Application of Isotope Trace Technology in the Management of Nitrogen Fertilizer to Improve Sugar Productivity of Sugar Beet Plant under Different Irrigation Systemsr

Nitrogen (N) is the most usually used crop nutrient which represent importance of the efficient use of nitrogen fertilizers. At this study، the optimum fertilizer application pattern by using of 15N isotope technique in different irrigation systems and the influence of the fertilizer application time on amino-N accumulation in roots has been investigated. The experimental design was a randomized complete block (sampling method) design with four main treatments (irrigation methods) and three replications (unit area 144 m2). Irrigation treatments include: T1; surface drip fertigation، T2; sprinkler fertigation، T3; sprinkler irrigation T4; furrow irrigation. In the middle of the each plot an area about 1- 2 m2 (15 plants) was allocated as isotopic sub plot. Results indicated that the least tendency to utilize the fertilizer sources was related to the fertigation treatments. Despite the highest root weight، treatment T2 is not recommended to use. The method of application of fertilizers in treatment T3 lead on to the highest nitrogen uptake efficiency and pure sugar. The method of application of fertilizers in T1 and T2 increase the rate of α-amino acid N in the sugar beet roots and decrease their quality. Treatment T4 produced relatively high quality roots that confirm the method of application of fertilizer in treatment T3. In the weather condition of central Iran، during the sugar beet growing season، the application of fertilizer should be begun 45 days after sowing seeds and must be completed within one month. Occurrence of isotopic fractionation phenomenon cause that the average percentage of labeled nitrogen fertilizer (Ndff %) in underground and aerial parts of the plant considered to be 20. 1 and 16. 1% respectively.