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.

Multi-element uptake and growth responses of Rice (Oryza sativa L.) to TiO2 nanoparticles applied in different textured soils.

The aim of present work was to evaluate the effects of titanium dioxide nanoparticles (TiO2 NPs) on rice's growth (Oryza sativa L.) and nutrient availability under different soil textures. Greenhouse experiment was carried out with three soil textures (sandy loam, silt loam and silty clay loam) and two concentrations of TiO2 NPs (500, 750 mg kg-1). Control (without TiO2 NPs) was also maintained for the comparison. Growth parameters including chlorophyll content, root/shoot length, fresh/dry biomass and nutrients' uptake including calcium (Ca), copper (Cu), iron (Fe), magnesium (Mg), phosphorous (P), potassium (K) and zinc (Zn) were determined. The results revealed that application of 500 mg kg-1 TiO2 NPs in silty clay loam soil increased the chlorophyll content (3.3-folds), root length (49%), shoot length (31%), root and shoot biomass (41% & 39%, respectively) as compared to other soil textures. The maximum plant growth was observed in silty clay loam > silt loam > sandy loam. Concentration of Cu, Fe, P and Zn in shoot was increased by 8 - , 2.3 - , 0.4 - , 0.05 -folds in silty clay loam upon 500 mg kg-1 TiO2 NPs application as compared to the control. Backward selection method to model the parameters (nutrients in soil) for the response variables (root/shoot length and biomass) showed that Ca, Fe, P are the main nutrients responsible for the increase in plant length and biomass. Overall, the growth of rice was better in silty clay loam at 500 mg kg-1 of TiO2 NPs.

Zinc Foliar Application Mitigates Cadmium-Induced Growth Inhibition and Enhances Wheat Growth, Chlorophyll Contents, and Yield.

Cadmium (Cd) is a toxic heavy metal that significantly threatens plants and the environment. Its toxicity in plants can result in various adverse effects, including reduced growth, altered metabolism, and cell damage. Cadmium can also interfere with nutrient uptake, particularly zinc (Zn), leading to Zn deficiency and further exacerbating Cd toxicity. On the other hand, foliar application of zinc might be a useful strategy to mitigate cadmium (Cd) toxicity in plants. Hence, a pot experiment was conducted with three replications. The wheat plants were treated with various concentrations of Zn as a foliar spray (control, 0.1, 0.2, 0.4, and 0.5%) in Cd-spiked soil in pots. The results showed that foliar use of Zn at 0.4 or 0.5% resulted in higher plant height, grain yield, and dry matter yield than the control group. Using Zn as foliar spray enriched shoot and grain Zn content while reducing Cd content in the shoot and grain. The leaf's electrolyte leakage (EL) decreased by 15.4, 29.8, 40.7, and 45.9% in the Zn 0.1%, Zn 0.2%, Zn 0.4%, and Zn 0.5% treatments, respectively, compared to the control treatment. Regarding superoxide dismutase (SOD) activity, Zn 0.5% treatment showed a decrease of 42.9% over control. Specifically, the Zn 0.1% showed a 27.2%, Zn 0.2% showed a 56.8%, Zn 0.4% showed a 91.1%, and Zn 0.5% showed a 133.7% increase in total chlorophyll content than control. Based on the results, it is recommended that 0.4% Zn solution may be used for foliar application for enhancing crop productivity and Zn concentration in plants under high Cd stress. Additionally, continued research on the mechanisms of cadmium uptake, transport, and detoxification in plants may lead to the identification of new targets for intervention.

Evaluating the Efficacy of Activated Carbon in Minimizing the Risk of Heavy Metals Contamination in Spinach for Safe Consumption.

