Soil temperature effect on root growth of cherry trees [Prunus avium L. cv Bing/Gisela®6]

Abstract

The effect of soil temperature on the extension, longevity and branching of roots was studied in a sweet cherry [Prunus avium L. cv Bing/Gisela®6] orchard in Rancagua, Chile. Rhizotrons were installed in the field and digital images were collected periodically to determine root length and branching using an image editing software. Root pictures were taken every 7 days, from September 2008 to March 2009. Root system was measured at four depths: 0-20, 20-45, 45-70 and 70-95 cm. White roots growth was computed as the difference in length between consecutive pictures. Results showed four major growth peaks. The earliest peak appeared September 16, 4 weeks before bud break. This peak occurred with average maximum soil temperatures of 14.73 and 13.19° C at depths of 25 and 50 cm, respectively. Root growth lasted 6 months approximately. Most root growth concentrated in the deeper portion of the soil profile (below 50 cm). Even in late in the season, growth rates were higher at 70 cm depth. A significant positive relation was found between growth and soil temperature in the upper soil layer. However, root growth rate at greater depths was explained by other factors such as soil texture, and soil water content. Based on the measurements in the upper layer, roots cease to grow when soil temperature reaches 31° C. Additionally, maximum soil temperature was efficiently controlled by covering the soil surface with a reflective-white polyethylene layer. This plastic mulch reduced the near-surface soil temperature by about 2.3° C relative to bare soil (without mulch).