Pb. Barraclough et J. Haynes, THE EFFECT OF FOLIAR SUPPLEMENTS OF POTASSIUM-NITRATE AND UREA ON THEYIELD OF WINTER-WHEAT, Fertilizer research, 44(3), 1996, pp. 217-223
Winter wheat crops were grown with ostensibly adequate supplies of all
soil nutrients in 1990 and 1991 with the aim of testing if late folia
r supplements of K and N, applied at key development stages, could imp
rove grain yield and grain N content. Foliar sprays of KNO3 solution,
supplying up to 40 kg K ha(-1) in total, at flag leaf unfolded, inflor
escence completed and the watery-ripe stage of grain filling, had no e
ffect on yield, yield components or grain N. Urea, supplying 40 kg N h
a(-1) at flag leaf unfolded, had no effects on grain yield and grain N
in 1990, but in 1991 grain N was increased by 0.14% whilst yield was
reduced by up to 0.6 t ha(-1). Urea scorched flag leaf tips in both ye
ars. In 1990, the spring was very dry and foliar supplements might hav
e been expected to have had an effect, but on this highly fertile soil
all crop K and N requirements were met from the soil.