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Effects of atmospheric ammonia enrichment and nitrogen status on the growth of maize

Enhanced atmospheric ammonia (NH3) concentration could impact growth of crops. The effect of atmospheric NH3 in combination with nitrogen‐deprived and ‐sufficient supply (ND and NS, respectively) on growth of maize plants (Zea mays L.) was investigated. Plants were exposed to 0 and 1000 nL L−1 NH3 for 50 days in open‐top chambers (OTCs). At different growing stages after injecting NH3, elevated NH3 significantly increased plant height, leaf area per plant and shoot biomass (total biomass) in the nitrogen‐deprived plants in 2006 and 2007, but the corresponding values in the nitrogen‐sufficient plants remained the same or slightly decreased. The values for net photosynthesis rate (Pn ) and relative content of chlorophyll (SPAD value) increased with NH3 enhancement both in the presence and absence of nitrogen in nutrient solution, but the increment of Pn and SPAD value in nitrogen‐deprived plants was two times higher than that of the nitrogen‐sufficient plants in each year. The shoot: root ratio (S/R) for maize first decreased and then rose during the growing season. At 50 days after injecting NH3, the S/R in the ND‐1000 plants was significantly higher than that in the ND‐0 plants in both years. Under these conditions, increased growth was observed, and it was concluded that the effect of atmospheric NH3 on maize could be mainly due to the shoot growth response.