Alkaline Calcareous Soils Research Articles

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.

Effects of biochar and magnesium oxide on cadmium immobilized by microbially induced carbonate: Mobilization or immobilization in alkaline agricultural soils?

Microbially induced carbonate precipitation (MICP) is a promising technique for remediating heavy metal-contaminated soils. However, the effectiveness of MICP in immobilizing Cd in alkaline calcareous soils, especially when applied in agricultural soils, remains unclear. Biochar and magnesium oxide are two environmentally friendly passivating materials, and there are few reports on the combined application of MICP with passivating materials for remediating heavy metal-contaminated soils. Additionally, the number of treatments with MICP cement and the concentration of calcium chloride during the MICP process can both affect the effectiveness of heavy metal immobilization by MICP. Therefore, we conducted MICP and MICP-biochar-magnesium oxide treatments on agricultural soils collected from Baiyin, Gansu Province (pH = 8.62), and analyzed the effects of the number of treatments with cement and the concentration of calcium chloride on the immobilization of Cd by MICP and combined treatments. The results showed that early-stage MICP could immobilize exchangeable cadmium and increase the residual cadmium content, especially with high-concentration calcium chloride MICP treatment. However, in the later stage, soil nitrification and exchange processes led to the dissolution of carbonate-bound cadmium and cadmium activation. The fixing effect of MICP influence whether the MICP-MgO-biochar is superior to the MgO-biochar. Four treatments with cement were more effective than single treatment in MICP-biochar-magnesium oxide treatment, and the MICP-biochar-magnesium oxide treatment with four treatments was the most effective, with passivation rates of 40.7% and 46.6% for exchangeable cadmium and bioavailable cadmium, respectively. However, attention should be paid to the increase in soil salinity. The main mechanism of MICP-magnesium oxide-biochar treatment in immobilizing cadmium was the formation of Cd(OH)2, followed by the formation of cadmium carbonate.

Iron (Fe) and zinc (Zn) coated urea application enhances nitrogen (N) status and bulb yield of onion (A. cepa) through prolonged urea-N stay in alkaline calcareous soil

Onion (A. cepa) is an important horticulture crop which is sensitive to nutrient limitations worldwide. Urea hydrolysis to ammonia (NH3) and carbon dioxide (CO2), due to soil urease activity, causes urea-N loss. Comparative to several commercial products, the potential use of micronutrient coated urea to reduce urea hydrolysis based NH3-volatilization losses is novel to-date. In this study, boron (B), iron (Fe), zinc (Zn) and copper (Cu) were coated on urea at their full or half recommended rates as (B)-half, (Fe)-half, (Zn)-half, (Cu)-half, (B)-full, (Fe)-full, (Zn)-full, (Cu)-full, (B+Fe)-half, (B+Zn)-half, (B+Cu)-half, (Fe+Zn)-half, (Fe+Cu)-half, (Zn+Cu)-half, (B+Fe)-full, (B+Zn)-full, (B+Cu)-full, (Fe+Zn)-full, (Fe+Cu)-full and (Zn+Cu)-full having gum-only coated urea as an internal control. Parallel to these, p-Phenylenediamine (PPD-0.2 %, 0.4 %, 0.6 %, 0.8 % and 1.0 %) and hydroquinone (HQ-0.5 %, 1.0 % and 2 %) coated urea treatments were also used with acetone-only coated urea as an internal control. Whereas the uncoated urea treatment was taken as an overall control. In pot experiment, the soil residual urea concentrations were increased by 2, 0.5, 1.85, 2.69 and 3.15 folds at 8 days after incubation (DAI), by 5.6, 1.89, 5.97, 0.54 and 6.23 folds at 12 DAI and by 119, 123, 155, 84 and 87 folds at 16 DAI under (B)-full, (B+Zn)-full, (Fe+Zn)-full, PPD-0.8 % and PPD-1.0 % coated urea treatments, respectively, as compared to uncoated urea. Among these five coating combinations, 54.26 % and 44.82 % bulb yield increments were observed under (Fe+Zn)-full and PPD-1 % coated urea, respectively, in comparison to uncoated urea in field experiment. However, the 33.33 % increment in nitrogen agronomic efficiency (NAE) and subsequent economic gains proved (Fe+Zn)-full coated urea application as a solution to address N losses in alkaline calcareous soils.

