Effect of spring plowing on the spatial distribution of aquatic organisms in a paddy field during the off-crop season under drained conditions
2002
Yamazaki, M. (Nagoya Univ. (Japan)) | Hamada, Y. | Kamimoto, N. | Momii, T. | Kimura, M.
This paper demonstrated the effect of spring plowing on the dormant aquatic organisms with size between 30 micro m to 2 cm in a paddy field. Although there was no floodwater in the paddy field during the off-crop season, the soil was wet (about 25% water content) before the plowing because of the coverage by rice straw. But the plowing in spring resulted in the soil desiccation (to about 2%). On the 10th day after the plowing, we collected following soil and rice straw samples: rice straw, bulk soil, rice stubble, 0-1.5 cm soil below rice stubble, and 1.5-3.0 cm soil below rice stubble in both the dry surface soil layer (0-4 cm) and the wet soil layer (4-15 cm). After incubated the samples under flood conditions for fifty days, we identified the aquatic organisms that appeared during the incubation and mainly classified them at the order level. Thirty two varieties (classified groups) of aquatic organisms emerged during the incubation. The number of varieties that emerged during the incubation from the respective samples was larger in the wet soil layer than in the dry surface soil layer. Pennales and Haplotaxida, and Colpodida chose the wet soil layer and the dry surface soil layer, respectively, as their survival site. The difference in the composition of aquatic organisms among sites was larger than the difference between the dry surface layer and the wet soil layer, and the composition of aquatic organisms at the respective sites was not changed significantly by the plowing in spring.
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