Abstract
In high density plantings, it is unclear whether competition for light or root competition limits tree growth to a greater extent. The relative effects of these variables on 'Garnet Beauty' peach [Prunus persica (L.) Batsch] growth and yield was tested using a factorial combination of 3 in-row spacings (1.0, 1.5, 2.0 m) and 3 rooting volumes (10-cm wide trenches 0.3, 0.6, or 0.9 m deep). The rooting volume was maintained by a fabric lining in trenches which allowed only small roots to escape to surrounding soil. Four seasons of growth data and the fourth year's yield data are reported. Trunk cross-sectional area (TCA) increased with aerial spacing every year, but TCA increased with rooting volume in only the 2.0 m spacing during the first year. Shoot length increased with increasing spacing in 3 out of 4 years, but was affected by rooting volume in only 4 out of 18 possible cases, when shoot length generally decreased as rooting volume increased. In the fourth year, yield (kg/tree) and yield efficiency (kg/cm(2) TCA) increased with aerial spacing but decreased as rooting volume increased at the 1.5 and 2.0 m spacings. Overall, competition for light among trees (spacing) had a stronger effect on tree growth through the first four years than did root competition.