The Effects of Urea, Biuret, and Ammonia on Germination and Early Growth of Corn (Zea mays L.)

Corn seeds were germinated near bands of fertilizer containing urea, biuret, cyanuric acid, ammonium, and certain other materials in sand‐solution cultures varying in urea and biuret, in closed systems containing gaseous NH 3 , and in soils with varying amounts of exchangeable NH 4 . Seeds were also soaked, before germination, in solutions of urea, biuret, (NH 4 ) 2 SO 4 , or NH 4 OH. Germination was greatly inhibited by gaseous NH 3 in closed systems, by more than 32% NH 4 ‐saturation of the soil, and by soaking seeds in NH 4 OH; seeds that did germinate produced normal plants. In the field, germination was not affected but seedlings were injured by 1.5 lb or more of biuret‐N per acre (38‐inch rows); up to 1.5 lb cyanuric acid per acre had no harmful effects. Seed injury by NH 3 released from urea is dependent upon hydrolytic activity, soil aeration, rate of nitrification, exchange capacity, and volume of soil between fertilizer and seed. Germination is affected by NH 3 ; biuret principally affects seedling development after germination.