The Eleventh Regional Wheat Workshop For Eastern ... - Cimmyt

Delayed N application and late tiller production in wheat - Adjetey and Campbell
Tiller Production
Late tiller production occurred when N was applied at any time during the first 30 DAA. Also,
in the split N treatments, the time of N application had little influence on the number of late
tillers produced. However, there were more productive late tillers when N was applied at
anthesis. (Table 2).
Grain Yield
When N was applied at sowing, total grain yield per plant increased from 3320 mg in N250 to
5934 mg in N700 (Table 3). Such responses to N are commonly reported (Spiertz and Ellen,
1978; Strong, 1982). With split treatments, application of N from anthesis until 15 DAA
produced the highest grain yield per plant due to the relatively large contribution of grain by late
tillers (Table 3), which provided up to 36% of the total yield per plant as in AO. However, the
percentage contribution by the late tillers declined in A30. Such grain yield production by late
tillers is not commonly reported. Instead, late application of N has been associated with
increased grain N content - which was also observed in this study. The contribution by main
stems or early productive tillers generally did not differ between the split treatments (P>0.05).
Production of late tillers has reportedly occurred when wheat plants were recovering from water
deficits (Talukder et al. j 1987). In this experiment and that of Talukder et al. (1987), it is less
likely that increase in water or N supply would cause differentiation of cells in the stem into tiller
initials. Instead, it is possible that the tiller initials were present in a latent state and were
stimulated to grow in response to the extra assimilates from photosynthesis.
CONCLUSION
We conclude that plants can absorb N that is applied late in the growing season. This N can
increase tissue N concentration when applied within 30 days after anthesis. Nitrogen application
after anthesis is also capable ofstimulating the production of late tillers, perhaps when the plant
reaches a critical N concentration after anthesis; these tillers can contribute up to a 36% increase
in grain yield in pots. Such a response to an anthesis or post-anthesis N application does not
appear to be of common occurrence in wheat, which is characterized as a determinate crop. If
the greenhouse results were duplicated in the field, the long time lag, up to 40 days, between
maturity of early and late season tillers would pose practical problems to mechanical harvesting.
REFERENCES
Benzian, B. and Lane, P. 1981. Interrelationship between nitrogen concentration in grain, grain yield and added
fertilizer nitrogen in wheat experiments in south-eastern England. J. Sci. Food Agric. 32: 35-43.
Ellen, J. and Spiertz, J.H.J. 1980. Effect of rate and timing of nitrogen dressing on grain yield formation of
winter wheat (Triticum aestivum L.). Fert. Res. I: 177-190.
Mossedaq, F. and Smith, D.H. 1994. Timing nitrogen application to enhance spring wheat yields in a
Mediterranean Climate. Agron. J. 86: 221-226.
Randall, P.l, Freeney, lR., Moss, H.J., Wrigley, C.W. and Galbally, L.E. 1990. Effects of addition of nitrogen
and sulphur to irrigated wheat at heading on grain yield, composition and milling and baking quality.
Aust. J. Agric. Res. 30: 95-101.
Smith, C.J., Whitfield, D.M., Gyles, A.G. and Wright, G.c. 1989. Nitrogen fertilizer balance of irrigated wheat
grown on a red-brown earth in south-eastern Australia. Field Crops Res. 21: 269-275.
Spietz, J.H.J and Ellen, J. 1978. Effects of nitrogen and crop development and grain growth of winter wheat in
relation to assimilation and utilization of assimilates and nutrients. Neth. J. Agric Sci. 25: 210-231.
Strong, W.M. 1982. Effect of late application of nitrogen on yield and protein content of wheat. Aust. J. Expt.
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