Water use and yield response of rainfed safflower (Carthamus tinctorius L.) in Vertisols with varying soil depths

Safflower (Carthamus tinctorius L.) is an edible oilseed crop mainly cultivated in marginal lands. This study evaluates safflower crop water requirements to understand its feasibility to cultivate under rainfed ecosystem through a field experiment undertaken at the International Crops Research Institute for the Semiarid Tropics research farm, India. Eight improved and stress-tolerant safflower cultivars (five spiny and three non-spiny) were evaluated in Vertisols at three soil depths, that is, shallow: <0.60 m, medium: 0.60-1.20 m, and deep:1.20-1.80 m, over 3 years (2009-2012). Wet, normal, and deficit rainfall years were experienced during 2009/2010, 2010/2011, and 2011/2012, respectively. Soil moisture, crop yield, and growth parameters were measured, and field-scale hydrology was captured through a calibrated one-dimensional water balance model. Safflower responded to available residual soil moisture which varied with soil depth and rainfall received in different years. Total crop water use was 300-320 mm during the postrainy season, of which about 70% was extracted in deep Vertisols and 55% in medium Vertisols through residual soil moisture. In addition, 30% of water requirement was met through postrainy season rainfall. Safflower grown in shallow Vertisols could only meet 40% of crop water requirement. Spiny cultivar NARI-H-15 grown in deep soil recorded a maximum yield of 1890 kg ha(-1) in the wet year. Seed yield from spiny cultivars grown in deep and medium soils was nearly similar (1500-1600 kg ha(-1)) during wet and normal years; a significant reduction in yield (>50%) occurred in shallow soils and also during a rainfall deficit year. Spiny cultivars produced 10%-50% higher seed yield compared to non-spiny cultivars. Growing safflower in medium and deep Vertisols provides opportunities for crop intensification.