Nitrogen accumulation and translocation for winter wheat under different irrigation regimes

The translocation of pre-anthesis nitrogen to the grain is an important source for winter wheat. The relation between the nitrogen translocation and irrigation regime was studied in the field under a rain-proof trough shelter. Nitrogen (N) translocation amount, N translocation efficiency decreased with a decline in irrigation amount or by excessive irrigation. Compared with different organs, the leaf and stem had higher N translocation amounts, and contributions to grain for both cultivars - Jinan 17 and Lumai 21, indicating that stem also is a major N source for grain development. The contribution of pre-anthesis total above ground N to grain N ranged from 57 to 76 %, indicating the importance of pre-anthesis storage of N for achieving high grain N concentrations. Grain nitrogen and yield (kg ha(-1)) were positively and significantly correlated with the N translocation amounts and contributions, respectively, suggesting that the sink strength may be involved in the translocation of N from a vegetative organ to the grain. N harvest index (NHI) was significantly correlated with N translocation efficiency, suggesting that the latter is a prerequisite for increasing grain N and improving grain quality. The experiment showed that N translocation status is enhanced by better irrigation practices, but limited by severely deficient or excessive irrigation.