Drip irrigation systems are mostly installed permanently or semi-permanently above the ground. When applied to irrigate trees and vine crops, they promote no problem. However, when applied to irrigate field and vegetable crops, certain problems occur, mostly because the drip irrigation systems have to be installed and retrieved annually. The annual handling is harmful to the life time span of the system, even under the best handling conditions. Hence the subsurface drip irrigation system emerges.
The depth installment of subsurface drip irrigation system is determined by the soil type and the crops planted. An efficient installation has water moving at the depth of 4 to 30 inches beneath the surface, forming a continuous watered area along the plants row. Frequent irrigation cycles, up to several times every day, maximize capillary action and minimize water surfacing.
Four subsurface drip irrigation systems have been designed, installed and successfully produce better yields by the Water Management Research laboratory of the USDA in Fresno. The oldest one was installed in 1981 and used for three years to irrigate tomatoes. During those years, they also successfully produced twice as much broccoli, at the same farm.
Subsurface drip irrigation system allows the precise application of water, nutrients and other agricultural chemicals directly to the plants root zones. It allows the optimization of growing environment, which leads to higher quality and quantity crop yields.
With the same amount of water, subsurface drip irrigation system waters 46% larger volume of soil than any conventional (surface) drip irrigation system. It decreases the soil saturation, which not only leaves room for more air, but also improves water capillary movement and decreases water loss due to deep percolation. The top 15 – 20 cm of soil remains dry, therefore evaporation of water at the top of the soil may decrease and less salt will accumulate at the surface.
Permanent installation of subsurface drip irrigation system also provides considerable labor saving since irrigation can be applied while the whole equipment stays in the farm.
Any soil surface crusts which usually lead to infiltration problems are no longer trouble makers; they are bypassed if this subsurface drip irrigation system is installed. Other farming applications required to support the conventional drip irrigation system is no longer required, too.
Since subsurface drip irrigation system is installed below the ground, all components are not exposed to sun light, constant wetting, weather changes and other environmental changes. It is expected to last longer than the conventional drip irrigation system.