Calcareous Soils Research Articles

Prediction of soil organic carbon and total nitrogen affected by mine using Vis-NIR spectroscopy coupled with machine learning algorithms in calcareous soils.

The utilization of visible-near infrared (Vis-NIR) spectroscopy presents a nondestructive, fast, reliable and cost-effective approach to predicting total nitrogen (TN) and organic carbon (OC) levels. This study employed a combination of Vis-NIR spectroscopy, partial least-squares regression (PLSR), and support vector machine (SVM) models to investigate the effects of mining on TN and OC stocks in both the topsoil (0-10 cm) and subsoil (10-40 cm). 105 soil samples were collected from agricultural areas near an iron mine, polluted, moderately-polluted, and non-polluted sites. Results indicated that soils at the non-polluted site had the highest of soil OC stocks (7.5 kg m-2) and total nitrogen (2.5 kg m-2), followed by the moderately-polluted site. Furthermore, it was observed that soils from the polluted site displayed the highest spectral reflectance. The spectral bands in the range of 500-700 nm showed the strongest correlation with soil organic carbon content. Notably, the SVM method utilizing Vis-NIR spectroscopy provided superior predictions for both subsoil and topsoil organic carbon and total nitrogen compared to the PLSR methods. Additionally, SVM demonstrated better performance in predicting topsoil soil organic carbon (R2 = 0.87, RMSE = 0.13%, and RPD = 2.8) and total nitrogen (R2 = 0.91, RMSE = 0.13%, and RPD = 2.4) compared to the subsoil, owing to the larger OM content in the topsoils.

Prediction and pathway models for assessing soil properties influencing soil selenium enrichment and bioavailability in Aksu Prefecture, northwest China.

Selenium (Se) in soil is the primary source of human Se intake, and its content and bioavailability are influenced by soil physicochemical properties. However, the influence of soil physicochemical properties on Se enrichment and bioavailability in soil remains uncertain. Therefore, this study investigated 536 soil samples and their corresponding wheat grain samples collected from the oasis zone of Aksu Prefecture, located in northwest China. The Se content, spatial distribution, and bioaccumulation factor (BCF) in soil and wheat grains as well as soil Se fractions were examined, and the effects of soil physicochemical properties on Se enrichment and bioavailability were assessed. The results indicated that the mean Se content of soil (0.32 mg/kg) surpassed the national Se background level for Chinese soil by a factor of 1.10. The average Se content (0.13 mg/kg) in wheat grains met the national standard for Se-rich cereal products. The prediction model established using multiple linear regression showed that soil calcium carbonate (CaCO3), organic matter (OM), cation exchange capacity (CEC), and electrical conductivity (EC) were the main physicochemical factors influencing Se enrichment in soil, accounting for 29 % of the variation. The main physicochemical factors affecting Se bioavailability were CaCO3, OM, and iron, and the main Se fractions were the exchangeable and humic acid-bound Se fractions, which together explain 12 % of the variance. Additionally, a structural equation model was employed to analyze the pathways and interactions of soil factors on soil Se enrichment and bioavailability. The results indicated that soil CaCO3 and OM were the most critical factors affecting Se enrichment and bioavailability in soil. These findings can provide technical guidance for the cultivation and layout of Se-rich wheat in local and other similar regions around the world.

Effects of nano urea on Indian mustard (Brassica juncea) productivity and nutrient uptake in calcareous soils

