Effect of the nitrogen fertilizer type on the enzyme activity in the rhizosphere of calcic chernozem and soybean production
2015
Emnova, E. E. | Daraban, O. V. | Bizgan, Ya. V. | Toma, S. I. | Vozian, V. I. | Iacobuta, M. D.
Three varieties (Aura, Magie, and Indra) of soybean (Glycine max [L.] Merr.) were grown in a small-plot experiment on a calcic chernozem with the application of two types of nitrogen fertilizers: ammonium nitrate (Nₐₙ) or carbamide (Nc). These fertilizers at the rate of 20 kg N/ha were applied before sowing together with potassium phosphate (60 kg P₂O₅/ha). The microbial nitrification capacity and the activity of enzymes related to the nitrogen cycle (urease and nitrate reductase) were measured in the rhizosphere (0–20 cm) at the stage of soybean flowering. It was determined that the biological (enzyme) activity of the calcic chernozem in the soybean rhizosphere was more intense on the plots with the Nₐₙfertilizer than on the plots with the Ncfertilizer. The urease activity depended on the type of nitrogen fertilizer (Nₐₙor Nc) under the conditions of soil water deficiency. In the soil under the Aura variety, the urease activity was significantly lower in the treatments with Ncapplication, and this was accompanied by a decrease in the crop yield. The nitrification capacity of the calcic chernozem was generally low; in the case of the Ncfertilizer, it was significantly lower than in the case of the Nₐₙfertilizer. The nitrate reductase activity of the soil was also lower in the case of the Ncfertilizer. Each of the three soybean varieties had its own response to changes in the nitrogen nutrition aimed at improving the soybean tolerance to fluctuations in the soil water content during the growing season.
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