Several of the researchers whose work is reported by H.G. Heinemann and R.F. Piest (‘Soil Erosion—Sediment Yield Research in Progress’ EOS, 56(3), 149—159, 1975) agree that mulch helps stop erosion. Although the comparative values quoted are encouraging, it should be pointed out that still better results are obtainable. Study of the mechanism that initiates sediment movement not only explains why mulch is beneficial but also shows how it is possible to achieve greatly improved protection. Whether this can be done economically depends upon the local availability of suitable material.