Evaluation of broad bed and narrow ridge furrow irrigation methods

The objective of this study was to determine the advance and the infiltration function and to evaluate the broad bed furrow irrigation method and narrow ridge furrow irrigation method with respect to application efficiency, distribution uniformity and wetting pattern. The experiments were carried out at Alifisol field plot in ICRISAT Research Farm, Hyderabad, India. Furrows were 66 m long, close ended, with an average slope of 0.4% The furrow spacings were 150 cm and 75 cm defined as broad bed and narrow ridge furrow irrigation methods, respectively. The treatments were three inflow rates of 10, 20 and 30 litres per minute (1pm). During the experiment, the following measurements were taken: 1) rate of advance of water front, 2) depth of low, 3) inflow and 4) outlow. Soil samples were also taken to study moisture distribution besides digging a trench and sampling therein. The advance function showed a good fit with the equation X = ptr. The value of r increased with increase of inflow rate while the value of p decreased correspondingly in narrow ridge system. But it did not show any such trend in broad bed system. Advance rate did not differ significantly between the two furrow spacings, but it increased with the increase in inflow rate. More variation was observed with 10 1pm treatment than other twos. Multiple regression analysis with two independent variables time and inflow rate, gave the equation X = 0.65 X0.69 t 0.68. The analysis showed that both variables were significant. The infiltrated depth is calculated by the volume balance method. The final infiltration rate calculated per perimeter surface ranged between 2.7 cm/hr to 3.4 cm/hr initial infiltration was higher with large inflow rate but the final infiltration rate was not affected. No appreciable difference in infiltration rate was observed between two furrow spacings. The data was analysed to fit Kostiakov equation and Philip's equation fitted well. The coefficients were highly varying. The data were pooled together and the general equation Y = 0.54t .50 + 0.30t was obtained. Because of irrigation depth of only 3.3 to 4.1 cm, and lack of data to estimate percolation rate, the percolation loss was neglected and application efficiency were computed. It was found that by applying cutbacks, application efficiency can be improved in both systems. The runoff losses were obviously greater with l arger inflow rate when no cutback was applied. The distribution uniformity (DU) were computed for each treatment as DU = Average volume of water infiltrated in low 1/3 length over Average volume of water infiltrated. The values of DU are fairly good in all cases. DU was nearly same in all treatments of narrow ridge system (around 0.74), while in broad bed system, it decreased with inflow rate increase. The DU value reached high up to 0.86 in broad bed system when cutback was applied.