Resumo
From a study of the variation of nitrates in the soil known as terra roxa misturada (mixed purple soil), the following conclusions were drawn : a) The nitrate content of this soil reveals a periodic variation through the year. The same kind of variation is expected in the majority of S. Paulo soils, because the climate, with minor exceptions, is fairly uniform over the State. b) As nitrification proceeds at a higher rate in the hot wet (September-May) than in the cool dry season (May-September), nitrates accumulate in the soil during the first period and disappear in the second. However, as an exception to the above rule, there appeared to be a fall in nitrates during December. This may have been due, either to leaching by rain, or to absorption by weeds, then in their growing period in the experimental fields. Since inorganic nitrogenous fertilisers do not generally give good results in the State of S. Paulo, when applied at the beginning of the rainy season, it is logical to attribute the decrease in nitrogen content to leaching, although the investigation did not lead to a conclusive explanation. c) This study did not support the view of an upward migration of salts in our soils during the dry months, since a steady level of nitrate content was observed during this period. d) Although the author was able to establish an association between nitrate losses and rainfall, it was not possible to determine the relation quantitatively.
Estudo da variabilidade dos nitratos num solo tipo terra roxa-misturada(1 (1 ) Trabalho apresentado à III Reunião Brasileira da Ciência do Solo, realizada em Recife, de 17 a 29 de julho de 1951, e adaptado para a revista "Bragantia". (2 ) Expressamos nossos agradecimentos ao Dr. Hernâni Godói, chefe do Serviço Meteorológico do Instituto Agronômico de Campinas, pelos dados que nos forneceu. )
F. C. Verdade(2 (1 ) Trabalho apresentado à III Reunião Brasileira da Ciência do Solo, realizada em Recife, de 17 a 29 de julho de 1951, e adaptado para a revista "Bragantia". (2 ) Expressamos nossos agradecimentos ao Dr. Hernâni Godói, chefe do Serviço Meteorológico do Instituto Agronômico de Campinas, pelos dados que nos forneceu. )
Engenheiro agrônomo, Secção de Agrogeologia, Instituto Agronômico de Campinas
SUMMARY
From a study of the variation of nitrates in the soil known as terra roxa misturada (mixed purple soil), the following conclusions were drawn :
a) The nitrate content of this soil reveals a periodic variation through the year. The same kind of variation is expected in the majority of S. Paulo soils, because the climate, with minor exceptions, is fairly uniform over the State.
b) As nitrification proceeds at a higher rate in the hot wet (September-May) than in the cool dry season (May-September), nitrates accumulate in the soil during the first period and disappear in the second. However, as an exception to the above rule, there appeared to be a fall in nitrates during December. This may have been due, either to leaching by rain, or to absorption by weeds, then in their growing period in the experimental fields. Since inorganic nitrogenous fertilisers do not generally give good results in the State of S. Paulo, when applied at the beginning of the rainy season, it is logical to attribute the decrease in nitrogen content to leaching, although the investigation did not lead to a conclusive explanation.
c) This study did not support the view of an upward migration of salts in our soils during the dry months, since a steady level of nitrate content was observed during this period.
d) Although the author was able to establish an association between nitrate losses and rainfall, it was not possible to determine the relation quantitatively.
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LITERATURA CITADA
- 1. Batham, H. N. e L. S. Nigam. Periodicity of the nitrate content of soils. Soil Sci. 29: 181-190. 1930.
- 2. Verdade, F. C. Dosagem dos nitratos do solo pelo método do ácido fenoldissulfônico. Bragantia 11: 1-12, fig. 1, 1951.
- 3. Demolon, A. e E. Bastisse. Results of lysimeter experiments. Soil Sci. 46: 1-7. 1939.
- 4. Gowda, R. N. Nitrates and nitrification in field soils. Soil Sci. 17: 333-342. 1924.
- 5. Hall, T. D. Nitrification in some South African Soils. Soil Sci. 12: 301-363. 1921.
- 6. Hall, T. D. Nitrification in some South African Soils. Part II. Soil Sci. 18: 219-235. 1924.
- 7. Sachs, W. H. Effect of cultivation on moisture and nitrates of field soil. Univ. Arkansas Agric. Exp. Sta. Bul. 205. 1926.
- 8. Smith, J. B. Distribution of nitrates in three layers of fallow soil. Soil Sci. :26 347-350. 1928.
Datas de Publicação
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Publicação nesta coleção
01 Jun 2010 -
Data do Fascículo
Dez 1951