Biofortification of wheat in salt-affected soil through seed priming and soil application of zinc

ContextGiven the global significance of wheat production and consumption, it is imperative to achieve high yields of nutritious wheat grains. However, the inadequate availability of zinc (Zn) in salt-affected soils can aggravate salt stress, decrease wheat grain yield, and grain Zn concentration. This study compared the effectiveness of soil Zn application and seed Zn priming in increasing Zn biofortification and grain yield of Zn-biofortified wheat grown in alkaline-calcareous soil affected by salts. MethodsEighteen pots were filled with alkaline-calcareous soil containing elevated levels of soluble salts and exchangeable sodium (Na). The pots were subjected to soil Zn application (0 or 8 mg kg−1) and seed priming (control/non-, hydro-, or Zn-primed seeds) treatments, applied to a Zn-biofortified wheat (cv. Zincol-2016). Plant samples were collected at the heading and maturity stages to measure parameters related to plant growth and grain quality. FindingsSoil Zn application increased grain and straw yields across seed priming treatments by a maximum of 23 %, and seed Zn priming increased grain and straw yields across soil Zn rates by a maximum of 21 %. This yield response was accompanied by significant increases in grain potassium and Zn concentrations at maturity, as well as non-significant to significant increases in photosynthetic parameters (stomatal conductance, photosynthetic rate and transpiration rate) in flag leaves during heading. Additionally, compared to control, the combined treatment of soil Zn application and seed Zn priming decreased grain Na concentration by 14 %. Compared to control, both soil Zn application and seed Zn priming significantly increased grain Zn concentration. With the combined application treatment, the grain Zn concentration reached 27 mg kg−1, but it remained significantly below the desired level of >37 mg kg−1. Seed Zn priming decreased the phytate-to-Zn molar ratio in grains, while the treatments that received soil Zn application exhibited the lowest values of this ratio, potentially increasing Zn bioavailability to humans. ConclusionsThe findings suggest that soil Zn application is more effective in enhancing grain yield and Zn concentration, while seed Zn priming remains crucial in low-Zn and high-salt soils. Future research should optimize Zn application strategies for Zn-biofortified wheat cultivated in salt-affected fields.

Effects of Organic Amendments and Mineral Fertilizers on Optimizing Nutrient Cycling in Alkaline Soil

Soil microbial biomass carbon (MBC) and nitrogen (MBN) are indicators of microbial size and soil fertility, representing a vital living nutrient reservoir in the soil. This study aimed to evaluate the impact of various organic sources, such as poultry manure (PM), farmyard manure (FYM), compost (CM), and biochar (BC), along with different levels of mineral fertilizers on soil microbial dynamics and nutrient (N, P) mineralization through laboratory incubation experiments. The organic amendments were applied at rates of 0.25%, 0.5%, and 1.0% of soil carbon (w/w), combined with 75%, 50%, and 25% of recommended doses of NPK (120:90 and 60 kg N, P2O5, and K2O ha-1), respectively. Following the application of amendments, the soil underwent a 16-day incubation period to measure CO2 emissions and a 28-day period for N and P mineralization. The rate of CO2 evolution exhibited a significant increase with higher carbon levels but declined over time. Compost showed the highest CO2 evolution at any given time, followed by PM, FYM, and BC, likely due to a higher readily available fraction of carbon. Compost, particularly at the 1% C level in combination with inorganic fertilizer, led to a significant increase in soil microbial biomass C and N. Nitrogen and phosphorous mineralization increased with the duration of the 28-day incubation period. However, the net release of N and P decreased with higher carbon levels, potentially associated with both immobilization and the fact that higher levels received lower (25%) NPK levels. Nevertheless, soils treated with CM and PM maintained higher levels of N and P, associated with their higher fraction of labile nutrients. These findings suggest that the continuous application of organic sources enhances N and P mineralization, soil microbial biomass, and their activity. Therefore, the regular application of carbon sources emerges as a strategic approach to improving the soil health of less fertile alkaline calcareous soils.