The experiment was conducted during winter (rabi) seasons of 2021–22 and 2022–23 at ICAR-Directorate of Rapeseed Mustard Research, Bharatpur, Rajasthan to assess the effect of nano urea (NU) spray in conjunction with different rates of soil applied fertilizer (conventional urea) N on growth, yield, nutrient content and uptake of Indian mustard [Brassica juncea (L.) Czern. and Coss.] in a calcareous soil of arid and semi-arid region. The experiment was conducted in a randomized complete block design (RCBD) and replicated thrice The treatment combinations consisted of basal applications of fertilizers and foliar spray (FS) of nano urea (NU) either once 30 days after sowing (DAS) or twice 30 and 50–55 DAS. The field experiment comprised of 9 treatments, viz. Control; Recommended dose of fertilizer (RDF); RDN25 + NU-1FS; RDN25 + NU-2FS; RDN50 + NU-1FS; RDN50 + NU-2FS; RDN100 + NU-1FS; RDN75 + NU-1FS; and RDN75 + NU-2FS. Results revealed that treatment RDN100 + NU-1FS (single sprays of nano urea together with the 100% prescribed dose of N) produced the maximum values of 24.30 and 66.62 q/ha yield of seed and stover, respectively. However, RDN75 + NU-2FS produced statistically comparable yield to the treatment RDN100 + NU-1FS. By applying nano urea, the recommended N dose can be reduced up to 25% without compromising yield. One FS of NU with RDN100 registered highest plant height, main shoot length, main shoot siliquae number, total siliquae number/plant and the number of secondary branches of the plant, and proved superior over other treatments. Further, results exhibited that RDN100 + NU-1FS increased N, P, and K uptake values to 66.74, 10.42, and 17.85 kg/ha in seed and 44.23, 9.48, and 78.98 kg/ha in stover. Overall, it has been determined that the most efficient way to increase the yield, concentration, and uptake of N, P, and K in Indian mustard is to apply nano urea foliar at 30 and 60 DAS in conjunction with RDF.

Differences in species composition between calcareous and siliceous herbaceous communities are primarily explained by competition in favourable climates

Difference in vegetation composition between communities from calcareous and siliceous soils might be due to high competition on siliceous soils for species from calcareous origin, and high rock‐induced drought stress on calcareous soils for species from siliceous origin. We tested the hypothesis that, with increasing climate stress, competition should decrease on siliceous rock for species of calcareous origin and drought stress increase on calcareous rock for species of siliceous origin because of decreasing community biomass with increasing cold or drought stress. This question is of high interest for predicting changes in species distribution with climate change since bedrock type and climate change are both complex factors that are likely to interact with climate. We set up a transplant removal experiment in contrasting climate conditions of the south of France, warm and wet temperate, warm and dry Mediterranean, and cold temperate in the Alps and the Pyrenees. In each climate condition, three targets (two species and one population from a third species) from each origin were transplanted with and without neighbours on the two rock types and during two years with different levels of drought stress. Variation in the effects of neighbours and rock‐induced drought stress on transplant survival with and without neighbours were analysed with linear modelling at each site, separately, and with ANCOVA in the whole design. Competition was the highest on siliceous rock in the more favourable climate conditions but for species of siliceous origin. The lower competition found for species of calcareous origin was likely due to the occurrence of allelopathic effects that decreased the negative effect of neighbours as measured with the removal method. The rock‐induced drought stress was the highest on calcareous rock, in particular for species of siliceous origin. Thus, the decrease in competition intensity on siliceous rocks with increasing climate stress was more important for species from siliceous than calcareous origin. Additionally, the importance of the rock‐induced drought stress was relatively low in the most stressful climate conditions as compared to the overwhelming importance of climate drought stress over the two years of our experiment, which likely induced a collapse of the positive effect of growing on a siliceous rock.

A contribution to the study of phosphate’s effects on calcareous soils to be stabilized with lime and natural pozzolana

When investigating the potential use of lime and natural pozzolana for subgrade soils containing phosphate, especially on agricultural lands, the effectiveness of these traditional binders needs to be assessed because of the possible deleterious effect of phosphates anions. This paper addresses this question using the problematic marly soil of Medea which was deliberately contaminated with a common fertilizer mono ammonium phosphate (0, 2, 4 and 6% by dry weight) and then stabilized with lime and/or natural pozzolana (0, 8%),(0, 20%) by dry weight respectively. Micro and macrostructural changes of these mixtures were studied under X-Ray diffraction test and Scanning electron microscope imaging. Variations of pH levels on a 90 days period, Atterberg limits between 1 to 30 days of curing, normal Proctor parameters, immediate bearing index at optimum moisture were also carried out. Overall, the results indicate that the uncontaminated marly clay soil wasn’t very reactive to lime stabilization even with 8% lime and it required the addition of natural pozzolana with lime to exhibit some improvements. Aside from that, phosphates proved to be deleterious for stabilizing marly clay of Medea producing considerable impact on all the results. It was also shown that calcite present in the soil can interfere with the employed stabilization technique.

