Effect of amount and time of wheat straw application as mulch on flowering and morphological characteristics of replacement corms of saffron (Crocus sativus L.)

In order to investigate the effect of spreading time and application rates of wheat straw as mulch on Saffron corm and flower yield, a field experiment was conducted as factorial layout based on randomized complete block design with three replications at Gonabad Agricultural and Natural Resources Research Station, Center for Research and Agricultural Education and Natural Resources of Khorasan Razavi in years 2015-16. The treatments were all combination of wheat straw in four levels (2, 4, 6 and 8 t.ha-1) and time of wheat straw spreading in three dates (22 June, 6 July and 23August). The results showed that the rate and time of straw application and their interaction had significant effect on all studied characteristics of saffron flower. Spreading of wheat straw at 22 June compared to 6 July and 23August had the highest significant effect on increasing flower number, fresh flower yield, dry stigma and style yield (up to 41.7, 16.9 and 50 percent, respectively). In addition, all studied criteria of saffron replacement corms were significantly affected by the time of wheat straw spreading, different levels of wheat straw application and their interactions. Among the studied treatments, the highest corm yield in terms of more than 8g (595.65 g) and total saffron replacement corms yield were obtained in applying 8 t.ha-1 wheat straw at 22 June (1163 g). Compared to the treatment of 2 tons per hectare, the remnants on the same date show an increase of 112.2 and 12.9 percent, respectively.