Biological and chemical properties of arable soils affected by long-term organic and inorganic fertilizer applications

 Using soils from field plots in four different arable crop experiments that have received combinations of manure, lime and inorganic N, P and K for up to 20 years, the effects of these fertilizers on soil chemical properties and estimates of soil microbial community size and activity were studied. The soil pH was increased or unaffected by the addition of organic manure plus inorganic fertilizers applied in conjunction with lime, but decreased in the absence of liming. The soil C and N contents were greater for all fertilized treatments compared to the control, yet in all cases the soil samples from fertilized plots had smaller C:N ratios than soil from the unfertilized plots. The soil concentrations of all the other inorganic nutrients measured were greater following fertilizer applications compared with the unfertilized plots, and this effect was most marked for P and K in soils from plots that had received the largest amounts of these nutrients as fertilizers. Both biomass C determined by chloroform fumigation and glucose-induced respiration tended to increase as a result of manure and inorganic fertilizer applications, although soils which received the largest additions of inorganic fertilizers in the absence of lime contained less biomass C than those to which lime had been added. Dehydrogenase activity was lower in soils that had received the largest amounts of fertilizers, and was further decreased in the absence of lime. This suggests that dehydrogenase activity was highly sensitive to the inhibitory effects associated with large fertilizer additions. Potential denitrification and anaerobic respiration determined in one soil were increased by fertilizer application but, as with both the microbial biomass and dehydrogenase activity, there were significant reductions in both N₂O and CO₂ production in soils which received the largest additions of inorganic fertilizers in the absence of lime. In contrast, the size of the denitrifying component of the soil microbial community, as indicated by denitrifying enzyme activity, was unaffected by the absence of lime at the largest rate of inorganic fertilizer applications. The results indicated differences in the composition or function of microbial communities in the soils in response to long-term organic and inorganic fertilization, especially when the soils were not limited. Received: 10 March 1998     

A screening method for simultaneous immunochemical detection of aflatoxins and ochratoxin A in cereals and feed]

An immunochemical method was proposed for simultaneous determination of aflatoxin and ochratoxin A with the use of mixed solutions of the following reagents: standards of both mycotoxins, antiserums against the mycotoxins, and radioligands of 125I-aflatoxin B1 and 125I-ochratoxin A. The result of the analytical procedure is the value of concentration of the aflatoxin + ochratoxin A sum in the sample. The procedure needs half the amount of reagents as separate determination of each of the two mycotoxin, and is far less laborious. The proposed simultaneous immunoanalysis is suitable for large-are inspection of grain and feed safety from the viewpoint of aflatoxin and ochratoxin A levels.     

Influence of estrus synchronization of prepubertal gilts on embryo quality

Synchronization and superovulation are commonly used to obtain large numbers of embryos for experimental and practical purposes. This study compared the number, quality, and in vitro development of embryos recovered from gilts following single or double estrus synchronization and superovulation. Prepubertal gilts from the single synchronization group were injected with 1500 I.U. PMSG and 1000 I.U. hCG 72 h later. The double synchronized group of gilts was treated with 750 I.U. PMSG and 500 I.U. hCG 72 h later. After 17 days, 1500 I.U. PMSG followed by 1000 I.U. hCG was administered. Five days after insemination embryos were recovered and cultured for 6 days. Both single and double hormonal stimulation schedules resulted in recovery of elevated numbers of embryos (28.4 and 23.4 vs. 11.3; p<0.01 and p相似文献   

Changes in drug action in growing animals

Some results are given from a long-term study of possible changes in drug action in growing animals. It was found that the changes were of different character according to the drug studied, amongst other factors. A non-parallelity in changes of toxic effects and therapeutic effects of some drugs during aging appears to be important. The influence of age on effects in drug interactions is of great interest. All the findings show that it will be very difficult to correct for dose with respect to developmental changes in animals without further pharmacodynamic and pharmacokinetic studies in this field of pharmacology.     

Correlations between shape index and shell deformation of hens’ eggs over a laying year

The egg shape index and shell deformation of 2466 pullet and 2214 hen eggs have been studied each week over a period of 45 weeks. The weekly and 5‐week averages were utilised for correlation analysis.

A pronounced negative correlation between shape index and shell deformation variations was found for both pullet and hen eggs. The pullet egg correlation coefficient, determined on the basis of the weekly and 5‐week averages, was ‐0.605 and ‐0.885, respectively; while the corresponding values for hen eggs were ‐0.433 and ‐0.510.

It has been pointed out that although a correlated variation of shape index and shell deformation with time might be due to specific conditions, it is reasonable to assume that if the time‐dependent changes of the relevant properties were taken into account in the investigations, an improved correlation might be expected.