Transpiration and water use efficiency of maize in different soil moisture conditions

Globally, agriculture accounts for 80–90% of the fresh water used by humans, and in many crop production systems; this water use is unsustainable. Irrigation of large areas of field and horticultural crops is impossible. Studies of the impact of drought on important field and horticultural crops are necessary to estimate dimensions of adaptation and mitigation measures to climate change. For this purpose, maize was monitored as a model crop in this study. In a three-year experiment (i) using the sap flow measurement method, the transpiration of maize was evaluated during flowering and grain filling, (ii) water use efficiency (WUE) was evaluated in four soil moisture conditions. The intensity of transpiration was closely correlated with the values of global radiation and vapor pressure deficit. However, soil water content was a major factor influencing transpiration under drought stress. The transpiration decreased when water content in the soil reached 28% of available water holding capacity (AWHC), but the yield of corn cobs decreased only under stress of 25% AWHC. Thus, the yield reacted less sensitively to lower water availability than transpiration. WUE increased with decreasing transpiration. Statistically significantly higher WUE was already observed at a water content of 42% AWHC, however, a higher WUE did not lead to a higher yield of corn cobs.