Organic carbon and nutrient enrichment in clay-rich calcareous soils in self-regenerating fallows in humid tropical agroecology

Organic carbon and nutrient enrichment in clay-rich calcareous soils in self-regenerating fallows in humid tropical agroecology

Soil zinc dynamics over time on applied organics, bacterial inoculant and zinc fertilizers in calcareous soil of southern India

Bioavailability of zinc was impacted by soil properties, externally applied sources, time, and various fractions of zinc. An experiment was conducted to investigate the bioavailable and other zinc fractions in calcareous soil and the efficiency of organic and inorganic sources on bioavailability with the presence and absence of zinc solubilizing bacteria (ZSB). The sequential extraction procedure followed at every interval of the incubation period for all forms of zinc was studied. Externally added inorganic sources significantly affected all fractions of zinc compared to untreated soils. Among them, ZnSO4 influences all forms of zinc, mainly Ws+Ex (water soluble+exchangeable) and carbonate-bound zinc, whereas Zn-EDTA maintains a high status of bioavailable zinc throughout the experimental period. On the 60th day of incubation, Zn-EDTA and ZnSO4 applied to soil maintained bioavailable zinc content of 3.71 and 2.94 times higher than that of control. Irrespective of sources, the available zinc of Zn fertilizers applied to soils was reduced with an increase in incubation days. Organic and microbial addition effects solely or combined increase the soil zinc content significantly in both fertilized and unfertilized soils. Among two different organic sources, the zinc solubility performance of farmyard manure was higher than that of vermicompost. In untreated soil, residual and carbonate-bound fractions contribute a major portion towards total zinc based on quantity. The bioavailable fraction mainly the Ws+Ex and organically bound fractions were markedly influenced in all treatments.

Efficiency of Vivianite from Water Purification Depending on Its Mixing with Superphosphate and Application Method

Vivianite precipitation is gaining attention in phosphorus (P) removal from water purification. It is an iron (Fe)- and P-rich compound that can be used as a slow-release P fertilizer. However, this slow release can constrain P supply to crops in the initial growing stages. This limitation can be overcome by mixing with soluble P fertilizers and with banding application. Thus, the objective of this study was to assess the fertilizer effect of vivianite and superphosphate mixtures and determine the most effective application method for vivianite and its mixture with superphosphate as a soluble fertilizer. A pot experiment was conducted by growing sunflowers in calcareous soil under controlled conditions involving two factors. The first factor was the combinations of vivianite and superphosphate: 100% Vivianite + 0% Superphosphate –T2–, 70% Vivianite + 30% Superphosphate –T3–, 30% Vivianite + 70% Superphosphate –T4–, 0% Vivianite + 100% Superphosphate –T5—at a single P rate of 50 mg P kg−1 and a non-fertilized control –T1–. The second factor was the application method: (i) mixing vivianite powder with the bulk soil and (ii) applying it in bands at three points around the plants. The dry matter (DM) yield in the roots and shoots of the sunflower when all P was applied as superphosphate was higher than when it was applied as vivianite. However, the combination of superphosphate and vivianite in different proportions (T3 and T4) led to a considerably higher DM yield compared to sole vivianite application (T2). The highest plant P uptake was observed in T5, while the lowest was in T1 and T2. The replacement values on a dry matter (PFRVDM) and P uptake (PFRVP Uptake) basis and the nutrient use efficiency of T3 and T4 were higher than that of T2. However, the PFRVDM and the PFRVP Uptake were in the same range as the proportion of the superphosphate added to the fertilizer mix. Thus, increased P use efficiency could be achieved with mixtures of vivianite and superphosphate. However, the contribution of vivianite to the fertilizer mix is difficult to access in a short growing cycle. Hence, further research is recommended on the residual effect of vivianite in such fertilizer mix on subsequent growing cycles.

