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Field experiments comparing ammonium nitrate and urea top-dressing for winter cereals and grassland in the U.K.

Summary The results of 173 field experiments carried out between 1957 and 1986 are presented comparing ammonium nitrate and urea as top-dressings for winter cereals and grassland. The trials show that urea was an inferior nitrogen source to ammonium nitrate. The yield from ammonium nitrate was significantly greater than that from urea for winter wheat, winter barley and for first, second and third cut silage. The results suggest (a) that winter wheat and winter barley respond differently to the two nitrogen sources and (b) that yield losses from urea are just as likely on first cut silage as second or third cut. A breakdown of results according to soil texture, soil pH and region showed no consistent differences in yield loss. This indicates that broad generalizations based on soil characters and geographical location are not helpful in distinguishing situations where urea performance may be either better or worse than average.