To obtain more detailed information about N processes in agricultural soils, nondestructive measurement techniques with high spatial and temporal resolution are needed. The ability of time domain reflectometry (TDR) in combination with small polysulfone hollow fiber (PHF) solution samplers to follow NO − 3 production and transport in soil fertilized with cattle slurry and exposed to different rainfall events was investigated. The experiments were conducted in minilysimeters using a coarse sandy soil and two different slurry application methods: (i) surface application followed by harrowing (homogenous incorporation) or (ii) direct injection (incorporation as a manure string). Comparison between soil‐water electrical conductivity (EC w ) obtained with TDR and the sum of NO − 3 and Cl − concentrations in the soil water measured with solution samplers showed a good agreement both with respect to concentration levels and temporal and spatial development. Except for an initial leaching of the natural ion content in the soil water when water application was started, NO − 3 released from the manure was the dominating anion in the soil water and changes in NO − 3 corresponded well to changes in EC w . Both slurry and water application strategy had a large effect on the temporal development in nitrification and NO − 3 leaching. In the case of homogeneously incorporated slurry and constant water application for 3 wk, NO − 3 formation and leaching started after 4 to 5 d, while it started after 9 to 10 d in the case of directly injected slurry. If water was applied only in the last (third) week to the directly injected slurry system, a large amount of the NH + 4 in the slurry was oxidized to NO − 3 before water application and subsequently leached. The TDR measurements of EC w with high spatial and temporal resolution combined with a few measurements of ion concentrations by PHF solution samplers is a new, valuable method for analyzing turnover and transport of nonconservative ions in soil.
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Nissen et al. (1998) studied this question.