Influence of Different Sources and Levels of Phosphorus on Nutrient Use Efficiency (NUE) and Properties of Low Calcareous Soil

A field experiment was conducted during kharif season of 2023 at Post Graduate Instructional Farm, College of Agriculture, Pune to study the impact of different phosphorus sources and levels on soybean growth and nutrient uptake in low calcareous soil. The experiment was laid out in randomized block design having eight treatments with three replications. The treatments comprised T1 - Absolute control, T2 - RDF (50:75:45 kg ha-1 N: P2O5: K2O), T3 - 50% P2O5 through PROM, T4 - 75% P2O5 through PROM, T5 - 100% P2O5 through PROM, T6 - 100% P2O5 through DAP + FYM @12.5 t ha-1, T7 - 100% P2O5 through SSP + FYM @12.5 t ha-1 and T8 - 100% P2O5 through vermicompost. The soil of experimental site was clay loam in texture. The findings of the present investigation revealed that the higher nutrient use efficiency was registered in treatment 100% P2O5 through SSP + FYM @12.5 t ha-1 (16.25 kg kg-1). The application of 100% P2O5 through PROM recorded higher nutrient use efficiency (13.31 kg kg-1) over RDF (11.52 kg kg-1). In respect of agronomic nutrient use efficiency, 100% P2O5 through SSP + FYM @12.5 t ha-1 registered higher nitrogen (40 kg grain kg nutrient-1), phosphorus (26 kg grain kg nutrient-1) and potassium efficiency (44 kg grain kg nutrient-1) to soybean crop. The agronomic efficiency of nitrogen, phosphorus and potassium was observed higher in treatment 100% P2O5 through PROM over treatment RDF. After harvest of crop the soil pH was remained unaffected while the electrical conductivity of soil was significantly higher in 100 % P2O5 through vermicompost and PROM to soybean crop. The application of 100% P2O5 either through vermicompost or PROM recorded at par organic carbon content in soil (0.66% and 0.64% respectively). The application of 100% P2O5 through PROM significantly reduced calcium carbonate (6.29%) in soil. The 100% P2O5 through SSP + FYM @12.5 t ha-1 showed higher available nitrogen in soil (297.33 kg ha-1) while the application of 100% P2O5 through DAP + FYM @12.5 t ha-1 exhibited higher level of available phosphorus and potassium content in soil (41.33 and 745.33 kg ha-1, respectively). Further, the application of 100% P2O5 through vermicompost was also significantly superior in available micronutrients like iron (5.7 mg kg-1), manganese (9.9 mg kg-1), zinc (4.6 mg kg-1) and copper (10.4 mg kg-1). The application of 100% P2O5 through PROM registered significantly higher available nitrogen (287.33 kg ha-1), available phosphorus (37.33 kg ha-1), available potassium (737.67 kg ha-1), available micronutrients viz. iron (5.4 mg kg-1), manganese (9.2 mg kg-1), zinc (4.4 mg kg-1) and copper (10.4 mg kg-1) over recommended dose of fertilizers. In general, the integration of organic fertilizers, FYM, PROM and vermicompost, with chemical fertilizers can significantly enhance nutrient use efficiency, soil nutrient content, improve soil health and increase soybean yield in low calcareous soils.

Impact of Drying–Wetting Cycles on Nitrification Inhibitors (DMPP and DMPSA) in a Greenhouse Experiment with Two Contrasting Mediterranean Soils

