Subsurface Drip Lateral Line Depths to Protect against Root Intrusion

Abstract

Root intrusion into emitters poses a threat to the lifespan of subsurface drip irrigation systems. In an attempt to address this problem, an experiment was conducted on spring wheat (Mengmai 30) grown in soil columns installed in a greenhouse to study the effects of lateral line depths to reduce root intrusion into emitters. The soil columns are rectangular containers, and the dimensions were 15 cm, 60 cm, 100 cm. The soil matric potential at a 20 cm depth immediately over (lateral line depth <20 cm), under (lateral line depth >20 cm), or next to (lateral line depth = 20 cm) the drip emitters was used to schedule the subsurface drip irrigation regime. Five different lateral line depths, with depths of 10, 20, 30, 40, and 50 cm, were maintained. The lateral line depths influenced the spring wheat root distribution, emitter flow rate, root intrusion, and spring wheat yield and quality. Results indicated that the shallower the lateral line depth, the more root was distributed in the surface layer. Root density values increased with soil depth. The emitter flow rate (eventual flow rate divided by the initial flow rate) increased as the lateral line depth decreased. All the treatments had root intrusion except 50 cm treatment. Root intrusion increased as the lateral line depth decreased. The lowest root intrusion rate (0%) was achieved with a lateral line depth of 50 cm. The greatest relative yield was achieved with a lateral line depth of 30 cm. After root intrusion and yield were both considered, the lateral line depth of 30–40 cm was a better choice.