Toxicity of Preplant Anhydrous Ammonia to Germination and Early Growth of Corn: II. Laboratory Studies1

Abstract

AbstractLaboratory experiments were conducted to determine concentrations of NH3 in soil which are toxic to germination and early root growth of corn (Zea mays L.). In one experiment seeds were germinated in soil uniformly mixed with a given rate of anhydrous ammonia, and in another experiment roots were grown into successive layers of soil containing increasing amounts of NH3. Germination and early growth was retarded when soil [NH3 + NH4+)‐N concentration reached 944 ppm (pH 3.1) and essentially completely inhibited when it reached 1,628 ppm (pH 9.0). Roots grew through 3‐cm layers of soil containing 1,172 ppm (NH3 + NH4 +)‐N (pH 8.4), but did not grow into layers containing 1485 ppm (NH3 + NH4+)‐N (pH 8.7). Radicles stunted by NH3 were thicker and had more branching than those of control plants. Root tips which encountered toxic amounts of NH3 had a brown, scorched appearance.