Effect of a growing maize canopy on solid-set sprinkler irrigation: kinetic energy dissipation and water partitioning

Abstract

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.

Drop Size Distribution and Effective Determination of the Constitution of Throughfall Droplets under Maize Canopy

“…There is spatial variability in plant canopy structure, and the spatial distribution of the maize canopy structure is such that the greater the distance from the stalk is, the lower the canopy thickness. The results of Nanko et al [38] and Zapata et al [19] on the effects of canopy thickness on the size of throughfall droplets showed that if the plant canopy thickness was relatively large, the diameter of the throughfall droplets would be small. Therefore, when the data collection point was far away from the plant stalk or located in a gap in the canopy, the diameter of throughfall droplets was larger than that at the other location measurement points.…”

“…The leaf area index and canopy thickness of the plant are substantial canopy structural variables affecting the throughfall DSD. [19,37,38] Nanko et al [37] found that the plant canopy status (i.e., the presence or absence of leaves) was one of the most important factors influencing the throughfall DSD, and that D 50 of throughfall droplets under plants during the leafless stage was significantly greater than that during the leafy stage. Nanko et al [38] and Zapata et al [19] investigated the effects of plant canopy thickness on the DSD and D 50 of throughfall droplets.…”

“…[19,37,38] Nanko et al [37] found that the plant canopy status (i.e., the presence or absence of leaves) was one of the most important factors influencing the throughfall DSD, and that D 50 of throughfall droplets under plants during the leafless stage was significantly greater than that during the leafy stage. Nanko et al [38] and Zapata et al [19] investigated the effects of plant canopy thickness on the DSD and D 50 of throughfall droplets. Their results showed that if the plant canopy thickness was relatively low (i.e., the leaf area or leaf area index was low), the throughfall DSD shifted toward larger droplets, and the D 50 increased.…”

“…[18] However, in a recent report, Zapata et al comparatively analyzed the effects of maize canopy on droplet size and velocity under fixed sprinkler irrigation conditions, and their results showed that the maize canopy decreased the size of droplets more than their velocities, and the proportion of small droplets in the throughfall under the maize canopy tended to increase. [19] The planting area of maize, one of the three major food crop species worldwide, is continually increasing. Although many scholars have studied the effects of maize canopy on the DSD, no specific conclusions have been made concerning the effect pattern of maize canopy on the DSD and diameter of throughfall droplets.…”

“…comparatively analyzed the effects of maize canopy on droplet size and velocity under fixed sprinkler irrigation conditions, and their results showed that the maize canopy decreased the size of droplets more than their velocities, and the proportion of small droplets in the throughfall under the maize canopy tended to increase. [ 19 ]…”