G. Holshof

Precisiewatermanagement op veenweidegrond met pompgestuurde onderwaterdrains

Characteristic of peat soil is the great resistance for water transport in the soil to and from the ditch. Submerged drains are an effective tool to accelerate water transport in the soil and this results in a significantly flatter groundwater table. The operation of submerged drains is, however, highly dependent on the ditch water level, which cannot easily be changed. By connecting drain pipes to a closed water reservoir, the groundwater table can be regulated with a pump independently of the ditch water level. Therefore the draining and infiltrating effect improves considerably.

Nitrogen Fertilizer Replacement Value of Concentrated Liquid Fraction of Separated Pig Slurry Applied to Grassland

ABSTRACT Seven grassland experiments on sandy and clay soils were performed during a period of 4 years to estimate the nitrogen (N) fertilizer replacement value (NFRV) of concentrated liquid fractions of separated pig slurry (mineral concentrate: MC). The risk of nitrate leaching when applying MC was compared to when applying mineral fertilizers. Grassland yields in 2009–2012 fertilized with MC were compared with grassland fertilized with two mineral fertilizers: granulated calcium ammonium nitrate and liquid ammonium nitrate (LAN). The mineral fertilizers comprised 50% nitrate-N and 50% ammonium-N, and MC comprised 95–100% ammonium-N. Treatment application rates included zero N and three incremental rates of N fertilization. The liquid fertilizers were shallow injected (0–5 cm). The NFRV of MCs was 75% on sandy and 58% on clay soil with granulated ammonium nitrate as reference, and 89% on sandy and 92% on clay soil with LAN as reference. Risk of nitrate leaching after application of MC, measured in residual soil mineral N post-growing season and N in the upper groundwater in the following spring, was equal to that for mineral fertilizers.