Soil temperature profiles during infiltration and redistribution of cool and warm irrigation water

Soil temperatures were measured in field profiles irrigated with cool and warm water and also measured in nonirrigated soil. Differences in soil temperature between plots after irrigation with cool (4.1°C) and warm (21.6°C) water, persisted longer at the lower soil depths. The time required after an irrigation for these differences to decline to less than 1°C was 14 hours at the 1‐cm depth, 36 hours at the 10‐cm depth, and 42 hours at the 20‐cm depth. A numerical procedure developed for predicting changes in soil temperature through the soil profile after irrigation with cool and warm water gave good agreement between observed and calculated values in the subsoil but not in the surface soil. During infiltration heat transfer occurred mainly by mass movement, whereas after 10 hours soil heat transfer below 10 cm occurred mainly by conduction.