Long-Term Pinus radiata Productivity Gains from Tillage, Vegetation Control, and Fertilization

The effects of tillage, vegetation control, and fertilizer treatments applied at stand establishment of Pinus radiata D. Don. at three sites (Sand, Clay, and Ash) in Chile were examined 10 years after planting. Selected sites were typical of sites that routinely received tillage as a normal part of site preparation operations in Chile. At each site, we used four blocks of a split plot design with whole plots testing tillage effects (none or subsoiling ^ bedding) and subplots testing a factorial combination of vegetation control (none or 2-year banded) and fertilization (boron at establishment or nitrogen, phosphorus, and boron at establishment ^ nitrogen, phosphorus, potassium, and boron after 2 years). We estimated the main effect growth responses, determined response types (Type A, B, C, D), and calculated main effect volume growth age shifts for each site. Vegetation control increased volume growth 7-99% through 10 years (Type A, B, or C responses), which resulted in volume age shifts of 3.4, 1.3, and 1.0 years for the Sand, Clay, and Ash sites, respectively. Fertilization increased volume growth at the Clay site (14%, Type A) and decreased volume growth at the Ash site (6%, Type D), with volume age shifts of 1.0 and 1.0 years for the Sand and Clay sites, respectively. Tillage increased survival at the Sand site and decreased height growth at the Ash site (4%, Type D) with volume age shifts of 0.9 and 0.1 years for the Sand and Ash sites, respectively. Vegetation control likely ameliorated water (Sand and Clay sites) and light (Ash site) limitations that were critical for improved growth. Fertilization addressed secondary nutrient limitations, especially on the Clay site. Tillage provided little benefit, likely because the sites were well drained and soil bulk density was not at a level where limitations to root growth would be found. When determining which treatments to apply, managers should have an understanding of what resources may be limiting and select the appropriate treatment to ameliorate those limitations in the most cost-effective manner. For sites similar to those in this study, vegetation control would likely ameliorate resource limitations in a cost-effective manner.