Nitrogen nitrate. Low amount of this chemical

Nitrogen plays a important role in plant growth and is usually absorbed by plants as nitrate or 155 ammonium ions. It is the essential elements of metabolism of plants and very important for making 156 proteins, enzymes and chlorophyll structure of plants. Soils which are deficient in nitrogen, usually 157 result in low crop yield. Farmers supply nitrogen to agricultural land in the form chemical fertilizers 158 such as urea and ammonium nitrate. Low amount of this chemical fertilizers is used to stimulate the 159 growth of plants and also required to induce the activity of nitrogen fixing bacteria (Jefing et al., 160 1992). But these chemical fertilizers harm the environment in various ways, therefore, researchers are 161 focused to develop the ecofriendly agriculture practices, for example by applying the biofertilizers 162 like endophytic bacteria. 163Rhizobium is the best example to fix nitrogen in a sustainable manner. These microorganisms 164 were traditionally considered to be responsible for legume infection process, however rhizobia can 165 behave as endophytes in nodules and the isolated rhizobial strain from nodule have ability to again 166 infect the similar legumes from which they were recovered and also promote their growth. Lei et al. 167 (2008) isolated the endophytic rhizobia from the vicia nodules. Two of the endophytes R. 168 leguminosarum and Mesorhizobium loti were isolated from the clover nodules and when these were 169 coinoculated, showed increase in plant growth (Strutz et al., 1997). 170 As the legumes possess nodules on their roots where this bacterium Rhizobium locates with a 171 defined function of converting the atmospheric N2 into plant available form, called biological 172 nitrogen fixation. Increases in amount of biological nitrogen fixation can result from the use of 173 different commercial or wild strains. Significant increase in biological nitrogen fixation suggests that 174 more nitrogen can be fixed if they are inoculated more often or with more effective rhizobia. In this 175 manner, an appreciable quantity of biological nitrogen is accumulated in the soil which can be used by 176 similar crop and the subsequent one. Two main reason for the low crop yield is unavailability of good 177 quality seeds and effective rhizobial inoculation. Seed treated with native rhizobia in soil lacking 178 effective rhizobia is useful for improving nodulation and crop yield (Rupela and Dart, 1979; Patil and 179 Sbinde, 1980; Shamim and Ali, 1987; Shah et al., 1994). Chickpea respond positive to rhizobial 180 inoculation when grown in soils that contain native rhizobia (Sharma et al., 1983). However with the 181 introduction of improved varieties or sowing of this crop in new areas, inoculations with effective 182 rhizobial strain is essential for getting higher yields.