Toxicity induced by heavy metals is a major concern in agriculture as it decreases crops' growth and yield and leads to the deterioration of food quality. Recently, activated carbon has been identified as a possible solution. It can potentially improve crop nutrition and immobilize heavy metals in soil. That is why a glasshouse trial was conducted to investigate the effects of sugarcane bagasse-derived biochar on spinach growth and the availability of cadmium (Cd) and chromium (Cr) in artificially contaminated soil. The soil was placed in pots and contaminated with Cd and Cr at a rate of 10 mg kg-1. Biochar was added to the soil at concentrations of 0 (control), 0 (contaminated control), 100, 150, and 200 g, and 10-day-old nursery spinach plants were transplanted to the pots. The results showed that applying 200 g of biochar significantly increased shoot weight (235 g), soil pH, electrical conductivity, and organic matter. The highest levels of Cd (27.71 mg kg-1) and Cr (20.44 mg kg-1) were observed in the contaminated control pots, while the lowest levels of Cd (16.80 mg kg-1) and Cr (9.80 mg kg-1) were found in pots treated with 200 g of biochar (2%). Similarly, the highest levels of Cd (35.80 mg kg-1) and Cr (40.24 mg kg-1) in the roots were found in the contaminated control pots, while the lowest levels of Cd (19.26 mg kg-1) and Cr (21.34 mg kg-1) were observed in pots treated with 200 g of biochar. Biochar application at a rate of 2% can immobilize Cd and Cr in the soil and improve chlorophyll contents, carotenoids, photosynthetic rate, transpiration rate, and stomatal conductance in spinach in Cd- and Cr-contaminated soils. Further long-term field studies will be necessary to determine the feasibility of applying biochar as an organic amendment for enhancing spinach growth and reducing Cd and Cr bioavailability in contaminated soil.

Effect of Nitrogen in Combination with Different Levels of Sulfur on Wheat Growth and Yield.

As macronutrients, management of nitrogen (N) and sulfur (S) is prime in importance when wheat is cultivated. Both have a significant impact on the improvement of growth and yield attributes. In addition, S and N also play an imperative role in the enhancement of seed protein contents. However, the need of the time is the selection of their optimum application rate for the achievement of maximum wheat productivity. That is why the current study was planned to examine the impact of variable application rates of S and N on wheat. There are 12 treatments, i.e., control (no nitrogen (0N) + no sulfur (0S)), 40 kg/ha N (40N + 0S), 80 kg/ha N (80N + 0S), 120 kg/ha N (120N + 0S), 30 kg/ha sulfur (30S), 40N + 30S, 80N + 30S, 120N + 30S, 60 kg/ha sulfur (60S), 40N + 60S, 80N + 60S, and 120N + 60S, applied in three replications. The results showed that plant height, grains/spike, spike/m2, and 1000 grain weight were significantly improved by the addition of 120N + 60S. A significant enhancement of grain N contents, N uptake, and protein contents of wheat validated the efficient role of 120N + 60S over 0N and 0S. In conclusion, 120N + 60S is a better treatment for the achievement of maximum wheat yield. More investigations under variable soil textures and climatic conditions are suggested under different climates to declare 120N + 60S as the best amendment for wheat growth and yield improvement.

Maize productivity and soil nutrients variations by the application of vermicompost and biochar.

Poor soil organic matter is one of the major causes of the deterioration of soil health. Most soils fertility is also decreased when enough organic carbon is not present in the soil. Maize is most susceptible to this poor soil fertility status. A significant amount of maize growth and yield is lost when it is cultivated in low organic matter and poor fertility soil. To overcome this issue organic amendments can play an imperative role. Biochar and vermicompost are organic amendments that can not only improve organic residues but also increase soil nutrient concentration. The current experiment was conducted to explore the sole and combined application of both organic amendments with recommended NPK fertilizer. Four treatments were tested i.e., control, biochar (BC1), vermicompost (VC1) and VC1+BC1 with and without nitrogen (N), phosphorus (P) and potassium (K) in the experiment. Results showed that VC1+BC1+NPK performed significantly best for improvement in maize plant height (6.25 and 3.00%), 1000 grains weight (30.48 and 29.40%), biological yield (18.86 and 43.12%) and grains yield (30.58 and 39.59%) compared to BC0+VC0+NPK and control respectively. A significant improvement in soil N, P and K also validated the efficacious role of VC1+BC1+NPK over BC0+VC0+NPK and control. Treatment VC1+BC1+NPK is recommended for the achievement of better maize growth and yield in poor organic matter soils. More investigations are suggested in variable climatic conditions to declare VC1+BC1+NPK as the best amendment compared to control for enhancing soil N, P and K status as well as maize productivity.

