Assessment of Changes in Weed Dry Weight and some Characteristics of Safflower (Carthamus tinctorius) under Different Sources of Fertilizer and Intercropping

To study the effect of different organic and chemical fertilizers on weed biomass and some characteristics of safflower, a factorial experiment based on randomized complete block design with three replications was done at the Urmia University Reaearch Farm in 2013. Treatments consisted of growing of cover crops (red clover, grass pea, hairy, bitter vetch) along with the safflower rows and two weed control treatments (with and without weed) as a first factor and application of organic manure (cattle manure+biofertilizer) and the different nitrogen and phosphuros fertilizer levels (100 % of recommended chemical fertilizer, 67 and 63 % of recommended N and P, 50 and 40 % of recommended N and P) as second factor. Results showed that the biomass yield of broad and narrow leaf weeds affected by the combined treatments of cover crops and use of fertilizers. The biomass yield of broad and narrow leaf weeds were redused by 74.78, 82.22% under vetch cover crop when 50 and 40% of recommended N and P fertilizers were used, in comparison with sole culture of safflower and use of 100% of recommended chemical fertilizers. The maximum of seed yield (3431 kg.ha-1) and biological yield (8239 kg.ha-1) of safflower obtained from using 100% of recommended chemical fertilizers and without growing cover crops. Results, as a whole, showed that at higher levels of chemical fertilizers the competitive effects of weeds on safflower were higher than lower levels of fertilizers.