the effect of different n fertilizer sources on forage yield of berseem clover (trifolium alexandrinum l.) in an additive intercropping system with basil (ocimum basilicum l.) in karaj climatic conditions

in order to study the effect of different n fertilizer on berseem forage in an intercropping with basil, this experiment was conducted in research farm of college of agriculture, university of tehran during growing season 2011. experimental treatments were arranged as split plots based on a randomized complete block design with three replications. different fertilizers consisted of control (no n fertilizer), 100% chemical fertilizer, biological fertilizer, and integrated fertilizer (biological fertilizer + 50% n fertilizer) were assigned to the main plots while different additive intercropping patterns of basil mono cropping (weed free), basil mono cropping (weed infested), berseem clover mono cropping (weed free), berseem clover mono cropping (weed contaminated), berseem clover + %25 basil, berseem clover + %50 basil, berseem clover + %75 basil, berseem clover + %100 basil were assigned to the sub plots. the biological fertilizer comprised of rhizobium (rhizobium trefoli) + azotobacter (azotobacter sp.) + azosprilium (azosprilium sp.) + bacillus (bacillus sp.) + mycorrihza (mycorrihza sp.). the results showed that the highest basil forage yield (two harvests) (4223 kg.ha-1) was obtained from basil mono cropping (weed free) treatment when received integrated fertilizer. the highest forage yield (4833 kg.ha-1) for berseem clover was obtained from clover mono cropping (weed free) at 100% chemical fertilizing treatment. the highest total forage yield (berseem clover + basil) (5983 kg.ha-1) was obtained from berseem clover + %50 basil and berseem clover + %75 basil at integrated n fertilizer treatment. the best land equivalent ratio and relative competition ratio were obtained at berseem clover + %75 basil and berseem clover + %100 basil treatments. our results suggested that integrated fertilizer could be considered as the best fertilizing system to substitute for chemical n fertilizer (urea) in additive intercropping of berseem clover and basil.