Subsurface Drip Irrigation Offers Management
Advantages
By C. J. Phene
USDA-ARS
Many drip irrigation systems are permanently or
semi-permanently installed for irrigation of trees and vine
crops, but field and vegetable crops are normally irrigated with
systems which are installed and retrieved annually. The storage
of laterals poses extreme logistical problems. The annual
handling is detrimental to the life expectancy of the system,
even under the best handling conditions.
Methods for permanently installing subsurface drip irrigation
systems will facilitate agricultural operations, improve
conservation of natural resources, increase productivity,
minimize labor requirements, and permit further expansion of drip
irrigation.
Four subsurface drip irrigation systems have been designed,
installed and successfully operated by the Water Management
Research laboratory of the USDA-ARS, Fresno, with several crops.
The oldest one, located at the California State University,
Fresno (CSUF) Research farm was installed in 1981 and used for
three years to grow tomatoes. We also successfully double-cropped
broccoli with tomatoes during one of the three years. Cowpeas
(two years) and cantaloupes (one year) have been grown with the
same system.
Subsurface drip irrigation offers many advantages beyond those
of surface drip irrigation:
- Permanent installation below the plow depth provides
considerable labor savings and irrigation can be applied
while equipment is in the field.
- The top 15-20 cm of soil remains dry; hence, evaporation
of water from the soil surface will be limited to vapor
diffusion because of the mulching effect of the dry soil
and less salts will accumulate at the surface.
- Any soil surface crusts which usually cause infiltration
problems will be bypassed and infiltration will not be a
problem. Nonuniformity of application usually associated
with water running off the surface or ponding will be
eliminated, hence water distribution throughout the field
along the laterals should be improved.
- The subsurface drip system is buried and not handled
annually. The subsurface system is out of the sunlight
and not subjected to constant wetting and drying and
heating and cooling, therefore it is expected that the
system will last longer than one which is on the surface
and exposed to the changing environment.
- Equipment traffic through the field will be easier and
less cumbersome because all pipes and laterals are
buried. In addition, the soil surface is kept dry after
the initial irrigation for germination, thus, traction
through the field should be improved and less soil
compaction should result
- Water and nutrients are applied directly to the root
zone. In addition, the roots will take up and use
nutrients more efficiently provided that the irrigation
and fertilization schedules are adequate.
- Application of fumigants and/or pesticides through the
subsurface drip system will provide enhanced use of
chemicals for weeds and pest control; particularly if the
surface is irrigated simultaneously to seal the soil
surface temporarily.
- Since the topsoil is kept dry during most of the growing
season, occurrence of fruit rot and soil borne diseases
enhanced by wet soils should be minimized. Germination of
shallow weed seeds will be decreased because of lack of
necessary soil water.
- Double cropping will be easier because laterals remain in
place.
