Effects of long-term fertilization on the yield of winter wheat and N forms on Luvic Phaeosem soil determined in 0.01 M CaCl2

Bertáné Szabó, E. and Loch, J. and Zsigrai, Gy. and Blaskó, L. (2010) Effects of long-term fertilization on the yield of winter wheat and N forms on Luvic Phaeosem soil determined in 0.01 M CaCl2. Agrokémia és Talajtan, 59 (1). pp. 135-144. ISSN 0002-1873

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Abstract

The effects of regular NPK fertilization on the amounts of winter wheat yield and the amounts and proportion of different N forms (NO3-N, NH4-N, Norg , Ntotal) of a Luvic Phaeosem soil determined in 0.01 M CaCl2 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 CaCl2 reflected fertilization well. All of the fractions, but especially NO3-N and Ntotal , increased significantly in response to N fertilization. Close relationships (r = 0.87–0.88) were found among the NO3-N and Ntotal fractions and the N balance, which means that the amounts of NO3-N and Ntotal are suitable for assessing both the N deficit and the N surplus. The strength of the correlation between the NH4-N content and N balance was moderate (r = 0.65). The Norg 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 Norg fraction and yield amounts. It can be established that organic residuals remaining on the site resulted in a significant increase in the Norg content of soils. The gained results confirm that the Norg 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 CaCl2 method is recommended for the precise estimation of nutrient requirements.

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