Mineralización de nitrógeno en suelos de pasturas con Arachis pintoi

Abstract

There is a lacking on information about the role of forage legumes to improve soil fertility on native pastures within tropical Mexico. Under this type of vegetation, continuous incorporation of residues from introduced forage legumes may contribute, from the N stored on its organic matter, to soil health restoring. Nitrogen soil mineralization using both anaerobic (ANA) and aerobic (AER) laboratory incubation methods was assessed in Ultisols soil samples at 0-5, 5-15 and 15-30 cm depths, from four tropical native pasture sites located at Veracruz, Mexico. Each pasture was associated to the introduced forage legume Arachis pintoi, with 3, 5, 8 and 11 yr after the forage legume was introduced. Also, pure stands of native pasture sites no mixed to A. pintoi were used as reference sites. In all cases mineralization rate decreased with the depth, AER method confirmed ANA results, since only 5 A. pintoi years old site yielded more mineralized N (207+-3.4 I¼,,g N g-1 soil) than native pasture soils (166+-3.1 I¼,,g N g-1 soil). Topsoil (0-5 cm) mineralized more N (104+-7.0 I¼,,g N g-1) than 5-15 cm soil depth (70+-5.4 I¼,,g N g-1). Although no significant positive effect of the legume on N mineralization with either method was observed, discussion is focused regarding to define if differences between types of pastures were due to low inherent soil N rather than changes in soil organic matter quality.