Improving boron use efficiency via different application techniques for optimum production of good quality potato (Solanum tuberosum L.) in alkaline soil.

Boron (B) deficiency is a widespread problem in alkaline soils which affects yield and quality of potato but is often ignored by the growers. That's why, we compared the impact of different methods of boron application (foliar spray, fertigation and soil dressing) along with control on boron use efficiency (BUE), quality and yield of potato in alkaline soils. Boron (0.5 kg ha-1) applied as a foliar spray had significantly increased plant height, tuber per plant, tuber volume and enhanced the quality in terms of vitamin C, starch and B content of potato compared to other methods. Moreover, foliar applied B significantly improved B uptake and it use efficiency over other application methods. B concentration in tubers were strongly correlated with vitamin C and starch contents. The application methods were ranked as foliar spray>fertigation>soil dressing in term of their effectiveness towards potato yield and quality improvement. Thus, for optimum production of good quality potato, B should be applied as foliar spray at the rate of 0.5 kg B ha-1 in existing agro-climatic conditions.

Bacillus subtilis and saponin shifted the availability of heavy metals, health indicators of smelter contaminated soil, and the physiological indicators of Symphytum officinale.

Bacillus subtilis and saponin were tested for the uptake of heavy metals (HMs) by Symphytum officinale grown in a smelter-contaminated soil in completely randomized design. Soil pH and electrical conductivity increased by 0.11 unit (T3) and 754 mS cm-1 (T2), respectively. The bioavailable Zn decreased by 5.80% (T2); Cd and Pb increased by 6.21% (T2) and 13.46% (T3), respectively. Soil urease increased by 24% (T3) and alkaline phosphatase, ß-glucosidase, and dehydrogenase decreased by 20% (T2), 27.70% (T2), and 21% (T1), respectively. Soil amendments altered the microbial diversity. Fourier-transform infrared spectroscopy and X-ray diffraction reported no obvious changes, except saponin application, which led to possible release of HMs in soil. The fresh weight of Symphytum officinale increased by 21.3 and 5.50% in T2 and T3, respectively. Chlorophyll (a) and carotenoid decreased by the sole application of B. subtilis and saponin and vice-versa for chlorophyll (b). Mono-application of B. subtilis efficiently increased the peroxidase (POD: 27%) and polyphenol oxidase (PPO: 13.56%), whereas, co-application enhanced the phenylalanine ammonia-lyase (PAL: 6.50%) level in shoots. Zn concentration in the shoots and roots declined by 12.75 and 27.32% in T1, respectively. Cd increased (3.92%, T3) in shoots and decreased (39.25%, T1) in roots; Pb concentration remained below detection in shoots and increased by 40% (T3) in roots due to accumulation in dead cells and cell vacuoles. Overall, B. subtilis and saponin influenced the bioavailability of HMs, enzymatic activities, and bacterial abundance in the soil; plant growth indicators, antioxidants activities, and metal uptake in shoots and roots.

Evaluation of exotic oat (Avena sativa L.) varieties for forage and grain yield in response to different levels of nitrogen and phosphorous.

A field experiment was conducted during the Rabi season 2017-2018 (October-March) at the University of Agriculture, Peshawar research farm to examine the influence of different nitrogen (N) and phosphorus (P) levels on two different oat varieties: Australian and Ukrainian. The treatments included control and three levels of nitrogen and phosphorus at 30, 60, and 90 kg ha-1. The treatments were arranged in randomized complete block design (RCBD) and replicated three times. The findings showed that the oat varieties were significantly different from one another in yield and yield parameters. The Australian variety recorded higher emergence (49 plants m-2), days to emergence (15 days), days to flowering (122 days), days to maturity (145 days), plant height (142.7 cm), number of leaves (6.03 leaves plant-1), number of tillers (92.2 tillers m-1), biological yield (8,179.2 kg ha-1), and grain yield (3,725.6 kg ha-1) than the Ukrainian variety. Similarly, different N and P levels, the maximum days to emergence, days to flowering, and days to maturity were recorded in a control plot. The application of 105 kg N + 90 kg P ha-1 was statistically similar to the application of 105 kg N + 60 kg P ha-1. Maximum emergence (60 plants m-2), number of leaves (7.0 leaves plant-1), plant height (118.6 cm), number of tillers m-1 (102.6), biological yield (9,687.5 kg ha-1), and grain yield (4,416.7 kg ha-1) were determined in Australian variety. Based on the findings of this study, the Australian variety performed better in terms of yield and yield components and the application of N and P fertilizers at the rate of 105 kg N + 60 kg P ha-1 produced the best results in both oat varieties.

