Hydraulic-infiltration Characteristics and Proportion Optimization of Coconut Coir-type Ecological Conservation Substrate

[Objective] Stressed by harsh environmental factors such as scarce precipitation and large evaporation, the desert Gobi is characterized as spare vegetation and severe soil and water losses. Therefore, exploring suitable soil improvement methods to improve soil water retention and water holding capacity is very important for the development of Gobi ecological agriculture. [Methods] The hydraulic-infiltration characteristics of the 3 groups of coconut coir-type ecological conservation substrates with better physicochemical properties (aeolian soil∶ coconut coir∶ organic fertilizer∶ artificial peat = 3.5∶3∶3∶1 or 3∶4∶3∶1 or 2∶5∶3∶1, i.e., T1, T2, T3) were tested compared to the control substrate with no coconut coir (aeolian soil∶ organic fertilizer∶ artificial peat = 7∶3∶1, T0). The relationship between matrix water and suction was determined by the centrifuge method, and then the hydraulic characteristics were explored. Then, the infiltration characteristics of the substrates were analyzed by the indoor infiltration test of the soil column with constant water head; and, based on the measured indicators, the proportion optimization was carried out by the coordinate comprehensive evaluation method. [Results] Compared with the T0 group, the field water retention capacity of the T1, T2 and T3 groups increased by 10.22%, 12.13% and 14.99%, and the total effective water content increased by 8.10%, 8.81% and 12.83%, respectively. In the stage of Pf=1.8~3.8 (logarithmic matrix suction), the average specific water capacity of each group showed a law of T3 > T2 > T1 > T0, and according to the gray correlation analysis (RGA) method, the infiltration capacity was ranked as T3 > T2 > T0 > T1. [Conclusion] The results showed that a suitable proportion of coconut coir mixing changes the effective water content and pore distribution ratio, which can significantly improve the water retention capacity of the substrate. From the perspective of physicochemical properties, hydraulic and infiltration characteristics, the T3 ratio is optimal.