Khalid Saifullah Khan

Changes in microbial biomass and P fractions in biogenic household waste compost amended with inorganic P fertilizers.

The present study was conducted to evaluate the changes in microbial biomass indices (C, N, and especially P) and in P fractions in compost amended with inorganic P fertilizers. In the non-amended control, the average contents of microbial biomass C, N, and P were 1744, 193, and 63 microg g(-1) compost, respectively. On average, 1.3% of total P was stored as microbial biomass P. The addition of KH(2)PO(4) and TSP (triple super phosphate) led to immediate significant increases in microbial biomass C, N, and P. Approximately, 4.6% of the added TSP and 5.8% of the added KH(2)PO(4) were incorporated on average into the microbial biomass throughout the incubation. Approximately, 4.7% of the 1mg and 5.8% of the 2mg addition rate were incorporated on average into the microbial biomass. In the amendment treatments, the average contents of microbial biomass C, N, and P declined by 44%, 64%, and 49%, respectively. Initially, the average size of the P fractions in the non-amended compost increased in the order (% of total P in brackets) resin P (0.7%)<NaOH-extractable P(i) (inorganic P, 3.0%)<NaOH-P(o) (organic P, 6.9%)<NaHCO(3)-P(i) (11.9%)<NaHCO(3)-P(o) (17.0%)<residual P (24.6%)<HCl-P (35.7%). Initially, the relative contributions of the P fractions in the amended compost treatments increased in the order: NaOH-P(i) (1.0%)<resin P (2.5%)<NaOH-P(o) (4.5%)<NaHCO(3)-P(o) (4.9%)<residual P (14.8%)<HCl-P (15.2%)<NaHCO(3)-P(i) (57.1%). At the end of the 56-day incubation, the largest and highly soluble fraction of NaHCO(3)-extractable P(i) had decreased in place of the less soluble fractions NaOH-extractable P(i) and P(o), but especially HCl-P, but not in place of the insoluble fraction of residual P. The microbial biomass is able to rapidly store significant amounts of easily soluble P and to prevent it from adsorption or other fixation processes.

Comparison of methods for measuring heavy metals and total phosphorus in soils contaminated by different sources

The relationships between the concentrations of zinc (Zn), lead (Pb), copper (Cu), nickel (Ni) and chromium (Cr) as measured by X-ray fluorescence analysis (XRF), aqua regia, and HNO3 pressure digestion were studied in soil samples covering a wide range of heavy metal concentrations. The soils were contaminated by sewage sludge, exhaust depositions, river sediments of mining residues, and dump material. The question was addressed whether the source of heavy metals or other soil properties affect the relationship between these three methods. The aqua regia-digestible fraction of the five heavy metals reached on average 64% of the XRF-detectable content. The pressure accelerated HNO3-digestible fraction of the five heavy metals was on average 71% of the XRF-detectable content; the respective phosphorus (P) fraction reached a median of 75%. This suggests that HNO3 pressure digestion can also be used for characterizing the total P content of soils. Aqua regia extraction and HNO3 pressure digestion gave similar values for Zn, Pb, and Cu, which dominate the heavy metal load of most contamination sources. Significantly higher Cr values were obtained by HNO3 pressure digestion than by aqua regia extraction. Additionally, the Cr contents were affected by the source, e.g. sewage sludge had relatively high contents of aqua regia and HNO3 pressure extractable contents in comparison to the XRF values. The element-specific relationships between the three methods were all highly significant. However, the respective multiple linear regression models were in most cases affected by soil organic carbon (C), in some cases by clay or soil pH.

