An Investigation of the Effect of Two Drainage Envelope Types on Subsurface Drainage Flow Rates in Paddy Fields of Mazandaran Province

One of the important components of suitable operation of subsurface drainage systems is its envelope. Several researchers have evaluated the efficiency of dry land drainage، but the operation of these materials in subsurface drainage systems of paddy fields has not been investigated. In this research، the effects of two mineral and artificial envelopes on flow rates of drainage system in paddy fields of Sari Agricultural Sciences and Natural Resources university lands have been investigated. For this purpose، a drainage system consisting of 4 drain lines at 0. 65 m depth and 15 m spacing was installed. For two drain lines، mineral envelopes and for other two drains artificial envelopes were used. During one canola growing season، the drain discharges were measured daily. There was significant difference (p=1%) between the mean discharge of drains so that the average drain discharge of drain with artificial envelope was 88 percent higher than the corresponding value of drain with mineral envelope. Based on the drainage water depth-rainfall relationship، the average of daily discharges of drains with artificial and mineral envelopes was equivalent to 2. 5 and 1. 8 mm rainfall، respectively. Also، comparison of the total costs of the two drainage systems showed that the drainage system with artificial envelope was 30% less expensive than drainage system with mineral envelope.