Effects of potato hilling on water runoff and soil erosion under simulated rainfall

Abstract

The practice of planting potatoes (Solanum tuberosum) in rows and hilling the plants at some stage of growth has been universally adopted. Using a rainfall simulator and runoff-erosion plots (0.9 m wide × 1 m long), the effects of hilling on runoff, infiltration, and soil loss were examined on an Orthic Dystric Brunisol. Tests of the rainfall simulator revealed that variations in operating pressure (36.5–62.1 kPa) and soil slope conditions (0–15%) did not significantly (P < 0.05) affect the intensity and spatial uniformity of the simulated rainfall. The potato hills studied were 90 cm apart with heights of approximately 25 cm, row-sideslopes of 35° and furrow widths of 10 cm, which are similar to those used in commercial production. Although not significantly different at P < 0.05, the runoff rate from the hilled plots was approximately 20% higher than that from the unhilled plots. Hilling resulted in a significant reduction in infiltration rate (P < 0.05). Average soil loss from the hilled plots was approximately four times higher than from the unhilled plots. For runoff rates below a critical value of 0.93 L min−1, the rate of soil loss correlated linearly with the runoff rate, whereas a non-linear exponential equation was generated for the entire range of runoff with r = 0.94. The increase in soil loss as a result of hilling was adequately predicted from row-sideslope gradients using an existing equation derived from erosion data obtained from fields having conditions similar to that of potato hills. Key words: Universal soil loss equation, slope steepness, cover and management factor, row-sideslope, spatial uniformity, infiltration