Arsenic speciation and biotransformation pathways in the aquatic ecosystem: The significance of algae.

The contamination of aquatic systems with arsenic (As) is considered to be an internationally-important health and environmental issue, affecting over 115 countries globally. Arsenic contamination of aquatic ecosystems is a global threat as it can enter the food chain from As-rich water and cause harmful impacts on the humans and other living organisms. Although different factors (e.g., pH, redox potential, iron/manganese oxides, and microbes) control As biogeochemical cycling and speciation in water systems, the significance of algal species in biotransformation of As is poorly understood. The overarching attribute of this review is to briefly elaborate various As sources and its distribution in water bodies and factors affecting As biogeochemical behavior in aqueous ecosystems. This review elucidates the intriguing role of algae in biotransformation/volatilization of As in water bodies under environmentally-relevant conditions. Also, we critically delineate As sorption, uptake, oxidation and reduction pathways of As by algae and their possible role in bioremediation of As-contaminated water (e.g., drinking water, wastewater). The current review provides the updated and useful framework for government and water treatment agencies to implement algae in As remediation programs globally.

Risk of heavy metals accumulation in soil and wheat grains with waste water irrigation under different NPK levels in alkaline calcareous soil.

A field study was conducted on the reuse of wastewater from Mardan city to evaluate its risk of contaminating soil and wheat grains at different NPK levels. Three irrigation sources i.e. waste water (WW), canal water (CW) and alternate waste + canal water (WW+CW) were applied to wheat (cv Atta Habib 2010) grown at 0, 50, 75 and 100% NPK levels of 120:90:60 kg N:P2O5:K2O ha-1 at Palatoo Research Farm, Amir Muhammad Khan Campus, Mardan during 2015.The results showed higher grain and biomass yields in WW irrigated plots as compared to CW at NPK levels up to 50% of recommending dose revealing supplementing nutrient requirements in deficient conditions. However, irrigation of WW at higher NPK levels especially at or beyond 75% of recommended dose tended to reduce the crop yield that could be associated with heavy metals toxicity and nutritional imbalances. The use of WW substantially increased AB-DTPA extractable Zn, Mn, Pb, Ni and Cd indicating a potential threat to soil contamination. Similarly, WW irrigated wheat had higher concentrations of these heavy metals as compared to CW which limits its use for production purposes without any remediation measures. The alternate use of CW and WW as revealed by its comparative lower contamination in soil and wheat than sole WW could be one of the possible solutions and may increase the time required for threshold soil contamination.

Biochar and urease inhibitor mitigate NH3 and N2O emissions and improve wheat yield in a urea fertilized alkaline soil.

In this study, we explored the role of biochar (BC) and/or urease inhibitor (UI) in mitigating ammonia (NH3) and nitrous oxide (N2O) discharge from urea fertilized wheat cultivated fields in Pakistan (34.01°N, 71.71°E). The experiment included five treatments [control, urea (150 kg N ha-1), BC (10 Mg ha-1), urea + BC and urea + BC + UI (1 L ton-1)], which were all repeated four times and were carried out in a randomized complete block design. Urea supplementation along with BC and BC + UI reduced soil NH3 emissions by 27% and 69%, respectively, compared to sole urea application. Nitrous oxide emissions from urea fertilized plots were also reduced by 24% and 53% applying BC and BC + UI, respectively, compared to urea alone. Application of BC with urea improved the grain yield, shoot biomass, and total N uptake of wheat by 13%, 24%, and 12%, respectively, compared to urea alone. Moreover, UI further promoted biomass and grain yield, and N assimilation in wheat by 38%, 22% and 27%, respectively, over sole urea application. In conclusion, application of BC and/or UI can mitigate NH3 and N2O emissions from urea fertilized soil, improve N use efficiency (NUE) and overall crop productivity.

