Nitrogen, Phosphorus and Year Effects on Grain Yield, Thousand Kernel Weight and Hectoliter Weight in Maize Crop

Efficient nitrogen (N) and phosphorus (P) fertilization is essential for optimizing maize yield. A three-factorial field experiment was conducted at the Agricultural Research and Development Station (ARDS), Turda, Romania, during 2022 to 2024, using the maize hybrid Zea mays L. Turda 344. The experimental factors included year (2022, 2023, 2024), nitrogen fertilization (0-200 kg/ha N), and phosphorus fertilization (0-160 kg/ha P₂O₅), established in a randomized complete block design with six replications on clay-loam Chernozem soil. The results showed significant main effects of year and nitrogen on yield, with 2023 producing significantly higher yields compared with the other years. Grain yield increased from 5093 kg/ha under unfertilized conditional (N0) to a maximum of 6666 kg/ha at an optimal nitrogen rate of 150 kg/ha N. Phosphorus application resulted in a modest yield increase, from 5,881 kg ha⁻¹ (P0) to 6,146 kg ha⁻¹ at the highest P rate. Thousand-kernel weight (TKW) showed a strong response to nitrogen, whereas hectoliter weight (HW) remained mostly unchanged. These findings indicate that nitrogen is the primary driver of yield improvements under the local agro-climatic conditions, with an optimal application rate of 150 kg/ha N recommended for sustainable maize production.