental S (S0) under three moisture (40, 60, 120% water-filled pore space; WFPS) and three temperature regimes (12, 24, 36°C) on changes in pH and available P (0.5 N NaHCO3-extractable P) concentrations in acidic (pH 4.9), neutral (pH 7.1) and alkaline (pH 10.2) soils. Repacked soil cores were incubated for 0, 14, 28 and 42 days. Application of S0 did not alter the trends of pH in acidic and neutral soils at all moisture regimes but promoted a decrease in the pH of alkaline soil under aerobic conditions (40%, 60% WFPS). Moisture and temperature had profound effects on the available P concentrations in all three soils, accumulation of available P being greatest under flooded conditions (120% WFPS) at 36°C. Application of S0 in acidic, neutral and alkaline soils resulted in the net accumulation of 16.5, 14.5 and 13 μg P g−1 soil after 42 days at 60% WFPS, but had no effect under flooded conditions. The greatest available P accumulations in the respective soils were 19, 19.5 and 20 μg P g−1 soil (equivalent to 38, 41, 45 kg P ha−1) with the combined effects of 36°C, 60% WFPS and applied S0. The results of our study revealed that oxidation of S0 lowered the pH of alkaline soil (r=−0.88, P<0.01), which in turn enhanced available P concentrations. Also, considering the significant relationship between the release of sulphate and accumulation of P, even in acidic soil (r=0.92, P<0.01) and neutral soil (r=0.85, P<0.01) where the decrease in pH was smaller, it is possible that the stimulatory effect of sulphate on the availability of P was due to its concurrent desorption from the colloidal surface, release from fixation sites and/or mineralization of organic P. Thus, in the humid tropics and irrigated subtropics where high moisture and temperature regimes are prevalent, the application of S0 could be beneficial not only in alleviating S deficiency in soils but also for enhancing the availability of P in arable soils, irrespective of their initial pH.

Agricultural production is severely limited by an iron deficiency. Alkaline soils increase iron deficiency in rice crops, consequently leading to nutrient deficiencies in humans. Adding iron to rice enhances both its elemental composition and the nutritional value it offers humans through the food chain. The purpose of the current pot experiment was to investigate the impact of Fe treatment in alkaline (pH 7.5) and acidic (pH 5.5) soils to introduce iron-rich rice. Iron was applied to the plants in the soil in the form of an aqueous solution of FeSO4 with five different concentrations (100, 200, 300, 400, and 500 mM). The results obtained from the current study demonstrated a significant increase in Fe content in Oryza sativa with the application of iron in both alkaline and acidic pH soils. Specifically, Basmati-515, one of the rice cultivars tested, exhibited a notable 13% increase in iron total accumulation per plant and an 11% increase in root-to-shoot ratio in acidic soil. In contrast to Basmati-198, which demonstrated maximum response in alkaline soil, Basmati-515 exhibited notable increases in all parameters, including a 31% increase in dry weight, 16% increase in total chlorophyll content, an 11% increase in CAT (catalase) activity, 7% increase in APX (ascorbate peroxidase) activity, 26% increase in POD (peroxidase) activity, and a remarkable 92% increase in SOD (superoxide dismutase) in acidic soil. In alkaline soil, Basmati-198 exhibited respective decreases of 40% and 39% in MDA and H2O2 content, whereas Basmati-515 demonstrated a more significant decrease of 50% and 67% in MDA and H2O2 in acidic soil. These results emphasize the potential for targeted soil management strategies to improve iron nutrition and address iron deficiency in agricultural systems. By considering soil conditions, it is possible to enhance iron content and promote its availability in alkaline and acidic soils, ultimately contributing to improved crop nutrition and human health.

In the rice soils, the alternate wetting and drying conditions and the leakage of O2 from rice roots provides a favorable environment for many N transformation processes, such as DNRA, nitrification, mineralization, and denitrification. Since nitrification is an inevitable process providing available NO3 − for DNRA and other NO3 − loss pathways, it is logical to hypothesize that a relationship exists between nitrification and DNRA. Thus, we quantified the specific gross N transformation rates occurring simultaneously to investigate the correlation among the N transformation rates in the rice soil. In this study, three rice soils with different pH values were selected. The combination of 15N tracing experiment and numerical modeling method was performed to quantify the specific gross N transformation rates (e.g., DNRA), to analyze the correlation between DNRA and the other N transformations, and to estimate the functional role of DNRA comparing to other N transformation in the rice soil. The results showed that there were two NH4 + production pathways, organic N mineralization and DNRA, in the neutral (pH 6.2) and alkaline (pH 8.2) soils, while the DNRA process was negligible in acidic soil (pH 4.7). The mineralization rate in the acidic soil (2.69 mg kg−1d−1) was significantly higher than that in neutral and alkaline soils. The DNRA rate was 0.48 and 1.09 mg kg−1d−1, which was almost equal to the mineralization rate, in the neutral (pH 6.2) and alkaline (pH 8.2) soils, offsetting efficiently the effect of low mineralization on N availability in ecosystems. The DNRA rate linearly increased with the increase in gross nitrification rate (p < 0.05). This significant coupling relationship between DNRA and nitrification favors N conservation and availability for paddy growth in the rice ecosystem. DNRA plays an important role in soil N conservation and availability in neutral and alkaline but not acidic rice soil.

