Nitrogen and Dry Matter in Five Spring Wheat Varieties at Successive Stages of Development
1966
McNeal, F. H. | Berg, M. A. | Watson, C. A.
Dry weight and nitrogen content of leaves, stems, kernels, and roots were determined for five spring wheat varieties on seven dates. Maximum leaf development occurred by July 19 (flowering), and maximum stem development ocurred by July 29 (filling). By August 19 (maturity) the top weights were similar for all varieties except ‘Mindum’, which was significantly higher. The average ratio of root (to 5-ft depth) to top growth on August 19 was 1:14.9. Uptake Uptake of nitrogen continued until harvest, although the rate was much slower after July 19. Nitrogen content in the roots was low at all sampling dates, indicating rapid translocation to aboveground parts. If all root nitrogen had been translocated to the kernels, the effect on kernel nitrogen would have been insignificant. The average ratio of root to top nitrogen on August 19 was 1:23.4. The r value of 0.95 between pounds of kernel nitrogen and pounds of top dry weight indicates that 90.2% of the variation in kernel nitrogen in this experiment is due to differences in plant dry weir.hr. This leaves only 9.8% of the variation in kernel nitrogen which the plant breeder might be able to manipulate. We suggest that if wheat varieties which will translocate as much as 70% or more of leaf and stem nitrogen to the kernels can be found, they might be useful in breeding programs.
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