Does Growing Safflower before Barley Reduce Barley Yields under Mediterranean Conditions?

Safflower (Carthamus tinctorius L.), which has deep roots, can be grown as an economical oil crop in semiarid, rain‐fed areas of West Asia and North Africa, where barley (Hordeum vulgare L.) monoculture is a common practice. In this study, we sought to: (i) evaluate the effect of safflower on the yield of the following barley crop and (ii) compare such effect with other crops to determine the potential of rotating safflower with barley. Two series of experiments were conducted under rain‐fed conditions in Lebanon's Bekaa Valley (2002–2003 to 2003–2004 and 2005–2006 to 2010–2011). In Series 1, there were 12 2‐yr rotation systems, whereas in Series 2, 3 rotation systems were studied. Results from the two and three rotation cycles were reported from the first and second series of experiments, respectively. Rotation effects were significant (P ≤ 0.05) for barley grain yield, straw yield, and harvest index, but rotation × year interaction was not significant. In Series 1, barley after safflower gave the highest harvest index (0.40 kg kg−1) and mean grain yield (1400 kg ha−1), that is, 28 to 72% higher grain yield than after the other crops, except after cumin (Cuminum cyminum L.) and common vetch (Vicia sativa L.) for grazing. In Series 2, grain yield and harvest index of barley after safflower (4090 kg ha−1, 0.36 kg kg−1) were higher than that after barley (3010 kg ha−1, 0.32 kg kg−1). Thus, growing safflower before barley increased rather than decreased barley yields, and was comparable to or better than after some legumes. Barley/safflower therefore appears to be a viable rotation in semiarid, rain‐fed Mediterranean areas.