Soil zinc application decreases arsenic and increases zinc accumulation in grains of zinc-biofortified wheat cultivars

Context Arsenic (As) is a noxious metalloid for plants, animals and humans. Elevated levels of As in soils may cause it to accumulate to above-permissible levels in wheat grains, posing a threat to human health. Moreover, vulnerable population groups in developing countries have inadequate dietary zinc (Zn) linked to cereal-based diets. Aims The present study evaluated the effect of soil Zn application on accumulation of As and Zn in grains of two Zn-biofortified wheat (Triticum aestivum L.) cultivars (Akbar-2019 and Zincol-2016). Methods Wheat plants were grown on an alkaline calcareous soil spiked with three levels of As (0, 5 and 25 mg kg−1). Before sowing, two rates of Zn (0 and 8 mg kg−1) were also applied to the soil. Key results Arsenic spiking in soil decreased plant dry matter yield, chlorophyll pigments, and phosphorus (P) and Zn accumulation, and increased As accumulation in wheat. By contrast, soil Zn application enhanced crop yield and increased P and Zn accumulation, with a simultaneous decrease in As accumulation in both cultivars. Compared with the Zn control, soil Zn application decreased grain As concentration by 26%, 30% and 32% for plants grown in soil spiked with 0, 5 and 25 mg As kg−1, respectively. Conclusions Applying Zn to As-spiked soil mitigates the harmful effects of As by increasing Zn and decreasing As concentrations in wheat, resulting in improved grain quality for human consumption. Implications Zinc application to crop plants should be recommended for addressing the health implications associated with As-contaminated crops and human Zn deficiency.

Assessment of the stabilization effect of ferrous sulfate for arsenic-contaminated soils based on chemical extraction methods and in vitro methods: Methodological differences and linkages

Stabilization of arsenic-contaminated soils with ferrous sulfate has been reported in many studies, but there are few stabilization effects assessments simultaneously combined chemical extraction methods and in vitro methods, and further explored the corresponding alternative relationships. In this study, ferrous sulfate was added at FeAs molar ratio of 0, 5, 10 and 20 to stabilize As in 10 As spiked soils. Stabilization effects were assessed by 6 chemical extraction methods (toxicity characteristic leaching procedures (TCLP), HCl, diethylenetriamine pentaacetic acid (DTPA), CaCl2, CH3COONH4, (NH4)2SO4), and 4 in vitro methods (physiologically based extraction test (PBET), in vitro gastrointestinal method (IVG), Solubility Bioaccessibility Research Consortium (SBRC) method, and the Unified Bioaccessibility Research Group of Europe method (UBM)). The results showed that the HCl method provides the most conservative assessment results in non-calcareous soils, and in alkaline calcareous soils, (NH4)2SO4 method provides a more conservative assessment. In vitro methods provided significantly higher As concentrations than chemical extraction methods. The components of the simulated digestion solution as well as the parameters may have contributed to this result. The small intestinal phase of PBET and SBRC method produced the highest and lowest ranges of As concentrations, and in the range of 127–462 mg/kg and 68–222 mg/kg when the FeAs molar ratio was 5. So the small intestinal phase of PBET method may provide the most conservative assessment results, while the same phase of SBRC may underestimate the human health risks of As in stabilized soil by 51 %(at a FeAs molar ratio of 5). Spearman correlation analysis indicated that the small intestinal phase of PBET method correlated best with HCl method (correlation coefficient: 0.71). This study provides ideas for the assessment of stabilization efforts to ensure that stabilization meets ecological needs while also being less harmful to humans.

Determining soil conservation strategies: Ecological risk thresholds of arsenic and the influence of soil properties

The establishment of ecological risk thresholds for arsenic (As) plays a pivotal role in developing soil conservation strategies. However, despite many studies regarding the toxicological profile of As, such thresholds varying by diverse soil properties have rarely been established. This study aims to address this gap by compiling and critically examining an extensive dataset of As toxicity data sourced from existing literature. Furthermore, to augment the existing information, experimental studies on As toxicity focusing on barley-root elongation were carried out across various soil types. The As concentrations varied from 12.01 to 437.25 mg/kg for the effective concentrations that inhibited 10% of barley-root growth (EC10). The present study applied a machine-learning approach to investigate the complex associations between the toxicity thresholds of As and diverse soil properties. The results revealed that Mn-/Fe-ox and clay content emerged as the most influential factors in predicting the EC10 contribution. Additionally, by using a species sensitivity distribution model and toxicity data from 21 different species, the hazardous concentration for x% of species (HCx) was calculated for four representative soil scenarios. The HC5 values for acidic, neutral, alkaline, and alkaline calcareous soils were 80, 47, 40, and 28 mg/kg, respectively. This study establishes an evidence-based methodology for deriving soil-specific guidance concerning As toxicity thresholds.

