The Effect of Different Levels of Humic Acid Fertilizer on Components of Biological Nitrogen Fixation in Cowpea Cultivars in Ahvaz

摘要

Making use of humic acid in agriculture due to different physiological effects not only increases the yield but alsodecreases the consumption of chemical fertilizers and reduces environment pollution. Humic acid is among thesubstances which have dual effect on biological nitrogen fixation, i.e. it can develop the roots and has positiveeffect on activity of soil microorganisms and can increase biological nitrogen fixation in legumes. In order tostudy the effect of different levels of humic acid on components of biological nitrogen fixation in cowpea cultivarsa factorial experiment in the form of randomized complete block design was carried out in Ahvaz in 2011. Threelevels of humic acid (H1 = 0, H2 = 75 PPM, H3 = 150 PPM) and two cowpea varieties (V1 = local, V2 = Egyptian)were placed in plots as a combination. Humic acid was once sprayed to crops at the end of vegetative growth. Theresults showed that humic acid foliar spray fertilizer significantly increased root growth, number of roots, andnumber of nodules, root dry weight, and nitrogen percentage of crop nodule. The highest percentage of nitrogenfixation belonged to H3 treatment by 6.10%. Moreover, the effect of cowpea cultivar on all traits was significantexcept on the number of roots and the length of pod. The highest percentage of nitrogen fixation belonged toEgyptian cultivar by 5.81%. In this experiment, Egyptian cultivar was more efficient than local cultivar.