Crop management based on multi-split topdressing enhances grain yield and nitrogen use efficiency in irrigated rice in China

- Approaches for achieving high-yields and improving NUEs were investigated.
- Rice grain yield and NUEs were significantly varied on crop managements.
- The Super-high-yielding management and the Multi-split topdressing fertilizer-N achieved greatest grain yield, and the former was based on higher inputs, the later was due to stimulate the plant uptake capacity for nutrients.
- Multi-split topdressing fertilizer-N management increased grain yield and NUEs simultaneously, which may result in a highest production profit among the investigated crop managements.

Numerous prior studies on improving crop managements in new commercial rice varieties focused on optimizing N rates and its splitting during the rice growth cycle. Studies concerning how multi-split topdressing fertilizer-N can affect rice growth, grain yield, and nitrogen use efficiencies (NUEs) are limited. A field experiment was conducted in an irrigated rice system using hybrid rice variety Yangliangyou-6 during 2012 and 2013 in Wuxue county, Hubei Province, China. Five treatments were investigated, including nitrogen omission plot (N0), and the other four typical crop management patterns in irrigated rice system in southern China: the conventional farmer's practice (FP), modified farmer's practices (MFP), super-high-yielding management (to obtain a high yield regardless labour or fertilizer input, SHY), and multi-split topdressing fertilizer-N (MST). Data from the two years revealed that the SHY produced the highest grain yields (10.27 and 9.63 t ha−1) in two of the four trials, while the MST achieved the highest grain yields (10.08 and 9.67 t ha−1) in the other two trials. The higher grain yields of the SHY and MST were ascribed to the greater N uptake, biomass accumulation, and total spikelet numbers per m2 compared to the other treatments. The FP showed a lower N uptake, agronomic efficiency (AE), and recovery efficiency (RE) than those of the MFP, SHY, and MST. Compared with the FP, the MFP increased the planting density and delayed partial fertilizer-N at the panicle initiation stage, which resulted in greater N uptake and RE. However, the MST reduced N application but significantly increased N uptake, AE, and RE compared to that observed in the FP and MFP. Overall, these results indicate that the crop management for N application to achieve greater yield and higher NUEs in hybrid rice is primarily associated with fertilizer-N application splits, rather than N rates. Our findings demonstrate that the crop management based on the MST may obtain a higher grain yield and reduced N application comparing to other crop managements, which results in a greatest profit assuming it is adapted by the large-scaled farmers in South China. Therefore, the MST is recommended as one of alternative approaches to synchronously increase the grain yield, NUEs and production profit with a lower N application in the irrigated rice systems in the Yangtze River Basin in China.