Evaluation of acidified biochar and farmyard manure as sustainable soil management and maize cultivation in alkaline calcareous soils

Evaluation of acidified biochar and farmyard manure as sustainable soil management and maize cultivation in alkaline calcareous soils

Enhancing nitrogen use efficiency and yield of maize (Zea mays L.) through Ammonia volatilization mitigation and nitrogen management approaches

Management of nitrogen (N) fertilizer is a critical factor that can improve maize (Zea mays L.) production. On the other hand, high volatilization losses of N also pollute the air. A field experiment was established using a silt clay soil to examine the effect of sulfur-coated urea and sulfur from gypsum on ammonia (NH3) emission, N use efficiency (NUE), and the productivity of maize crop under alkaline calcareous soil. The experimental design was a randomized complete block (RCBD) with seven treatments in three replicates: control with no N, urea150 alone (150 kg N ha−1), urea200 alone (200 kg N ha−1), urea150 + S (60 kg ha−1 S from gypsum), urea200 + S, SCU150 (sulfur-coated urea) and SCU200. The results showed that the urea150 + S and urea200 + S significantly reduced the total NH3 by (58 and 42%) as compared with the sole application urea200. The NH3 emission reduced further in the treatment with SCU150 and SCU200 by 74 and 65%, respectively, compared to the treatment with urea200. The maize plant biomass, grain yield, and total N uptake enhanced by 5–14%, 4–17%, and 7–13, respectively, in the treatments with urea150 + s and urea200 + S, relative to the treatment with urea200 alone. Biomass, grain yield, and total N uptake further increased significantly by 22–30%, 25–28%, and 26–31%, respectively, in the treatments with SCU150 and SCU200, relative to the treatment with urea200 alone. The applications of SCU150 enhanced the nitrogen use efficiency (NUE) by (72%) and SCU200 by (62%) respectively, compared with the sole application of urea200 alone. In conclusion, applying S-coated urea at a lower rate of 150 kg N ha−1 compared with a higher rate of 200 kg N ha−1 may be an effective way to reduce N fertilizer application rate and mitigate NH3 emission, improve NUE, and increase maize yield. More investigations are suggested under different soil textures and climatic conditions to declare S-coated urea at 150 kg N ha−1 as the best application rate for maize to enhance maize growth and yield.

Optimizing Nitrogen Sources in Top Dressing for Wheat: Field Study on Growth, Yield, and Ammonia Volatilization.

In alkaline calcareous soils, ammonia volatilization is the primary nitrogen (N) loss process, resulting in the reduced N use efficiency of crops. This study aimed at assessing the impact of different N sources for top dressing on ammonia volatilization, as well as their effects on wheat growth and yield over two years. In each year, half of the recommended N was applied as a basal dose using diammonium phosphate (DAP) and urea. The remaining half was top-dressed 35 days after sowing with various sources: prilled urea (PU), granular urea (GU), ammonium sulfate (AS), and calcium ammonium nitrate (CAN) in the first year; PU, urea coated with a urease inhibitor from 20 g (VnU-20) and 40 g (VnU-40) leaves of Vachellia nilotica, biochar-coated urea (BU), and urease inhibitor paraphenylenediamine-coated urea (PPDU) in the second year. Ammonia volatilization losses were tracked for up to 12 weeks from sowing. Ammonia losses from basal-applied N remained consistent in both years, comprising around 4% of the applied N. In the first year, top-dressed AS resulted in the highest losses, followed by GU, while losses from urea and CAN were statistically similar. In the second year, coated fertilizers showed lower ammonia losses compared to PU, with VnU-40 displaying the least losses, 48% less than PU. Nitrogen concentration in wheat grain and straw exhibited a negative correlation with ammonia losses. The choice of top-dressed N source influenced tillering, biological, straw, and grain yields of wheat. In the first year, CAN provided maximum yield benefits, and in the second year, VnU-20 exhibited 27% more grain yield than PU. These findings suggest that top dressing with coated urea, especially VnU-20, has the potential to reduce ammonia losses, improve crop nitrogen status, and enhance economic yield compared to other nitrogen sources.

