SDI - Sub-Surface Drip Irrigation

Author: Kobi Shilo, Agronomist, NaanDanJain

The history of SDI in Israel started at the beginning of the 1980's. Dripline was installed in hundreds of acres around the country, for irrigation of various crops such as cotton, corn, tomatoes and other vegetables. The main reason for this approach was tight scheduling for handling large drip systems covering 150-400 Ha., where 500,000-1,000,000 meters of dripline were installed and retrieved season after season.

The SDI system was received with great enthusiasm. The advantages of direct watering to the root system included weed-free, dry top soil, water saving and obstacle-free cultivation during the irrigation season.

Later came the experiments which showed the increased benefits of fertilization with SDI. The availability of phosphorous (p) directly to the root system contributed to better yields.

At the same time that deep installation (30-50cm) of SDI was starting, the concept of shallow SDI in orchards and plantations was already a common practice. Damages to the dripline caused by animals and birds forced farmers to search for a solution. Hundreds of hectares of drip laterals were installed 5-10 cm. under the surface as protection against animals and birds.

After the initial experiences of deep SDI, there was a ten year interval in the development of new projects, due mainly to management difficulties.

The New Era of SDI
The potential of SDI as a new irrigation concept is starting to rise above the immediate agrotechnical advantages. Advanced research reveals changes in the wetted area configuration compared with the above ground drip system and the resulting improved conditions of aeration. Fertilizers, especially the slow moving ones, are more readily available to the root under this system.

Reclaimed Effluent Water in Agriculture
SDI is a logical solution for the use of reclaimed water without health hazards while minimizing ecological environmental effects.

The results of numerous field tests and experiments show no side effects of the effluent water on the harvest fruits. The soil profile operates as a biological filter.

Difficulties & Limitations
The management of SDI is more difficult compared to management of above surface irrigation. The successful SDI cases are the ones that have been designed and installed carefully, with a follow up of a complete new concept of management and cultivation techniques.

Design & Installation
The design of SDI has to take into consideration all the standard factors of above surface drip irrigation, such as soil and water analysis, filtration, dripper spacing etc., together with the special characteristics of SDI:

Management and Maintenance
The SDI system requires a high level of management. In order to receive optimum results, the irrigation and fertigation program must be carefully studied and controlled.

Long term salinity problems, high water table effects and long term effects of shallow cultivation on soil compaction must be taken into account.

The maintenance of SDI is more difficult due to the fact that the drippers cannot be seen or checked.

Article tags: field crops, tomatoes, corn, cotton, sub-surface drip irrigation