MTech.

Irrigation technology envisages the development of irrigation systems that uses water more effectively for plants. The process of subsurface drip irrigation was conceived with this objective. One of the subsurface irrigation types is the porous pipe irrigation. This is a relatively new technology and an evaluation is necessary to assess the suitability for Indian crops and conditions. With this objective, the discharge evaluation of porous pipe irrigation was done in the laboratory and field for Amaranthus spp., to find out the moisture distribution and the optimum depth of installation. The study was conducted at KCAET, Tavanur entitled "Feasibility Studies on the Use of Precision Porous Pipes for Subsurface Irrigation".

The chosen variety for the field study was Kannara local which was popular in the region. Three depths of placement of porous pipes were chosen for the study ie 10, 15 and 20 cm with and without sand envelope. The treatments also comprised paired and double paired row with three replications each. A drip irrigation plot with two treatments and a control plot were kept for comparing the yield, water use efficiency and the cost economics.

The type of soil found in the study area was sandy loam. It has a bulk density of 1.68 gm/cc and the infiltration rate of the soil was 5.2 cm/hr. The coefficient of variation of the porous pipe was 13.98% and the emission uniformity was 82.60 %. Among porous pipe treatments, the water use efficiency was highest in the treatment with sand envelope and paired row planting at the depth of placement 20 cm. The water use efficiency of drip irrigated treatment for double paired row planting was higher than that for porous pipe irrigated treatments.

The average distribution efficiency of porous pipe in the field was 86.72%, 24 hours after irrigation and that of drip irrigation was 76.2 %. The optimum operating pressure for porous pipe irrigation system under field conditions was found to be 0.2 kg/cm2 when the discharge was a minimum with less energy requirement. The discharge in the field under this condition was 1.27 lph/m.

From the statistical analysis, we find that there is no significant difference in yield between the treatments with and without sand envelope. Hence we conclude that for amaranthus, sand envelope is not essential in sandy loam soil. The maximum yield of Amaranthus was obtained from porous pipe irrigation from 20 cm depth of spacing with sand envelope in paired row planting in sandy loam soil.

The cost of installation of different irrigation systems was evaluated. It was found that the porous pipe irrigation with paired row spacing incurred the maximum expenditure.