Restricted colloidal-bound phosphorus release controlled by alternating flooding and drying cycles in an alkaline calcareous soil

Colloid-facilitated phosphorus (P) migration plays an important role in P loss from farmland to adjacent water bodies. However, the dynamics of colloidal P (Pcoll) release as influenced by irrigation in alkaline calcareous soil remains a knowledge gap. The present study, monitored the dynamic change of Pcoll under different water management strategies: 1) control, 2) flooding, and 3) alternating flooding and drying cycles. Soil water-dispersible colloids (0.6 nm-1 μm) were extracted by combining filtration and ultrafiltration methods. The contents of P, cation and organic carbon in the water-dispersible colloids were determined and the stability and mineral composition of colloidal fractions were characterized. The results showed that Pcoll ranged from 16.5 to 25.5 mg kg−1 and represented 42.8%–64.9% of the water-extracted P in the control. Flooding significantly decreased the Pcoll content by 16.0%–62.1% (mean 32.7%) and it may be attributed to the dissolution of colloidal iron (Fe) bound P. The alternating flooding and drying treatment significantly reduced the Pcoll content by 11.6%–88.0% (mean 67.6%). The Pcoll content of the flooding event was always greater than the Pcoll content of the drying event during flooding and drying cycles. Redundancy analysis and random forest modeling showed that the colloidal calcium (Ca) and ionic strength in soil solutions had negative correlations with the Pcoll content, and pH, ionic strength and truly dissolved P were the critical factors affecting Pcoll. Drying of the flooded soil led to the decrease of pH and the increase of ionic strength, colloidal Ca content and positive charges of colloid surfaces, which promoted colloid aggregation and enhanced soil P sorption capacity. This restricted the loss potential of Pcoll. In summary, controlled flooding and drainage when managed correctly have a role to play in mitigating Pcoll loss from P-enriched calcareous soils.

Granular bacterial inoculant alters the rhizosphere microbiome and soil aggregate fractionation to affect phosphorus fractions and maize growth

The constraint of phosphorus (P) fixation on crop production in alkaline calcareous soils can be alleviated by applying bioinoculants. However, the impact of bacterial inoculants on this process remains inadequately understood. Here, a field study was conducted to investigate the effect of a high-concentration, cost-effective, and slow-release granular bacterial inoculant (GBI) on maize (Zea mays L.) plant growth. Additionally, we explored the effects of GBI on rhizosphere soil aggregate physicochemical properties, rhizosphere soil P fraction, and microbial communities within aggregates. The outcomes showed a considerable improvement in plant growth and P uptake upon application of the GBI. The application of GBI significantly enhanced the AP, phoD gene abundance, alkaline phosphatase activity, inorganic P fractions, and organic P fractions in large macroaggregates. Furthermore, GBI impacted soil aggregate fractionation, leading to substantial alterations in the composition of fungal and bacterial communities. Notably, key microbial taxa involved in P-cycling, such as Saccharimonadales and Mortierella, exhibited enrichment in the rhizosphere soil of plants treated with GBI. Overall, our study provides valuable insight into the impact of GBI application on microbial distributions and P fractions within aggregates of alkaline calcareous soils, crucial for fostering healthy root development and optimal crop growth potential. Subsequent research endeavors should delve into exploring the effects of diverse GBIs and specific aggregate types on P fraction and community composition across various soil profiles.

Enhancing phosphorus use efficiency in wheat grown on alkaline calcareous soils

Phosphorus (P) use efficiency is crucial for sustainable wheat production, particularly on alkaline calcareous soils. This study investigates the relative importance of two factors; P acquisition efficiency (PAE) and P utilization efficiency (PUtE), in determining P use efficiency (PUE) in wheat. A field trial with ten wheat genotypes was conducted under two P levels (no P application and P application at 110 kg P2O5 ha−1). Results revealed significant genetic variability in PUE, PAE, and PUtE among wheat genotypes under varying P availabilities. Genotypes MK-4 and MK-8 exhibited superior PUE, making them ideal candidates for soils with differing P levels. PAE played a more substantial role in influencing PUE, with PUtE contributing less to the variability. The findings underscore the importance of improving PAE, particularly for wheat genotypes grown in P-deficient conditions. Moreover, selecting genotypes with lower grain P concentration can enhance PUtE, contributing to improved PUE. These insights can improve breeding efforts and crop management practices to enhance P use efficiency in wheat, ultimately reducing production costs and fertilizer demand, especially in P-limited alkaline calcareous soils.

