Effect of phosphoric fertilizer and starter rates of nitrogen fertilizers on the phosphatase activity in the rhizosphere soil and nonlignified soybean roots under drought conditions

Abstract

In a smallplot field experiment, two soybean ( Glycine max L.) cultivars were grown on a calcare� ous chernozem under the drought conditions of 2012 with the preplanting application of simple superphos� phate (Ps) at 60 kg/ha, urea (Nu) at 10 and 20 kg/ha, and ammonium nitrate (Nan) at 20 kg/ha. The phos� phatase activity was measured in the rhizosphere soil (0� to 20�cm layer) and the fine nonlignified roots of soybean plants at the blossoming and podformation stages (the soil water content was 19 and 33% of the total water capacity, respectively). The maximum content of available phosphorus in the rhizosphere of both soy� bean cultivars (4.3-4.8 mg/100 g dry soil) was found at the simultaneous application of Ps and N u 20. Higher activities of the predominant phosphatases (alkaline phosphatase in the rhizosphere and acid phosphatase in the roots) were observed in the rootinhabited zone of the soil under the Indra cultivar compared to the Aura cultivar, which correlated with the lower content of available phosphorus in the rhizosphere soil (especially at the simultaneous application of Ps and N u 20) and the higher productivity of this cultivar in this treatment.