The effect of brackish water drip irrigation on soil enzymatic activities and yield of greenhouse cucumber

Abstract

【Objective】 Brackish groundwater can be used as a complementary irrigation resource to safeguard crop production in regions lacking freshwater resources. The purpose of this paper is to study the effect of the salinity of brackish water and soil water content on spatiotemporal variations in soil enzymatic activities, as well as growth and yield of cucumber. 【Method】 The experiment was conducted in an greenhouse, with the cucumber irrigated by brackish waters with salt concentrations of 5 (E1), 3.5 (E2), 2.5 (E3), 0.5 g/L (E4), respectively. We measured soil matric potential at the depth of 20 cm underneath the drip emitter, such that irrigation was resumed when the matric potential decreased to -15 kPa (L1), -25 kPa (L2) or -35 kPa (L3), respectively. In each treatment, we measured the spatiotemporal changes in activities of urease, alkaline phosphatase and sucrase in the soil, as well as growth and yield of the cucumber. 【Result】 The activities of all three enzymes decreased vertically with the soil depth and horizontally with the distance from the drip emitters. The three enzymes were most active in the top 0-20 cm soil layer, 0-15 cm away horizontally from the drip emitters. Irrigation with water at salt concentration of 0.5-2.5 g/L improved the alkaline phosphatase activity, with limited effect on the activities of urease and sucrase. Increasing water salinity to 3.5-5 g/L suppressed the activities of all three enzymes. With the decrease in soil matric potential used for irrigation control, the activity of sucrase increased steadily, while the activities of urease and alkaline phosphatase increased first followed by a decrease. Irrigation with water at salt concentration of 3.5-5 g/L significantly inhibited the growth and development of the cucumber, while reducing the soil matric potential used for irrigation control to -35 - -25 kPa improved the cucumber growth and yield. 【Conclusion】 Irrigating greenhouse cucumber using brackish water with salt concentration of 0.5-2.5 g/L and resuming irrigation whenever the soil matric potential at the depth of 20 cm underneath the drip emitters decreased to -35 - -25 kPa can improve cucumber production without resulting in noticeable soil quality deterioration.

Keywords

• cucumber
• slightly saline water
• soil enzyme activity
• yield