Seasonal changes in root growth of kiwifruit

Abstract

Kiwifruit root growth over a 12-month period was examined by extracting soil cores taken to 1 m from a population of 6-year-old clonal vines at approximately 4-week intervals, and measuring total and white root lengths. Root growth was compared with growth of shoots and fruit during the same period, and to soil and air temperatures. White root growth was most rapid in late summer, clearly after the periods of peak growth for the shoots (early spring) and fruit (early summer). This result suggested that the root system was a poor competitor for resources within the vine. While soil temperature variations were related to the annual periodicity of root growth, and probably contributed to short-term fluctuations, it is concluded that resource competition within the vine rather than soil temperature was the major factor influencing the seasonal pattern of root growth. Similarly, declining root growth rates with increasing soil depth were not directly related to soil temperature, but may have been influenced more by soil porosity. “Turnover” within the root system during the 12-month period was estimated at 29% of the average root length.