5th International Conference on Rain Water Cistern Systems
"Rainwater Catchment for Future Generations"
Keelung, Taiwan, R.O.C. - August 1991

Section 8: Irrigation and Uses of Water

Page 436

The Merits Of Smoothing Irrigation Furrows To Improve The Uniformity And Reduce The Total Application Of Irrigation Water

Ebrahim Hejrati
Agriculture Head Office of Eastern Aearbaijan, Iran

Summary

The infiltration rate changes with time. It is a fairly high value when the soil is first wetted, then it quickly decreases to a much smaller, but stable, rate known as the basic infiltration rate. There are many factors which will change the initial part of the infiltration curve, the two major factors are the soil moisture content before irrigating and the surface roughness. Smoothing the roughness in a furrow acts to speed up the furrow advance and the recession so that for a given' inflow time the opportunity time remains nearly constant. The accumulated infiltration is a function of the opportunity time and the infiltration rate curve for the particular soil. The uniformity of the water which is infiltrated into a soil is dependent on the uniformity of the opportunity time along the length of the furrow being irrigated.

The data reported were collected during the third irrigation in a field planted to corn on a silty loam soil in Eastern Nabras. Two basic ditching treatments, using a conventional ditcher and using a Hawkins ditcher, were each compared with and without an additional smoothing operation.

Smoothing the furrows increased the uniformity coefficients for the opportunity times along the furrow in both ditching methods. No test of significance was conducted on the data due to the lack of replications.

Reducing the roughness coefficient by smoothing the furrows speeded up the furrow stream advance which would have allowed a shorter set time, thereby reducing the total application of water. The objective of applying 2 inches of water could have been achieved if the well had been shut off: sooner. This would not have adversely affected the uniformity of water application.

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