Studies of the impact of nitrification inhibitors (NIs), specifically DMPP and DMPSA, on N2O emissions during “hot moments” have produced conflicting results regarding their effectiveness after rewetting. This study aimed to clarify the effectiveness of NIs in reducing N2O emissions by assessing residual DMP concentration and its influence on ammonia-oxidizing bacteria (AOB) in two pot experiments using calcareous (Soil C, Calcic Haploxerept) and acidic soils (Soil A, Dystric Xerochrepts). Fertilizer treatments included urea (U), DMPP, and DMPSA. The experiments were divided into Phase I (water application to dry period, 44 days) and Phase II (rewetting from days 101 to 121). In both phases for Soil C, total N2O emissions were reduced by 88% and 90% for DMPP and DMPSA, respectively, compared with U alone. While in Phase I, the efficacy of NIs was linked to the regulation of AOB populations, in Phase II this group was not affected by NIs, suggesting that nitrification may not be the predominant process after rewetting. In Soil A, higher concentrations of DMP from DMPP were maintained compared to Soil C at the end of each phase. Despite this, NIs had no significant effect due to low nitrification rates and limited amoA gene abundance, indicating unfavorable conditions for nitrifiers. The study highlights the need to optimize NIs to reduce N2O emissions and improve nitrogen efficiency, while understanding their interactions with the soil. This knowledge is necessary in order to design fertilization strategies that improve the sustainability of agriculture under climate change.

Influence of Different Sources and Levels of Phosphorus on Yield and Quality of Soybean in Low Calcareous Soil

Influence of Different Sources and Levels of Phosphorus on Yield and Quality of Soybean in Low Calcareous Soil

Kinetics of Cd adsorption by biochar, activated carbon, and zeolite in some calcareous soils

AbstractDifferent methods have developed to reduce the risks of potentially toxic elements in contaminated soils. Among them, adsorption is one of the most important and effective strategies. In this research, kinetics of Cd adsorption by biochar, activated carbon, and zeolite in some calcareous soils were investigated. A factorial experiment was conducted based on a completely randomized design with three replications. The factors included three types of adsorbents (sunflower's biochar, activated carbon, and zeolite), four levels of Cd (0, 20, 50, and 100 mg/L as Cd (NO3)2), and three soil samples, differing in their cation exchange capacity, soil organic matter, and calcium carbonate equivalent. Batch experiments were carried out to evaluate Cd adsorption isotherms and kinetic models. Furthermore, the effect of adsorbent dosage, contact time, and initial pH on the adsorption efficiency was examined. Optimizing studies revealed that the best pH for Cd adsorption was 5, while the optimal equilibrium time was achieved at 24 h. The results showed that the Freundlich model fitted to the experimental data slightly better than the Langmuir model. Moreover, the pseudo‐second‐order kinetic model better described the kinetic behavior of Cd adsorption for the investigated adsorbents. The maximum Cd removal efficiency (99%) belonged to soil No. 2 with biochar. Lastly, it was concluded that sunflower biochar, a cheap and cost‐effective adsorbent, had high efficiency in Cd adsorption in calcareous soils.

Sugarcane bagasse derived biochar potential to improve soil structure and water availability in texturally different soils

Low organic matter content is one of the main constraints in arid and semiarid regions. This constraint and its negative influences on soils and plant growth may be alleviated by biochar (BC). Furthermore, improving soil physical and hydraulic attributes by application of biochar has received increased attention. Therefore, in the present study, the effects of sugarcane bagasse-derived biochar on the structural stability, water availability, and pore-size distribution (PSD) of three texturally different calcareous soils collected from different agro-climatologically regions were examined during a long-term experiment. Low and high-temperature biochars, produced in a muffle furnace by the traditional slow pyrolysis method at 300 °C (BC300) and 600 °C (BC600) were evaluated. Pots (15 kg) were filled with three different silty-clay Inceptisols (SCInc), silty-clay-loam Alfisols (SCLAlf), and loam Aridisols (LArid) soils mixed with 0 (control), 1, 2, and 3 w/w% of BC300 and BC600 during 540 days of incubation. The high energy moisture characteristic (HEMC) data was modeled using a modified van Genuchten function to quantify aggregate stability through stability ratio (SR) and structural stability index (SSI). The plant available water (PAW), least limiting water range (LLWR), and integral water capacity (IWC) were calculated with two matric suctions (h) of 330 cm for field capacity (FC) and 15,000 cm for permanent wilting point (PWP). Then the integral energy (EI) values were calculated (EIIWC). Results indicated that the incorporation of 3 w/w% biochar significantly (p < 0.01) increased SR (35 to 100%) and SSI (21 to 28%) indices in all three soils. Biochar significantly increased modal suction (MS) in LArid soils (5 to 158%); whereas, decreased MS of the other soils (3 to 43%). MS, SR, and SSI of BC300 and BC600-treated soils were not significantly different. PAW, LLWR, and IWC significantly decreased in the SCInc (18 to 61%, 8 to 44%, and 6 to 35%) and SCLAlf (8 to 44%, 18 to 35%, and 20 to 47%) soils and increased in LArid (4 to 54%, 3 to 61%, and 24 to 111%) soil with increasing biochar doses. There were no changes in EIIWC in biochar-treated LArid soil where PAW, LLWR, and IWC increased. Biochar increased EIIWC across the studied soil from 1% to 3.38 folds, thereby increasing the gradient of water potential to absorb the available water. Soil and soil-biochar mixtures exhibited heterogeneous and multimodal pore-size distribution (PSD). Biochar promoted the PSD peaks related to water-transmitting pores in SCInc and SCLAlf soils while decreased in LArid soil. In conclusion, results indicated that among the applied levels of biochar, the application of 3 w/w% biochar is suggested as a suitable way to improve soil physical behavior and structural stability.

