In Pattern 3, there were isolated patches of dry soil within the wetted zone but 

 not at the soil surface. The dry patches occasionally surrounded roots from nearby 

 shrubs or trees, but not all roots were surrounded by dry soil, nor were the dry patches 

 confined to the vicinity of roots. This pattern usually, but not invariably, occurred 

 in bare openings. Little or no runoff was produced by plots having Patterns 1, 2, or 3. 



In Pattern 4, portions of the surface soil remained dry and were bypassed by the 

 wet front. Litter was always present over the dry patches. When live vegetation was 

 present, it was usually growing on the wetted portions of the soil surface. Dry patches 

 varied widely in area and thickness, and the amount of runoff produced varied accordingly. 



In Pattern 5, there was a discontinuous water-repellent layer 1 to 3 inches below 

 the bare soil surface. The surface soil was readily-wettable and breaks in the water- 

 repellent layer allowed the wet front to penetrate the wettable soil below the layer. 

 Runoff from plots with this pattern was severe unless there were many breaks in the 

 water-repellent layer. 



Pattern 6 was found on litter-covered plots where the discontinuous water-repellent 

 layer was at the soil surface. This pattern was rarely found when there were live 

 shrubs on the plot. Runoff from plots with this pattern varied widely but tended to be 

 less than that of plots with Pattern 5 because there were usually more breaks in the 

 water-repellent layers formed under litter. 



Pattern 7 was found in bare plots where there was a continuous water-repellent 

 layer 1 to 3 inches below the soil surface. Runoff was severe because the surface layer 

 of soil provided the only available storage for water. 



Pattern 8 is the extreme case where there were no breaks in a water-repellent layer 

 at the surface. This pattern was found under pine litter only on plots that had no 

 understory. Pattern 8 produced more runoff than any other because the only available 

 water storage was in the litter that--being somewhat water repellent also--held very 

 little water. 



In.filtz*a.tioxi Cixr'ves 



There was little or no runoff from the plots with wetting patterns 1, 2, or 3. 

 Many of these plots appeared to have infiltration capacities well in excess of 4.7 

 inches/hr. , the application rate. Runoff from plots with Pattern 4 was generally slight 

 because the wettable portions of the soil surface absorbed the runoff from the water- 

 repellent portions. However, if more than about two-thirds of the soil surface remained 

 dry during the 30-minute application of water, runoff was great enough to indicate that 

 infiltration capacity was less than the rate of application. All plots with wetting 

 Patterns 5 through 8 produced appreciable runoff. 



Typical infiltration curves are shown in figures 2 and 3. These curves are based 

 on actual measurement of runoff during the 30-minute application. Curve 4 is the average 

 of two plots with wetting Pattern 4 on which more than two-thirds of the soil surface 

 remained dry during the 30-minute test. The gradual increase during the latter part of 

 the test is typical of plots with incomplete water repel lency. In fact, runoff began at 

 about 3 minutes and ceased after about 15 minutes on four plots in this category. This 

 phenomenon is believed to be caused by mild water repel lency in the wettable portions 

 of the soil surface. Once the wet front penetrates the slowly-wettable portions of the 

 soil surface and enters the more absorbent soil below, its rate of advance increases. 



Curve 6A is the average of infiltration rates on three plots that had wetting Pat- 

 tern 6 and many breaks in the water-repellent layer. Curve 6B is based on four plots 

 that had few breaks. The curves are basically similar, but infiltration is greater in 

 plots that water penetrated at more points. 



7 



