Nitrogen fertilization on uptake of soil inorganic phosphorus fractions in the wheat root zone

Plant nutrient uptake from the soil is dependent on fertilizers applied, soil chemicals, and other factors. The purpose of this study is to quantify the effects of applied N fertilizers on P uptake by winter wheat (Triticum aestivum L.) and on the change of soil pH in the root zone related to reductions of inorganic P fractions in the rhizosphere soil. An experiment was conducted using different forms of N fertilizers (i.e., NH₄⁺-N and NO₃^--N) with three N concentrations (0, 100, and 300 mg kg^-1) applied in a calcareous soil. Biomass and total N uptake of the plant increased with the N concentrations and NH₄⁺-N fertilizer resulted in a greater biomass than NO₃^--N nutrition. Total P uptake in the plant was also higher with NH₄ ⁺-N fertilizer than with the NO₃^--N nutrition. Compared with the zero N treatment, the soil pH around the roots decreased by 0.30 and 0.65 units, respectively, with N treatments of 100 and 300 mg kg ^-1 of NH₄⁺-N fertilizer. The amount of soil inorganic P fractions in the root zone decreased with increasing NH ₄⁺-N applied. The NO₃^--N treatments reduced rhizosphere acidification and had a less impact on the soil inorganic P fractions. The results suggest that enhancing rhizosphere acidification attributable to applications of NH₄⁺-N fertilizer can increase P availability in calcareous soils for plant uptake.