Microbial biomass, nutrient availability and nutrient uptake by wheat in two soils with organic amendments

A 72-day greenhouse pot experiment was conducted with a sandy loam or a silt loam soil to examine the effects of farmyard manure (FYM), poultry litter (PL) and biogenic waste compost (BWC) at 10 g dw kg-1 soil on microbial biomass and activity and growth and nutrient uptake by wheat. Soil samples were collected at days 0, 14, 28, 42, 56 and 72 after planting. Growth and nutrient uptake by wheat were determined on day 72. All three amendments increased microbial biomass C, N and P, dehydrogenase activity, plant growth and nutrient uptake with a greater effect by FYM and PL than by BWC. All amendments increased microbial biomass C, N and P and enzyme activity particularly on day 0. These microbial parameters decreased after day 0 indicating microbial biomass turnover. All amendments increased plant growth and nutrient uptake. It is concluded that organicamendments can stimulate microbial growth and nutrient uptake as well as plant growth and nutrient uptake. Microbes can increase plant nutrient availability by nutrient mobilisation but also because nutrients taken up by the microbial biomass initially could become available to plants when the microbial biomass turns over as the easily available C is depleted.

Development of ergosterol, microbial biomass C, N, and P after steaming as a result of sucrose addition, and Sinapis alba cultivation

A pot experiment was carried out to monitor the recovery of a steaming-reduced microbial biomass (C, N, and P) and fungal ergosterol by sucrose addition. The second objective was to investigate the recovery of a steaming-reduced microbial biomass by white mustard (Sinapis alba) cultivation and its interactions with microbial residues, freshly formed from sucrose addition. Thirty days after steaming, the soil microbial biomass C and N was still significantly reduced by 80%, leading to a rather constant microbial biomass C/N ratio around 7 throughout the experiment. The steaming-induced decreases of microbial biomass P and ergosterol were only roughly 50%, leading to a decrease in the microbial biomass C/P ratio and an increase in the ergosterol-to-microbial biomass C ratio. Sucrose addition led to a 25% reduction in the ergosterol-to-microbial biomass C ratio. Mustard cultivation had significant positive effects on microbial biomass C, N, P, and ergosterol, but the effects were smaller than those of sucrose addition. Cultivating mustard had no significant effects on the C loss or on the incorporation of sucrose C into the microbial biomass. In contrast, the application of sucrose led to a significant decrease in the mustard shoot biomass and especially in the mustard root biomass.

Relationship of Phosphorus Uptake with Its Fractions in Different Soil Parent Materials

The objectives were to determine inorganic P fractions in selected parent material soils and to develop a relationship of various P fractions with P uptake by Zea mays . Experimental study was conducted at Soil Chemistry Laboratory, Department of Soil Science and Soil and Water Conservation, Pir Mehr Ali Shah Arid Agriculture University, Rawalpindi, Pakistan, during February, 2013 to January, 2014. Triplicate soils were selected at three different level of development in each of loess, alluvium, shale residuum, and sandstone residuum, and surface and subsurface samples were taken. Samples were analyzed for pH, soil test P, total P, CaCO 3, dissolved and total organic carbon, dithionite extractable and amorphous iron. Soil P was fractioned into Ca 2-P, Ca 8-P, P adsorbed by Fe and Al, P occluded in iron oxides bodies, and apatite-P. Apatite-P was 33-71 %, and secondary phosphates i.e. occluded P, iron oxides surface adsorbed P and aluminum oxides surfaces adsorbed P ranged between 0.80 – 4.0 %, 2.65 – 14 % and 1.20 – 5.0 % of total P, respectively. Phosphorus uptake also differed significantly with soil parent material. The bioavailability of soil P fractions follow the order Ca 2-P > Org-P > Al-P > Fe-P > Ca 8-P > Occluded P > apatite-P. Dicalcium phosphates, iron adsorbed P, aluminum oxides adsorbed P and organic P control P bioavailability in Zea mays . Olsen P and occluded P gave better prediction for P uptake rather than Olsen P alone. This study will help to improve P fertilizer management and ultimately result in increase crop production. Original Research Article

Use of Coal Derived Humic Acid as Soil Conditioner to Improve Soil Physical Properties and Wheat Yield

In Pothwar area of Punjab Pakistan (33 o N to 74 o E), intensive soil tillage, soil erosion and low crop residue input are the reasons which have lead to the deterioration of soil structure. Structurally unstable soils are more susceptible to erosion which, in turn, leads to poor crop productivity. Therefore, a field study was conducted in dry land region of Punjab, Pakistan to improve soil physical health at campus of University R esearch Farm (PMAS Arid Agriculture University, Rawalpindi). Two different grades (Laboratory and commercial grade) of humic acid along with eight levels were applied for two years. The treatments were HL 0 (control), HL 1 10 kg H.A ha - 1 , HL 2

