Resumen de Effect of drip tape placement depth and irrigation level on yield of potato
Subsurface drip irrigation (SDI) is the most advanced method of irrigation, which enables the application of the small amounts of water to the soil through the drippers placed below the soil surface. One of the most commonly discussed aspects of SDI system is installation depth of drip lateral. Determining the appropriate depth of installation involves consideration of soil structure, texture, and crop's root development pattern. Site-wise and crop-wise variations of these parameters preclude the possibility of framing general recommendations for installation depths of SDI system. An experiment was conducted on potato (var. Kufri Anand) during October�February for 3 years (2002�2003, 2003�2004 and 2004�2005) to study the effect of depth of placement of drip tape and different levels of irrigation application on potato yield. Drip tapes were buried manually in the middle of different ridges. Tests for uniformity of water application through the SDI system were carried out in the month of October every year. Three different irrigation levels of 60, 80 and 100% of the crop evapotranspiration and five depths of placement of drip tape namely, 0.0, 5.0, 10.0, 15.0 and 20.0 cm were maintained in the study. The coefficient of variation (CV) of flow rates was found 0.046, 0.047 and 0.064 during 2002�2003, 2003�2004 and 2004�2005, respectively. The low CV indicated good performance of the SDI system throughout the cropping season. The values of statistical uniformity (SU) and distribution uniformity (DU) were more than 92.0% during all the three cropping seasons. Soil water distribution at different growth stages of potato under different depths of placement of drip tape for varying irrigation levels was monitored. When drip tape was placed at surface and buried at 5.0 cm soil depth, upward movement of water takes place, 21.5% soil water content was found throughout the crop season of potato. When drip tape was buried 10.0, 15.0 and 20.0 cm below the surface, upward water movement due to capillary forces was not sufficient and soil surface remained relatively dry.
The maximum yield was recorded when drip tape was buried at 10.0 cm during 2002�2003 and 2004�2005 and at 15.0 cm during 2003�2004 that was followed by drip tape placement at 20.0, 10.0 and 5.0 cm depths in 2002�2003 to 2004�2005, respectively. Treatment 0.6T4 gave maximum IWUE of 2.07, 2.13 and 2.05 t ha-1 cm-1 during 2002�2003, 2003�2004 and 2004�2005, respectively. The highest benefit cost ratio of 1.7 was obtained for treatment T3. Lowest benefit�cost ratio of 0.9 was found for treatment 0.6T5. The cost incurred for the installation of drip tape at successively higher depths, increases the annual cost of production. The placement depth of drip tape significantly affected potato yield. Maximum yield was obtained by applying the 100% of the crop evapotranspiration (23.6 cm of irrigation water) and by placing the drip tape at 10.0 cm depth. In the sandy loam soil at the experimental site, the gravity force predominated over the capillary force causing a greater downward movement of water. Therefore, shallow depth of placement of drip tape (10.0 cm) was recommended in potato crop to get higher yield. Appropriate depth of placement of drip tape however, will differ with crop and the change in soil type
