R Ghorbani - Department of Agronomy Faculty of Agriculture Ferdowsi University of Mashhad P. O. Box: ۹۱۷۷۵-۱۱۶۳ Mashhad Iran
M.H Rashed Mohassel - Department of Agronomy Faculty of Agriculture Ferdowsi University of Mashhad P. O. Box: ۹۱۷۷۵-۱۱۶۳ Mashhad Iran
H Makarian - Department of Agronomy Faculty of Agriculture Ferdowsi University of Mashhad P. O. Box: ۹۱۷۷۵-۱۱۶۳ Mashhad Iran
M Rastgoo - Department of Agronomy Faculty of Agriculture Ferdowsi University of Mashhad P. O. Box: ۹۱۷۷۵-۱۱۶۳ Mashhad Iran.

To study the effects of sheep (Ovis aries L.) rates and grazing duration on weed control and saffron biomass, a field experiment was conducted during the year 2006, in a saffron (Crocus sativus L.) field located in Boshrooyeh (33° North latitude, 57° East longitude), Razavi Khorasan, Iran. A split plot design based on randomized complete block with three replications was used. The treatments comprised three sheep rates, 200, 400 and 750 sheeps per hectare allocated in main plots and three grazing durations, 2, 3 and 4 days (8 hours per day) allocated in subplots. The factors studied consisted of above ground dry weight of common grasses (Hordeum spontaneum, Lolium rigidum), broadleaf weeds (Cardaria draba and Carduus pycnocephalus) and dry weight above ground biomass of saffron. Results showed that sheep rates had significant effects on above ground dry weight of grass and broadleaf weeds. Duration of grazing had a significant effect on saffron above ground biomass. With increasing sheep rates from 200 to 400 per ha, dry weight of weeds (grass and broadleaf) decreased significantly. In the highest rate of sheep (750 per ha) with increasing the duration of grazing from 2 to 4 days, dry weight of saffron leaves decreased significantly. Our results suggest the idea that grazing with 400 sheep per hectare for duration of 3 days is required for acceptable control of weeds in saffron field without any significant reduction in above ground saffron biomass.

biological control, organic farming, population