effects of drought stress and humic acid application on quantative yield and content of macro-elements in medical plant borage (borago officinalis l.)

in order to evaluate effects of water stress and foliar application humic acid on quantities and qualitative in borage, a field experiment was conducted as a split plots design with three replication in 2012 at agricultural research station, university of zabol. water stress treatments included control or 90 percent of field capacity (w1), 70 percent field capacity (w2) and 50 percent field capacity (w3) as the main plots and four foliar application humic acid, including control or without any humic application (h1), h2=1.5, h3=3 and h4=4.5 liter at 1000 l water. the results showed that water stress had significant effect on flower yield, biological yield, number of branch per plant and shoot yield in borage plant. water stress until w2 increased flower yield and at higher levels of water stress (w3), flower yield, biological yield, number of branch per plant and shoot yield decreased. except potassium in flower and magnesium at leaves and flower, water stress had significant effect on phosphorus, potassium and sodium in leaves and flower and until w2 treatment, the content of them were increased. humic acid application had positive effect on flower yield, biological yield, number of branch per plant, shoot yield, plant high, phosphorus, potassium and sodium (except of calcium in flower st h3, calcium and magnesium in leaves at h4 treatment ), and increased them until h2 treatment.