Translocation and recovery of 15N-labeled N derived from the foliar uptake of 15NH3 by the greenhouse tomato(Lycopersicon esculentum Mill.)

In order to completely evaluate ammonia emission from greenhouse vegetable fields, crop canopy absorption should not be neglected. The foliar uptake of NHapplied at two growth stages and the subsequentN-labeled N translocation to other plant components were investigated under greenhouse conditions using chambers covered with the soil of a tomato field. Treatments comprised three NH-N application rates(70, 140, and 210 mg/plot) usingN-labeled ammonium sulfate. Plants were harvested immediately after exposure for 24 h, and the total N concentrations andN/14 N ratios were determined. With increased NHconcentration, totalNH-N absorption increased considerably, whereas the appliedNH-N uptake decreased gradually. The tomato plants absorbed 33–38% and 24–31% of theNH-N generated at the anthesis and fruit growth stages, respectively. A total of 71–80% of the recovered NHwas observed in the leaves and 20–30% of the recovered NHwas remobilized to other components. Among them, an average of 10% of the absorbedNH-N was transferred into the tomato fruits. All these results indicated the potential of the tested tomatoes for the foliar uptake of atmosphericNHand the distribution ofN-labeled vegetative N among different plant components. The results are of great importance for the complete evaluation of nitrogen use efficiency in the greenhouse tomato fields.