Nitrogen mineralization of roots of maize and selected woody species

A laboratory experiment was carried out to assess nitrogen (N) mineralizati on of roots of four woody agroforestry species (Dactyladenia barteri, Senna siamea, Gliricidia sepium, and Leucaena leucocephala) and maize (Zea mays) . Addition of Gliricidia and Leucaena roots with high N contents and low ca rbon (C)-to-N ratio (less than or equal to 14.0) resulted in net N minerali zation, while the addition of maize roots with low N and high C-to-N ratio (40.3) immobilized N. Addition of Dactyladenia and Senna roots with interme diate N content and C-to-N ratio immobilized N to a lesser extent. Nitrogen mineralization was negatively and significantly correlated with C-to-N rat io of the added roots. Addition of roots of the five species also different ially affected soil pH during the first 12 weeks of incubation. Soil pH was positively and significantly correlated with the roots initial C-to-N rati o and negatively correlated with their initial N content. At 24 weeks of in cubation, the pH of all treatments reverted to initial value.