Tomato (Solanum lycopersicum) yield response to drip irrigation and nitrogen application rates in open-field cultivation in arid environments

A field experiment at Qatar University's Agricultural Research Center examined how varying drip irrigation water and nitrogen levels affect tomato yield, quality, and water-use efficiency. The study employed a split-plot design in a randomized block setup, with full irrigation (FI) at 100 % and deficit irrigation (DI) at 50 % of FI as main plots, and nitrogen rates (N1: 50 kg ha-1, N2: 70 kg ha-1, N3: 100 kg ha- 1) as subplots. Treatments were labeled as T1 (DIN1), T2 (DIN2), T3 (DIN3), T4 (FIN1), T5 (FIN2), and T6 (FIN3). Results revealed significant improvements in vegetative growth, SPAD Index, yield, yield components, water use efficiency, and quality parameters with increasing nitrogen levels up to N2 under 50 % DI. Compared to FI, DI saw a significant 1.41 % increase in shoot height (SH) and similar trends in other parameters, with enhancements ranging from 4.84 % to 27.78 %. Overall, DI exerted a more pronounced influence on tomato production than nitrogen levels. The interaction between irrigation and nitrogen treatments significantly affected all variables except dry matter and pH. The highest yield (65.14 t ha- 1) occurred at T3, 23.92 % higher than the lowest yield at T4 (49.56 t ha- 1), followed by T5, T2, T1, and T6 (64.16, 58.46, 55.66, and 55.60 t ha- 1). At DI, which yielded the highest fruit yield, the highest WUE was observed at N3 (T3) with a value of 0.78 kg ha- 1 mm-1, while the lowest WUE of 0.46 kg ha- 1 mm-1 was recorded at T4, corresponding to the lowest yield of 49.56 t ha- 1. Total soluble solids (TSS) peaked at T2 (7.05 degrees Brix) and were lowest at T6 (5.04 degrees Brix), while acidity showed a significant interaction with the highest level at T2 (0.51 %) and the lowest at T1 (0.31 %). No significant interactions were observed for DM and pH. This study underscores the importance of implementing deficit irrigation strategies, especially when paired with appropriate nitrogen levels, to boost tomato yield, quality, and water use efficiency in arid environments like Qatar.