Prospects of iron solubilizing Bacillus species for improving growth and iron in maize (Zea mays L.) under axenic conditions

Iron (Fe) deficiency in calcareous soils is a significant agricultural challenge, affecting crop productivity and nutritional quality. This study aimed to isolate, characterize, and evaluate Fe solubilizing rhizobacterial isolates from maize rhizosphere in calcareous soils as potential biofertilizers. Forty bacterial isolates coded as SG1, SG2, …, SG40 were isolated and screened for siderophore production, with ten showing significant Fe solubilizing capabilities. These isolates were further assessed for phosphate solubilization and exopolysaccharides production. The selected bacterial isolates were also screened under axenic conditions for their ability to improve maize growth. The isolates SG8, SG13, SG24, SG30 and SG33 significantly enhanced growth parameters of maize. Notably, SG30 showed highest increment in shoot length (58%), root length (54%), root fresh and dry biomass (67% and 76%), SPAD value (67%), relative water contents (69%), root surface area (61%), and Fe concentration in shoots (79%) as compared to control. The biochemical characterization of these strains showed that all these strains have capability to solubilize insoluble phosphorus, produce indole-3-acetic acid (IAA), and ammonia with catalase, urease and protease activity. Molecular identification through 16s rRNA gene sequencing confirmed high similarity (99.7–100%) of the selected isolates to various Bacillus species, including B. pyramidoids, B. firmicutes, and B. cereus. The study provides a strong base for developing eco-friendly, cost-effective biofertilizers to address Fe deficiency in crops and promote sustainable agriculture.

Identifying hidden factors influencing soil Olsen-P in an alkaline calcareous soil using machine learning and geostatistical techniques

Phosphorus (P) deficiency is one of the major constraints for sustainable crop production in calcareous soils. This study aimed to elucidate the key soil characteristics modulating the variability of soil Olsen P in these typical soils. A comprehensive soil sampling initiative (1.5 samples per hectare) was conducted on a 100-hectare farm, considering 31 attributes that included soil physical and chemical properties, and geographic attributes. Three machine learning algorithms—partial least square regression (PLSR), random forest (RF), and cubist regression (CR)—were employed to understand key variables controlling soil Olsen P. Furthermore, the same data set was used to spatially map the variations in Olsen P levels using ordinary kriging. The results revealed that soil chemical factors, specifically exchangeable manganese and zinc, cation exchange capacity, and carbonate, played a crucial role in controlling P levels. Among the machine learning models, the best performing model was RF (R2= 0.95, RMSE= 1.30 mg kg-1) followed by CR (R2= 0.92 and RMSE= 1.43 mg kg-1). Additionally, the analysis using a Gaussian semi-variogram model showed a good performance (R2= 0.78, RMSE = 2.05 m) in visualizing the spatial distribution of Olsen P, revealing its heterogeneity. The resulting pattern of Olsen P distribution may be attributed not only to soil properties but also to external factors, such as sediment transport through watercourses across the study area and atmospheric deposition from a nearby P mining. Overall, the combination of geostatistical methods and machine learning approach demonstrates a significant potential in understanding the complexity of soil available P (Olsen-P)that could help to develop sustainable and precise P management.

