The Role of Subsurface Water Retention Technology (SWRT) for Growing Chili Pepper in Iraqi Sandy Soils

Abstract

A study was carried out to assess the impact of using SWRT on irrigation water use efficiency IWUE and yields of chili pepper crop. Experiments were performed by planting chili pepper in greenhouses during the spring season of 2015 at two locations in Iraq. One location was at north of Baghdad (latitude 33 north and longitude 44 east) at Jadedat Al-Shat, Diyala Province. The other location was at Najaf Province (latitude 32 north and longitude 44 east). Soils of these both locations are classified as sandy loam in texture. Four treatments (SWRT, organic matter, tillage and no – tillage farming) were used to represent different tillage practices in the Iraq. The experimental design was randomized complete blocked design RCBD with four replications. Irrigation scheduling was performed according to soil moisture content as 50-55% of available water was depleted then irrigation water was added from subsurface drip system to bring soil moisture content back to field capacity. Soil sensors GS3 from the Decagon Devices, USA were used to measure volumetric water content hourly. Water balance equation was used to determine the actual water consumption during each stage of plant growth for the whole season.

The result showed that the amount of irrigation water and plant yield varied with treatment. Average chili pepper yield per plant were was 0.61, 0.51, 0.47 and 0.53 kg for Diyala location and 0.2, 0.18, 0.17 and 0.16 kg for Najaf location for treatments SWRT, organic matter, tillage and no–tillage treatments, respectively. Depths of irrigation water for season were 338, 582, 693 and 693 mm for Diyala location and 346, 446, 544 and 544 mm for Najaf location for treatments SWRT, organic matter, tillage and no–tillage treatments, respectively.

Values of IWUE for chili pepper at Diyala location were 16.652, 8.087, 6.236 and 7.076 kg m^-3 for SWRT, organic matter, tillage and no – tillage treatments, respectively. This shows that SWRT is higher in IWUE by 106, 167 and 135% than organic matter, tillage and no – tillage treatments, respectively. Similar trend of IWUE values for chili pepper in Najaf was obtained which were 3.724, 2.692, 2.094 and 1.972 kg m^-3 for SWRT, organic matter, tillage and no – tillage treatments, respectively, as an increase of SWRT by 38, 79 and 89% over organic matter, tillage and no – tillage treatments, respectively.

Keyword: Subsurface Water Retention Technology, Chili Pepper, Iraqi Sandy Soils