International Conference on Rain Water Cistern Systems
"Rainwater Catchment for Future Generations"
Keelung, Taiwan, R.O.C. - August 1991
8: Irrigation and Uses of Water
The Merits Of Smoothing
Irrigation Furrows To Improve The Uniformity And Reduce The Total Application
Of Irrigation Water
Agriculture Head Office of Eastern Aearbaijan, Iran
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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