| 【Objective】The amount of nitrogen (N) application was reduced and topdressing was delayed to
further enhance N utilization efficiency and grain yield of rice.【Method】In the early and late cropping seasons of 2014,
comparison trials were conducted with 4 treatments, including zero applied N (T1) , farmer’s practice (T2) , “ThreeControl” technology with moderate-delayed N topdressing (T3) , and highly-delayed N topdressing (T4) . Tillering dynamics, growth, grain yield and N utilization efficiency of rice were determined. 【Result】In comparison to that under T2, the grain
yields under T3 and T4 were increased by 8.8% and 12.0% in early season (ES) or by 12.7% and 18.4% in late season (LS) ,
respectively. In both seasons, the total N uptake amount, N utilization efficiency, agronomic utilization efficiency and partial
fertilizer productivity of T3 and T4 were increased significantly compared with those of T2. The nitrogen uptake and growth
of plants under T3 and T4 were roughly slower than those under T2 before panicle initiation and they were both getting faster
afterwards. Compared with T2, leaf area index (source size) under T3 and T4 was increased by 11.5% and 35.4% and leaf
nitrogen content was enhanced by 27.7% and 50.8% at heading. The productive tiller rate (in absolute term) was enhanced by
6.8% and 18.3% in ES or by 5.5% and 19.4% in LS. Sink size was enlarged by 12.7% and 19.4% in ES or by 18.3% and 47.6%
in LS. In comparison to that under T3, the grain yield under T4 was increased by 3.0% and 5.0% in ES and LS, the productive
tiller rate was enhanced by 11.5% and 13.9%, the leaf area index and leaf nitrogen content were enhanced by 21.5% and
18.1% at heading stage and sink size was enlarged by 6.0% and 24.8%, respectively, but both grain filling rate and 1000-grain
weight were reduced moderately. The agronomicl efficiency of nitrogen was enhanced by 8.0% and 26.0%, respectively.
【Conclusion】Under the reduced and delayed N applications, both source and sink of rice were enlarged dramatically, and the
grain yield and nitrogen utilization efficiency were enhanced substantially. |
