Irrigation levels and dense planting affect flower yield and phosphorus concentration of saffron corms under semi-arid region of Mashhad, Northeast Iran

•Daughter corm formation is controlled by environmental conditions, under which mother corms have been grown.•In general, dense corm planting increased saffron flower and corm yield.•Small daughter corms contained less phosphorous compared with large corms.•Flower and corm yields significantly decreased by irrigating at 50% of saffron water requirement.

In arid and semi-arid regions of Iran, drought and water management are considered as important challenges in developing sustainable agriculture. The effects of irrigation levels and dense corm planting on flower yield, daughter corms behavior and phosphorus uptake of saffron (Crocus sativus L.) were studied as two-year field experiment based on a randomized complete blocks design arranged in split-plot with three replications at Faculty of Agriculture, Ferdowsi University of Mashhad, Iran, during 2012–2013 and 2013–2014 growing seasons. The irrigation levels including 50, 75 and 100% of saffron water requirement (SWR) and dense corm planting (50, 100, 200 and 300 corm m−2) were allocated to the main and sub-plots, respectively. The lowest yield, minimum number of daughter corms and phosphorus content of saffron were observed by planting 50 corms m−2 and supplying 50% of SWR. In the first year, flower characteristics were not affected by irrigating at 50% of SWR. However, in the second year, flower number, fresh flower and dry stigma yields significantly decreased by irrigating at 50% of SWR compared with 75 or 100% of SWR. In the second year, phosphorous concentration (g kg−1) and content (g m2) in small (0.1–4 g), medium (4.1–8 g) and large (over 8 g) daughter corms were significantly more than the first year. In general, small daughter corms contained less phosphorous compared with large (over 8 g) corms.