Annual Changes in Soil Nitrogen and Microflora In Paddy Fields not Fertilized Long-term and Fertilized Paddy Fields*

Masaharu Kamata, Saburo Kawamura, Mamoru Sl:G
Mem. Fac. Agr. Kinki Univ   unpublished
Synopsis From 1987 to 1989, we measured changes in soil nitrogen and microflora in two kinds of paddy fields, one not fertilized for 40 years and one fertilized regularly. 1) The soil total-N content was significantly higher in the fertilized field (F-field) than in the non-fertilized field (r- ;-F-field) ; in both fielis, the content increased from starting in the maxi­ mum-tillering stage until the heading and flowering stage, then temporarily decreased in the middle growing stage, and then
more » ... turned to the initial level. The soil totalC reached a maximum in both F-and i\F-fields at the ripening stage; its variation was smaller than that of total-N. Thus, the C/N ratios ranged from 7.0 to 8.0 over the growing period of the rice plants. 2) Fungal populations were significantly larger in the NF-field than in the F~field while the rice plants were growing. Actinomycetes were much more abundant in the F-field than in the ;\F-field. The total number of bacteria increased in the NF-field at the middle growing stage of the rice plants. Consequently, the B/F value (bacterial number/fungal number) in the upper plow layer was high in the NF-field. The numbers of anaerobic bacteria in the NF-field were far below those in the F-field through the 2-year period, which reflected the extent of the oxidative state in the whole soil horizon of the N F-field because of its continuous supply of irrigation water. 3) The genus Paecilomyces was abundant in the NF-'field, and the genera Paecilomyces and Triclwdenna were both abundant in the F-field. The fungal florae in the F-field were less abundant than those in the i\ F ~field. Of the actinomycetous florae, the genus Strepotomyces was most numerous in both fields, followed by the genus Nocardia.