Abstract: 【Objective】The objective of these experiments is to clarify the effects of sub-soiling during the fallow period(SS) on soil water storage, explore the optimum seeding rate for constructing rational community of dryland wheat, and find out the best tillage and seeding technique, which could improve yield and quality coordinately. 【Method】 Field experiments were carried out from 2012 to 2014 in Wenxi, Shanxi province, with or without SS as the main plots and three seeding rates (67.5, 90, 112.5 kg·hm^-2) as subplots. Soil water storage during the fallow period, community tiller amount of plants before winter, dry weight and nitrogen content in different organs of plant, the yield and its components were measured to assess effects of seeding rate under SS on plant nitrogen absorption and utilization, yield, and grain protein content. 【Result】 The soil water storage efficiency during the fallow period was improved by more than 60% under SS compared with CK. Plant community tiller amount before winter, dry weight and nitrogen accumulation in plant at wintering stage, pre-anthesis accumulated nitrogen translocation amount from leaf and glume+spike to grains and nitrogen accumulation in the whole plant after anthesis were significantly increased under SS compared with CK. Plant community tiller amount before winter, dry weight at wintering stage and pre-anthesis accumulated nitrogen translocation amount from vegetative organs to grains and the contribution of pre-anthesis accumulated nitrogen translocation amount from leaf and glume+spike to grains were increased with the increase of seeding rate under SS while no significant difference between the seeding rate of 90 kg·hm^-2 and 112.5 kg·hm^-2 was presented. Spike number and grain number per spike were significantly increased under SS compared with CK, meanwhile, the yield was improved by 26%-66% and 17%-34% in two growing years respectively. Grain protein content was decreased under SS compared with CK, however, no significant difference was observed between them under 90 kg·hm^-2 condition. Spike number, 1000-grain weight and the yield were increased with the increase of seeding rate under SS, however, there was no significant difference between seeding rate of 90 kg·hm^-2 and 112.5 kg·hm-2. In addition, the highest grain protein content and its yield were observed under the seeding rate of 90 kg·hm^-2 under SS. Water use efficiency was significantly improved by 13%-22% and 9%-16% in two growing years, respectively, under SS compared with CK. Nitrogen uptake efficiency and nitrogen productive efficiency were significantly improved, and nitrogen use efficiency was significantly improved under the seeding rate of 67.5 kg·hm^-2 and 90 kg·hm^-2 condition under SS compared with CK. The highest water use efficiency was significantly observed under the seeding rate of 90 kg·hm^-2 condition under SS. Nitrogen uptake efficiency and nitrogen productive efficiency were improved with the increase of seeding rate under SS, while nitrogen productive efficiency had no significant difference between the seeding rate of 90 kg·hm^-2 and 112.5 kg·hm^-2 treatments. Moreover, under the condition of SS combined with different seeding rates, the yield and grain protein yield have significant and very significant correlation with pre-anthesis accumulated nitrogen translocation amount from vegetative organs to grains after anthesis, especially with the glume + spike under the condition of more precipitation. And nitrogen accumulation after anthesis was more significantly correlated with the yield under the condition of more precipitation. 【Conclusion】 Sub-soiling during the fallow period plus the seeding rate of 90 kg·hm^-2 was not only beneficial to form the strong seedlings before winter for dryland wheat, increase nitrogen accumulation of various organs at anthesis, promote pre-anthesis accumulated nitrogen translocation from leaf and glume + spike to grains, form the effective spike number, construct plant rational community of dryland wheat, and improve yield, water use efficiency, nitrogen uptake efficiency and nitrogen productive efficiency, and ultimately achieve the coordinated improvement of yield and grain protein content.

Key words: dryland wheat, sub-soiling during the fallow period, seeding rate, nitrogen absorption and utilization, yield, grain protein content