Lysis of mycelium ofFusarium oxysporum f. sp.udum in soil amended with organic matters

Summary Autoclaved or natural field soil amended with 0.1 to 5.0 per cent (W/W) of margosa cake, rice husk and sawdust with or without supplemental nitrogen were tested for lytic activity and bacterial numbers. Generally, non-amended autoclaved soil caused little or no lysis of mycelium ofF. oxysporum f. sp.udum; non-amended natural soil caused more lysis. Amendment of soil with margosa cake, rice husk or saw-dust with or without supplemental nitrogen greatly enhanced its lytic effect on the fungus. The degree of lysis depended on the dosage of amendment used and the stage of its decomposition in the soil. The extent of lysis increased as the bacterial population increased. Amongst bacteria,Bacillus subtilis was very common in most lytic zones.     

Contribution of bacterial cell nitrogen to soil humic fractions

Summary Living cells ofSerratia marcescens, uniformly labelled with¹⁵N, were added to samples of maple (Acer saccharum) and black spruce (Picea mariana) forest soils. After different periods of incubation from zero time to 100 days, the soils were subjected to alkali-acid and phenol extraction to provide humic acid, fulvic acid, humin and humoprotein fractions. Significant amounts of the cell nitrogen were recovered in the humic and fulvic acids immediately after addition. After incubation, less cell, nitrogen appeared in the humic acid and more in the fulvic acid. The amount of cell nitrogen recovered in the humin fraction increased with incubation. Roughly 5 to 10 per cent of the added cell nitrogen was found as amino acid nitrogen from humoprotein in a phenol extract of the humic acid. The data are consistent with the occurrence of co-precipitation of biologically labile biomass nitrogen compounds with humic polymers during the alkaline extraction procedure involved in the humic-fulvic fractionation.     

The relation between nitrogen percent and dry weight of inoculated legumes

Summary Results of numerous tests of tropical and temperate legume hosts and Rhizobium strains accumulated between 1952 and 1966 were examined for a relation between N percent (y) and dry weight per plant (x). The data fitted the equation y=A–be^–cx. The most effective Rhizobium strains can be selected on the basis of dry matter yields of whole plants or plant tops only, without the need for N analyses, using statistical analyses. A previously proposed method which employs the linear relation between N-yield and dry matter yield was shown to apply only when data for strains which are not fully effective are excluded.It is postulated that symbiotically fixed N forms a different compound from that resulting from applied mineral N and that this compound cannot be remobilised before flowering.deceased     

Nitrogen mineralization in acid sulfate soils

Summary Mineralization of soil nitrogen studies with two acid sulfate soils under anaerobic and aerobic incubation at 30°C for 2 weeks showed that the mineral N was released and accumulated entirely as NH ₄ ⁺ in both soils. Nitrification did not occur in either of the soils under conditions that stimulate nitrification. The acid sulfate soils studied release good amounts of mineralizable N, and, because of lack of nitrifying activity, denitrification may not be a serious problem in these soils.     

Effect of heating on properties of some soils from Southern Nigeria and growth of rice

Summary The effect of heating on the properties of Apomu (Psammentic Usthorthent), Egbeda (Oxic Paleustalf) and Gambari (Typic Plinthustalf) surface soils were studied under laboratory conditions. Heating at low temperatures (100°C) have no detrimental effects on soil properties, on the contrary it increased the soil extractable P, Mg, Fe, Mn and Zn levels. Pronounced reductions in total N, Org. C, Org. P and extractable Ca and Mg levels and marked increases in extractable P, Zn, Mn and Fe were observed by heating to 200°C. Heating to 500° had an adverse effect on soil chemical and physical properties.Plant height and dry matter yeild of rice plants were higher when grown on Egbeda soil previously heated to 100°C. With addition of N, P and K there was no observed beneficial effect of the heating treatment. Rice plants grown on Egbeda soil previously heated to 200°C showed high uptake of Mn. Plants grew badly in soil previously heated to 500°C.     

Benthic macroinvertebrates of northwestern lake victoria,East Africa: Abundance,distribution, intra-phyletic relationships and relationships between taxa and selected element concentrations in the lake-bottom sediments

Phytoplankton assemblage and seston composition of the San José's gulf (Argentine, 42° S) were studied during a period of two years. Cell counts, chlorophyll, particulate nitrogen and particulate carbon determination were made. Phytoplankton synecology was studied using principal component analysis.

     

Distribution and movement of toxaphene in anaerobic saline marsh soils

The biological oxygen demand (BOD) of filtered water from Lake Wingra, Wisconsin is significantly higher in the littoral zone than in the pelagial zone. Laboratory experiments indicate that BOD is not influenced by water temperature at the time of sampling or by enrichment with nitrate or ammonia. Rather, enrichment with macrophyte leachate sharply increases BOD, and enrichment with phosphate produces a small but significant increase in BOD. We conclude that high BOD in littoral waters of the lake is an indication of production of labile organic matter in the water by dense beds of the macrophyte Myriophyllum spicatum.     

Assessment of surface sediment dynamics and response of benthic macrofauna assemblages in Boughrara Lagoon (SW Mediterranean Sea)

A study was conducted in the spring of 2009, the winters of 2010 and 2013, and in the summer of 2012 at 13 stations in Boughrara Lagoon, Tunisia (southern Mediterranean). The country⿿s largest lagoon, it is considered to be an anthropogenically stressed area, though a major tourist centre⿿Djerba Island⿿is located along its northern shores. The lagoon bottoms were studied via analyses of grain size, surface sediment composition, total organic matter (TOM) and through the trophic and functional organisation of benthic macrofauna. The results indicate that the bottoms are composed of fine, medium or coarse sands and that sediment distribution is controlled by water movement. Estimation of TOM content revealed that the studied samples present both normal and imbalanced sediments. The structure and organisation of the lagoon⿿s benthic macrofauna are dominated by select deposit feeders and underwent significant changes during the period 2010⿿2013.Subjected for decades to increased pollution due to growing human activities in the surrounding area, Boughrara Lagoon now appears to be impacted by certain environmental/anthropogenic stressors, as indicated by the presence of pollution-tolerant bio-indicator species in the imbalanced area. The response of the lagoon ecosystem to changes in benthic sediment deposition provides a potential assessment tool for similar habitats elsewhere.     

A rapid method for the determination of microbial biomass by dry weight using a moisture analyser with an infrared heating source and an analytical balance

Aims: Microbial biomass is an important biotechnological parameter. The traditional method for its determination involves an oven‐drying step and equilibration to room temperature before weighing, and it is tedious and time consuming. This work studied the utilisation of a moisture analyser consisting of an efficient infrared‐heating module and an analytical balance for the determination of microbial biomass by dry weight. Methods and Results: The method duration depended on the sample volume and was between 7 and 40 min for sample volumes of 1–10 ml. The method precision depended on the total dry weight analysed – 10 mg of total dry weight being sufficient to achieve coefficients of variation of 5% or less. Comparison with the conventional oven method provided a correlation coefficient r² of 0·99. The recovery of an internal standard ranged between 94·2 and 106·4% with a precision of 1·39–4·53%CV. Conclusions: Validation revealed sufficient method accuracy, precision and robustness and was successfully applied to the study of yeast and bacterial growth kinetics. Techniques are discussed that allow for increased method precision at low biomass concentrations, and equations are provided to estimate required drying time and method precision based on sample volume and total sample dry weight, respectively. Significance and Impact of the Study: This work presents a rapid method for the determination of microbial biomass, allowing for the timely implementation of biomass‐based information in biotechnological and laboratory protocols.