Application of anhydrous ammonia or urea during the fallow period for winter cereals on the Darling Downs, Queensland, 1. Soil mineral N at sowing
1992
Strong, W.M. | Cooper, J.E. (Queensland Dept. of Primary Industries, Toowoomba (Australia). Queensland Wheat Research Inst.)
In 9 field experiments conducted in 1978, 1981 and 1982, nitrification of applied N was usually quite rapid in moist soil, particularly with early application (January, February or March) when mean soil temperature was greater than 20 deg C. Extreme drying of soil following N application reduced nitrification to a very low rate. Low recovery of early applied N as soil mineral N was associated with very heavy rain received during the latter part of the fallow period (March-May). Low recoveries of early applied N in mineral forms at the end of relatively drier fallows were also associated with soil saturating rainfall during the latter part of the fallow period. Where wheat crops responded to applied N, January or February applications were less effective than May applications to increase yield and N content of grain.
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