Abstract
This study assessed effects of irrigation water regimes and humic acid (HA) application on vegetative growth, yield, tuber quality and water use efficiency (WUE) of potato. Five irrigation treatments were applied at three developmental stages; (WR1) control (100 % crop evapotranspiration, 100 % ETc) at all plant growth, (WR2) 75 % ETc at all stages, (WR3) 75 % ETc at stage S1 (vegetative growth), (WR4) 75 % ETc at stage S2 (tuber initiation), and (WR5) 75 % ETc at stage S3 (tuber bulking). HA was applied at a rate of 1.5 g L-1 30 day after seed pieces planting. Plants experiencing water stress at S1 were shorter with fewer branches and lower fresh and dry vine weights. Water stress imposed at S2 significantly reduced tuber number, size, and yield. HA application increased vegetative growth, tuber weight, yield, WUE, and tuber quality (specific gravity and starch content). Thus, applying 1.5 g L-1 HA during vegetative growth and a 75 % ET water regime at S3 can increase potato production and tuber quality while reducing water use.