Thursday, November 16, 2006 - 9:15 AM

Effect of Soil Tillage on Soil Physical Properties and Their Relationship to Early Loblolly Pine Growth.

Bruno Furtado, Univ of Georgia, 253 E Cloverhurst Ave #17, Athens, GA 30605 and Lawrence Morris, Warnell School of Forest Resources, Univ of Georgia, Athens, GA 30602.

Compaction during harvest can decrease forest productivity by increasing soil physical impedance and by reducing oxygen supply to the roots due to reduction of macropore volume. Site preparation tillage, such as subsoiling, disking or bedding, can ameliorate these impacts but the costs of these tillage treatments are high and growth response is variable. Although basic relationships between loblolly pine root growth and soil physical properties have been established, these have not been incorporated into models useful for predicting growth response to soil tillage under field conditions. Soil physical conditions and tree growth were measured during the first two growing seasons following operational soil tillage on 11 sites, covering the Piedmont, Upper Coastal Plain and Flatwoods regions of the Southeastern USA. Values for growth response to tillage were site-specific and varied from 53 % to -19% in terms of ground line diameter. Soil resistance, measured using a cone penetrometer, was linearly related to volumetric water content. Water content-resistance relationships differed for tillage treatments but not for treatments of competition control and fertilizer. A model using soil strength, water availability, air-filled porosity, along with information on competition level, was evaluated to determine predictive ability for responses based on known root-soil relationships.