Nitrogen Mineralization and Fertilization Response of Mid-Rotation Pinus Radiata D.Don Stands At Three Contrasting Soils.

Fertilization can change nitrogen availability in pine plantations, but growth response respect to magnitude and duration are not fully understood, particularly respect the long-term response. We studied monthly dynamics of nitrogen (availability, uptake and mineralization) in three trials of mid-rotation fertilization in Pinus radiata with contrasting soils (Chile, South America) for 2 years, where stands in sandy and granitic soils showed 5 to 6 years persistent growth responses to nitrogen fertilization, with gains volume of 24 m³ ha^-1 in sand and 51 m³ ha^-1 in granitic soils. However, red-clay soils did not respond 3 year after fertilization. Differences in long-term response between sites were mainly attributed to differences in soil nitrogen availability before the fertilization, and increases in the nitrogen mineralization rates in long-term. We found all sites increased nitrogen mineralization and availability rates, but granitic and sandy soil had higher uptake in fertilized treatment.