Comparison of drip fertigation and negative pressure fertigation on soil water dynamics and water use efficiency of greenhouse tomato grown in the North China Plain

Maintaining a stable soil water supply is the key for solar greenhouse vegetable production across the North China Plain. A three-season field experiment was conducted over 2 years to evaluate two methods of applying Yamazaki tomato nutrient solution (negative pressure and drip fertigation; NF and DF, respectively) for production of greenhouse tomato and water use efficiency (WUE). Soil moisture in the surface (0-20 cm) and entire soil profile (0-100 cm), as well as soil water storage (SWS) and crop evapotranspiration (ET) levels were measured during the growing season. Then, plant growth, fruit yield, and WUE were compared. The variations in soil moisture (0-20 cm) were small for the NF treatment, with ranges of 20.0-25.0% and 22.2-24.3% in the early spring and autumn winter seasons, respectively, which were less than the ranges of 19.7-28.5% and 21.4-26.7% for DF. The average SWS did not significantly differ between DF and NF treatments, while SWS in NF (318.6-339.3 mm) during the growing season showed small fluctuations compared with DF (315.7-342.9 mm). The ET over the whole growing season varied in the range of 224.0-319.9 mm, which was higher during fruit-set and flowering than other growth periods. With its higher irrigation amount, DF had a higher ET level than NF, but there was no significant difference in early spring. The consecutive and stable water supply of NF improved tomato plant height and stem diameter (P < 0.05) and improved fruit yield and WUE by 1.6-8.2% and 9.9-30.5% (P < 0.05), respectively, compared with DF. These results demonstrate that the NF system can save more water (11.3% and 32.0% in the ES and AW seasons, respectively) than DF. As a new mode of integrated water and fertilizer management, NF is appropriate for vegetable production in solar greenhouses.