A H; A E; H S
Abstract
In on-farm development projects, implementation of subsurface drainagesystem is one of the most important issues. Considering the high costs ofpreparing mineral envelope for subsurface drain pipes, continued executionof such projects, especially in Khuzestan province, has faced somedifficulties. To overcome ...
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In on-farm development projects, implementation of subsurface drainagesystem is one of the most important issues. Considering the high costs ofpreparing mineral envelope for subsurface drain pipes, continued executionof such projects, especially in Khuzestan province, has faced somedifficulties. To overcome such a problem, use of synthetic envelopes or,where soil characteristics allow, subsurface drainage without using envelopemay also be an option. Thus, in this research, in an experimental field of 20ha under wheat in Shadegan region (Khuzestan province), the performance ofsubsurface drainage without using envelope was compared with theconventional drainage by mineral envelope. Each experimental unit had fivesubsurface drain pipes (laterals) spaced at 50 m and installed at depth of1.7m, with a length of 220 m. To study water table condition, somepiezometers were installed perpendicular to the middle laterals of each unit.Also, the rates of drains discharge and drainage water quality of the middlelaterals in each unit were measured in manholes constructed on them. Themaximum salinity of drainage water from drains with mineral envelope(replicates 1 and 2) and drains without envelope were 36.9, 52.1, and 47dS/m, respectively, and the minimum salinities were 25.7, 23.6 and 12.6dS/m. The maximum drain discharge in the first replication of mineralenvelope was 0.59 lit/sec, and for the second one was 0.28 lit/sec and in thedrains with no envelope was 0.23 lit/sec. Investigation of Salt Exit Index(SEI) of soil showed that salt leaching continued during the wheat growingseason. Results of drains discharge showed the acceptable operation of drainswithout envelope and proper performance of drains with mineral envelopeduring the growing season. No sediment discharge was observed in anytreatment.