Fate and interaction with soil N of fertilizer 15N applied to wheat at different growth stages

A greenhouse study was conducted to compare three wheat cultivars for fertilizer-N (applied as N-15-labelled ammonium sulphate) and soil-N uptake at different growth stages. Differences were observed for bread wheat and durum wheat for different plant parameters. Contribution of fertilizer-N to the total plant-N of the three wheat cultivars ranged between 4.1 and 23.7%. Applied fertilizer N had a significant bearing on the plant-uptake of soil-N resulting in substantial added nitrogen interaction (ANI); the interaction of the two N sources was variable for the three wheat cultivars. Although the three wheat cultivars differed in uptake of fertilizer N applied at different growth stages, durum was least efficient in making use of N applied at anthesis. Losses of N applied at different growth stages varied (22-56%), but were maximum from that applied at anthesis. Post-anthesis dry matter accumulation (PADMA) and post-anthesis N uptake (PANU) were more for bread wheat than durum wheat and seemed to contribute significantly to higher dry matter and N yield in the former.