English

Effects of the urease inhibitor N-(n-butyl) thiophosphoric triamide (NBPT) on transformations of urea N in an alkaline calcareous soil were investigated at different temperatures. The urease inhibitor was incorporated in urea granules at 7 different concentrations ranging from 0 to 6% of N. The amended urea granules were applied at 250 mg N kg−1 on the soil surface and incubated for 20 days at 18, 25 and 35°C. Effects of NBPT on NH3 volatilization from the surface applied urea were also investigated at different temperatures. In the absence of urease inhibitor, most (96–98%) of the applied urea was hydrolyzed within 5 days. During this period, NBPT significantly inhibited urea hydrolysis at all temperatures (6–46% reduction); the extent of inhibition increased with increasing NBPT application rate and with decreasing temperature. After 10 days, almost all urea was hydrolyzed at all temperatures with NBPT applied up to 2% of N, whereas up to 23% inhibition was recorded with higher NBPT application rates. In the absence of NBPT, 23–41% of the applied urea-N was lost as NH3 during 20 days, with the highest loss recorded at 35°C. However, the application of NBPT significantly reduced NH3 volatilization loss at all temperatures; the beneficial effect of NBPT increased with increasing application rate. Results suggested that application of the urease inhibitor NBPT can cause up to 50% reduction in NH3 volatilization loss when applied at economically feasible application rates ranging from 0.5% of urea-N (during winter season; 18°C) to 1% of urea-N (during fall and summer seasons; 25–35°C).

English

The canola is an important oilseed crop of the world and Pakistan that grows in a substantial area, but the required quality and yield of canola oil is still not enough to meet the country’s need. Iron (Fe) and Zinc (Zn) are important human nutrients and biofortification of these elements in canola oil is a challenge especially under alkaline calcareous soil conditions owing to less bioavailability of these metal ions in soil. With the same objective, the present investigation was conducted in 2 experiments (Pot and Field trials) with 7 treatments (Control, So-200 kg ha-1, Iron-3 kg ha-1, Zinc-6 kg ha-1, S+Fe, S+Zn and S+Fe+Zn) under pot and filed conditions, separately. The application of S, Fe and Zn resulted in a significant increment in canola crop growth, yield, improved plant physiology and enhanced Fe and Zn uptake and accumulation. The elemental S alone was found to be affecting these properties significantly and combined application with Fe, Zn, and Fe+Zn resulted in further increment in growth, yield, oil percentage and shoot/grain elemental components. For Fe distribution, S application with Fe enhanced its shoot and grains accumulation 16% and 14% compared to alone Fe control under pot settings while 16% and 15% higher shoot and grain Fe was observed under field trial. The shoot and grains’ Zn contents were also found to be significantly improved (10% and 9% higher Zn in shoot and grain of pot-grown canola plants while 19% and 10% increment was observed under filed investigation compared with respective controls).

Fate and Plant Uptake of Different Zinc Fertilizer Sources upon Their Application to an Alkaline Calcareous Soil

Fate and Plant Uptake of Different Zinc Fertilizer Sources upon Their Application to an Alkaline Calcareous Soil

Effect of exogenous application of biogenic silicon sources on growth, yield, and ionic homeostasis of maize (Zea mays L.) crops cultivated in alkaline soil

Salinity has emerged as a major threat to food security and safety around the globe. The crop production on agricultural lands is squeezing due to aridity, climate change and low quality of irrigation water. The present study investigated the effect of biogenic silicon (Si) sources including wheat straw biochar (BC-ws), cotton stick biochar (BC-cs), rice husk feedstock (RH-fs), and sugarcane bagasse (SB), on the growth of two consecutive maize (Zea mays L.) crops in alkaline calcareous soil. The application of SB increased the photosynthetic rate, transpiration rate, stomatal conductance, and internal CO2 concentration by 104, 100, 55, and 16% in maize 1 and 140, 136, 76, and 22% in maize 2 respectively. Maximum yield (g/pot) of cob, straw, and root were remained as 39.5, 110.7, and 23.6 while 39.4, 113.2, and 23.6 in maize 1 and 2 respectively with the application of SB. The concentration of phosphorus (P) in roots, shoots, and cobs was increased by 157, 173, and 78% for maize 1 while 96, 224, and 161% for maize 2 respectively over control by applying SB. The plant cationic ratios (Mg:Na, Ca:Na, K:Na) were maximum in the SB applied treatment in maize 1 and 2. The study concluded that the application of SB on the basis of soluble Si, as a biogenic source, remained the best in alleviating the salt stress and enhancing the growth of maize in rotation. The field trials will be more interesting to recommend the farmer scale.

