ISHS Acta Horticulturae 563: International Conference on Environmental Problems Associated with Nitrogen Fertilisation of Field Grown Vegetable Crops
TIME DOMAIN REFLECTOMETRY FOR MONITORING SOIL NITROGEN DYNAMICS |
| Authors: | S. De Neve, G. Hofman |
| Keywords: | N mineralization, N immobilisation, denitrification, electrical conductivity, incubation |
| Abstract:
The study of soil nitrogen transformations, both under laboratory conditions and in situ, requires a large number of time consuming and expensive chemical analyses. In this paper we present a possible alternative to chemical analysis when monitoring N dynamics. Time domain reflectometry (TDR) allows simultaneous monitoring of soil moisture content and bulk soil electrical conductivity (EC). In non-saline soils the nitrate ion plays an important part in the changes of soil solution electrical conductivity over time. We used the strong correlation between NO3--N concentration and EC for on-line monitoring of the mineralization process in two soils with different mineralization potential. Agreement between measured and TDR calculated NO3--N concentrations were good. The observed discrepancies between measured and calculated NO3--N concentrations can be explained by the influence on the EC of other anions, mainly SO42- and HCO3-. In a second experiment we used TDR to monitor the immobilisation of native and added NO3--N in soil with addition of glucose. The TDR calculated NO3--N concentrations showed a strong immobilisation of N in the first 2-3 days, followed by a gradual remineralization. From the results presented here it can be concluded that TDR has potential to monitor soil N transformations, especially under controlled environmental conditions such as in laboratory incubation studies. | |
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