Mitigate nitrate contamination in potato tubers and increase nitrogen recovery by combining dicyandiamide, moringa oil and zeolite with nitrogen fertilizer.

Potato is considered a nitrogen (N) intensive plant with a low N use efficiency (NUE). The current study introduced an excellent approach by combining dicyandiamide (DCD), moringa seed oil (MSO), or zeolite (ZE), with N fertilizer for maximizing potato tuber yields and NUE as well as minimizing tubers nitrate (NO) accumulation. The impact of these materials on soil N availability and gaseous emissions (NH, and NO) was investigated under incubation conditions. A 2-year field experiment were carried out with seven treatments [without N (control), N fertilizer (350 kg N-urea ha as a recommended dose; Urea), 75% of N recommended dose with DCD (Urea+DCD), Urea with 2% MSO (Urea+MSO), Urea with 4% MSO (Urea+MSO), Urea with 0.5 Mg ZE ha (Urea+ZE), and Urea with 1.0 Mg ZE ha (Urea +ZE)]. We also conducted a 40-days incubation trial with the same treatments; however, urea was added at the rate of 200 mg N kg soil for all treatments, excluding the control. The addition of DCD, MSO, and ZE with urea under incubation conditions delayed the nitrification process, thereby causing a rise in NH-N content and a decrease in NO-N content. Ammonia-oxidizing bacteria (AOB) was inhibited (p ≤ 0.01) in treatments Urea+DCD, Urea+MSO, and Urea+ZE. The highest NUE indexes were recorded in treatment Urea+DCD. The highest NO accumulation (567 mg NO kg) in potato tubers was recorded in treatment Urea. Whilest, the lowest NO content (81 mg NO kg) was in treatment Urea+DCD. The lowest cumulative NO emissions and highest cumulative NH volatilization were observed in the treatment Urea+DCD under incubation conditions. Our findings demonstrated that N fertilizer rate could be reduced by 25%, while the tuber yields increased with an acceptable limit of NO content, resulting in economical, agronomical, and environmental benefits.