Objectives The shortage of water resources in the Qinghai-Tibet Plateau affects the yield of hulless barley, however, it is still unclear about the extent of impaction on yield components and grain quality. This paper studied the impact of different water supply conditions, aimed at providing a theoretical basis for high efficient cultivation of hulless barley.

Methods Using hulless barley cultivar Kunlun 14 as the tested materials, a field experiment with random blocks design was conducted in a shelter. Three water supply treatments of adequate (75% field water capacity), mild water deficit (50% field water capacity) and severe water deficit (25% field water capacity) were designed. The yield components, and nutrition qualities including contents of NPK, protein and amino acids in grain were determined.

Results Compared with adequate water supply treatment, water deficit significantly reduced the number of ears per hectare, spike length, grains per spike, yield, tiller numbers, plant height. Mild water deficit significantly reduced the number of ears per hectare and the number of grains per spike, while severe water deficit significantly reduced the three factors of yield components. Under water deficit, the contents of nitrogen, potassium, protein and total amino acid in hulless barley grain were all increased, and severe water deficit exaggerated the effect. The contents of phosphorus, essential and nonessential amino acids of grain were significantly higher under severe water deficit than under adequate water supply.

Conclusions Mild water deficit is conducive to the root growth of hulless barley, and contributes to accumulate more protein and amino acids in grain. Therefore, appropriate irrigation should be further studied for saving water resources and reducing agricultural costs, and high quality of hulless barley products.