Wheat can be grown in high NH4+ with little effect on growth and yield
Counter ion had no effect on Ca2+ uptake in these studies.
Inoculation with nitrifying microorganisms may help alleviate high NH4+ problems
Muhlestein, D. J.; Hooten, T.; Norton, J. M.; and Bugbee, Bruce, "The Long-Term Effects of High NH4 +/NO3 - Ratios on Wheat Growth and Nitrification in Hydroponic Culture" (1999). Hydroponics/Soilless Media. Paper 6.