Effect of surfactants on lettuce growth and water and nitrogen transport in soil

Abstract

【Objective】 Surfactants are soil conditioners to improve soil water flow and reduce soil erosion. This paper investigates their impact on water-nitrogen transport in soil, as well as yield, quality and root growth of greenhouse lettuce. 【Method】 The experiment was conducted in laboratory using a calcareous cinnamon soil. The soil was amended by three surfactants: HydravanceTM200 (T1, moisturizing and synergistic surfactant mix), Methylglucosan polyether-20 (T2, moisturizing single surfactant), and IrrigAid (T3, moisture-regulating surfactant mix), separately. For each surfactant amendment, there were two nitrogen treatments: without fertilization (N0) and nitrogen fertilization (N1). Soil without amendment by any surfactant was taken as the control (CK). During the experiment, we measured the changes in soil water content and soluble nitrogen content, as well as the growth and yield of the lettuce. 【Result】 ① Compared to CK, T1, T2 and T3 enhanced the lateral movement of water in the soil, thereby leading to an even soil water distribution and a reduction in nitrate nitrogen content in the subsoil layer (20-30 cm). ② According to the pot experiment, the above-ground fresh mass and VC content of lettuce in the T1N1 treatment increased by 26.61% and 175.61%, respectively, in addition to the 2.10 times increase in nitrogen utilization efficiency (P˂0.05). Compared to CKN1, T2N1 significantly increased VC content by 104.88%, while T3N1 significantly increased total root length and volume by 61.98% and 112.90% (P<0.05), respectively. In comparison with CKN0 treatment, the aboveground fresh mass, VC amount and nitrate amount of lettuce in T1N0 treatment were significantly reduced by 19.57%, 43.84% and 81.75%, respectively; T2N0 reduced VC content and nitrate content by 24.66% and 86.52% (P˂0.05) respectively, and T3N0 reduced nitrate content by 68.50% (P˂0.05) and increased total root length and volume by 51.64% and 87.18% (P˂0.05) respectively. 【Conclusion】 All three surfactants increased lateral movement of water in the soil, thereby improved water and nitrogen distribution and their adsorption by lettuce roots. However, their efficiency in improving growth, yield, quality and nitrogen utilization of the lettuce depends on nitrogen fertilization.

Keywords

• surfactant
• lettuce
• water-nitrogen transport