Assessment of tillage translocation and erosion by the disk plow on steepland Andisols in Costa Rica

Abstract

One of the major threats to the sustainability of agriculture within the Americas is that posed by soil erosion due to the actions of rain, wind, and tillage. Soil degradation by tillage erosion is of greatest concern in regions where intensively tilled crops are grown on highly erodible landscapes. To date, very little research has been conducted on the potential for tillage erosion within intensively cultivated vegetable and potato (Solanum tuberosum L.) production, especially within steep mountainous agroecosystems. Therefore, the objective of this study was to measure tillage translocation and tillage erosion by the arado de disco (disk plow), an implement used across Latin America and the most common mechanized primary tillage implement used in the potato-growing volcanic highlands of Costa Rica. Our results suggest that tillage erosion is a major problem in this region. Soil movement downslope by the arado de disco was approximately twice that moved upslope, and a highly significant relationship was observed between both the mean displacement distance of the tilled layer and the mass of translocated soil and slope gradient when all up- and downslope cultivated tillage translocation plots were included in the regression analysis. When the data were separated and only those plots cultivated downslope were analyzed, the potential for tillage erosion more than doubled. If tillage operations are only conducted downslope, the rate of tillage erosion is equivalent to ~250 Mg ha⁻¹ pass⁻¹ (~112 tn ac⁻¹ pass⁻¹) from the top 5 m (16.4 ft) below a field boundary. These results show that not only is the arado de disco an erosive implement but that downslope-only cultivation is a highly erosive tillage practice—as the measured erosivity values are larger than those typically reported for implements in Europe and North America (where tillage operations are normally conducted in alternating up- and downslope directions). Our results also suggest that the variability in both speed of tillage and depth of tillage across the landscape were important factors controlling tillage translocation by the arado de disco. However, since tillage operations on the steep slopes of Volcán Irazú are typically conducted downhill, depth of tillage had a much greater effect on tillage translocation under these conditions than did speed of tillage. It is clear that a reduction in tillage erosion is necessary to reduce soil losses in this intensively cropped region of Costa Rica and for similar steepland agricultural regions in the Americas.