Dynamics of leaf transpiration in two contrasting maize (Zea mays L.) hybrids under water stress and biochar amendment

A pot experiment was conducted at the experimental Farm of Legnaro (Padova, NE Italy) to study the dynamics of leaf transpiration in two maize (Zea mays L.) hybrids, i.e., one drought sensitive (S: P1921) and one drought tolerant (T: D24), under biochar addition in conditions of progressive limited water availability. The investigation compared two treatments: soil amendment with wood-derived biochar (1% w/w) vs. untreated controls, with five replicates. The effects of water stress were evaluated by calculating the “linear plateau regression” obtained by relating daily relative transpiration (RT) over the fraction of transpirable soil water (FTSW). Results showed that in both hybrids biochar was able to maintain a high rate of transpiration down to low FTSW values. The linear plateau regression model of un-amended D24 starts to decline earlier (82 % FTSW value) than in P1921(45% FTSW value), confirming the water-saving strategy of D24. Instead, soil amended with biochar allowed plants of both hybrids to transpire at their maximum down to lower FTSW, i.e., 45% and 22% in D24 and P1921, respectively. It is concluded that biochar can delay the inhibition of transpiration in condition of limited water availability and it is most commonly observed the capacity of biochar to improve the water holding capacity, a fact that is attributed to the high surface area of biochar which helps it to increase water retention.