Using Azolla and Cyanobacteria to Reduce Nitrate Accumulation in Lettuce Leaves and Optimize Nitrogen Fertilization in Hydroponics

• Shahad. Mohamed. bander 1* , Ali Abbas Kadhum 2 , Mohamed Obaid

  Author

A study was conducted in Anbar Governorate, Fallujah District, located near the Euphrates River west of Baghdad, to evaluate the use of cyanobacteria and Azolla in reducing nitrate accumulation in lettuce (Lactuca sativa L.) leaves under hydroponic conditions, as well as optimizing nitrogen fertilization rates. Two hydroponic systems were employed: the pond system and the nutrient film technique(NFT) system.

A factorial experiment was designed with two factors. The first factor consisted of biotic treatments, including cyanobacteria, Azolla, and a combination of Azolla with cyanobacteria. The second factor included three nitrogen levels (72, 108, and 144 mg kg⁻¹), in comparison with the full recommended nitrogen fertilization rate.

The results demonstrated a significant superiority of the pond system in reducing nitrate concentration in lettuce leaves. Moreover, the combined biotic treatment (Azolla + cyanobacteria) significantly decreased nitrate levels and improved nitrogen use efficiency. This effect was particularly pronounced at the 108 mg kg⁻¹ (N₂) level in the pond system, where both nitrate reduction and fertilizer optimization were achieved.

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