The 'acid rain' problems in forests in The Netherlands are largely due to excessive aerial inputs of NH3 and NH4 from intensive livestock farms. Nitrification is slow under acid soil conditions, so a large part of the V available to the trees is in the ammonium form. In pot experiments the response of Douglas-fir to various NH4:NO3 ratios was tested, using a nitrification inhibitor. Rhizosphere pH was measured with microelectrodes. If nitrate contributed less than 20% to total N uptake, net carboxylate production was insufficient for internal pH control and the tree died. If more than 65% of the N absorbed was taken up as nitrate, net OH excretion by the roots occurred, leading to alkalization of the rhizosphere at the root tip and at the root growth zone. Thus, root growth can continue in strongly acid soils.
DOI:
https://doi.org/10.1007/978-94-011-3438-5_19Dimensões Contagem de citações:
Ano de publicação
1991
Autores
Gijsman A J; van Noordwijk, M.
Idioma
English
Palavras-chave
nitrification, soil water content, growth
Geográfico
Indonesia
