The effect of drought on barley yield and water use in two contrasting years

Summary Results are presented for an experiment in 1979 in which mobile shelters were used to exclude rainfall; responses are compared with those in a hotter and drier year, 1976. The continuous drought treatment achieved a larger maximum deficit in 1979 than in 1976. The relationship between rate of water use as a fraction of the potential evaporation rate and soil water deficit was similar in the two years. Yield reductions due to drought were smaller in 1979, as expected from the smaller evaporation rates and therefore smaller potential soil water deficits. Dry matter production was related to water use, but the relationship differed between years. The difference can be related to the saturation vapour pressure deficit. Components of yield were affected differently in the two years; drought after anthesis decreased yield in 1979 by decreasing grain numbers not grain size.