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Preliminary Critical P-limit Values of 0.01 M CaCl2 Soil Test Procedure
18-21Views:103In the last decade, the 0.01 M CaCl2 extraction procedure was tested as a multi-nutrient extractant. In 1995-97, international joint research activities were carried out within the COPERNICUS project. Detailed calibration of conventional and the 0.01 M CaCl2 extraction procedures for pH, Mg and K were published.
The amount of phosphorus extracted using a 0.01 M CaCl2 solution is very low and reflects the intensity parameter of phosphorus bio-availability. As a readily desorbed P fraction of soils can reflect the soil P-supply and the CaCl2-P values are in close correlation with P-fertiliser rates and P balance. However, the effects of various soil characteristics on CaCl2-P values are different and their interpretation is difficult.
Relatively poor correlations were found between amounts of P extracted by conventional and CaCl2 soil test methods and, therefore, P limit values could not be calculated directly. To characterise the soil P supply at different sites, the CaCl2 desorbed P and the adsorbed P in a modified Baker Soil Test were also applied.
Soil test results of Hungarian long-term fertiliser experiments and recommended CaCl2-P limit values, calculated on yield effects and soil characteristics, are discussed. -
Measuring of nitrogen leaching using ceramic suction cups at different locations
10-17Views:71Ceramic suction cups were used for the measurement of N-concentration in soil solutions under different soil and climate conditions in both field experiments of Rostock University and Agricultural University of Debrecen (Hungary). Depending on the soil utilisation the change in the N concentration of the soil solution can be proved on both sites.
The experimental field of Rostock University can be characterised by its high groundwater table. The nitrogen concentration of soil solutions in the different soil layers were determined by the trend downward of water. In the dactylis (Dactilis glomerata) experiment, the quadruple treatments involved the following: with and without N-fertiliser, with and without harvesting, respectively. In the lower soil layers, the least rising N concentrations were established in case of the treatment without N-fertiliser combined with harvesting. The nitrogen leaching calculated from the infiltrated water quantity and the nitrate N concentration increased in the following order: without N-fertiliser, with harvesting < without N-fertiliser, without harvesting < with N-fertiliser, with harvesting << with N-fertiliser, without harvesting.
The field experiment site of Debrecen can be characterised by a low groundwater table. The effect of N-fertilisation on the nitrate-N concentration of soil solution in the soil layers can be stated unanimously. Permanent nitrate-N leaching cannot be established due to the water upward movement under semiarid climate conditions. Intermittently transfer of nitrate-N between the soil layers is probable in cases of remarkable precipitation.