Optimizing planting density and nitrogen application to enhance maize yield while mitigating carbon emission in...

Optimizing planting density and nitrogen application rate are key factors for increasing maize yield, but they also significantly affect farmland CO₂ emissions. The appropriate nitrogen application rate and planting density for achieving high-yield and low-carbon maize production in southern Xinjiang remain to be determined.

A field experiment was conducted to investigate the effects of planting density and nitrogen rate on soil CO₂ emissions, carbon balance, and maize yield in 2024 and 2025. The treatments included four nitrogen rates (0 (N0), 180 (N1), 270 (N2), 360 (N3) kg N ha^-1) and four planting densities (90,000 (D1), 120,000 (D2), 150,000 (D3), 180,000 (D4) plants ha^-1).

The results showed that soil respiration rate exhibits a distinct unimodal curve, reaching its maximum during the maize flowering stage, and showed a highly significant positive correlation with soil temperature. Soil CO₂ emission under N0, N1, and N2 treatments were lower than under the N3 treatment, under the D1, D2, and D3 treatments were lower than under the D4 treatment. Compared to N0 and N1, the N2 increased grain yield by 47.9% and 15.8%, increased carbon emission efficiency by 32.6% and 8.9%, no significant between N2 and N3. Compared to the D1, the D2 and D3 increased grain yield by 7.5% and 11.9%, carbon emission efficiency under the D1, D2, and D3 increased by 9.1%, 10.2% and 8.4%, compared to the D4, respectively. The N2 treatment increased NEP compared to N0 and N1, but no significant with N3. NEP under D2 was higher than under D4 in 2024, no significant difference was found among D2, D3, and D4 in 2025.

In conclusion, applying nitrogen at approximately 270 kg ha^-1 and adopting planting densities of 120,000-150,000 plants ha^-1 under maize fields in southern Xinjiang can ensure high yields while mitigating CO₂ emissions. This approach also optimizes carbon emission efficiency and enhances the carbon sequestration potential of farmland, representing an optimized strategy for achieving green and intensive agricultural production.