Qaiser Hussain

Microbial phytase activity and their role in organic P mineralization

Plants respond to their external environment to optimize their nutrition and production potential to minimize the food security issues and support sustainable agriculture system. Phosphorus (P) is an important nutrient for plants and is involved in plant metabolic processes. It is mostly available as orthophosphate and has a tendency to form complexes with cations. It has low mobility in soil, thus becoming unavailable for plant uptake that causes a reduction in plant growth and yield. Besides free P, phytate is the major form of organic P in soil and plant tissues. Phytases obtained from different sources, that is, plants, animals, and microorganisms, catalyze the hydrolysis of phytate and release available forms of inorganic P. The knowledge of mechanisms involved in catalytic activity of phytase obtained from microorganisms in soil is limited. This review summarizes the role of microbial phytase in releasing organic P by hydrolysis of phytate and factors affecting its activity in the soil.

High-efficiency remediation of cadmium (Cd2+) from aqueous solution using poultry manure- and farmyard manure-derived biochars

ABSTRACT Farmyard manure (FYM-BC) and poultry manure (PM-BC) derived biochars were applied as adsorbents to remove Cd2+ from water. Results indicated that PM-BC was a more efficient adsorbent than FYM-BC at all experimental conditions. Maximum Cd2+ adsorption was observed at pH 4, temperature 318 K and contact time 1 h, regardless of biochar type. The Langmuir model predicted maximum adsorption capacity of 90.09 mg g−1 for PM-BC. The data fitting to pseudo-second-order model proposed chemisorption of Cd2+ onto biochars. Thermodynamics indicated that adsorption was spontaneous and endothermic. Post-adsorption analysis provided evidences of strong chemical interactions between biochars’ functional groups and Cd2+ ions.

An efficient phosphorus scavenging from aqueous solution using magnesiothermally modified bio-calcite

ABSTRACT Bio-calcite (BC) derived from waste hen eggshell was subjected to thermal treatments (calcined bio-calcite (CBC)). The BC and CBC were further modified via magnesiothermal treatments to produce modified bio-calcite (MBC) and modified calcined bio-calcite (MCBC), respectively, and evaluated as a novel green sorbent for P removal from aqueous solutions in the batch experiments. Modified BC exhibited improved structural and chemical properties, such as porosity, surface area, thermal stability, mineralogy and functional groups, than pristine material. Langmuir and Freundlich models well described the P sorption onto both thermally and magnesiothermally sorbents, respectively, suggesting mono- and multi-layer sorption. Langmuir predicted highest P sorption capacities were in the order of: MCBC (43.33 mg g−1) > MBC (35.63 mg g−1) > CBC (34.38 mg g−1) > BC (30.68 mg g−1). The MBC and MCBC removed 100% P up to 50 mg P L−1, which reduced to 35.43 and 39.96%, respectively, when P concentration was increased up to 1000 mg L−1. Dynamics of P sorption was well explained by the pseudo-second-order rate equation, with the highest sorption rate of 4.32 mg g−1 min−1 for the MCBC. Hydroxylapatite [Ca10(PO4)6(OH)2] and brushite [CaH(PO4)·2H2O] were detected after P sorption onto the modified sorbents by X-ray diffraction analysis, suggesting chemisorption as the operating sorption mechanism. GRAPHICAL ABSTRACT

Effects of chemical oxidation on surface oxygen-containing functional groups and adsorption behavior of biochar

Biochar is a beneficial soil amendment but the changes in its surface properties during the aging process, especially the oxygen-containing functional groups and the associated adsorption behaviors, are not well documented. In this paper, the aged wheat straw biochar was simulated by chemical oxidation with HNO3-H2SO4 and NaOH-H2O2 systems. Characterization results showed that carbon loss and oxygen incorporation ran throughout the aging process. Surface oxygen-containing functional groups were found to be increased in all treated biochars, especially for carboxyl. Much more developed mesopores were observed in aging biochar, specific surface area was increased by 126% for biochar treated with NaOH-H2O2, and 226% for biochar treated with 40% of HNO3-H2SO4. Thermogravimetric analysis showed that the increasing oxygen-containing functional groups led to 14% and 30% mass loss by treating biochar with alkali and acid, respectively. The improved biochar surface through the increase of oxygen-containing functional groups enhanced the cadmium sorption capacity, and the sorption capacity increased by 21.2% in maximum. Roughed surface from oxidation was another reason for increasing cadmium adsorption. Results indicated that the adsorption performance of biochar on pollutant would be changed during aging process along with the changing surface properties.

