Objective  Synchronous side deep fertilization technique of rice machine-transplanting realized the combination of agricultural machinery and agronomic technology. The appropriate amounts of nitrogen (N) in the synchronous deep side fertilization technique of rice machine-transplanting were selected and the cost-saving and efficient-increasing effects were discussed.

  Method  Field experiments were conducted in 2019 and 2020 with a randomized complete block design at two different places, with different N application levels: CK, without N fertilizer; FP, Farmers’ fertilization amount; T1-T5, side deep fertilization for N-reducing amounts. The N use efficiency (NUE), yield components, yield and economic benefit of rice were determined.

  Result  Each N fertilizer application treatment had similar effects on yield formation and NUE in Panjin and Liaoyang in the two years. When the N application rate decreased by 17.08% and 17.17%, the target yield of farmers could still be obtained, and the economic benefit increased by 1232-1440 yuan hm⁻² and 581-799 yuan hm⁻², which reached a significant level. Stable yield could be obtained after reducing N application. Nitrogen uptake and use efficiency (NRE), nitrogen agronomic efficiency (NAE) and partial productivity (NPFP) of rice were significantly increased. In Panjin and Liaoyang, NRE increased by 8.41%-21.19% and 10.44%-15.77%, NAE increased by 2.23-3.57 kg kg⁻¹ and 0.10-2.23 kg kg⁻¹. NPFP was significantly higher than that of FP.

  Conclusion  Under stable yield condition, mechanical transplanting synchronous deep side fertilization technology can reduce N fertilizer dosage by 17%, reduce transplanting operation cost by 600 yuan hm⁻², save fertilizer input cost by 3.16%-4.53%, increase economic benefit by 581-1440 yuan hm⁻², and significantly save cost and increase efficiency.