Influence of nitrogen content in the soil solution on potential nitrogen mineralization of organic residues

Abstract

Application of organic residues to soil may supply nutrients to plant, namely, nitrogen (N). But, generally, organic residues contain mostly organic N that has to be mineralized prior to plant uptake. This process depends on several parameters such as the carbon to nitrogen ratio of the residues or the soil moisture. The aim of the present work was to assess the effect of the ammonium (NH₄ ⁺) and organic N contents of the soil solution on potential N mineralization (PNM) of organic residues applied to soil. Seven organic residues (rice straw, wheat straw, maize straw, sewage sludge, liquid pig manure, poultry manure, and poultry excreta) combined each with three soil solutions: N_org+min (63 mg L⁻¹ total N with 47% organic N and 53% NH₄ ⁺-N), N_org (5.6 mg L⁻¹ total N with 92% organic N and 8% NH₄ ⁺-N), and control (no N) were compared. Our results indicated that a small amount of organic N and low NH₄ ⁺-N in the soil solution enhanced the PNM of organic residues, whereas larger amounts of NH₄ ⁺-N and organic N in the same proportions decreased the PNM and could lead to N immobilization.

Keywords:

• nitrogen
• potential mineralization
• anaerobic incubation
• organic residues
• soil solution