Calcareous soil modified with metallic and organic ZnO nanoparticles limits photosynthetic pigment accumulation and macronutrient uptake in Swiss chard (Beta vulgaris var. cicla)

Previous studies on the effects of zinc oxide nanoparticles have mainly examined controlled agricultural settings, failing to consider their behavior in real agricultural soil. As a result, our knowledge of their environmental impact remains incomplete. This study was specifically developed to observe the comparative effects of metallic zinc oxide nanoparticles, zinc sulfate, and zinc oxide green nanoparticles at different concentrations (25, 50, 75 and 100mg of Zn kg-1 of soil) on growth parameters, the mineral content (N, P, K and Zn) in root and leaf, the content of chlorophyll a (CHLa), b (CHLb), and total (CHLt), and carotenoids in Swiss chard plants grown in calcareous soil. Leaf area and dry root weight increased by 23.27% and 46.20%, respectively, in zinc sulfate modified soil. Total chlorophyll and carotenoids also increased by 40.12% and 32.59%. The concentration of N, P, K and Zn in roots was 2.89, 1.74, 1.70 and 1.52 times higher, while in leaves, the concentration was 1.48, 1.44, 1.76 and 2.22 times higher in plants grown with zinc sulfate. The effects on plant growth can be attributed to the type of fertilizer used and its influence on macronutrient absorption in the soil. The utilization of zinc sulfate as a soil treatment led to elevated absorption of macronutrients and zinc, suggesting a connection between the fertilizer type and the crop’s agronomic and physiological reactions.

Permanent deformation and particle crushability of calcareous sands under cyclic traffic-induced loadings through simple shear apparatus

This study focuses on investigating permanent deformations, encompassing normal and shear strains, of calcareous sandy soils subjected to drained cyclic traffic-induced loadings. The investigation utilizes a Simple Shear (SS) apparatus allowing for variations in both normal and shear stress components over each cycle and incorporates Principal Stress Rotation (PSR), a feature not replicable in conventional cyclic uniaxial triaxial tests which is the key aspect of this research. The study also accounts for the harmonically changing the effective horizontal stress resulting from cyclic variations of effective vertical stress, conducted under a horizontally constrained boundary condition with zero lateral strain. A series of drained cyclic simple shear experiments is carried out, implementing a heart-shaped stress path, encompassing up to 1000 cycles. The objective of the study is to analyze permanent normal and shear deformations, along with associated total particle crushing, using both sieving analyses and 2D image processing of particles. The study also evaluates the impact of an initial static shear stress originating from the longitudinal slope of roads. The findings highlight the influences of induced cyclic amplitudes of stress components, principal stress and strain rate rotation, and initial static shear stress on the development of permanent strains. Furthermore, the research characterizes particle crushability in terms of total crushability over such loading, examining its dependency on relative density and variations in both shear and normal stress components.

Challenges in developing reliable phosphorus predictive models: Unpredictable release under soil redox changes

Phosphorus (P), crucial for plant nutrition, is unevenly distributed in the Earth's crust, necessitating its supplementation in agriculture through fertilizers. However, excessive use can lead to water pollution. Our research focuses on the P adsorbing complex, investigating P release due to flooding, using 12 well- characterized soils with contrasting properties. Our research measures directly the P-adsorbing complex using adsorption/desorption isotherms. We observed that the P concentration in the solution —sufficient to prevent desorption yet low enough to avoid further sorption by the soil— decreases when the soil undergoes complete reduction (anoxia). When grouped by similarity, calcareous soils exhibit higher maximum P adsorption capacities (Xmax) under alternating reducing conditions (ARC) compared to continuous reducing conditions (CRC). In slightly acidic soils, CRC leads to a wider spread in Xmax values than ARC. For acidic, organic matter-rich soils, ARC results in the highest Xmax values (123 mmol P kg-1 soil) compared to CRC, whereas in acidic, light-textured soils, CRC shows significantly higher mean Xmax values than ARC. Nevertheless, we were unable to develop a predictive model for soil P desorption based on key intrinsic properties and climate. When an environmental or anthropogenic transformation induces anoxia, the P released does not follow a predictable pattern.