Responses of nitrification and ammonia oxidizers to a range of background and adjusted pH in purple soils

In this paper, effort has been made to determine the durability of polyurethane coating on mild steel in acid, alkaline and neutral soil. A total of 42 mild steel coupons were used. Out of the 42 coupons, 21 were coated with polyurethane and the remaining 21 were left uncoated. Acid soil (pH = 4.5), Alkaline soil (pH =13.5) and neutral soil (pH = 6.8) were used as the test media. Seven each of the coated and uncoated coupons were buried in each soil media. On weekly basis, one coated and one uncoated coupon were withdrawn from each of the soil media and reweighed. The durability of the coating in each soil media was calculated using a proposed model. From the results obtained, the durability of polyurethane coating was found to be 7.0yrs, 4.5yrs and 2.9yrs in neutral, acid and alkaline soil respectively.

Phospholipid fatty acid (PLFA) method has been popular and powerful for characterizing soil microbial communities over decades. However, little is known about efficiencies of acidic vs. alkaline extractants and catalysts in PLFA extraction and methylation. More urgently, it remains unclear whether methanol could efficiently elute phospholipids while avoiding recovering non-target lipids. Here, by adding pure lipid standards representative of major neutral, glyco-, and phospholipids into acidic and alkaline soils collected from subtropical China, we comprehensively evaluated efficiencies of extraction, elution, and methylation of three steps in the PLFA method. A good proportion of PLFAs could be extracted by phosphate buffer with both acidic (42-51%) and alkaline (43-68%) soils while citrate buffer worked better for acidic (43-46%) than alkaline (36-47%) soils. Phospholipids were expected to be mainly eluted in methanol, yet we found a non-negligible proportion of phospholipids eluted by chloroform for both acidic (36-71%) and alkaline (9-55%) soils, which is much larger than previously reported. Only 42-50% (acidic soils) and 45-68% (alkaline soils) of phospholipids were recovered in methanol. Meanwhile, 16% (acidic soils) and 5% (alkaline soils) of glycolipid DGDG were unexpectedly eluted into methanol. The alkaline catalyst (mean 86% across all investigated phospholipids) was more efficient in facilitating phospholipids methylation than the acidic one (mean 67%). Overall, incomplete separation among lipid types caused loss of phospholipids and introduction of glycolipid interferences in the methanol fraction, leading to biased estimation of soil microbial biomass and composition. Chloroform elution of phospholipids challenges the principle of "like dissolves like" in solid-phase chromatography, although we cannot rule out the uncertainty caused by background PLFAs and future experiments are needed to provide more evidence. To effectively remove lipid interferences and efficiently elute phospholipids, possible solutions include replacing chloroform with hexane, increasing elution volumes of acetone and methanol, and/or using anion exchange columns.

Growth and root colonization of mycorrhizal maize grown on acid and alkaline soil

The study examines if a short period of reaction after addition of biosolids to soils can reduce the solubility and potential phytotoxicity of biosolid-borne Zn and Cu. The effects of period of aging (zero, 60, and 120 days) of biosolids (applied at 0, 10, 20, and 30 g kg⁻¹) with an acid, neutral, or alkaline soil on pH and concentrations of Zn, Cu, and dissolved organic C in solution over a 60-day growth period of spinach were investigated using Rhizon pore water samplers. In the acid and neutral soils, increasing aging period markedly reduced the concentrations of Zn and Cu in solution and there were concomitant increases in solution pH. The effect was much less pronounced in the alkaline soil. Soluble Zn and Cu concentrations were generally positively correlated with dissolved organic C concentrations, negatively correlated with pH in the alkaline and neutral soils but positively correlated with pH in the acid soil. Spinach yields were lower in the acid than neutral and alkaline soils and tended to increase with increasing rates of biosolids in all three soils. The concentrations of tissue Zn and Cu were notably high in shoots of plants grown in the acid soil. For all biosolid-amended soils, the concentrations of tissue Cu were lower in plants grown after 60 days rather than no aging. Following biosolids applications to soils, an aging period of only a few months is likely to lower the solubility, and potential phytotoxicity, of biosolid-borne Zn and Cu particularly in acid and neutral soils.