Active Soil Organic Carbon Fractions and Aggregate Stability Effected by Minimum Tillage and Crop Rotations on a Marginal Dryland Soil in Punjab, Pakistan

Conservation Agriculture (CA) is an important technique for enhancing soil organic carbon (SOC) content in the surface layer and improving structural stability. CA is not widely practiced in dryland soils of developing countries where marginal farming practices are extensively used. Therefore, a field study was conducted in dryland region of Punjab, Pakistan to compare minimum tillage and intensified cropping systems effects on active SOC fractions and aggregate stability. The experiment was laid out in a split-plot design having moldboard plough (MP) and minimum tillage (MT) as main plots, and crop sequences as sub-plots. The latter comprised of fallow–wheat (Triticum aestivum L.), (FW, control), mungbean ( Vigna radiate L.) –wheat (MW), sorghum (Sorghum bicolor L.)–wheat (SW), green manure–wheat (GW) and mungbean-chickpea (MC) (Cicer arietinum L.). Tillage systems had more pronounced effects than cropping sequences on microbial biomass carbon (MBC), potentially minerlizeable carbon (PMC) and particulate organic carbon (POC). The PMC in second year was significantly more in the soil under MT than that under

Adsorption Behaviour of Pymetrozine by Four Kinds of Biochar from Aqueous Solution

A laboratory experiment was performed to investigate the potential of biochar (BC) as an adsorbent for removing pymetrozine from aqueous solution. The adsorption data were well described by Langmuir isotherm, with maximum pymetrozine adsorption capacities of 13.8, 20.6, 11.0 and 18.8 mg g−1 for bush-, wheat straw-, peanut- and corn-derived BC in a single solution at 25 °C, respectively. The functional groups of BCs were –NH (1628.25 cm−1), –OH (3443.78 cm−1), –PO4 (1089.2 cm−1) and –C–Cl (769.23 cm−1), which were responsible for binding pymetrozine. The adsorption capacity of BC was increased by 7.2–106.4% at different solution pH (1, 3, 5 and 7). The removal efficiency increased with the addition of BCs and over 70% pymetrozine removal was observed upon addition of up to 8 g l−1. The rate of pymetrozine adsorption was fast, with 50–80% of the adsorption occurring in the first 120 minutes, followed by a much slower approach to equilibrium. The ΔG° values decreased (increasingly negative) from −165.3% to 235.9% at 298 K compared with 318 K for the adsorption of pymetrozine onto different BCs in a single solution. The study results indicate that plant residue- or agricultural waste-derived BC can act as an effective surface sorbent, but their ability to treat mixed waste streams needs to be carefully evaluated on an individual basis.

Influence of organic and inorganic passivators on Cd and Pb stabilization and microbial biomass in a contaminated paddy soil

PurposeSoil contamination with heavy metals, such as Cd and Pb, has caused severe health and environmental risks all over the world. Possible eco-friendly solutions for Cd and Pb immobilization were required to reduce its mobility through various cost-effective amendments.Materials and methodsA laboratory incubation study was conducted to assess the efficiency of biochar (BC), zeolite (ZE), and rock phosphate (RP) as passivators for the stabilization of Cd and Pb in paddy soil as well as soil microbial biomass. Various extraction techniques were carried out: a sequential extraction procedure, the European Community Bureau of Reference (BCR), toxicity characteristic leaching procedure (TCLP) test, and single extraction with CaCl2. The impact of passivators on soil pH, dissolved organic carbon (DOC), and microbial biomass (carbon, nitrogen, and phosphorus) was examined in the metal contaminated soil.Results and discussionThe results showed that the exchangeable portion of Cd in soil was significantly reduced by 34.8, 21.6, and 18.8% with ZE, RP, and BC at a 3% application rate, respectively. A similar tendency of reduction in Pb soluble portion was observed by ZE (9.6%), RP (20%), and BC (21.4%) at a 3% application rate. Moreover, the TCLP leachate of Cd and Pb was apparently reduced by 17 and 30.3% with BC at a 3% application dose, respectively, when compared to the control. Soil pH, nutrients, and microbial biomass C, N, and P were significantly increased with the addition of BC, RP, and ZE passivators.ConclusionsThe results showed that the incorporation of BC, ZE, and RP significantly reduced the Cd and Pb mobility in paddy soil as well as enhanced soil nutrients and microbial biomass. Overall, among all the amendments, rice straw derived-BC performed better for Cd and Pb immobilization in paddy soil.

