Case of a stronger capability of maize seedlings to use ammonium being responsible for the higher 15N recovery efficiency of ammonium compared with nitrate

Abstract

Matching a crop’s nitrogen (N) preference with the specific form of N is critical to enhance N recovery efficiency (NRE). Many studies show that maize (Zea mays L.) has a preference for NH4+ uptake over NO3−, but the contribution of this preference to NRE is unclear. This study evaluated the utilization of ammonium (NH4+) and nitrate (NO3−) by maize and its relationship with NRE. Maize (cv. ‘Zhengdan 958’) seedlings were grown in a soil culture experiment with 15NH4+ or 15NO3− applied to sterilized or non-sterilized soils, and in a hydroponic experiment supplied with NH4+ or NO3−. We recorded maize root and shoot growth and N uptake, and the distribution of 15N-labeled N in the soil–plant system. Ammonium application enhanced maize root and shoot growth and N uptake compared with those of NO3−-treated plants in both culture systems. This enhancement by NH4+ was further promoted in sterilized soil. More applied N remained in soil supplied with NO3− than with NH4+ after seedling harvest. The NRE of NH4+ in maize was significantly higher than that of NO3−, while a similar proportion of applied N was lost with NH4+ or NO3−supply. Ammonium supply enhances maize growth and NRE compared with NO3− under the present experimental condition, which may be attributable to the superior capability of maize to utilize NH4+.