Internal nitrogen cycling compared in surface samples of an Andept and a Mollisol

This study was conducted to examine the hypothesis that slow N mineralization and associated organic matter accumulation in Andept, was related to the internal N cycling regime, and if so, to determine at what stage.The results indicated that N was mineralized from native organic matter in an Andept less rapidly than occurred in a Mollisol of similar organic matter content but N mineralization from added alfalfa was similar in both soils. Both soils immobilized N rapidly in the presence of glucose, but remineralization of immobilized N was more rapid in the Mollisol than in the Andept samples. Partial sterilization resulted in substantial remineralization of N from both soils.It was concluded that slow N mineralization in the Andept soil is due to slow N recycling from recently synthesized biomass. Associated with this is a low supply of soluble C in the Andept soil. Whether slow N recycling from recently synthesized biomass results from some toxic effect on predatory organisms, from lytic enzyme adsorption, adsorption of lytic products or some mineral nutrient deficiency awaits further study.