Abstract:
Abstract: It is very important to improve water use efficiency for the development of water-saving agriculture in high altitude semi-arid cold region of Tibet. In order to obtain a suitable lower control limit of soil moisture content for irrigation and set up water-saving irrigation regime, the responses of spring highland barley to water deficit level in various growth stages were investigated by a field experiment under straw mulching condition in 2014. Experimental treatments included full irrigation treatment in whole growth period (control) and water deficit treatments that exerted in seedling, jointing, heading, filling, and mature stages respectively. The lower control limit of soil moisture content was 75% of soil field capacity in full irrigation treatment. In water deficit treatments, the lower control limit of soil moisture content was 65% (slight water deficit) and 55% (heavy water deficit) of soil field capacity in the growth stage that water deficit was imposed, and that in the other growth stages was 75% of the soil field capacity. The upper control limit of soil moisture content for irrigation was soil field capacity for all the experimental treatments. The results showed that water deficit treatments in various growth stages significantly decreased water consumption amount and daily water consumption intensity of spring highland barley (P<0.05), and the degree of decrease increased with the increased water deficit level. Mean water consumption intensity all over the whole growth period was 4.9 mm/d with a maximum value of 7.3 mm/d that occurred at heading stage under full irrigation treatment, and the water consumption intensity was 4.0-4.6 mm/d under various water deficit treatments. The effect of water deficit treatment imposed in the filling stage of spring highland barley on crop water consumption amount was biggest and that of water deficit treatment in the heading stage was second in all water deficit treatments. Compared with full irrigation treatment, the water consumption amount of spring highland barley was decreased by 56.4-68.0, 82.1-124.7, 36.0-71.3, 142.2-175.9, and 43.6-48.2 mm, respectively, for the water deficit treatments exerted in seedling, jointing, heading, filling, and mature stages. Water deficit did not significantly affect the ear length, seeds per ear, thousand seed weight, harvest index, and grain yield of spring highland barley. Under the experimental conditions, water deficit treatments exerted in various growth stages did not significantly result in the reduction of grain yield, but water use efficiency was increased by 10.5% and water-saving percentage was 11.7% on average. Water deficit treatment imposed in the filling stage of spring highland barley resulted in a highest water use efficiency of 1.77-1.84 kg/m3 and a biggest water-saving percentage of 19.6%-24.2% in all experimental treatments. In a word, when the lower limit of soil moisture content was controlled at 55% of soil field capacity, water deficit did not significantly affect the yield and its components of spring highland barley, and meanwhile a high water-saving percentage was obtained. This indicates that spring highland barley has a great water-saving potential and possibility if straw mulching management measure is adopted in the high altitude semi-arid cold region of Tibet. The effects of water deficit treatments in multiple growth stages on the growth of spring highland barley need to be studied further.