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  • Author or Editor: J. Loch x
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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. 

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Current concerns about soil and water quality deterioration, limited possibility of fossil fuels, loss of biodiversity, and in general the viability of rural communities urge to work out methods of sustainable agriculture in the Nyírség region of Hungary. Sustainable agriculture seeks solutions for environmental, economic and agricultural problems at the same time. The aim is to develop new production methods which provide the protection of nature. In sustainable agricultural systems the management of organic matters and, more widely, the whole nutrient management are based on the total self-sufficiency of the farm. The entire cycle of organic matter production and decomposition takes place within the farm boundaries and makes the farm an actual biological system. The rate of metabolism and the organic matter cycle are characteristic features of each farm and define their activity for a long time. Present investigation conducted in Westsik's crop rotation experiment has found a highly significant correlation between organic nitrogen extracted by 0.01 M CaCl 2 solution and potato yield. It has shown that soil organic nitrogen extracted by 0.01 M CaCl 2 solution is a reliable indicator of nitrogen available for mineralization during the growing season. When precise nitrogen fertilizer recommendations are required, the method can supply additional information for environmentally friendly, sustainable agriculture.

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The effects of regular NPK fertilization on the amounts of winter wheat yield and the amounts and proportion of different N forms (NO 3 -N, NH 4 -N, N org , N total ) of a Luvic Phaeosem soil determined in 0.01 M CaCl 2 were studied in the B1740 variant of the National Long-Term Fertilization Experiment at Karcag. According to the yield data, N and P fertilization increased winter wheat yield significantly. When applying the 200 kg N·ha -1 dose, P fertilization resulted in a more than 2 t·ha -1 yield increase, as compared to the treatments without P fertilization. K fertilization had no effect on the yield, similarly to preceding years. These findings may be adapted to fields of the Middle-Tisza Region with similar conditions to the trial site. The N forms of the soil determined in CaCl 2 reflected fertilization well. All of the fractions, but especially NO 3 -N and N total , increased significantly in response to N fertilization. Close relationships (r = 0.87–0.88) were found among the NO 3 -N and N total fractions and the N balance, which means that the amounts of NO 3 -N and N total are suitable for assessing both the N deficit and the N surplus. The strength of the correlation between the NH 4 -N content and N balance was moderate (r = 0.65). The N org fraction increased significantly as a function of N and P fertilization. These results can be explained with the yield increase. A significant correlation (r = 0.55) was found between the N org fraction and yield amounts. It can be established that organic residuals remaining on the site resulted in a significant increase in the N org content of soils. The gained results confirm that the N org fraction is suitable for the characterization of the readily mobilizable N reserves previously ignored in fertilization practice. On the basis of the presented results the CaCl 2 method is recommended for the precise estimation of nutrient requirements.

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