Effects on management of crop residues and cover crop planting on density and population of weeds and agronomical characteristics of saffron (Crocus sativus L.)

In order to investigate the effects of mulch types and different cover crops on relative frequency, density and biomass of weeds and agronomic characteristics and flower and stigma yield of saffron (Crocus sativus L.), an experiment was conducted based on a randomized complete block design with three replications at the Agricultural Research Station, Ferdowsi University of Mashhad, during two growing season 2009-2010 and 2010-2011. Treatments were three crop residues such as sunflower, barley and garlic and six cover crop species included barley, matter pea, rye, Persian clover, vetch and arugula and control. Studied characteristics were population, density and biomass of weeds and flower number, fresh weight of flower, stigma yield, leaf emergence rate and flowering rate. Results showed that the effect of treatments was significant (p≤0.01) on dry weight and density of weeds. The lowest weed density of narrow-leaf and broadleaf species were observed in vetch with 0.7 and 0.8 species.m-2 and highest was for control with 11.3 and 16.2 species.m-2, respectively. Also, treatments had significant effects (p≤0.01) on leaf emergence rate, flowering rate, flower number, fresh weight of flower and stigma yield of saffron. The maximum flower number and stigma yield were achieved in vetch with 244550.0 flowers.ha-1 and 1010.1 g m-2 and the minimum were for control with 66241.7 flowers ha-1 and 187.5 g m-2, respectively. Applying different crop residues and cover crops decreased density and dry weight of weeds decreased due to allelopathy trait of them. Cover crops increased growth and yield of saffron due to enhancement in nutrient and nitrogen availability as nitrogen fixation and improvement in soil characteristics.