The short term agronomic impact of raising canal water levels in grassland areas: A case study in the Belgian polders

This study tested the hypothesis that raising canal water levels with 30 cm beyond the growing season in intensively managed lowland grassland (2.4–3.7 m above sea level) in Belgium decreases the agronomic value of pastures The study ran 3 years before and 3 years after the water elevation. Using five pairs of plots inside and outside the wetted perimeter, it was not possible to demonstrate significant impacts of the elevated water level on dry matter yield, forage quality, botanical composition, and penetration resistance of the top soil layer of the grassland. In an ex situ lysimeter experiment, simulating the effect of a water level in canals up to 50 cm beneath the surface of the pastures indicated a significant decrease of the penetration resistance of the top soil layer. Results are discussed and confronted with the difficulties of field research addressing the elevation of water levels.