Effects of biofertilizers (Azotobacter and nitroxine) and different rates of chemical fertilizers on some attributes of cowpea (Vigna unguiculata (L.)Walp.)

This research was conducted to study the effects of biofertilizers, instead of chemical fertilizers on some attributes of cowpea. It was carried in a factorial experiment based on randomized complete block design with three replications at the Research Station of Islamic Azad University, Tabriz Branch, Iran, during growing season of 2007-2008. Factors were biofertilizers (without biofertilizers, Azotobacter, nitroxine, nitroxine + Azotobacter) and nitrogenous chemical fertilizers (without urea, 50 kg/ha, 100 kg/ha and 150 kg/ha urea). Results indicated significant effect of biofertilizer on leaf number, plant height, protein percentage and seed yield. However, chemical nitrogen (urea) had significant effect only on the leaf and pod number per plant and percentage of protein. There were significant interactions between the two factors for leaf dry weight and percentage of protein. Maximum and minimum leaf numbers were obtained by the presence and absence of N, respectively. The tallest plants were obtained from urea and nitroxine, while the shortest plants belonged to Azotobacter and Azotobacter + nitroxine. The highest leaf dry weight was observed for 100 kg/ha chemical N + Azotobacter and 150 kg/ha + nitroxine, while the lowest value belonged to 150 kg/ha urea + nitroxine + Azotobacter. Maximum number of pods per plant belonged to 50 kg/ha chemical N. The highest percent of protein was obtained from 100 and 150 kg/ha chemical N without biofertilizer and the lowest from Azotobacter when no N chemical was used. The results indicated that biofertilizers didn't increase the protein yield alone and they should be applied along with chemical fertilizers.