Furrow irrigation spacing effects on water movement in a vertisol: A case study of wide‐skip furrow irrigation

Abstract

Vertisols, also known as cracking clay soils when dry, can be prone to excessive infiltration from every‐furrow irrigation. To mitigate this problem, some farmers in the Yazoo‐Mississippi Delta practice wide‐skip furrow irrigation, which concentrates irrigation water into one furrow every 3 m or wider. How this spacing of irrigated furrows affects water movement in a vertisol was investigated through monitoring an irrigation event during an experiment with four spacing treatments: 1 m (0.25 L s ⁻¹ in every furrow), 2 m (0.51 L s ⁻¹ in every other furrow), 4 m (0.98 L s ⁻¹ in every fourth furrow), and 8 m (2.13 L s ⁻¹ in every eighth furrow). Furrow advance was similar between the 1‐m and 2‐m treatments but was 34% and 122% faster for the 4‐m and 8‐m treatments, respectively. In the 8‐m treatment, the time when wetting began was not significantly different among depths deeper than 0.3 m nor among distances 0.5–3.5 m perpendicularly away from the irrigated furrow. Such rapid vertical and lateral spread was attributed to gravity‐driven preferential flow through soil cracks. At depths shallower than 0.3 m in the 8‐m treatment, however, distances beyond 2 m from the irrigated furrow experienced delayed start of wetting, slower wetting rates, and smaller soil water increases. This trend was the principal cause of 32% less infiltration in the 8‐m treatment than in the 1‐m treatment. By characterizing the hydrological performance of wide‐skip furrow irrigation on vertisols, these findings will guide users in managing this practice to optimize the benefits and risks of purposefully nonuniform wetting.