Root dynamics, production and distribution in agroecosystems on the Georgia Piedmont using minirhizotrons.
Abstract
Growth rates, death rates and distribution of grain sorghum and weed roots in conventional tillage (CT) and no-tillage (NT) plots were measured in field trials near Athens, Georgia in 1986, using the minirhizotron technique. Total root production was estimated by combining minirhizotron and soil coring methods. 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. In contrast, 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, the av. of the specific growth rate and the specific death rate, was introduced to assess the intra-seasonal root turnover or change rate. The root turnover index of NT was higher than that of CT during most of the time before flowering and slightly lower than CT after flowering. No-tillage plots 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 with CT. The estimated total root production in the top soil layer (0-28.2 cm) was 220 g/m2 for NT and 224 g for CT, and was not significantly different between treatments.