Beziehung zwischen dem Stickstoff-Entzug der Pflanzen und der Abnahme von spezifisch gebundenem NH4-N im Boden

Relationship between the N uptake of plants and the mobilization of nonexchangeable NH₄-N In a pot experiment with ryegrass (Lolium multiflorum) the relationship between the release of nonexchangeable NH₄⁺ and the N uptake of plants was studied. For this purpose the surface soil of an alluvial soil and of a grey brown podsolic soil was labelled with ¹⁵NH₄-N. The following results were obtained: After treating the soil with 15-N the alluvial soil contained 4,55 mg and the grey brown podsolic soil 1,64 mg nonexchangeable ¹⁵NH₄-N/100 g soil. In the alluvial soil 72% and in the grey brown podsolic soil 66% of the nonexchangeable ¹⁵NH₄⁺ had been released during the growing season when ryegrass was planted. However, without plants there was no change in the content of labelled nonexchangeable NH₄⁺ in the alluvial soil or only a slight decrease in the grey brown podsolic soil. A highly significant correlation was found between the ¹⁵NH₄-N released and the ¹⁵N uptake of ryegrass in the alluvial soil (r = 0,78⁺⁺⁺) as well as in the grey brown podsolic soil (r = 0,98⁺⁺⁺).