Efficiency and surface characterization of different plant derived biochar for cadmium (Cd) mobility, bioaccessibility and bioavailability to Chinese cabbage in highly contaminated soil

Cadmium (Cd) contamination in red soil has become a serious environmental concern due to its toxic effects on organisms and the food chain. Possible eco-friendly solutions for Cd immobilization were required to reduce its mobility through biochar. This study evaluated the comparative efficiency of rice straw (RSB), rice hull (RHB) and maize stover (MSB) derived biochar (BC) on Cd mobility and its accumulation in Chinese cabbage (Brassica chinensis L.), which is highly Cd accumulating crop. Results showed that the soil chemical properties (pH, organic carbon and nutrients) significantly increased with increasing the biochar application rate from 1.5% to 3%. Concentration of Cd decreased in CaCl2 extract by 58.6, 39.7 and 46.49% and in toxicity characteristics leaching test (TCLP) by 42.9, 32.7 and 36.7% for RSB, RHB and MSB, respectively at 3% application rate. The simple bioaccessibility extraction test (SBET) techniques showed a significant decrease in Cd by 30.5, 20.6 and 27.5% for RSB, RHB and MSB, respectively at the 3% application rate. Moreover, the Cd contents in the cabbage shoots decreased by 25, 21.3 and 23.1% for RSB, RHB and MSB at a 3% application rate and in the roots by 31.3, 23.9 and 26.5% for RSB, RHB and MSB at a 3% application rate, respectively. Bioaccumulation (BCF) and translocation factors (TF) were significantly decreased upto 26.5% and 11%, respectively among all biochar types. Overall, RSB demonstrated positive results as soil amendments for Cd immobilization and thereby, reducing its bioavailability in the Cd contaminated soil to mitigate food security risks.

Interactive Use of Biochar and Chemical Fertilizer on Soil Nutrients (NPK), Soil Water Retention and Biological Nitrogen Fixation by Mash Bean

Loss of soil fertility, reduction in soil productivity and water scarcity is the major limitation of rain fed area of Pakistan. Applications of biochar on low fertile and degraded soil enhance soil fertility, nutrients uptake and water retention thus improves soil productivity. Field study was conducted to examine the effect of biochar on biological nitrogen fixation (BNF) by mash bean (Vigna mungo. L), soil nutrients availability and soil water retention. Biochar was applied at 0, 0.25 and 0.5 t ha-1 along with and without chemical fertilizer (20, 50, 50 kg ha-1 NPK) with four replications. Crop was harvested at maturity and soil samples were collected from each experimental plot before sowing and after harvesting and was analyzed for soil ECe, soil pH, total nitrogen, phosphorus, potassium, soil infiltration rate, soil aggregate stability, soil water retention and cation exchange capacity (CEC). Biological nitrogen fixation was determined by xylem-sap method and xylem sap was extracted at pod filling stage. Soil treated with biochar @ 0.5 t ha-1+chemical fertilizer (NPK 20, 50, 50 kg ha-1 respectively) showed maximum pH (7.78) and soil electrical conductivity (0.67 ds m-1). Application of biochar and chemical fertilizer to soil (0.5 t ha-1+NPK 20,50,50 kg ha-1) increases total N from 3.9 mg kg-1 to 18 mg kg-1, Phosphorus from 4 mg kg-1 to 18.5 mg kg-1, potassium from 98 mg kg-1 to 143 mg kg-1 and soil CEC from 6.6 Cmolc kg-1 to 11.2 Cmolc kg-1. Biochar @ 0.5 t ha-1 stabilized soil aggregates (34%) and improves soil infiltration rates (164 mm h-1) without impacting any significant effect on soil water retention. Biochar applied @ 0.5 t ha-1 along with chemical fertilizer (NPK 20, 50, 50 kg ha-1 respectively) showed maximum increase in BNF (24 kg N ha-1), biomass yield (2.7 t ha-1) and grain yield (1.8 t ha-1). The study concluded that biochar application (0.5 t ha-1) along with chemical fertilizer increase availability of nutrients (NPK), soil pH and ECe where as sole application of biochar (0.5 t ha-1) promoted aggregation and infiltration rate. The significant increase was observed in case of BNF (40%), grain yield (77%) and biomass yield (64%) of mash bean. It is recommended that biochar application to soil along with chemical fertilizer improve soil productivity and BNF by mash bean.