, J. 1998. Measurement of rill erosion by snowmelt on potato fields under rotation in Prince Edward Island (Canada). Can. J. Soil Sci. 78: 449-458. Cool-period soil erosion from farmland in Prince Edward Island occurs predominantly through rilling mainly due to snowmelt. This is mostly evident on fields coming out of potatoes (Solanum tuberosum L.), a crop that is traditionally cultivated as part of a 2-yr rotation with cereal grains, or a 3-yr rotation with cereal grains and a forage crop for hay. Accurate assessment of snowmelt erosion (associated processes and effects) has been historically constrained by data inadequacy, particularly for rilling; and although a number of models have now been developed for estimating cool-period erosion, they still stand to benefit from the generation of actual field data. In the present study, actual volume measurements were made of erosion forms, for about 80 site-years, after the spring snowmelt in fields at various stages of potato rotation. Cool-period erosion, predominantly rills, amounted to about 30 t ha -1 for 2-yr and 3-yr rotations, thus an annual seasonal average of 15 t ha -1 and 10 t ha -1 , respectively. Potato fields left untilled over winter averaged about 20 t ha -1 which increased to 36 t ha -1 with fall ploughing. Sediment deposition in fields coming out of potatoes was 13.3 t ha -1 compared with the amount of 0.4 t ha -1 in fields coming out of forages and 1.6 t ha -1 in fields coming out of grain. Fields going into the winter in sod or stubble showed negligible erosion, averaging about 0.1 t ha -1 in spring. The results of this study demonstrate the dominant influence of cropping practice in the erosion process during the cool period, and the tendency for traditional computational procedures to underestimate soil loss.Key words: Cool-period erosion, rilling, rill volume, sediment deposition, soil-loss prediction, erosion mapping, crop rotation Edwards, L., Richter, G., Bernsdorf, B., Schmidt, R.-G. et Burney, J. 1998. Mesure de l'érosion en rigoles due à la fonte des neiges dans des champs à pomme de terre en rotation dans l'Île-du-Prince-Édouard au Canada. Can. J. Soil Sci. 78: 449-458. L'érosion des sols agricoles de l'Île-du-Prince-Édouard durant la période froide de l'année se manifeste le plus souvent par la formation de rigole due à la fonte des neiges. Elle s'observe particulièrement après une sole de pomme de terre (Solanum tuberosum L.), culture généralement pratiquée en rotation de deux ans avec une céréale ou de trois ans avec une céréale et une culture fourragère de fauche. L'évaluation de cette forme d'érosion (et des mécanismes et effets corollaires) a toujours été entravée par l'absence de données vraiment pertinentes, en particulier en ce qui concerne la formation des rigoles et bien qu'un certain nombre de modèles mathématique de prédiction aient été miss au point, on doit encore recourir aux données mesurées sur le terrain. Nos travaux consistaient à mesurer, sur environ 80 années-emplacements, le volume réel des formes d'érosion après ...