Abstract

The effect of soil temperature on root growth was studied in a sweet cherry orchard [Prunus avium L. cv. Bing/Gisela (R) 6] in Rancagua, Chile. A rhizotron was installed in the field and digital images were collected weekly from September 2008 to March 2009 to determine root length. Root length was measured at 0-20, 20-45, 45-70 and 70-95 cm depths. Differences in white root length between consecutive pictures were computed as growth rate. Results showed four major growth peaks of roots. The earliest peak occurred on September 16, four weeks before bud break and with an average maximum soil temperature of 14.7 and 13.2 degrees C at 25 and 50 cm depth, respectively. Root growth persisted for six months approximately, and was mainly concentrated in the deeper portion of the soil profile (below 50 cm). Even late in the season, growth rates were higher at 70 cm depth. Based on the measurements in the upper soil layer, root growth ceased when soil temperature reached 31 degrees C. Maximum soil temperature was efficiently controlled by covering the soil surface with a reflective-white polyethylene sheet. This plastic cover reduced the near-surface soil temperature by about 2.5 degrees C in relation to bare soil.