The responses to fertiliser-N of winter wheat and winter barley grown on sa
ndy soils were measured in 72 experiments in England from 1990 to 1994. Yie
ld without fertiliser-N (Y-0) was c 1.1 tha(-1) greater following root crop
s than following cereals. Following potato crops given organic manures, Y-0
was c 1.2tha(-1) greater than following unmanured potato crops, but Y-0 wa
s no greater following sugarbeet to which organic manures had been applied.
Only after the two driest winters was there sufficient variation in soil N
supply in spring (SNSs) for this to show a relationship with Y-0. However,
Y-0 increased with increasing N mineralisation during the growing season (
AM) in the three years it was measured. There was no consistent effect of s
owing date on Y-0. Following potatoes, yield at optimum fertiliser-N (Y-opt
) decreased as sowing date was delayed, but this was not so after cereals,
sugarbeet or overall. There was no increase in Y-opt with SNSS or AM, but Y
-opt decreased with increasing moisture stress (S) in June. The mean yield
response to N-opt (Delta(Y)) was c 0.4 and 0.8 tha(-1) smaller following po
tatoes and sugarbeet respectively than following cereals, but not consisten
tly so as there were large interactions between site, year and previous cro
p. Following root crops, Delta(Y) was c 0.6 and 1.4 tha(-1) less after suga
rbeet and potatoes respectively that had been given organic manures. Withou
t the addition of organic manures, Delta(Y) following potatoes was similar
to that following cereals. Regression on SNSs and AM accounted for 28 and 1
5% respectively of the variance in dy. The optimum economic fertiliser-N ap
plication (N-opt) was similar, at c 140kgha(-1), following cereals and pota
toes. Following sugarbeet, cereal N-opt was only c 110kgha(-1). The differe
nces according to previous crop reported here are consistent with mineralis
ation of crop residues on sandy soils being more rapid than on other soils;
the potato residues were rapidly mineralised in autumn and lost by leachin
g over winter. Residues from later-harvested sugarbeet were mineralised dur
ing the growing season of the subsequent cereal crop. Fertiliser-N requirem
ents were, at c 110-140kgha(-1), smaller than has been found on other soil
types, and less than current recommendations for wheat. Requirements were s
ignificantly reduced in years of drought stress. No differences were found
in N-opt between wheat and barley. These data do not justify the current ad
vice to invariably reduce fertiliser-N to cereals following potatoes by 20-
25kgha(-1) on these sandy soils. On average a reduction of c 20kgha(-1) cou
ld be made following sugarbeet, with a further reduction of c 40kgha(-1) N
if manures had been applied to the previous sugarbeet crop. A reduction of
40kgha(-1) N could also be made where cereals followed a potato crop to whi
ch manures had been applied. Further refinements on the basis of measuremen
ts of soil mineral N could not be justified. Seasonal variation in N respon
se due to drought stress makes recommendations difficult on these soils. Ad
opting the fertiliser-N recommendations proposed here would produce N surpl
uses to the soil of c 37, 10 and 27kgha(-1) respectively following cereals,
sugarbeet and potatoes when cereal grain is removed but straw incorporated
. On farms where straw is removed, N surplus would be largely eliminated.
Our recommendation that no reduction in fertiliser-N application to cereal
crops grown on sandy soils should be made following potatoes will not incre
ase fertiliser-N use and is not expected to increase nitrate leaching. Some
reduction in nitrate leaching may be achieved if recommendations following
cereal crops and sugarbeet are made in accordance with the results reporte
d here. (C) 2000 Society of Chemical Industry.