LAUSR

The energy of sprinkler irrigation drops splashing on the soil surface or the crop canopy depends on their size and velocity. The kinetic energy of sprinkler irrigation drops is a major factor degrading the soil surface. The effect of a growing maize canopy on sprinkler drop energy dissipation and water partitioning was analyzed. A field experiment was performed on a solid-set sprinkler irrigated plot cropped with maize. Measurements were performed at different locations and heights into the sprinkler layout. Tests were performed at five maize heights. At each maize height, drop population characteristics and pluviometry were measured above and below the maize canopy. Drop population was measured with an optical disdrometer. Catch-can devices were used to measure pluviometry. Solid-set sprinkler irrigation distributes water quite homogeneously, but drop characteristics largely differ between layout locations. The effect of the crop on drop characteristics intensified as the canopy height increased. The canopy cover reduced drop diameter more than it reduced drop velocity. As the canopy grew, its capacity to intercept and derive irrigation water to stemflow increased. The largest part of energy dissipation by the maize canopy took place in the top 1.5 m. A fully developed maize canopy reduced the drop kinetic energy reaching the soil to 13.6% of that reaching bare soil. As a management practice, in sensitive soils or in sprinkler systems applying water with high specific kinetic power, irrigation of bare soils should be avoided.