[Relationships of water conservation through mulching in fallow period with wheat nitrogen transportation and crop yield in dryland].

Field experiments were carried out to study the effects of different mulching times (30 or 60 d after previous wheat harvest) and mulching methods (whole-mulching, half-mulching and no- mulching) on wheat plant N absorption and assimilation after deep plowing in fallow period on dryland. The results showed that mulching improved water storage efficiency in fallow period and soil water storage of 0-300 cm at sowing stage significantly. Mulching in fallow period, especially the whole-mulching, increased the N accumulation amount of each growth stage, N translocation amount and rate before anthesis (NABA) , and N accumulation amount after anthesis (NAAA) and grain N. Yield, N uptake efficiency (NUPE), N partial factor productivity (NPFP) and N harvest index (NHI) were all significantly increased under mulching, and whole-mulching had better effects. Mulching at 30 d after previous wheat harvest significantly increased the soil water storage of 0-300 cm at sowing stage and the water storage efficiency in fallow period compared with mulching at 60 d after previous wheat harvest. Compared with mulching at 60 d after previous wheat harvest, mulching at 30 d increased the N accumulation amount of each growth stage, the N accumulation amount in leaf and shoot at maturity, the NABA of stem + sheath, leaf and shoot and the yield. The soil water at the depth of 0-300 cm at sowing stage was positively correlated to N mobilization amount before anthesis and N accumulation amount after anthesis. The N mobilization amount of stem + sheath had a remarkable direct effect on its yield with the direct path coefficient of 0.619. In summary, mulching in fallow period increased the soil moisture at sowing stage to promote N absorption and utilization, increase yield and improve quality, and whole-mulching in advance had better effects.