ROOT DYNAMICS, PRODUCTION AND DISTRIBUTION IN AGROECOSYSTEMS ON THE GEORGIA PIEDMONT USING MINIRHIZOTRONS

Growth rates, death rates and distribution of grain sorghum and weed roots in conventional tillage (CT) and no-tillage (NT) plots were measured. Most root growth occurred before flowering and most roots died after flowering. The specific root growth rates of both CT and NT were highest at the beginning of the season and then declined; the specific root death rates in the 2 systems were very low during the early season, increased markedly beginning at the early reproductive growth stage, peaked at flowering and declined afterwards. A root turnover index (average of the specific growth rate and the specific death rate) was introduced. The root turnover index of NT was higher than that of CT most of the time before flowering and slightly lower than CT after flowering. No-tillage had higher root density in the upper soil layer (0-5 cm) and in the deep soil layer (below 60 cm), but lower in the middle layer (5-60 cm) compared to CT. Estimated total root production in the top soil layer (0-28.2 cm) was 220 g m-2 for NT and 224 g m-2 for CT, and was not significantly different between treatments. -from Authors