Using the sensitivity of biomass production to soil water for physiological drought evaluation

Abstract

The analysis of drought as a phenomenon and the proposal of how to define and quantify the deficiency of water in soil for plants, so called physiological drought, are described. The presented approach is based on the theoretical considerations supported by empirically estimated relationships between the biomass production of a particular plant and the transpiration total of this plant during its vegetation period. This relationship is linear and is valid for particular plant and environmental conditions (nutrition, agrotechnics). Optimal plant production can be reached for maximum seasonal transpiration total, therefore the potential transpiration total corresponds to the maximum possible yield. The transpiration rate lower than the potential one leads to a biomass production decrease. This phenomenon can be used to define the physiological drought, under which the soil water content in the root zone decreases below the so called critical soil water content of limited availability for plants, under which the transpiration rate drops below its potential transpiration rate. Methodology is illustrated on the basis of the results of mathematical modelling of soil water movement in Soil – Plant – Atmosphere system, with loamy soil and maize canopy.