The present pot experiment was an
attempt to monitor the beneficial effects of silicon (Si) and/or
potassium (K) applications on growth and nitrogen uptake in barley
plants grown under water (FC1) and non water (FC2) stress conditions
using 15N and 13C isotopes. Three fertilizer
rates of Si (Si50, Si100 and Si200)
and one fertilizer rate of K were used. Dry matter (DM) and N yield
(NY) in different plant parts of barley plants was affected by Si and/
or K fertilization as well as by the watering regime level under which
the plants have been grown. Solely added K or in combination with
adequate rate of Si (Si 100) were more effective in alleviating water
stress and producing higher yield in barley plants than solely added
Si. However, the latter nutrient was found to be more effective than
the former in producing higher spike's N yield. Solely added Si or in
combination with K significantly reduced leaves ∆13 C
reflecting their bifacial effects on water use efficiency (WUE),
particularly in plants grown under well watering regime. This result
indicated that Si might be involved in saving water loss through
reducing transpiration rate and facilitating water uptake;
consequently, increasing WUE. Although the rising of soil humidity
generally increased fertilizer nitrogen uptake (Ndff) and its use
efficiency (%NUE) in barley plants, applications of K or Si fertilizers
to water stressed plants resulted in significant increments of these
parameters as compared with the control. Our results highlight that Si
or K is not only involved in amelioration of growth of barley plants,
but can also improve nitrogen uptake and fertilizer nitrogen use
efficiency particularly under water deficit conditions.
Key
words: Barley; Silicon; Potassium; 15Nitrogen;
∆13Carbon; water stress
