Edaphic nitrogen and nodulation of Leucaena leucocephala (Lam.) de Wit in silvopastoral systems

摘要

In order to reduce the impacts occasioned by cattle farming systems on the environment, strategies focused on the inclusion of legume species within these systems have been promoted because of their potential for improving soils conditions. The symbiotic association between bacteria from genus Rhizobium eases the nitrogen undertaking by legume plants and therefore their growth and productivity may be improved. Even though bacteria from this genus naturally occur, they also may be inoculated to plant seeds. Silvopastoral systems (SPS) are an alternative for cattle farming where trees are incorporated to spatial arranges. In this sense, woody legumes have been used as a possibility of being integrated to SPS. In order to evaluate changes associated with the availability of nitrogen and other nutriments within soils as well as the presence of rhizome nodules, in this work, the woody species Leucaena leucocephala was established within silvopastoral systems with high density (over 10,000 trees per ha) in aa cattle farm , located in Balboa, Colombia. For assessing changes in soils after the establishment an experiment with a randomize complete block design and two treatments (inoculation and not inoculated) was used. Measurements were carried out during 7 months after the establishing the experiment, being the response variables the total and ammonia nitrogen as well as the amount of active nodules of Rhizobium on roots. Under the ecological conditions occurred during the experiment the presence of nodules did not show significant differences between treatments (P0.05), however a total amount of 249, 31 kg/ha of nitrogen was provided to soils while the experimental period.