The interplay between water and nitrogen management in improving tomato ( <i>Solanum lycopersicum</i> Mill.) production: a comprehensive analysis of fruit yield and quality metrics

Tomato yield and quality are highly influenced by effective water and nitrogen management, making these factors critical for sustainable and profitable production. Balancing water and nitrogen inputs not only maximizes tomato productivity and enhances flavor, color, and shelf life but also minimizes resource waste and supports ecological health. A two-year study was carried out to study the effects of irrigation levels [75%, 100%, and 125% of crop water requirements (CWR)] and nitrogen rates [0%, 50%, 100% (recommended dose: 150 kg N ha−1), and 150% of the soil-test recommended dose] on tomato fruit yield and quality under controlled conditions. The results showed that the highest increases in fruit yield, diameter, and weight were recorded at CWR125%, along with 225 kg N ha−1. However, CWR125% reduced water use efficiency and fruit firmness. Moderate water stress (CWR75%) enhanced fruit total soluble solids, acidity, and firmness, particularly in later fruit clusters. Nitrate accumulation increased with higher N rates and peaked at CWR75%; however, higher N rates did not increase fruit nitrate content at CWR125%. Fruit lycopene and vitamin C contents were highest at CWR125% and 225 kg N ha−1. At CWR125% and 225 kg N ha−1, fruit vitamin C content was ∼14% higher in the 8th cluster. The response surface analysis revealed that the highest fruit yields (∼70–80 kg m−2) were obtained with a combination of 20 g N m−2 and a water supply of 0.35 m³ m−2. The results highlight that while CWR125% and 22.5 kg N ha−1 maximized yield, CWR100% balanced productivity, efficiency, and nitrate levels, promoting sustainable production.