Drip Irrigation Scheduling for Tomato Grown in Solar Greenhouse Based on Pan Evaporation in North China Plain

This study has investigated the suitable drip irrigation scheduling for tomato grown in solar greenhouse based on 20-cm pan evaporation (Epan) in North China Plain. Irrigation treatments included three irrigation frequencies (I1 10, I2 20 and I3 30 mm, and irrigation interval of 2–6 d for I1, 4–9 d for I2 and 8–12 d for I3) based on accumulated pan evaporation (Epan), and four plant-pan coefficients (Kcp1 0.5, Kcp2 0.7, Kcp3 0.9 and Kcp4 1.1). Results indicate that total irrigation amount, seasonal crop evapotranspiration (ET) and tomato yield (Y) were 185.1-365.8 mm, 249.1–388.0 mm and 99.6–151.8 t ha−1, respectively. Irrigation frequency and amount increased the yield, and second-degree polynomial relationship was found between Y and ET (R2=0.8671). Irrigation frequency did not increase mean fruit weight, diameter and length significantly but increased fruit number, total soluble solids content (TSS), TSS yield, fruit firmness and water use efficiency (WUE) and irrigation WUE (IWUE) significantly. Irrigation amount increased external quality of tomato but reduced TSS content, TSS yield, fruit firmness, WUE and IWUE significantly. Kcp3 and Kcp4 treatments had the highest fruit yield, but Kcp2 and Kcp3 treatments had the highest WUE. I1Kcp3 treatment (irrigation interval of 2–6 d, and Kcp=0.9) had higher IWUE, WUE, external quality, yield, and TSS yield, so it is recommended as the suitable irrigation scheduling for tomato grown in solar greenhouse in North China Plain.