Spatial Variability of Infiltration in Furrows

THE mean and spatial variability of infiltration measured with rings, blocked furrows with stagnant ponded water, blocked furrows with flowing water, and blocked furrows with surge flow were evaluated. Infiltration is generally greater with water flowing in blocked furrows than stagnant tests, especially on cracked soil. Spatial variability of cumulative infiltration is greater than for quasi-steady infiltration and the distance over which samples are spatially related is also greater for cumulative infiltration. Blocked furrow measurements with flowing water are preferred to the other stagnant tests because they more closely duplicate conditions under furrow irrigation. Spatial variability of infiltration characteristics should be included in evaluating the performance of furrow irrigation systems. The autocorrelogram is introduced as a tool to determine distance between samples to avoid spatial correlation and thus get the maximum new information regarding variability from sampling. A similar tool, the crosscorrelogram shows promise for estimating blocked furrow intake from ring infiltration test.