Guan'gai paishui xuebao (Jan 2022)
The Integrative Effects of Irrigation and Aeration on Growth and Water Use Efficiency of Greenhouse Tomato
Abstract
【Objective】 The rhizosphere can become hypoxia as soil water content increases thereby hindering root respiration and hampering crop growth. Bubbling subsurface drip-irrigation water is one remediation to ameliorate root-zone anaerobicity and has been increasingly used in facility agriculture production. Since water content and oxygen concentration in the soil counter each other, this paper is to investigate their optimal combination to sustain greenhouse tomato production in northern and central China. 【Method】 The experiment was conducted in a solar greenhouse with micro-nano air bubble mixed with water before drip-irrigating it to the subsurface. We compared three oxygen concentrations: 3~5 mg/L (O1), 15 mg/L (O2) and 25 mg/L (O3); each aeration had three irrigation treatments with the average soil moisture in the root zone controlled at 50%~70% (W1), 65%~85% (W2) and 80%~100% (W3) of the field capacity, respectively. We measured the change in growth, physiological traits, yield and water use efficiency in each treatment. 【Result】 Increasing soil water content not only increased plant height and stem diameter, but also affected the leaf net photosynthetic rate (Pn), stomatal conductance (Gs), intercellular carbon dioxide concentration (Ci) and transpiration rate (Tr) of the crop, all at significant levels. Irrigation and aeration jointly affected Tr. When irrigating with sufficient water (W3), a moderate aeration (O2) maximized the dry matter accumulation. The dry root matter increased with both soil water content and the dissolved oxygen concentration significantly (P<0.01), while soil water affected shoot biomass more significantly (P<0.01) and the irrigation-aeration integration (P<0.05). With the increase in soil water content, the root-shoot ratio declined first followed by an increase, while it monotonically increased with the dissolved oxygen concentration. The yield/per plant and water use efficiency (WUE) both increased with soil water content significantly, while with the dissolved oxygen concentration increasing, the yield increased first followed by a decrease. Of all treatments we compared, O2+W3 gave the highest yield, 1.77 kg/plant. Irrigation-aeration was also found to impact WUE significantly; compared with O1, O2 and O3 improved the WUE by 26.8% and 21.4%, respectively, when irrigating the crop with sufficient water (W3). 【Conclusion】 Aerated irrigation benefited tomato growth and yield due to the boosted root growth. For the treatments we compared, aerating the subsurface drip-irrigation water to 15 mg/L (dissolved oxygen) coupled with a sufficient irrigation (O2+W3) was optimal for greenhouse tomato production in the area we studied.
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