Heavy metals immobilization and improvement in maize (Zea mays L.) growth amended with biochar and compost.

Soil with heavy metals contamination, mainly lead (Pb), cadmium (Cd), and chromium (Cr) is a progressively worldwide alarming environmental problem. Recently, biochar has been used as a soil amendment to remediate contaminated soils, but little work has been done to compare with other organic amendments like compost. We investigated biochar and compost's comparative effect on Pb, Cd, and Cr immobilization in soil, photosynthesis, and growth of maize plants. Ten kg soil was placed in pots and were spiked with Pb, Cd, and Cr at concentrations 20, 10, 20 mg kg-1. The biochar and compost treatments included 0, 0.5, 1, 2, and 4% were separately applied to the soil. The crop from pots was harvested after 60 days. The results show that the highest reduction of AB-DTPA extractable Pb, Cd, and Cr in soil was 79%, 61% and 78% with 4% biochar, followed by 61%, 43% and 60% with 4% compost compared to the control, respectively. Similarly, the highest reduction in shoot Pb, Cd, and Cr concentration was 71%, 63% and 78%with 4% biochar, followed by 50%, 50% and 71% with 4% compost than the control, respectively. The maximum increase in shoot and dry root weight, total chlorophyll contents, and gas exchange characteristics were recorded with 4% biochar, followed by 4% compost than the control. The maximum increase in soil organic matter and total nitrogen (N) was recorded at 4% biochar application while available phosphorus and potassium in the soil at 4% compost application. It is concluded that both biochar and compost decreased heavy metals availability in the soil, reducing toxicity in the plant. However, biochar was most effective in reducing heavy metals content in soil and plant compared to compost. In the future, more low-cost, eco-friendly soil remediation methods should be developed for better soil health and plant productivity.

Coupling Phosphate-Solubilizing Bacteria with Phosphorus Supplements Improve Maize Phosphorus Acquisition and Growth under Lime Induced Salinity Stress.

Global warming promotes soil calcification and salinization processes. As a result, soil phosphorus (P) is becoming deficient in arid and semiarid areas throughout the world. In this pot study, we evaluated the potential of phosphate-solubilizing bacteria (PSB) for enhancing the growth and P uptake in maize under varying levels of lime (4.8%, 10%, 15% and 20%) and additional P supplements (farmyard manure, poultry manure, single super phosphate and rock phosphate) added at the rate of 45 mg P2O5 kg-1. Inoculation and application of P as organic manures (Poultry and farm yard manures) improved maize growth and P uptake compared to the control and soils with P applied from mineral sources. Liming adversely affected crop growth, but the use of PSB and organic manure significantly neutralized this harmful effect. Mineral P sources combined with PSB were as effective as the organic sources alone. Furthermore, while single supper phosphate showed better results than Rock phosphate, the latter performed comparably upon PSB inoculation. Thus, PSB plus P application as organic manures is an eco-friendly option to improve crop growth and P nutrition in a calcareous soil under changing climate.

Phosphorus Nutrient Management through Synchronization of Application Methods and Rates in Wheat and Maize Crops.

Management of inorganic fertilizer is very important to obtain maximum crop yield and improved nutrient use efficiency in cereal crops. Fixation of phosphatic fertilizers in alkaline soils due to calcareousness is one of the major hurdles. It induces phosphorus nutritional stress that can decrease the yield of maize and wheat. Selection of a suitable application method and proper stage of crop for phosphorus (P) fertilizer has prime importance in better uptake of P and crop production. Among different application methods, soil and foliar application are widely adopted. In wheat and maize, knee height + tasseling and stem elongation + booting are critical stages towards P deficiency. That is why field trials were conducted to evaluate the supplemental effect of foliar P on maize and wheat yields. For that, 144 mM KH2PO4 was applied as foliar at knee height + tasseling and stem elongation + boot stages in maize and wheat, respectively. Soil application of 0, 20, 40 and 60 kg P ha-1 was done through broadcast and band methods. Results showed that foliar spray of 144 mM KH2PO4 at knee height + tasseling and stem elongation + boot stages in wheat and maize significantly enhanced grains yield and phosphorus use efficiency (PUE) where P was applied as banding or broadcast at the time of sowing. A significant decreasing trend in response to increasing soil P levels validated the efficacious role and suitability of foliar P. In conclusion, the use of P as foliar at knee height + tasseling and stem elongation + boot stages is an efficacious way to manage P fertilizer.

