Root Activity and Suitable Application Time of Nitrogen in the Dormant Period of Grapes

Abstract

1. Root activity of grapes during the dormant period was measured by the respiratory activity of roots in relation to their absorption ability of nutrients.
2. Roots became active with increasing soil temperature as the season advanced. When the soil temperature reached 12°C late in March both respiration and nitrogen absorption of roots became very active, though new roots did not still appear.
3. From the standpoint of shoot growth, berry set and yield of vines planted in pots with loamy soil, the most suitable application time of chemical nitrogen such as ammonium sulphate was in December or January rather than in February or March.