Fertigation-N Scheduling and Plant Density Affect Canopy Development, Fresh-Ear Yield, and Economic Return of Waxy Maize in the Ili River Valley, China

Because fresh waxy maize is harvested as whole ears within the brief milk-stage (R3) window, its yield formation hinges on building a strong canopy and ear foundation before silking; nitrogen (N) applied afterward mainly provides supplementary support. A split-plot trial conducted in 2024–2025 in Xinjiang’s Ili River Valley used the cultivar Wannuo 2000 to test how fertigation-N scheduling and plant density jointly govern canopy function and marketable yield. Five N regimes, each supplying 300 kg N ha−1, were compared: conventional flood irrigation (CK) and drip fertigation split across three to six applications (DT-3 through DT-6), at densities of 79,500–88,500 plants ha−1. CK and DT differed in irrigation amount, and the highest planting density of 88,500 plants ha−1 was only set in 2025. Relative to DT-3, DT-5 sustained a larger canopy at R1 and a slower decline through R3, raising post-silking dry-matter accumulation by 24.9–25.8% over CK. Fresh-ear yield rose 10.8–11.8%, and the marketable-ear rate climbed from 81.4% to 87.7% (p < 0.001). Shifting 30% of N to after silking under DT-6, however, failed to offset a less balanced pre-/post-silking distribution: yield, marketable-ear rate, and net return all fell short of DT-5 by 478 kg ha−1, 1.37 percentage points, and 1301 CNY ha−1, respectively (p ≤ 0.026). Post-silking dry matter correlated positively with plot-level yield (r = 0.76), though this response to N scheduling weakened at the highest density (D × N, p < 0.001). These findings show that profitable fresh waxy maize production demands season-long coordination of N supply with crop demand, achieved jointly with density management, and that marketable-ear formation, not yield alone, should anchor how such strategies are judged.