ROOT-GROWTH OF WINTER-WHEAT UNDER FIELD CONDITIONS

Five-year field trials on loamy sand revealed a close correlation between root dry matter and root length density (r = 0.75 to 0.98). An average of 89 % of the root dry matter in the 0 to 60 cm soil layer was found in the upper 30 cm. Weather conditions affected the absolute amount of root dry matter (maximum at ear emergence, varying from 0.6 to 2.0 t/ha in different years) and the time course of root dry matter growth. Maximum root dry matter growth was observed prior to shoot dry matter growth. The shoot-to-root ratio changed steadily during the growing period in favour of the shoots, being lower at low yields than at high yields. Nutrient availability in the soil and the amount of N fertilizer applied had no distinct effect on root dry matter and root length density but strongly affected shoot and grain weights.