Evaluation of some chemical methods for predicting the availability of organic soil nitrogen

Autor: Rodrigues Filho,Francisco Solano de Oliveira, Lancaster,James D.
Jazyk: portugalština
Rok vydání: 1984
Zdroj: Bragantia, Volume: 43, Issue: 2, Pages: 313-325, Published: 1984
Bragantia v.43 n.2 1984
Bragantia
Instituto Agronômico de Campinas (IAC)
instacron:IAC
Popis: Vários métodos químicos recomendados para predizer a disponibilidade do nitrogênio orgânico no solo foram avaliados, usando-se nitrogênio mineralizável pela incubação aeróbica e anaeróbica, em condições de laboratório, como padrões. Sessenta e duas amostras de solo, variando amplamente em pH, textura, matéria orgânica e manejo da gleba, foram coletadas de áreas representativas do Estado do Mississippi. Baseados no grau de consistência de correlação com o nitrogênio mineralizado por ambas as incubações, aeróbica e anaeróbica, os métodos químicos se classificaram na seguinte ordem, como índices de disponibilidade do nitrogênio orgânico no solo, usando-se análise de correlação simples: hidrólises com Ca(OH)2 > nitrogênio total > digestão com permanganato alcalino > nitrogénio pelo método Walkley-Black > métodos de autoclavagens > matéria orgânica > absorção pela luz ultravioleta. Essa ordem foi inalterada pela inclusão da relação carbono:nitrogênio (C:N) aos métodos biológicos, usando-se regressão múltipla e análises de correlação, exceto no método da matéria orgânica, que passou então a situar-se entre os métodos químicos, apresentando as maiores correlações com os biológicos. A study was conducted to evaluate selected chemical methods for assessing the availability of organic soil nitrogen in Mississippi soils using nitrogen mineralized by aerobic and anaerobic incubation under controlled conditions as standards for comparison. Sixty-two soil samples were collected from agricultural and non-agricultural sites in representative physiographic areas of Mississippi. The soils varied greatly in texture, pH, management practices, and organic matter content. The chemical methods evaluated were: organic matter (M1) ; total nitrogen (M2) ; Ca(OH)2 hydrolysis (M3); initial inorganic nitrogen (M4); exchangeable ammonium (M5), autoclaving and washing with 1 M KCl (M6); autoclaving and washing with 0.01 M CaCl2 (M7) ; autoclaving in 0.01 M CaCl2 and washing with 1 M KCl (M8); Walkley-Black nitrogen (M13) ; alkaline permanganate digestion (M14) ; and ultraviolet absorption (M15). The biological methods, used as standards for evaluation of the chemical methods, were: aerobic mineralization - 1 week (M9); aerobic mineralization - 2 weeks (M10); aerobic mineralization - 1 week plus 2 weeks (M12); and anaerobic mineralization 3 weeks (M11). Except for initial inorganic nitrogen (M4), exchangeable ammonium (M5), and ultraviolet absorption by NaHCO3, soil extracts (M15), all the chemical methods were moderately to highly correlated with each other, and, therefore, may be divided into two groups: the autoclaving methods (M6, M7, M8) and the other methods (M1, M2, M3, M13, M14). The highest correlation obtained with the chemical methods was between total nitrogen (M2) and Ca(OH)2, hydrolysis (M3). Of the chemical methods only initial inorganic nitrogen (M4) and exchangeable ammonium (M5) were not highly statistically correlated with the biological methods. The chemical methods were correlated to a lower degree with aerobic mineralization by M10 than with other biological methods. Based on degree and consistency of correlation, the chemical methods were ranked numerically as to their effectiveness in the following order, from simple correlation analysis: Ca(OH)2 hydrolysis (M3) > total nitrogen (M2) > alkaline permanganate digestion (M14) > Walkley-Black nitrogen (M13) > autoclaving procedures (M6, M7, M8) > organic matter (M1) > ultraviolet absorption by NaHCO3 soil extracts (M15). When the C:N ratio was included with the biological methods in a multiple regression analysis, only the effectiveness of organic matter was increased substantially. Consequently, the order of effectiveness as established by simple correlation analysis was unchanged except that of organic matter (Ml) that was brought among the chemical methods having the highest correlation with the biological methods.
Databáze: OpenAIRE
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