Impact of planting density and nitrogen application on maize source-sink relationships and yield under drip irrigation

Increasing planting density and efficient N application are key agronomic practices for improving maize yield. However, the effects of these practices on the source-sink relationship and yield dynamics under drip irrigation with fertigation remain poorly understood. This study aimed to examine the impact of planting density and N application on maize yield and source-sink dynamics under drip irrigation with fertigation. The experiment was conducted in Northeast China over two years, with two planting densities :60,000 (D1) and 90,000 (D2) plants ha -1 and six N levels: 0 (N0), 90 (N90), 180 (N180), 270 (N270), 360 (N360), and 450 (N450) kg ha -1 . Drip irrigation combined with fertigation was used, where fertilizers were delivered through the irrigation system at regular intervals. The results indicated that at 90,000 plants ha -1 , applying 270 kg ha -1 of N resulted in maize yields of 17.27–17.70 t ha -1 , highlighting a synergistic effect between planting density and N application. Increasing planting density also led to a 29.88% increase in leaf area index (LAI) and a 2.17% increase in relative chlorophyll content (SPAD). Reducing N to 180 kg ha -1 at 60,000 plants ha -1 and 270 kg ha -1 at 90,000 plants ha -1 had little effect on photosynthesis (LAI and SPAD) or sink strength (grain-filling duration, maximum filling rate, and maximum grain weight). At 90,000 plants ha -1 with 270 kg ha -1 N, the source-sink ratio was closer to 1, compared to 60,000 plants ha -1 with 180 kg ha -1 N. Under N deficiency, maize yield was constrained by source capacity. However, with adequate or excessive N, source capacity was enhanced, improving the source-sink balance and increasing yield. These findings provide valuable insights into optimizing maize yield and N management strategies under fertigation.