The ABA concentrations of leaves, roots, soils and transport fluids of chickpea and lupin plants growing in acid (pH=4.8) and alkaline (pH=8.0) soils and an acid soil with an alkaline subsoil and an alkaline soil with an acid subsoil were measured with the aim of explaining the poor growth of narrow-leafed lupins in alkaline soil. The ABA concentration in the leaves was higher in lupin than chickpea, but did not differ when the plants were grown in alkaline compared to acid soil. The ABA concentration of the roots and xylem sap of lupin did not differ significantly when grown in acid or alkaline soil. Chickpea roots and xylem sap had, however, lower ABA concentrations in acid soil. The ABA concentration in the soil solution was higher in the acid than in the alkaline soil. Roots of lupin and chickpea showed no suberization of the hypodermis or exodermis whether grown aeroponically or hydroponically and the pH of the cytoplasm did not change significantly when root cells of lupin and chickpea were exposed to external pHs of 4.8 or 8.0. The chickpea roots had greater suberization of the endodermal cells adjacent to radial xylem rays and maintained a slightly higher vacuolar pH than lupin in both acid and alkaline external media, but these small differences are insufficient to explain the reductions in lupin growth in alkaline soil.

Low availability of phosphorus (P) in both acidic and alkaline soils is a major problem for sustainable improvement in wheat crops yield. Optimization of crops productivity can be achieved by increasing the bioavailability of P by phosphate solubilizing Actinomycetota (PSA). However, their effectiveness may vary with changing agro-climatic conditions. In this regard, a greenhouse experiment was conducted to assess the interaction inoculation of five potential PSA (P16-P18-BC3-BC10 and BC11) and RPs (RP1- RP2-RP3 and RP4) on the growth and yield of wheat crop in unsterilized P- deficient alkaline and acidic soils. Their performance was compared with single super phosphate (TSP) and reactive RP (BG4). The in-vitro tests showed that all PSA colonize wheat root and form a strong biofilm except Streptomyces anulatus strain P16. Our findings revealed that all PSA significantly improve the shoot/root dry weights, spike biomass, chlorophyll contents as well as nutrients uptake in plants fertilized with RP3 and RP4. However, the combined application of Nocardiopsis alba BC11 along with RP4 in alkaline soil, was effective in optimizing wheat yield attributes and improve the yield biomass up to 19.7% as compared to the triple superphosphate (TSP). This study supports the view that the inoculation with Nocardiopsis alba BC11 has a broad RP solubilization and could alleviate the agricultural losses due to P limitation in acidic and alkaline soils.

Charcoal produced from plant matter and stored in the soil as a means of removing carbon dioxide from the atmosphere. The purpose of this research was to study the impact of biochar application on soil pH and chemical properties in both acidic and neutral soils. Three types of biochar were used in a greenhouse experiment: 1) red gram straw biochar produced at 400°C, 2) pongamia fruit husk biochar produced at 500°C, 3) Calophyllum fruit husk biochar produced at 500°C, and a control in which neither of the biochar was used. Each treatment was applied with four levels of 4t/ha,8t/ha.12t/ha and 16t/ha biochars. Each treatment was replicated five times and whole experiment set up was done in factorial CRD (Completely randomised design). Two-way ANOVA was also used to analyze the impact of the biochars on soil acidity and other chemical properties. The results showed the application of biochar increased the soil pH in both soils. The increase in pH was more noticeable in acidic soil. In acidic soil calophyllum fruit husk biochar produced at 500 °C applied at 16t/ha showed highest pH at all intervals except at 120 days. The increase in pH in neutral soil doesn’t show any particular pattern throughout the incubation period. In acidic soil exchangeable bases such as Ca, Mg, K and Na were highest in red gram straw produced at 400°C. In both acidic and neutral soils, there was no definite trend in micronutrient contents such as extractible Mn, Fe, Zn, and Cu. The incorporation of biochar can cause beneficial changes in soil chemical properties and improve the bioavailability of plant essential nutrients.

Toxicity and bioavailability of antimony in edible amaranth (Amaranthus tricolor Linn.) cultivated in two agricultural soil types