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Bragantia

Print version ISSN 0006-8705

Bragantia vol.14 no.unico Campinas  1955

http://dx.doi.org/10.1590/S0006-87051955000100001 

A fixação do nitrogênio do ar pelas bactérias que vivem associadas com as leguminosas crotalária e mucuna(*)

 

Nitrogen fixation by bacteria in association with crotalária and velvet bean

 

 

R. A. Catani; H. Gargantini; J. Romano Gallo

Engenheiros agrônomos, Secção de Agrogeologia, Instituto Agronômico

 

 


RESUMO

Com a finalidade de conhecer a quantidade de nitrogênio fixado simbiòticamente por crotalária (Crotalaria juncea, L.) e mucuna anã (Stizolobium deeringianum, Bart.) e a influência de alguns fatôres sôbre o fenômeno, instalou-se uma experiência em vasos de Mitscherlich contendo solo tipo terra roxa misturada. Os tratamentos empregados foram os seguintes : 1) testemunha ; 2) NPK ; 3) NPK + calcário ; 4) NPK + inoculante ; 5) NPK + calcário + inoculante; 6) PK + calcário; 7) PK + calcário + inoculante.
Dois meses após a germinação das sementes colheu-se o material para análise, dosando-se o N nas raízes e nas partes vegetativas das plantas.
Nessa ocasião foram tiradas diversas fotografias, para documentação comparativa da nodulação das raízes nos diversos tratamentos.


SUMMARY

A study was made of nitrogen fixation by bacteria in association with crotalaria (Crotalaria juncea L.) and velvet bean (Stizolobium deeringianum Bart).
The experiment was performed according to the Mitscherlich pot technique. Three replications of each of the following treatment were made : 1) check ; 2) NPK ; 3) NPK + limestone ; 4) NPK + inoculation ; 5) NPK + limestone + inoculation ; 6) PK + inoculation ; 7) PK + limestone + inoculation. The amount of nitrogen, phosphorus, potassium, and limestone added to the pots that received these elements were as follows : 2.0 g of N in the form of NH4 NO3 ; 2.2 g of P2O5 as K2HPO4 ; 3.0 g of K2O as K2 HPO4 and KCl; 15 g of a dolomitic limestone in order to increase base saturation in the soil to 60 per cent. Inoculation of the seeds was made with a Rhizobium from the cowpea group.
The plants were allowed to grow for two months and were then cut, dried at 60° C, and weighed. The roots were dug, washed carefully, and photographed to show the differences in nodule formation (figures 1 and 2). Nitrogen was determined separately in the stems with leaves and in the roots. This element was also determined in soil samples from treatments n.° 6 and n.° 7 prior to planting and after the plants had been removed from the pots. The data obtained indicated that nitrogen had not been absorbed from the soil.
The amount of nitrogen fixed per pot by the nodule bacteria is given below :
Treatment                                                                                    Nitrogen fixed by

                                                                                                                Crotalaria             Velvet bean
                                                                                              (g)                        (g)
N.º 6 (PK + limestone) -------------------------------------------------------------  0,52                      1,18
N.° 7 (PK + limestone + inoculation) -------------------------------------------- 0,74                      1,20


 

 

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Full text available only in PDF format.

 

 

LITERATURA CITADA

1.  CLARK, F. E. Soil microorganisms and plant roots. In Normam, A. G. ed. Advances in Agronomy. New York, Academic Press Inc., 1949. v. 1, p. 241-288.         [ Links ]

2.  CHAPMAN, H. D., LIEBIG, G. F. & RAYNER, D. S. A lysimeter investigation of nitrogen gains and losses under various systems of cover-cropping and fertilization and a discussion of error sources. Hilgardia 19:57-128. 1949.         [ Links ]

3.  ENSMINGER, L. E. & PEARSON, R. W. Soil nitrogen. In Normam, A. G. ed. Advances in Agronomy. New York, Academic Press Inc., 1950. v. 2, p. 81-111.         [ Links ]

4.  LYON, L. T., BUCKMAN, H. O. & CADY, N. The nature and properties of soils. 5.ª edição. New York, The Mac Millan Company, 1942. xvii, 591 p.         [ Links ]

5.  NORMAN, A. G. Recent advances in soil microbiology. Soil Sci. Soc. Am. Proc. 11:9-15. 1946.         [ Links ]

6.  SHIELDES, L. M. Nitrogen sources of seed plants and environmental influences affecting the nitrogen supply. Bot. Rev. 19:321-376. 1953.         [ Links ]

7THORNTON, G. D. Green-house studies of nitrogen fertilization of soybeans and lespedeza, using isotopic nitrogen. Soil Sci. Soc. Am. Proc. 11:249-251. 1946.         [ Links ]

8.  WAKSMAN, S. A. Soil Microbiology. New York, Wiley and Sons, 1952. vii, 356 p.         [ Links ]

 

 

Recebido para publicação em 31 de julho de 1954

 

 

(*) Trabalho apresentado ao II Congresso Panamericano de Agronomia, realizado em Piracicaba e São Pedro, de 29 de março a 6 de abril de 1954.

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