Impacts of Drought and Irrigation on Root and Yield of Winter Wheat
By carrying out different degrees of drought, rehydration test at Zhengzhou Agricultural Meteorological Experimental Station, we studied the effects of different water conditions on the root vigor morphology and yield of winter wheat, to establish an optimized irrigation system for winter wheat in Henan Province, improve water use efficiency and achieve the goal of water saving and yield increasing. The results showed that under drought conditions, the root vigor and stem diameter of winter wheat decreases significantly, but the root length increases significantly, and the proportion of lower soil roots volume increases. In addition, with the development of the growth stages, the proportion of the lower soil roots volume increases, and the water use efficiency improves significantly. Along with the increase of drought degree, the above trend is more obvious. In the case of same amount of water recovery, overwintering irrigation is beneficial to the increase of root vigor and root diameter of winter wheat, but unfavorable for roots to extend downward. In the greening and jointing stages, irrigation is good for the roots stretching down, water use efficiency, grain weight and theoretical increase of yield, but not conducive to the increase of root vigor and diameter. For the purpose of improving water use efficiency, it is appropriate to increase irrigation volume and reduce the times of irrigation. Comprehensive analysis of root morphology and vitality, water use efficiency and yield shows that under the condition of persistent drought in winter wheat， irrigation is about 600 m3·hm-2 at the turning green stage and booting stage, so the amount of irrigation can be increased or decreased appropriately according to the degree of drought. Irrigation times can be increased appropriately under severe drought conditions. In severe drought years, under difficult irrigation conditions, only 600 m3·hm-2 can be irrigated at jointing stage to achieve the loss reduction of yield and water saving effect.