Spatial scale effects on the effectiveness of organic mulches in reducing soil erosion by water

Experimental research revealed that mulching the soil surface is an effective soil conservation practice. However, reported effectiveness of mulch covers varies widely and there are indications that spatial measurement scale (i.e. plot length) explains part of this variability. The objective of this study is therefore to analyse the impacts of plot length at which field and laboratory experiments were conducted on the effectiveness of mulch covers in reducing soil loss by water erosion. In this review, 41 studies investigating the impacts of mulch cover on soil erosion by water are analysed (plot length ranges between 0.1 and 30.5 m). Calculated mulch effectiveness factors, i.e. b-values from the mulch factor equation, range between 0.0097 and 0.1320 and increase linearly with plot length for the reviewed experiments: b = 0.022 + 0.0017 ⁎ plot_length (m); R2 = 0.37; n = 41. However, care should be taken when using this relationship for extrapolations to longer plots. Furthermore, slope gradient, soil type and mulch type determine the variability of the effectiveness of mulch covers in reducing soil erosion rates by water. Depending on the dominant soil erosion process (i.e. splash, interrill, rill and interrill or rill erosion), these variables also partly control the effectiveness of a mulch cover in reducing soil erosion by water.