CONSERVATION TILLAGE - A NEW STRATEGY IN FLOOD CONTROL

摘要

It may seem at first that there is no connection between tillage methods on arable land and flood disasters in a watershed. But flood disasters are frequently the consequence of extensive amounts of water originating from surface runoff from soils due to a lack of infiltration caused by soil sealing or crusting. The last has to be seen in context with soil erosion on arable land, which results from inhibited w; ter infiltration through soil siltation. Soil sealing is caused by raindrops hitting the soil surface with a force great enough to destroy soil aggregates. Dispersed surface clods and aggregates form a thin sealing soil layer, which inhibits water infiltration in a very efficient way. On sloped arable land, inhibited infiltration by soil sealing c; uses surface water runoff, which causes on- and off-site damages through soil erosion. The best way to decrease or to prevent surface runoff on arable land is to prevent soil sealing and crusting. In the following we want to show that conservation tillage combined with mulch seeding is one of the most efficient strategies against siltation on arable land. Conservation tillage has an influence on a number of physical and hydrological soil parameters. In most cases, this contributes to a drastic reduction of surface runoff on arable land. In Saxony more than 60 % of arable land (450,000 ha) is endangered and regularly afflicted by water erosion. To reduce or prevent on- and off-site damages caused by water erosion, extensive soil protection measures are needed in entire regions or watersheds. Conservation tillage and mulch seeding are recommended as effective methods against water erosion by the agricultural extension service and will be more and more practised on arable land in the future. Since reduced water erosion is closely connected v ith reduced water runoff, conservation tillage on arable land in the whole catchment may be both an effective strategy against water erosion and an efficient element of flood control. In the following this possible relationship will be demonstrated by field experiment results. These results were obtained at various sites in Saxony in different tillage systems with simulated rainfall experiments (Fig. 1).