Leaching and Water Flow Patterns in Every‐Furrow and Alternate‐Furrow Irrigation

Abstract

AbstractDeep water percolation and chemical leaching is a recognized environmental problem with furrow irrigation. Alternate‐furrow irrigation (AFI) was hypothesized as a method to increase water‐use efficiency and decrease chemical leaching compared with every‐furrow irrigation (EFI). The SWMS_2D finite‐element model was used to investigate water and CaCl2 movement in EFI and AFI with furrow‐placed or ridge‐placed fertilizer bands. Model simulations were conducted for a Crook loamy sand (mixed, mesic, Ustic Torripsamment) and a Nunn clay loam (fine, montmorillonitic, mesic Aridic Argiustoll). Water isolation zones occurred with AFI and EFI that contributed little to overall profile drainage. The soil water contents after infiltration and redistribution were more uniform for EFI than for AFI for both soils. Water distribution was more uniform with AFI in the clay loam than in the loamy sand. Chemical movement was least with AFI and CaCl2 placement under the nonirrigated furrow. The greatest chemical leaching was predicted with furrow placement of CaCl2 and EFI. Results with CaCl2 suggest soluble chemicals or fertilizers placed under the nonirrigated furrow in loamy sand may not be available for plant uptake because the soil did not wet during irrigation. With either form of furrow irrigation, placement of a fertilizer in the ridge rather than in the furrow would decrease leaching of the fertilizer and keep the fertilizer in the root zone.