THE EFFECT OF PREVIOUS CROPS ON THE CELLULOSE DECOMPOSITION ACTIVITY OF THE SOIL

1. THE EFFECT OF PREVIOUS CROPS ON THE CELLULOSE DECOMPOSITION ACTIVITY OF THE SOIL Schmidt R., Kerekes G., Szakál P., Kalocsai R., Giczi Zs., Szlovák G. University of West Hungary Mosonmagyaróvár

2. Nutrients in the soil take part in a continuous transformation process. The decomposition of organic materials is done by different groups of soil microorganisms. Environmental parameters in the soil are changing rapidly and the dominating groups of microorganisms vary with time also very quickly determining of the end products of the transformation processes. Plant residues are the substrates of the decomposition processes and also modify the environment where these processes take place.

3. In this experiment we studied how the different plant residues modify the cellulose decomposition activity of the soil. According to the common belief we supposed that legume plants have a more favourable effect on microbiological activity and promote more intense cellulose decomposition.

4. Methods The aim of the experiment was to study the effect of different previous crops on the microbiological activity of the soil. The experiment was carried out at the Experimental Station of the Mosonmagyaróvár Faculty of West-Hungarian University. The type of soil was calcareous Danube alluvial soil. The decomposition of cellulose, that indicates the microbiological activity of the soil was studied by “Unger cellulose test method” (Szegi 1979). SOYBEAN (Glycine max) MAIZE (Zea mais) HORSEBEAN (Vicia faba) SUNFLOWER (Helianthus annuus) The size of the experimental plots was 3 m2. The plant residues used in the experiment were collected from an area of the same size as the experimental plots, were dried and cut into pieces not longer than 20 mm. The prepared material was spread evenly on the surface of the experimental plots and mixed into the soil down to a depth of 200 mm.

5. Soil analysis results

6. The test sacks were placed into the soil on the next day to a depth of 150 mm. Sampling started on the 10th of March, on the 90th day from the date when the sacks were put into the soil. Samples were taken in each month in four repetitions till October.

7. Cellulose decomposition during the experimental period in the case of the four plant species

8. In the beginning the cellulose decomposition was the slowest in the soil treated with soybean residues, but the speed of the decomposition became faster by the end of the vegetation period and altogether we could measure the less amount of cellulose residue in the case of this treatment. The highest initial decomposition speed was measured in the case of sunflower, but the tendency was quite opposite comparing to soybean tratments and a significant amount of cellulose residue was measured at the end of the experimental period.

9. The cellulose decomposition was slower in the soil treated with sunflower residues than in the soil where maize residues were incorporated. The amount of the remained cellulose was lower in the maize treated plots during the whole experimental period, except May, though this difference disappeared by October. By the end of the experiment 80% of cellulose was decomposed in both cases.

10. In the beginning the residues of horsebean had the same effect as that of maize residues. Around the end of the experiment the decomposition speed decreased and the highest amount of cellulose remained could be measured in the soil of soybean treated plots. Altogether 30% of the total amount of cellulose did not decompose till the 10th of October.

11. Cellulose decomposition in the soil treated with sunflower residue

12. Cellulose decomposition in the soil treated with soybean residue

13. Cellulose decomposition in the soil treated with maize residue

14. Cellulose decomposition in the soil treated with horsebean residue

15. Conclusions The experiment carried out did not prove unquestionably that the residues of legume plants promote cellulose decomposition – that symbolised soil microbiological activity in the experiment – more efficiently than the residues of other plants. Our present results were also inconsistent with literature regarding that common statement that the decomposition of the residues of soybean is protected, slower than the decomposition of other annual legume plants.