On the hydro-geomorphology of steepland coffee farming: Runoff and surface erosion

Soil compaction and natural vegetation removal associated to agriculture tends to promote runoff and soil erosion with potentially adverse onsite, downstream, and global impacts. Although coffee farming represents a fraction of the world’s harvested lands, it is a vital crop for many developing nations where it is frequently cultivated on erosion prone, high-relief, wet tropical landscapes. However, limited empirical data exists on coffee farm erosion. This article attends this need by describing the results of rainfall simulation experiments designed to evaluate the impact of sun-grown coffee-farming on precipitation excess, soil infiltration rates, and surface erosion by overland flow. Results show that infiltration rates on coffee-cultivated fields are ∼60 – 80% relative to undisturbed forested slopes, and that cultivation increases erosion rates by one to two orders of magnitude depending on the presence or absence of mulch or weed cover. The magnitude of the impact suggests that erosion on coffee-cultivated land is unsustainable from both a soil formation and an agricultural productivity point of view. Unsurfaced access roads display an even greater impact than cultivated surfaces with infiltration rates ∼10% of undisturbed soils and erosion up to four-orders of magnitude above background depending on grading history and slope. Farm-scale annualized erosion is ∼3–24 Mg ha-1 yr-1 depending on actively used unpaved road abundance as roads account for ∼99% of net erosion. Implementing efficient erosion control strategies for coffee farms is therefore essential to reduce their current impacts, but also for the future given the worldwide surge in coffee harvesting areas projected for the upcoming decades.