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The Effect of Soil Coverings on Soil Respiration in Sandy Soil
21-25

The purpose of our experiments is to study effect of different soil coverings (porous black polyethylene called agroszövet and black polyethylene) on CO2 production in sandy soil. The CO2 production was measured in our laboratory according to Witkamp (1966 cit. Szegi, 1979), after 5 days’ incubation period. Samples were taken off four times (March, May, July, September) in every year of the experiment. In May, July and September of 2000, the CO2 production was significantly higher in the control than in the treatment soil. With the exception of September, the value of CO2 production was significantly higher under black polyethylene than under agroszövet. In March and May of 2001, the soil under black polyethylene, and in July and September the control soil produced the greatest quantity of CO2. With the exception of July, significantly more CO2 was produced under black polyethylene than under agroszövet. To study the dynamic of CO2 production there was find a significantly higher value May and September of 2001 than 2000. Similarly significant higher CO2 production was detected in September than in the other months In average of two experimental years the difference between the produced CO2 under different coverings was occasionally. Explicit upward tendency in soil CO2 production was detected only in case of control soil. There was a medium (r=0,413) relationship observed between the moisture content and the CO2 producing ability of soil. To sum up the soil coverings had favourable effect on soil CO2 production very rearly, but they could help to conserve the moisture content of soil.

103
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Effects of fermented chicken manure products on the N mineralization rate of the soil using the incubation method
199-204

In our study, the effect of fermented and specially added poultry manure products (superabsorbent polymer (SAP), bentonite and Aegis as a mycorrhizal inoculum) were investigated in a short soil incubation experiment – at 60% water capacity level - on sandy soil. Soil samples were collected from two layers of the incubation pots after the second and fourth week to check the status of the tested products and the processes in the soil. The pH and the electric conductivity (EC) of the samples were measured using an electrochemical method, while the ammonium and nitrate content of the samples was determined with a photometric method. Soil pH and EC values slightly were decreased during the experiment. Our results pointed out that the increasing dose of SAP caused lower soil pH. The nitrate content of the soil did not change significantly during the experiment. It was found that the increasing SAP content in the products, due to its cross-linked structural property, protected the nitrate ions from leaching. Our results suggest that applied SAP does not bind the nutrient ions so tightly in its structure that it competes with the plant for uptake.

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Effect of Soil Covering on CO2 Production and Cellulose Decomposition Activity
198-201

In our experiments the effect of different soil cover matters (agroszövet and black polyethylene) on the CO2 production capacity and on the soil cellulose decomposition activity was studied. We also examined the relationship between the CO2 production and the cellulose decomposition activity. The trial was carried out in an apple plantation in Újfehértó. The CO2 production were determined after Witkamp with 5 days’ incubation period, the cellulose decomposition activity was measured according to Unger. Results showed that CO2 production and cellulose decomposition activity was higher in control soil almost in every cases. In respect of CO2 production the black polyethylene gave better values than the agroszövet.
In 2000 the cellulose decomposition activity was significantly higher under covered soil than under uncovered every time. In spring of 2001 the controll but in summer and autumn agroszövet was significantly better. In summer and autumn black polyethylene prove non-significantly better than control. In average of two experimental years significantly higher cellulose decomposition activity was detected in covered soils than in control.
In the most occassion a close connection was observed between cellulose decomposition activity and CO2 production. In spite of this the correlation was not significant in controll at all. Significant relationship was only found in spring and summer of 2001 under agroszövet, in spring and autumn of 2000 and in summer of 2001 under black polyethylene.

23
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Effect of fertilization on the potentially mineralize N forms of soil of long term field experiment was set in an acidic sandy soil
20-24

The aim of this paper was to provide further information about the nitrogen mineralization processes of soil. A modified incubation technique was applied to establish the amount of easily soluble mineral and organic N forms during the incubation period. An acidic sandy soil was used for incubation, which was sampled from the „Westsik” long-term field experiment. The incubation was carried out on fifteen selected soil samples which were received different treatments since the experiment was set up. 
From the obtained results, the amount of potentially mineralizable N and the mineralization rate constant were determined. Results of chemical analysis and biological interpretation of results are discussed.

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The effect of different herbicide on the number and activity of living microorganisms in soil
76-82

Sustainable plant growth, considering the difficulties of weed elimination, cannot be effective without the application of herbicides. However, these chemicals have enormous ecological implications, including effects on the microbiological communities of soils. It is advisable to use herbicides that have minimal secondary effects on the environment and soil-living microorganisms. In contrast, herbicides with prolonged growth stimulating or inhibiting effects are not suitable, because both types have strong influences on the number and activity of bacteria, thus causing changes in the ecological equilibrium.
Preceding small plot experiments, laboratory tests were carried out to study the effect of herbicides used in maize cultures on the number of bacteria and growth of microscopic fungi.
Substances that were observed to have stronger influences were applied in small plot experiments set up in the experimental garden of the Department of Plant Protection of the University of Debrecen. We studied the effects of four herbicides (Acenit A88EC, Frontier 900 EC, Merlin SC and Wing EC) on the microbiological properties of the soil. These herbicides were used in different concentrations in maize culture, and we investigated the effects in different soil layers.
In the laboratory experiments, we determined the total number of bacteria and microscopic fungi and examined the growth of Aspergillus niger, Trichoderma sp. and Fusarium oxysporum on peptone-glucose agar containing herbicides.
During the small plot experiments, soil samples were collected 3 times a year from 2-20 cm depth. The total numbers of bacteria and microscopic fungi were determined by plate dilution method, while the method of most probable number (Pochon method) was used to determine the numbers of nitrifying bacteria and cellulose decomposing bacteria. To evaluate the microbiological activity of the soil samples we measured carbon-dioxide release (after 10 days incubation), nitrate production (after 14 days incubation) and the concentration of C and N in the biomass.
We can summarize our results as follows:
• In laboratory experiments, herbicides caused a decrease in the number of bacteria and inhibited the growth of microscopic fungi.
• Frontier 900 EC and Acenit A 880 EC had the strongest inhibiting effect on microorganisms.
• In small plot experiments, herbicide treatment decreased the total number of bacteria and microscopic fungi.
• Herbicides caused a significant increase in the number of nitrifying and cellulose decomposing bacteria.
• Different herbicides containing the same active compound had similar influences on soil microoorganisms.
• A significant increase was observed in the physiological processes of tolerant microorganisms surviving the effects of herbicides

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