Available Nitrogen for Corn and Winter Cereal in Spanish Soils Measured by Electro-ultrafiltration, Calcium Chloride, and Incubation Methods
2007
Quemada, M. | Díez, José Antonio
Comparison of methods is necessary to develop a quick and reliable test that can be used to determine soil-available nitrogen (N) in an attempt to increase the efficiency of N fertilizers and reduce losses. The objectives of this research were to compare the fractions extracted by the calcium chloride (CaCl2) and the electro-ultrafiltration (EUF) methods and to correlate them to the mineralization rate (k) obtained from a 112-d incubation of 61 soil samples. Thirty-five soil samples were collected from cornfields and 26 from winter cereal fields. Subsamples were either aerobically incubated to calculate k or extracted by the EUF and CaCl2 methods to identify three fractions: nitrate (NO3(-))-N, ammonium (NH4(+))-N, and Norg-N. The Norg-N extracted by both methods was larger in soils from cornfields than in soils from winter cereal fields. In samples from cornfields, the Norg-N fraction obtained by the EUF method was correlated to the Norg-N measured by the CaCl2 method (r = 0.46). Soil N content was related to k in samples from cornfields (r = 0.40) but not in samples from winter cereal fields. Also, k was correlated to inorganic N content extracted by both chemical methods. The CaCl2 method was a reliable alternative for laboratories to determine soil-available N for corn but not for winter cereal.
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