STUDIES ON INFILTRATION CHARACTERSTCS OF FURROW IRRIGATION UNDER MAIZE CROP

Abstract

The infiltration characteristics of soils are important parameters for the design, evaluation and management of furrow irrigation. These characteristics are the factors which determine the advance and recession times, the depth of infiltration and thus generally, the performance of irrigation water application. Poor design and management practices are generally responsible for non uniformity of infiltrated water depth along the furrow leti�µ which at the same time I , lead to wastage of water, water logging, salinization and pol:lW1on of surface water and ground water resources . The aim of this study was to investigate the effects of design r parrmeters and operational procedures on water distribution and infiltration characteristics of furrow irrigation in sandy clay loam soils. Based on intensive point and volume balance infiltration measurements empirical formulae have been developed. The formulae were used in FURDEV computer I program to measure furrow irrigation performance indicators (Application efficiency Ea, Distribution Uniformity DU, Uniformity coefficient UC, Deep percolation Dp, Runoff and infiltration depth profile) under different irrigation water application practices. I All these indicators were found to vary depending on design variables such as furrow length, , · inflow rates, fixed and cutback flow and accelerated advance time,' The results show that DU and UC increase with increasing inflow rate and decreasing furrow length. On the other hand an increased inflow rate doesn't result in improvement of Ea., The maximum attained application efficiency was 65.1 % under fixed flow system and 50 m furrow and 68% under cutback flow system and 125 m furrow length, and 65 .2% under moveable pipes and 200 m furrow. Shorter furrows combined with increased inflow rates resulted in lower deep percolation and higher runoff losses. Fixed flow system has the advantage of improving DU and UC under long furrows whereas cutback system enhanced Ea under short furrows. Hence, improvement of furrow irrigation performance requires proper combination of furrow lengths, inflow rates, cutback system as wbll as other advance time accelerating arrangements. The irrigation opportunity time was considered to be the cause for non uniformity of infiltrated depth along the furrow length which usually varies along the furrow length. Movable pipe as accelerator of the initial advance time was found tq improve all performance parameters compared to other practices. However, for its easy application further study is essential.