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 ۲۰۱۳. The experiment was arranged in a split-split plot based on a completely randomized block design with ۳ replications in which irrigation level was the main factor. The levels of factors used were: I۱= continuous submergence and I۲ = ۱۱ days’ irrigation interval; A۱ = application and A۲= no application of Azospirillum as the sub factor; and nitrogen fertilizer levels as a sub-sub factor includingN۱ = ۰, N۲ = ۳۰, N۳ = ۶۰ and N۴ = ۹۰ kg ha-۱. Continuous submergence and ۱۱ days’ irrigation interval produced ۴۲۴۷ and ۲۷۲۰ kg ha-۱, while the application of Azospirillum and the treatment without it produced ۴۰۶۴ and ۲۹۰۳ kg ha-۱, respectively. Moreover, N۴, N۳, N۲ and N۱ produced ۳۹۵۰, ۳۸۰۰, ۳۲۲۵ and ۲۷۰۰ kg ha-۱, while I۱A۱N۴ and I۱A۱N۳ had maximum and I۲A۲N۱ had minimum mean values with ۵۳۸۱, ۵۳۳۰ and ۱۸۸۲ kg ha-۱, 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.

Keywords:

biological fertilizer , nitrate pollution , paddy fields , rice