Resumo

PAJARES MORENO, Silvia  e  GALLARDO LANCHO, Juan F.. Impact of soil management practices on the distribution of soil organic nitrogen in an acrisol. Terra Latinoam [online]. 2010, vol.28, n.2, pp.165-175. ISSN 2395-8030.

Highly intense degradation and loss of fertility in the soils of the Mexican Trans-volcanic Belt is a consequence of inappropriate management practices. This paper presents information about the soil N forms in epipedons of a Mexican volcanic soil (Acrisol) located in the Atecuaro catchment (State of Michoacán, Mexico). This soil was cultivated for 4 years under the following soil-management systems: traditional (Tt); improved (Tm); organic (To); and fallow (Tv). To and Tm management systems showed the highest values of total N (Nt) but did not have a significant impact on soil N distribution among the different fractions of organic N. From 94 to 97% of the Nt was organic N, whereas the hydrolysable-N content was relatively low, indicating that soil N is in stabilized form. Although Nt increased after four years of cultivation, the percentage of hydrolysable-N (with respect to Nt) decreased with the Tm management, indicating that this treatment increased recalcitrant N. Ammonia and amino acids were dominant (around 23% of the Nt) after soil hydrolysis. Only a small percentage of Nt was recovered as hexosamine-N (1.6%), indicating a low contribution of this fraction in the formation of the soil structure. Prevalence of organic N forms causes ammonic forms to be dominant after acid hydrolysis of the soil. The To and Tm treatments were found to be the most appropriate of agronomic management systems for increasing N content in these cultivated volcanic soils.

Palavras-chave : volcanic soil; total N; hydrolysable N; traditional management; organic management.