Influence of Green Manures and Fertilization on Maize (Zea mays L.) Yield and Quality

Maize is one of the most important agricultural crops worldwide, due to its high production potential and the multiple uses of its products. In the context of the need to maintain high yields and preserve soil fertility, the use of green manures together with mineral fertilizers can represent a sustainable solution. For this purpose, during the period 2024–2025, at the Turda Agricultural Research and Development Station (Cluj, Romania), a field experiment was carried out to evaluate the effect of two cover crops used as green manures, white lupin (Lupinus albus) and phacelia (Phacelia sp.), on the Turda 344 maize hybrid. Within each agrofund (classical, after lupin, and after phacelia), five fertilization variants were tested, consisting of basic fertilization and the supplementary application of mineral fertilizers and biostimulants. The results highlighted the major influence of climatic conditions on yield and grain quality, with the experimental year having a significant effect on the main parameters analyzed. In 2024, under basic fertilization, lupin and phacelia increased grain yield by 8.0% and 1.4%, respectively, compared with the classic agrofund, while in 2025, phacelia maintained a yield advantage of 1.4%. The highest yields were obtained in 2025, when climatic conditions were more favorable, and additional fertilization with ammonium nitrate determined the highest values, reaching 9748 kg/ha in the phacelia agrofund (+6.3% compared with the basic fertilization), 9544 kg/ha in the lupine agrofund (+7.2%), and 9612 kg/ha in the classical agrofund (+6.3%). Additional nitrogen application also led to the highest values of thousand kernel weight, highlighting the essential role of nitrogen in the grain filling process. Grain quality analysis showed that variations in starch and protein content had an inverse evolution between the two experimental years, suggesting the influence of climatic conditions and nitrogen availability on grain composition.