Comparative Evaluation of Calcium Sources and their Mode of Use on Apple Production in Acidic Soil under High Density Plantation System

Apples grown in Kashmir province are extremely prone to deterioration, particularly in post-harvest storage. Calcium is amongst the vital mineral element deceiving apple fruit quality, predominantly in acid soils deficit in available calcium. Calcium in sufficient quantity helps to retain apple fruit firmness and reduces the occurrence of physiological disorders, it also plays essential role to improve yield and quality of produce. Modes of calcium application and its different doses on two apple varieties was tested to improve yield and quality at Ambri Apple Research Centre, Sher-e-Kashmir University of Agricultural Sciences and Technology, Kashmir, India. The direct application of calcium to apple as spray is most effective method for escalating fruit calcium content and quality. Among sources and their mode of application calcium nitrate foliar application performed better than foliar application of calcium chloride in improving fruit quality and yield of Golden Delicious than Red Chief Camspur, whereas soil application of calcium nitrate showed least response to improve fruit quality and yield in both varieties under acidic soil atmosphere. Physiological loss in weight at 30 days and 60 days after harvesting was lower in foliar applied calcium than soil calcium application. The significant variation in total sugar content and TSS of apple fruits were observed in different calcium sources and their mode of application. Calcium nitrate foliar spray performed better than calcium chloride foliar spray in improving fruit quality. Our study did not find any adversity of dosage in plants whether applied to soil or directly to plant and we did observe better yields and quality at higher calcium doses. Among varieties Golden Delicious performed better than Red Chief Camspur. Results of research evidenced that preharvest calcium sprays increase yield, improved fruit quality and reduced its deterioration in post-harvest storage.

Integration of organic amendments and phosphate-solubilizing bacteria improves wheat growth and yield by modulating phosphorus availability and physiological reponses

Saline calcareous soil presents significant challenges for crop production due to its poor nutrient availability and adverse effects on plant growth. Hence this study aimed to investigates the impact of integrating organic amendments—specifically Moringa seed residues, biogas manure, and vermicompost (Ver)—with and without phosphate-solubilizing bacteria (PSB), alongside two types of phosphatic fertilizers, ordinary super phosphate (OSP) and rock phosphate (RP), on the growth, yield, and nutrient uptake of wheat plants in saline calcareous soil conditions. The results indicate that the combined application of Ver + PSB, particularly when paired with OSP, consistently yields superior outcomes across all measured parameters, followed by Ver + PSB with RP. Notably, the Ver + PSB with OSP treatment exhibits the highest values across several key parameters: chlorophyll levels (chlorophyll a at 1.8, chlorophyll b at 0.84, and carotenoids at 0.72 mg g−1f wt), proline at 38.5 μg g−1 DW, relative water content at 80.76%, membrane stability index at 67.62%, as well as net photosynthetic rate (Pn), transpiration rate (Tr), and stomatal conductance (gs). Furthermore, this treatment showcases the highest antioxidant enzyme activities (Superoxide dismutase, SOD at 9.27 A564 min−1 g−1 protein, Catalase, CAT at 78.53 A564 min−1 g−1 protein, Peroxihdase, POX at 1.86 A564 min−1 g−1 protein), as well as NPK content and uptake in wheat straw and grains. Additionally, it leads to significant increases in wheat growth parameters, including plant height, straw weight, grain weight, 1000 grain weight, and protein content. However, it also results in a notable decrease in other parameters such as total soluble sugars and nonenzymatic antioxidants (Ascorbate, AsA; Total glutathione, GsH; and α-Tocopherol, α-TOC).