Author Correction: Phosphate-Solubilizing Bacteria Nullify the Antagonistic Effect of Soil Calcification on Bioavailability of Phosphorus in Alkaline Soils.

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has been fixed in the paper.

Phosphate-Solubilizing Bacteria Nullify the Antagonistic Effect of Soil Calcification on Bioavailability of Phosphorus in Alkaline Soils.

Phosphate-solubilizing bacteria (PSB) reduce the negative effects of soil calcification on soil phosphorus (P) nutrition. In this incubation study, we explored the ability of PSB (control and inoculated) to release P from different P sources [single super phosphate (SSP), rock phosphate (RP), poultry manure (PM) and farm yard manure (FYM)] with various soil lime contents (4.78, 10, 15 and 20%) in alkaline soil. PSB inoculation progressively enriched Olsen extractable P from all sources compared to the control over the course of 56 days; however, this increase was greater from organic sources (PM and FYM) than from mineral P sources (SSP and RP). Lime addition to the soil decreased bioavailable P, but this effect was largely neutralized by PSB inoculation. PSB were the most viable in soil inoculated with PSB and amended with organic sources, while lime addition decreased PSB survival. Our findings imply that PSB inoculation can counteract the antagonistic effect of soil calcification on bioavailable P when it is applied using both mineral and organic sources, although organic sources support this process more efficiently than do mineral P sources. Therefore, PSB inoculation combined with organic manure application is one of the best options for improving soil P nutrition.

Effect of wood ash application on the morphological, physiological and biochemical parameters of Brassica napus L.

The present study was conducted to determine the effect of wood ash application on different parameters of Brassica napus L. including seed germination, seedling growth, fresh and dry biomass, water content in seedlings, photosynthetic pigments, soluble sugars, total protein and cell viability. In addition, the effect of wood ash on soil microflora and accumulation of trace elements in seedlings were determined. The seeds of B. napus were grown at different doses of wood ash (0, 1, 10, 25, 50 and 100 g (wood ash)/kg (soil)) and the effect on various parameters was determined. Wood ash significantly inhibited seed germination at doses above 25 g/kg and there was no germination at 100 g/kg of wood ash. At lower concentrations of wood ash, most of the growth parameters of seedlings were stimulated, but at higher concentrations of wood ash most of the studied parameters were adversely affected. Wood ash was found to be very detrimental to B. napus when applied above 25 g/kg. Wood ash application resulted in an increased bioaccumulation of trace elements in seedlings of B. napus. Almost all trace elements were significantly higher in seedlings grown in wood ash above 10 g/kg as compared to the control. An increase in total microbial count was observed with wood ash treatment which was statistically significant at 1 and 10 g/kg of wood ash. It is concluded that at very high concentration, wood ash can be detrimental to plants; however, its application at lower application rate can be recommended.

The importance of ammonium mobility in nitrogen-impacted unfertilized grasslands: a critical reassessment.

The physico-chemical absorption characteristics of ammonium-N for 10 soils from 5 profiles in York, UK, show its high potential mobility in N deposition-impacted, unfertilized, permanent grassland soils. Substantial proportions of ammonium-N inputs were retained in the solution phase, indicating that ammonium translocation plays an important role in the N cycling in, and losses from, such soils. This conclusion was further supported by measuring the ammonium-N leaching from intact plant/soil microcosms. The ammonium-N absorption characteristics apparently varied with soil pH, depth and soil texture. It was concluded for the most acid soils especially that ammonium-N leached from litter horizons could be seriously limiting the capacity of underlying soils to retain ammonium. Contrary to common opinion, more attention therefore needs to be paid to ammonium leaching and its potential role in biogeochemical N cycling in semi-natural soil systems subject to atmospheric pollution.