Ibrahim Mohamed

Microcalorimetric assessment of microbial activity in long‐term fertilization experimental soils of Southern China

Microcalorimetry, plate count and PCR-denaturing gradient gel electrophoresis (DGGE) were employed to investigate microbial diversity and activity in soils from the Red Soil Experimental Station of the Chinese Academy of Agricultural Sciences, Hunan Province, China, where a wheat-corn rotation with 12 fertilization treatments was established in 1990. Fertilization greatly increased microbial biomass carbon (C) and nitrogen (N) (C(mic) and N(mic)) as well as the activities of phosphatase, urease, invertase, protease, catalase and dehydrogenase. Manure alone (M) enhanced the number of denitrifying and aerobic bacteria by 54.4% and 20.5%, respectively, whereas fallow (H) increased the number of aerobic cellulose decomposing bacteria by 31.4%. Fallow and soils amended with mineral fertilizers plus pig manure or straw increased both the DGGE band patterns and the Shannon index compared with mineral fertilizers or the control. Mineral treatments with lower bacterial numbers enhanced the values of the peak time (t(max)) more than did organic treatments. The peak height (P(max)) was positively correlated (P<0.01), with soil enzymes, C(mic) and N(mic), and the number of microorganisms, whereas the peak time (t(max)) was negatively connected (P<0.01) with these parameters. The microbial growth rate constant (k) was linked to bacteria (P<0.01), actinomycetes (P<0.05) and catalase (P<0.05). The total heat evolution (Q) had no relationships with any soil microbial properties (except for catalase). We propose that P(max) and t(max) could be used as indices of soil microbial activity, while the values of k and Q are poor indicators.

Microcalorimetric evaluation of soil microbiological properties under plant residues and dogmatic water gradients in Red soil

Abstract A study of 6 months duration was carried out to investigate the effect of water regimes and organic amendments on the soil microbial biomass and microbial population under Red soil collected from Hunan Providence, China. The soil microbial biomass and population were measured with traditional methods and results obtained by conventional methods, corroborated with microcalorimetry. The incorporation of rice (Oryza sativa L.) straw (RS) and green manure (GM), especially at high rates, enhanced the soil microbial activities. We observed that the use of GM exhibited more significant stimulating effects on microbial activities than RS. Similarly, water regimes, 25% (W1) and 200% (W2) of water holding capacity, also had significant effects on microbial activities. Comparing the effects of water levels, we noticed that W2 had a significant negative influence on soil microbial biomass and population. To compare the results of conventional methods and to check the sensitivity of microcalorimetry, the thermodynamic parameters, microbial growth rate constant (k), total heat evolution (Q), peak height (Pmax) and peak time (tmax) were calculated. Highest Pmax, k and Q were observed in GM treatments at water regime W1, while highest tmax values were recorded in CK (control) and RS treatments at W2. The microcalorimetric parameters, Pmax, k and Q were positively correlated, whereas tmax negatively linked with microbial biomass and population at p < 0.01. Our results suggest that microcalorimetry successfully verified the results obtained from customary methods and microcalorimetric parameters Pmax, tmax, Q and k proved that they are highly sensitive to microbial properties and could be used as indices of microbial community shifts and activities in soil ecosystems.

Field evaluation of intensive compost application on Cd fractionation and phytoavailability in a mining-contaminated soil.

A field experiment was conducted to investigate the effect of chicken manure compost on the fractionation of cadmium (Cd), soil biological properties and Cd uptake by wheat in a soil affected by mining activities in Hubei province, China. Compost was applied at five levels (0, 27, 54, 108, 216xa0txa0ha−1), and winter wheat (Triticum aestivum L.) was chosen as an indicator plant. Results showed that the application of compost increased soil pH and the content of total phosphorus and organic matter. Soil biological properties such as microbial biomass carbon, invertase, protease, urease and catalase activities were significantly enhanced by 0.24–3.47 times after compost application. Sequential extraction indicated that compost amendments decreased the acid-extractable Cd by 8.2–37.6xa0%, while increased the reducible and oxidisable Cd by 9.2–39.5 and 8.2–60.4xa0%, respectively. The addition of 27–54xa0txa0ha−1 compost reduced Cd content in wheat stems and seeds by 69.6–75.0xa0% and 10.3–18.4xa0%, respectively. However, only 25.5–26.5xa0% reductions in Cd content in wheat stems were observed in 108–216xa0txa0ha−1 compost amendments, and no significant decrease was detected for seeds. This study suggests that although compost is a suitable organic amendment to improve soil fertility and biological activities, the addition of compost should be moderated by an appropriate rate to optimize the use of compost for the reclamation of metal-contaminated soils at field scale.

