Growth and nutrition of Pinus radiata in response to fertilizer applied after thinning and interaction with defoliation associated with Essigella califomica

Abstract

Infestations of Essigella californica following the installation of post-thinning fertilizer trials in Pinus radiata plantations provided an opportunity to examine the impact of repeated defoliation over a period of 8 years (1997-2005). Replicated treatments (n = 4) of nil fertilizer (control), N (300 kg ha-1) as urea, P (80 kg ha-1) and S (45 kg ha-1) as superphosphates were applied immediately after thinning at three sites and this was followed by a second application of NPS fertilizers 6 years later with N applied at 300 kg ha-1 as urea and ammonium sulphate and P at 80 or 120 kg ha-1. Defoliation of untreated P. radiata gradually increased to 50% over a period of 8 years. Basal area grow..