A procedure for sampling the soil microenvironment at the site of fertilizer application

Abstract

A procedure was developed to sample and analyze levels of ammonium and urea as well as pH in the soil within the immediate zone of a single urea fertilizer granule. The method involved sectioning a 2 x 3.6 cm slice of soil (0.9 cm thick) into 45 subsamples, which were analyzed individually. After analysis, the data were presented in graphical format to show the nutrient concentrations in the zone. The method was relatively easy to carry out using equipment that could be easily constructed. The precision of the procedure was high as indicated by the low variability between replicates.

The determination of urea in soil extracts and related samples—a review

“…Enzyme-based determinations of urea in soil are impaired by the use of urease inhibitors, such as N-(n-butyl) thiophosphoric triamide [II] or phenylphosphorodiamidate [III], to reduce the loss of nitrogen by ammonia volatilisation after the addition of urea fertilisers (Bremner and Mulvaney 1978;Christianson and Baethgen 1994;Bremner 1995;Watson 2000). Furthermore, as described in the previous section, phenylmercuric acetate is often added to plant and soil extracts before analysis to reduce the breakdown of urea by endogenous urease (Douglas and Bremner 1970a;Kyllingsbaek 1975).…”