Effects of water and potassium stresses on potassium utilization efficiency of two cotton genotypes

Potassium utilization efficiency (KUE) for plants is related to genotype difference, soil characteristics, application of fertilizer and irrigation. Up to now, the KUE of different genotypes worldwide has been extensively studied, but the influence of environment stress on KUE of cotton is infrequently reported. Thus, we selected a high K utilization efficiency cotton genotype (HEG) and a low K utilization efficiency cotton genotype (LEG) as indicator plants. The results showed that both soil water stress and K stress limited the growth of cotton genotypes. The change of soil water levels had significant influence on yield, KUE, rates of fallen leaves and bolls (RF), biomass and potassium accumulation in cotton. Deficient of soil water restricted the uptake and translocation of K. The absence of soil K greatly increased the proportion of biomass of reproductive organs and K distribution to reproductive organs in this experiment. The HEG exhibited higher physiological compared with LEG under the stress conditions, especially under low K treatment.

Cow manure-loaded biochar changes Cd fractionation and phytotoxicity potential for wheat in a natural acidic contaminated soil

The current study aims to investigate the implications of amending a soil contaminated with Cd with peanut residues biochar (BP) solely or in combination with cow manure (CMPB) at different rates on phytotoxicity of Cd for wheat plants and its distribution in a mine contaminated soil. Soil pH and EC increased progressively in soils amended with either PB or CMPB. Exchangeable Cd was decreased while its non-exchangeable fractions were increased. Dry weights of wheat straw, roots and grains increased when soils amended with either PB or CMPB, especially at the higher application rate. Such increases were correlated significantly with the extractable soil-Cd. Concentrations of Cd in roots were higher than those in straw; whereas, the concentrations in grains seemed to be the lowest. Generally, values of bio-concentration and translocation factors did not exceed 1 and decreased with application of either PB or CMPB. In conclusion, enriching biochar with cow manure is a recommended strategy to reduce Cd uptake and translocation to straw and seeds. Moreover, Concentrations of Cd did not exceed the permissible levels in grains when soils amended with the highest rate of CMPB.

Interpreting soil CO2 transport and production in oasis cotton field, central Asia

In order to explore soil profile CO2 transport and production, values of vertical soil profile CO2 concentration, moisture and temperature were measured continuously during whole cotton growing season in oasis cotton field of Aksu National Experimental Station of Oasis Farmland Ecosystem, central Asia. Simultaneously, soil CO2 efflux was measured by chamber system to assess the deducing result by Fick’s first law. In our experiment, soil CO2 effluxes were determined by two related intimately methods. Soil CO2 releasing at 0–20 cm depth was calculated by gas transport equation and was found to be closely related to soil CO2 efflux. However, mean values of soil CO2 production at 0–20 cm depth were less than those of soil CO2 efflux during the whole cotton growing season. Moreover, there were some negative values of CO2 production at 0–20 cm depth found during the experimental period.

Evaluation of mannose-binding lectin serum level in prediction of neonatal sepsis

Background Despite improved neonatal care over the past decades, infections remain common and sometimes life threatening in neonates admitted to the neonatal ICU. Neonatal sepsis has the highest morbidity and mortality. Objective The aim of the study was to evaluate mannose-binding lectin (MBL) serum level as a marker for prediction of neonatal sepsis. Patients and methods This prospective case-control study was conducted on 90 neonates admitted to the neonatal ICU. The 90 neonates were divided into two groups: the patient group and the control group. The patient group included 45 cases with neonatal sepsis and the control group included 45 healthy neonates. Serum levels of MBL were measured by immunoassay. The results were tabulated and analyzed with SPSS. Results Serum MBL levels were significantly lower in the neonates with sepsis than in the control group (0.455 ± 0.245 vs. 1.212 ± 0.249 μg/ml; P < 0.001). The lowest MBL levels were detected in those infants with septic shock. MBL had high sensitivity (97.7%) and specificity (86.6%) as well as positive (88%) and negative (97.5%) predictive values to detect sepsis. Conclusion and key messages MBL serum level could be considered a sensitive and specific marker for prediction of neonatal sepsis. Neonates with significant decrease in MBL are at increased risk for developing sepsis and septic shock.