Impacts of long-term application of buctril super (bromoxynil) herbicide on microbial population, enzymes activity, nitrate nitrogen, Olsen-P and total organic carbon in soil

Long-term impact of buctril super (bromoxynil) herbicide in the wheat fields on soil microbial population, nitrate-N, Olsen-P, total organic carbon (TOC) and enzyme activities was evaluated in 18 sites in Pakistan. Nine sites were randomly selected from those places where bromoxynil herbicide had been used for the last 10 years designated as soil ‘X’ and other nine where no herbicide was used in that period designated as soil ‘Y’. Very importantly, it was found that long-term application of this herbicide in wheat fields reduced the actinomycetes and fungi population up to 19.7 and 14.3%, respectively, urease and dehydrogenase activity by 17.5 and 28.2%, respectively, and reduced nitrate-N, Olsen-P and TOC up to 55, 17 and 28.57%, respectively. Presence of high clay and organic matter contents enhanced the detrimental effect of herbicide by prolonging its persistence as compared to light-textured soils with low organic matter. As in Pakistan this herbicide is being used most frequently in wheat fields, data are scarce on the long-term effect of this herbicide on soil microbial activities and soil health. These findings could give new insights about the use of alternate herbicide in wheat fields, particularly in clay-textured and high organic matter contained soils for maintaining soil health.

Microbial use of sugarcane filter cake in an artificial saline substrate varying in anion composition and inoculant at different temperatures

An incubation experiment was carried out with the objective of assessing the short-term effects of sodium salts with different anions (Cl–, SO42–, HCO3–), saline and non-saline inoculants, and two temperature levels (20°C and 40°C) on microbial activity and biomass indices, using sterile quartz sand amended with sugarcane filter cake. Addition of NaCl significantly decreased CO2 production, O2 consumption, and ergosterol content; addition of Na2SO4 increased microbial biomass N, whereas addition of Na2CO3 increased the contents of K2SO4 extractable C and N. The inoculation with a saline soil significantly reduced respiration and resulted in higher respiratory quotients (RQ) as well as higher contents of microbial biomass and ergosterol. The rise in temperature increased CO2 production (+60%) and O2 consumption (+93%), leading to a 13% decrease in RQ values. The rise in temperature also led to significant increases in the contents of extractable C (+30%) and N (+42%) as well as ergosterol (+64%). The increased RQ values and the specific decline of extractable C and N in the bicarbonate treatment revealed the increased use of the mobile fraction by microorganisms, especially fungi adapted to saline and alkaline conditions.

Mesophilic Anaerobic Co-digestion of Cattle Manure with Malus domestica and Dalbergia sissoo during Biomethane Potential Assays

The burning of cattle manure for domestic use, and plant biomass left out in fields, is a common practice in South Asia, specifically Pakistan. According to the 2014 government of Pakistan (GOP) survey, Pakistan had 171 million head of cattle that would produce 345 billion kg of manure, which could easily be converted into 150 billion m3 of biogas. The focus of the present study was to evaluate the benefits from co-digestion of cattle manure (CM) with Dalbergia sissoo leaves (DSL) and Malus domestica leaves (MDL), with a focus on changes in the biodegradability, C/N ratio effect, and synergistic effect. The idea was to adjust the C/N ratio to increase biodegradability at mesophilic range to help the process to produce more methane than 100% manure-based digestion. First, the ideal pH and temperature conditions for mesophilic anaerobic digestion (AD) were optimized to carry out further co-digestion under the same conditions. The results of co-digestion revealed a 40% (251 NmL CH4/g VS) increase in methane yield by replacing 20% of volatile solid in CM-based AD reactors with MDL. This combination also presented a biodegradability of 59% and a synergistic effect (θ) value of 1.40, which corresponded to highly positive synergism reflecting the optimum growth conditions. The DSL/CM co-digestion also followed the same pattern, and the maximum methane yield of 229 NmL CH4/g VS was obtained using a 20/80 DSL/CM combination.