Evaluation of 0.01 M CaCl ₂ Extractable Nitrogen Forms in a Long-term Experiment

Soil nitrogen undergoes a series of chemical and biological transformations, which influence their availability to plants and the leaching losses. Methods for measuring various forms of nitrogen in soil are important in order to improve N management and to minimize losses of essential nutrients in soils. In the present study 0.01 M CaCl ₂ extraction was used to determine the concentrations of ammonium, nitrate and N-organic forms, as these are closely related to the N mineralization potential of the soil and play a major role in nitrogen availability to plants. Improving the precision of nitrogen requirement estimation is essential for increasing the efficiency and minimizing potential losses of nitrogen in agricultural production. A better knowledge of the plant-availability of nitrogen may help improve the efficient use of fertilizers and organic manure. In the present study the amounts of N-NO ₃ , N-NH ₄ and N organic were studied in Westsik's crop rotation experiment. The crop rotation experiment was established in 1929, and is the best known and most remarkable example of continuous production in Hungary, enabling the study of the long-term effects of organic manure treatment, the development of models and the prediction of the probable influences of different cropping systems on soil properties and crop yields in the Nyírség (sandy soil) region of Hungary. The study aimed the optimization of the fertilizer recommendation system by considering the soil N-organic content as a measurement of site-specific mineralization potential. The 0.01 M CaCl ₂ extraction method measures soluble organic N compounds that are related to the mineralization of organic nitrogen in the soil. The introduction of this concept can possibly result in a more environment-friendly nitrogen fertilization, without negative effects on the yield or the quality of produced crops. Taking practicability and costs into consideration, the 0.01 M CaCl ₂ extraction method is suitable for the routine analysis of measuring easily available organic nitrogen.