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Nitrogen fertilizer requirements of cereals following grass
Author(s) -
Withers P.J.A.,
SylvesterBradley R.
Publication year - 1999
Publication title -
soil use and management
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.709
H-Index - 81
eISSN - 1475-2743
pISSN - 0266-0032
DOI - 10.1111/j.1475-2743.1999.tb00092.x
Subject(s) - fertilizer , plough , nitrogen , agronomy , zoology , mathematics , yield (engineering) , crop , chemistry , biology , materials science , organic chemistry , metallurgy
. The effect of increasing rates of nitrogen (N) fertilizer on the yield response of 3 or 4 consecutive winter cereal crops after ploughing out grass was investigated at six field sites on commercial farms in England and Wales. Amounts of N required for an economically optimum yield (>3 kg of grain for each kg of fertilizer N applied) ranged from 0 to 265 kg ha −1 and were dependent on soil N supply, but not on crop yield. Optimum N rates were large (mean 197 kg N ha −1 ) at three sites: two sites where cereals followed 2‐year grass leys receiving low N inputs (<200 kg N ha −1 ), and at one site where a cut and grazed 4‐year ley had received c . 315 kg N ha −1 of fertilizer N annually. At the other three sites where 4 and 5‐year grass leys had received large regular amounts of organic manures (20–30 t or m 3 ha −1 ) plus fertilizer N ( c . 300 kg ha −1 each year), optimum N rates were low (mean 93 kg N ha −1 ) and consistently over‐estimated by the farmer by an average of 107 kg N ha −1 . Optimum N rates generally increased in successive years after ploughing as the N supply from the soil declined. Determination of soil C:N ratio and mineral N (NO 3 N+NH 4 N) to 90 cm depth in autumn were helpful in assessing fertilizer N need. The results suggest there is scope to improve current fertilizer recommendations for cereals after grass by removing crop yield as a determinant and including an assessment of soil mineralizable N during the growing season.