Apparent Atmospheric Nitrogen Loss from Hydroponically Grown Corn

Abstract

AbstractIsotopic 15N tracers have been important tools in the understanding of N cycling in agricultural and natural soil‐plant systems. The objectives of this research were to quantify losses of 15N under controlled conditions, evaluate 15NH3 transport between plants, and assess the potential for error associated with the use of N isotopes. Corn (Zea mays L.) was grown hydroponically in 5‐ to 15‐mm‐diam. gravel in twelve 162‐L barrels. All N was applied as NO3 with enrichment periods of full season, planting through anthesis, anthesis to harvest, or no 15N applied. Plant growth and total N accumulation followed normal growth curves and maximum N content was obtained at anthesis. When 15N treatments stopped at anthesis, plants lost 15N (presumably as 15NH3) equivalent to about 23% of total plant N between anthesis and harvest. In treatments in which 15N applications started at anthesis, total N content in the leaves and stems decreased between anthesis and harvest while 15N content increased indicating a substitution of recently absorbed N for N compounds translocated to the fruit. Volatile losses of N indicate that caution must be exercised when conducting and interpreting 15N experiments. Significant plant‐to‐plant transport of 15NH3 showed that decreases in plant 15N content could not be used to estimate NH3 volatilization for an entire field.