Sandy soils facilitate maize growth in cold regions. However, Danish coarse sands have poor water and nutrient retention capacity which may constrain crop growth during dry spells. A greenhouse maize experiment was conducted in which straw biochar was applied to the subsoil at concentrations of 0, 1, 2, and 3%. All the plants were fully irrigated until flowering. Thereafter, half of the plants were subjected to drought until 76% of soil water content at field capacity was depleted in the control. Plant height and number of leaves were not significantly different at flowering although significantly lower for 3% biochar at stem elongation stage. Leaf water potential, stomatal conductance as well as photosynthesis and transpiration were maintained in biochar 2 and 3% during the drying cycle reflecting the increase in soil water holding capacity. In the drought treatments, plant biomass tended to be greater for biochar 2% but decreased for biochar 1 and 3%. Cob biomass was increased by biochar 3% but decreased by 1 and 2 %. Biochar however decreased plant biomass and cob biomass under irrigation.