Bio-Organically Acidified Product-Mediated Improvements in Phosphorus Fertilizer Utilization, Uptake and Yielding of Zea mays in Calcareous Soil.

The demand for a better agricultural productivity and the available phosphorus (P) limitation in plants are prevailing worldwide. Poor P availability due to the high pH and calcareous nature of soils leads to a lower P fertilizer use efficiency of 10-25% in Pakistan. Among different technologies, the use of biologically acidified amendments could be a potential strategy to promote soil P availability and fertilizer use efficiency (FUE) in alkaline calcareous soils. However, this study hypothesized that an acidified amendment could lower soil pH and solubilize the insoluble soil P that plants can potentially uptake and use to improve their growth and development. For this purpose, the test plant Zea mays was planted in greenhouse pots with a recommended dose rate of 168 kg ha-1 of P for selected phosphatic fertilizers, viz., DAP (diammonium phosphate), SSP (single superphosphate), and RP (rock phosphate) with or without 2% of the acidified product and a phosphorus solubilizing Bacillus sp. MN54. The results showed that the integration of acidified amendments and PSB strain MN54 with P fertilizers improved P fertilizer use efficiency (FUE), growth, yield, and P uptake of Zea mays as compared to sole application of P fertilizers. Overall, organic material along with DAP significantly improved plant physiological-, biochemical-, and nutrition-related attributes over the sole application of DAP. Interestingly, the co-application of RP with the acidified product and MN54 showed a higher response than the sole application of DAP and SSP. However, based on our study findings, we concluded that using RP with organic amendments was a more economically and environmentally friendly approach compared to the most expensive DAP fertilizer. Taken together, the current study suggests that the use of this innovative new strategy could have the potential to improve FUE and soil P availability via pH manipulation, resulting in an improved crop productivity and quality/food security.

Cerium oxide nanoparticles alleviates stress in wheat grown on Cd contaminated alkaline soil

The cadmium contamination of soil is an alarming issue worldwide and among various mitigation strategies, nanotechnology mediated management of Cd contamination has become a well-accepted approach. The Cerium Oxide Nanoparticles (CeO2-NPs) are widely being explored for their novel works in Agro-Industry and Environment, including stress mitigation in crops. Very little work is reported regarding role of CeO2-NPs in management of Cd contamination in cereal crops like wheat. Present work was planned to check efficacy of CeO2-NPs in Cd stress mitigation of wheat under alkaline calcareous soil conditions. In this experiment, 4 sets of Cd contamination (Uncontaminated control-UCC, 10, 20, and 30 mg Cd per kg soil) and 5 sets of CeO2-NPs NPs (0, 200, 400, 600, and 1000 mg NP per kg soil) were applied in pots following completely randomized design (CRD) and wheat crop was grown. The growth, physiology, yield and Cd and Ce accumulation by wheat root, shoot and grain was monitored. The maximum Cd spiking level (30 mg kg−1) was found to be most toxic for plant growth. The results showed that the nanoparticles were overall beneficial for wheat growth and maximum level (1000 mg kg−1) being the most significant one under all Cd spiking sets. In Cd-30 sets, 1000 mg kg−1 NPs application resulted in decreased soil bioavailable Cd concentration (49.63% decrease compared to 30 mg kg−1 Cd spiked sets termed as Cd-30 Control), decreased Cd accumulation in all three tissues: root (58.36% decrease), shoot (52.30% decrease) and grain (55.56% decrease) while increased root dry weight (62.14%), shoot dry weight (89.32%), total grain yield (80.08%) and improved plant physiology with respect to Cd-30 control. Nanoparticles application substantially increased wheat root, shoot and grain Ce concentrations as well. The further prospects of these nanoparticles in relation to various biotic and abiotic stresses are advised to be explored.