Nitrate pollution reduction using biological fertilizers in paddy fields, the South Caspian Sea basin, Guilan Province, Iran

Application of chemical fertilizers, especially urea, causes groundwater pollution. Therefore, to decrease environmental pollution, biological fertilizers may be employed. In order to investigate the effect of irrigation levels, Azospirillum and nitrogen levels on rice yield and its components, an experiment was conducted in the north of Iran during the crop season in 2013. The experiment was arranged in a split-split plot based on a completely randomized block design with 3 replications in which irrigation level was the main factor. The levels of factors used were: I1= continuous submergence and I2 = 11 days’ irrigation interval; A1 = application and A2= no application of Azospirillum as the sub factor; and nitrogen fertilizer levels as a sub-sub factor includingN1 = 0, N2 = 30, N3 = 60 and N4 = 90 kg ha-1. Continuous submergence and 11 days’ irrigation interval produced 4247 and 2720 kg ha-1, while the application of Azospirillum and the treatment without it produced 4064 and 2903 kg ha-1, respectively. Moreover, N4, N3, N2 and N1 produced 3950, 3800, 3225 and 2700 kg ha-1, while I1A1N4 and I1A1N3 had maximum and I2A2N1 had minimum mean values with 5381, 5330 and 1882 kg ha-1, respectively. Therefore, it is concluded that the application of a balanced nitrogen fertilizer with Azospirillum could prevent the indiscriminate use of chemical fertilizers and reduce nitrate pollution, leading towards more sustainable agriculture in the north of Iran.