The abundance of Trichoderma propagules and the distribution of species in forest soils

Propagules of Trichoderma generally formed less than 3 per cent of the total fungal propagules in a variety of forest soils in the southeastern U.S. and Washington State. The largest populations were found in the F and H organic horizons of the forest floor or under conditions of excessive moisture. T. viride Pers. ex S.F. Gray and T. polysporum (Link ex Pers.) Rifai were largely restricted to cool temperate regions; whereas, T. harzianum Rifai was characteristic of warm climates. T. koningii Oud. and T. hamatum (Bon.) Bain, were the most widely distributed species aggregates and were found in all the climatic regions investigated. Under conditions of excessive moisture, strains of T. hamatum and T. pseudokoningii Rifai were the dominant forms.     

Residual fumigant effect of 1,2-dibromoethane (EDB) in fumigations against queensland fruit fly,Dacus tryoni (froggatt), infestations in mangoes

A residual fumigant effect is demonstrated for fruit held 1 to 3 days within its cardboard carton after fumigation with 1,2-dibromoethane (EDB). This residual fumigant effect reduces significantly the dosage required for a specified level of control when compared with that required for fruit removed from the carton immediately after airing when fumigation is completed. The effect is due to the slow release of gas sorbed during fumigation and to the slow dispersion of this gas from the carton.     

Comparison of the serum pharmacokinetics of a long acting and a conventional oxytetracycline injection

A crossover study was carried out in cattle to determine the serum pharmacokinetics of a standard dose (20 mg/kg bodyweight) of oxytetracycline given either as a conventional injectable formulation or as a long acting formulation. For reference purposes, an intravenous treatment (also given at 20 mg/kg) was included in the trial protocol. A comparison of the two treatment regimes showed that the long acting formulation gave a significantly lower peak oxytetracycline serum concentration, with a significant extension of drug serum concentration. The long acting formulation also showed a longer serum half life and a significantly greater area under the curve value, calculated from 36 hours onwards, together with serum oxytetracycline concentrations which exceeded 0.5 microgram/ml for 86.8 as opposed to 51.5 hours for the conventional formulation. It is concluded that the use of the long acting formulation in cattle leads to a more sustained serum oxytetracycline concentration than does the same dose of conventional formulation.     

Management of inappetant sheep during export by sea

In the first of 2 experiments, a simulated voyage was conducted to examine the effects of various treatments on bodyweight change and feeding frequency of inappetant sheep at the end of lot-feeding (non-feeders). The treatments, applied during simulated shipping, were: normal quantities of feed and length of troughs; extra trough length; extra feed. Adult Merino wethers (n = 108) were used in each treatment. A voyage to the Middle East was then conducted to establish whether shipboard mortality could be reduced by separating non-feeders (n = 305) from feeders (n = 5,620) late in the feedlot hase and housing the groups separately aboard ship. A control group of non-feeders (n = 215) mixed with feeders (n = 5,732) was used for comparison. Bars (marker bars), containing a coloured dye, were attached to feed troughs to mark sheep that fed. Most non-feeders (82%) began eating when placed in shipping pens in both studies. However, there was no significant difference in percentage of sheep that fed between non-feeders given extra trough length or extra feed compared with non-feeders given standard management at any stage of simulated shipping. There was no significant difference in mean bodyweights between treatment groups on days 1, 8 and 15 of simulated shipping. Differences in bodyweight on d 22 were probably associated with different levels of gut fill. Death rates were not significantly different in separated and control groups (1.1%, 0.9%, P = 0.6) in the voyage of 14 d to the Middle East.(ABSTRACT TRUNCATED AT 250 WORDS)     

桉树人工育种方法学

引言改良商业林的种植材料是一个长期不断的过程。种子最初是从自然林分和人工林的实生苗中采取;后来是采用林木选优,它是根据树木的特征,如材积、早期生长情况或抗病性来选择。可通过选出最好的基因进行组合,以进一行提高控制杂交群体增益。     

PROGRESS ON IMPROVING AGRICULTURAL NITROGEN USE EFFICIENCY: UK-CHINA VIRTUAL JOINT CENTERS ON NITROGEN AGRONOM

● Virtual joint centers on N agronomy were established between UK and China. ● Key themes were improving NUE for fertilizers, utilizing livestock manures, and soil health. ● Improved management practices and technologies were identified and assessed. ● Fertilizer emissions and improved manure management are key targets for mitigation. Two virtual joint centers for nitrogen agronomy were established between the UK and China to facilitate collaborative research aimed at improving nitrogen use efficiency (NUE) in agricultural production systems and reducing losses of reactive N to the environment. Major focus areas were improving fertilizer NUE, use of livestock manures, soil health, and policy development and knowledge exchange. Improvements to fertilizer NUE included attention to application rate in the context of yield potential and economic considerations and the potential of improved practices including enhanced efficiency fertilizers, plastic film mulching and cropping design. Improved utilization of livestock manures requires knowledge of the available nutrient content, appropriate manure processing technologies and integrated nutrient management practices. Soil carbon, acidification and biodiversity were considered as important aspects of soil health. Both centers identified a range of potential actions that could be taken to improve N management, and the research conducted has highlighted the importance of developing a systems-level approach to assessing improvement in the overall efficiency of N management and avoiding unintended secondary effects from individual interventions. Within this context, the management of fertilizer emissions and livestock manure at the farm and regional scales appear to be particularly important targets for mitigation.     

Loss of low molecular weight dissolved organic carbon (DOC) and nitrogen (DON) in H2O and 0.5 M K2SO4 soil extracts

Soil extracts are routinely used to quantify dissolved organic nutrient concentrations in soil. Here we studied the loss and transformation of low molecular weight (LMW) components of DOC (¹⁴C-glucose, 1 and 100 μM) and DON (¹⁴C-amino acid mixture, 1 and 100 μM) during extraction of soil (0-6 h) with either distilled water or 0.5 M K₂SO₄. The extractions were performed at 20 °C, at 4 °C, or in the presence of an inhibitor of microbial activity (HgCl₂ and Na-azide). We showed that both glucose and amino acids became progressively lost from solution with increasing shaking time. The greatest loss was observed in H₂O extracts at 1 μM for both substances (>90% loss after 15 min). Lower temperature (4 °C) and presence of K₂SO₄ both resulted in reduced loss rates. The presence of microbial inhibitors effectively eliminated the loss of glucose and amino acids. We conclude that microbial transformation of LMW-DOC and DON during H₂O or K₂SO₄ extraction of soil may affect the estimation of their concentrations in soil. This finding has significant implications for methods that rely on chemical extractions to estimate LMW-C components of DOC and DON.