Non-isotopic method for the quantification of biological nitrogen fixation and wheat production under field conditions

 A field experiment was conducted in the Inshas area (Sharkeia governorate) to study the potential of biofertilizers, when the quantities of commercial fertilizers were reduced, for optimal wheat production. The different treatments were arranged in a completely randomized block design with seven replicates. N fertilizer was applied in three treatments with one control, i.e. zero, full, half and one-fourth rates, in the presence or absence of inocula. Azospirillum brasilense strain Sp245 was used as a biofertilizer. Generally, inoculation increased the accumulation of shoot dry matter and grain yield by about 35%, relative to the control treatment. Similar trends were observed in the case of N and P uptake by shoots and grains, as well as the efficient use of both, where inoculation increased the acquisition of the two elements as compared with the uninoculated plants. The obtained data showed that N₂ fixed by shoots and grains ranged from 2 to 10 kg N ha^–1 and from 8 to 19 kg N ha^–1, respectively. With respect to fixed N₂, the best treatment was inoculation combined with the one-fourth dose of N, followed by inoculation combined with half of the recommended N dose. Most of the fixed N was utilized by grains and the results clearly reflected the negative effect of high N fertilizer rates on biological N fixation. It is obvious that inoculation, in general, enhanced the N fertilizer utilized by both shoots and grains of wheat plants. In conclusion, the application of biofertilization technology to a light-textured soil with low fertility had a positive effect on plant growth, N gained from the air and enhancement of fertilizer N uptake (apparent recovery fraction). Received: 22 April 1999