Terminal drought and subsoil boron on barley root growth and water use - An examination of possible interactions

In arid and semi-arid areas, drought and boron (B) toxicity are common dete rrents to high crop yield. There seems to be an interaction of B toxicity w ith drought because B symptoms in the field often express under drought. Th is study examined the possible interaction of terminal drought and subsoil B on barley root growth and water use. A B-toxicity sensitive barley line w as grown, in PVC tubes in a plastic house using a randomized complete block design with three replicates. There were two factors: water level (normal vs. terminal drought) and B level(+B vs. -B in the subsoil between 20-60 cm depth). No significant drought by B interaction was detected for soil wate r content and for all plant characters measured. The +B tubes held more wat er than the -B tubes from 100 days after sowing. High subsoil-B level reduc ed root dry weight in the whole profile except in the 2nd and 5th 10-cm sec tions. In contrast, terminal drought had no effect on root growth. Results indicate that if a high level of subsoil B exists, uptake of water and soil nutrients may be depressed in nearly the whole soil profile, not only in t he subsoil alone. This means that breeding for drought tolerance alone may not be adequate; B-toxicity tolerance is needed as well. The absence of dro ught by B interaction indicates that the effects of high B levels can be st udied under either terminal drought or normal conditions, and vice versa.