Two-thirds law of nitrogen mineralization under undisturbed soil conditions: A new theory

摘要

It is reported in literature that globally, only about two-thirds of N in nutrient sources is available to plants and microbes in soils under undisturbed conditions. The present study explores this phenomenon and suggests a new theory to explain this. Diffusion of NH4+ from microsite sources is considered here and analyzed for a capillary of the soil system. It has been found that 68% of NH4+ diffused from the nutrient source is initially preserved in the proximity of the nutrient source, whereas, the remaining 32% is diffused away from the nutrient source and possibly immobilized in the nonexchangeable abiotic pools or lost. The NH4+ that has been initially retained near the microsites is gradually released to the mineral pool. Thus, about two-thirds of NH4+ released from microsites is available only to plants and microbes in the soil. This is a universal, natural mechanism of nutrient conservation for plant and microbial availabilities. The theory has important implications and applications in recommending N fertilizations in the forms of organic or mineral sources to plants grown across various soil textures, for which further studies are needed. Any deviations from this theory can mainly be attributed to various disturbances to the soil; for example, mechanical disturbances, nutrient leaching, and variations in pH and soil faunal activities. This theory may apply to other elements mineralized in the soils under undisturbed conditions, which must be investigated in future studies.