Rooting characteristics and aboveground biomass development of sweet sorghum and ethanol maize under water deficit.

Although the mechanisms of sorghum and maize adaptation to drought are generally well understood, little is known about the response of newly developed sweet sorghum genotypes to water deficits, especially at the root level. Thus, the objective of this study was to determine the rooting and canopy characteristics of a sweet sorghum hybrid, Sucro 506, compared to ethanol maize at two levels of water restoration. Root growth was correlated to the above ground biomass and to some physiological traits related to drought resistance. The trial was set up in a total of 20 cubic rhizotrons, where calibrated soil moisture probes were installed for monitoring and adjusting the soil moisture content in the well-watered and dry treatments to 25% and 12% (v/v), respectively. The preliminary results show that under drought conditions sweet sorghum was able to sustain its physiological activity closer than maize to that of well-watered plants. Droughted sweet sorghum had higher leaf area, above and belowground biomass, and WUE than maize. The accumulated aboveground dry biomass of droughted sorghum was 62% of that produced under well-watered conditions, while that of maize was only half. Moreover, in contrast to maize the root length density of droughted sorghum was enhanced, especially in deep soil layers. These results suggest that the deep and well developed root system of sweet sorghum under drought stress allows it to sustain growth, development, and physiological activity somewhat similar to its potential.