Mid-Rotation Response of Soil Preparation Intensity and Timing of Weed Control on Radiata Pine

A good instance to improve the availability of resources for tree planting is during the establishment of stands, increasing the survival and initial growth of plants. Despite the common use of soil preparation, there are uncertainties about its long-term effects on stand growth and the intensity required. Weeds compete with crop plants for site resources, such as light, water, and nutrients, so evaluating the best time to apply this treatment is key. The objective of this study is to quantify the effects of soil preparation intensity and the timing of weed control on the long-term growth responses of radiata pine on a metamorphic soil in Chile. The study was established on a split-plot design with cultivation as the main plot treatment (shovel, subsoiling, and disking) and weed control as subplots (none, pre- and post-, and only post-planting) to remove all competing vegetation. Subsoiling was performed to 80 cm and disking to a 30 cm depth. Trees were planted in 2013 and were measured annually for diameter at breast height (DBH) and total height. Nine years after establishment, soil preparation treatments with weed control applied at pre- and post-establishment showed the lowest mortality. The best responses in cumulative volume were observed for disking and subsoiling plus weed control at pre-establishment, and the lowest responses were observed for treatments not including weed control. Weed control was the key treatment providing good growth response. Interestingly, the hypothesis that deep soil tillage was required on long dry season sites such as these was rejected given that disking to 30 cm provided equal or even larger growth responses.