Capillary rise affecting crop yields under different environmental conditions

Abstract. This paper describes analyses of different soil water flow regimes on growth and yields of grass, maize and potato crops in the Dutch delta, with a focus on the role of capillary rise. Different flow regimes are characterised by differences in soil composition and structure are derived from a national soil database. Capillary rise and its influence on crop growth and resulting yields is simulated using Swap-Wofost with different boundary conditions. Case studies and model experiments are used to illustrate the impact of capillary rise. This impact is clearly present in situations where a groundwater level is present (85 % of NL) but also in other situations the impact of capillary rise on crop growth and production is considerable. When one compares situations with average groundwater levels with free drainage conditions without capillary rise yield-reductions of grassland, maize and potatoes are respectively 25, 4 and 15 % or respectively about 3.2, 0.5 and 1.6 ton dry Matter per ha. Neglecting capillary rise also has impact on the downward leaching water flux, the groundwater recharge. Impact can be considerable; for grassland and potatoes the reduction is 17 and 46 % or 64 and 34 mm. Modelling of soil water flow should consider capillary rise of soil water which will results in improved yield and downward leaching simulations.