Management of nitrogen (N) fertilizer is a constant topic in crop cultivation aiming at high-yield and good-quality production as well as environmental protection. In winter wheat–summer maize rotation system, N fertilizer input in the wheat season has a subsequent influence on the maize season. In this study, we carried out a two-year field experiment in Linyi of Shandong Province, China from 2009 to 2011 with treatments of four N application rates and two topdressing schemes. In the wheat season, the N application rates were 0 (N0), 168.75 (N1), 225 (N2), and 281.25 kg ha-1 (N3), and the topdressing N was given at jointing stage (S1) and jointing + anthesis stage (S2). In the maize season, N fertilizer of 60 kg ha-1 was applied before sowing and 90 kg ha-1at 12-leaf stagein all treatments except for N0 (no N applied in the maize season as well). The dry matter accumulation and distribution, grain yield, nitrogen agronomic use efficiency (NAUE), and nitrogen partial factor productivity (NPFP) were investigated in both wheat and maize seasons. Under the S1 condition, dry matter accumulations in grains of wheat and maize and the biomasses of maize as well as the biomass of both crops heightened with N rate increased, but the grain yields of wheat and maize had no significant differences between N2 and N3 treatments. As the N rate increased, NAUE and NPFP decreased in winter wheat but increased gradually in summer maize; however, the difference in NPFP between N2 and N3 was not significant. Under the S2 condition, the dry matter accumulations in grain, biomasses, and grain yields of wheat and maize had no significant increases in N3 treatment compared to N2 treatment, although the N application amount was promoted by 25% in N3 treatment. The NAUE and NPFP of wheat decreased significantly due to the more distribution of dry matter in vegetative organs of wheat in N3 treatment than in N2 treatment; whereas, the NAUE and NPFP of maize had no significant changes. In the wheat season, compared to S1, S2 was favorable to increase dry matter accumulationsin grain and vegetative organs, biomass, grain yield, NAUE, and NPFP of winter wheat in treatments N1 and N2, but had no significant effects in treatment N3; in the maize season, S2 showed positive effects on these indices of summer maize in treatments N1, N2, and N3. With the comprehensive consideration of total biomass and grain yield of wheat and maize, NAUE, and NPFP, total N fertilizer of 225 kg ha-1 in wheat season associated with topdressing at jointing and anthesis stages of wheatare recommended as the optimal management mode in winter wheat–summer maize rotation system under similar conditions to this experiment.
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