01932naa a2200181 a 450000100080000000500110000800800410001910000160006024501870007626000090026352013000027265000110157265000190158365300130160265300270161570000170164277300910165918332132011-08-16       1978    bl ---       0--  u    #d1 aDREW, M. C.  aEffects of direct drilling and ploughing on root distribution in spring barley, and on the concentrations of extractable phosphate and potassium in the upper horizons of a clay soil.  c1978  aA comparison was made between the effects of three consecutive years of either direct drilling or ploughing, on the distribution of extractable soil phosphate and potassium, and the distribution of roots of a spring barley crop in the upper 20 cm of the soil. Samples were collected from a clay soil (Evesham series) in June 1975 when the crop was mid-way through the phase of stem extension (Feeke's growth stage 7–8). With ploughing, the concentration of nutrients was approximately uniform to the maximum depth of cultivation (20 cm). With direct drilling there were markedly higher concentrations of phosphate and potassium in the upper 5 cm of the soil, but at depths between 10 and 20 cm the concentrations of potassium, and particularly phosphate, were lower than with ploughing. Root weight and length, per unit soil volume, in the upper 5 cm, were also greater with direct drilling than with ploughing. However, the more superficial distribution of phosphate and of roots with direct drilling did not restrict phosphate uptake by the crop, despite the dry summer. The results are discussed in relation to factors contributing to differences in the distribution of nutrients and roots in land receiving contrasting cultivations, and possible consequences for crop growth are indicated.  aCevada  aPlantio Direto  aAração  aDistribuição de raiz1 aSAKER, L. R.  tJournal of the Science of Food and Agriculture, Londongv. 29, n. 3, p. 201-206, 1978.