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Effect of nitrogen on the development of yield components in wheat

E.E. Whingwiri and W.R. Stern

University of Western Australia, Department of Agronomy, Nedlands, W.A. 6009.

Nitrogen has been shown to increase tillers/plant (Halse et al 1969), spikelets/ear (Single 1964) and grain number/spikelet (Langer and Liew 1973). We are not aware of comparisons of yield components at an early development stage and at maturity, in relation to nitrogen.

Nitrogen at 3(N1), 15(N2) and 30 (N ) kg N ha-l wk-l was applied in 3 replicates in a randomize block, on a sandy loam near Perth. The crop was sown on 13 June and established at 130 plants m-1. At maximum floret formation (70 days from sowing) and at maturity (150 days) yield components were observed: shoots/ plant were counted on 5 plants/plot, shoot apices were examined on 3 plants/ treatment for spikelet numbers and florets/spikelet and at maturity on 10 plants/ plot.

Yield components in embryo (emb) at maturity (mat) and percent decline (% decl).

Effect of nitrogen. In the embryo ear total number of grain sites increased with nitrogen level, due to increases in shoots/plant and spikelets/ear. At maturity the only difference was between Nl and N2 and N3; although nitrogen did not affect florets/spikelet, there were more grains/spikelet in N2 than in Nl and N3.

Decline in yield components between the embryo ear stage and maturity. Failure of florets to develop, rather than nitrogen treatment was the major reason for the decline of 66 to 70%. In N1 shoots/plant declined by 55%. Number of spikelets/ear did not change. The almost consistent decline in total grain sites suggests that compensation among yield components was taking place. Decline in components was least in N2, implying that this was optimal for yield realization.

Conclusion: Shoots/plant was the most responsive component to nitrogen application. Survival of florets into grains was not strongly dependent on nitrogen. The data show interactions between yield components. It is thought the development of anatomical structures in spikelets may be involved.

Halse, N.J., et al (1969). Aust. J. Agric. Res. 30: 987.

Langer, R.H.M. and LIEW, F.K.Y. (1973). Aust. J. Agric. Res. 34: 647.

Single, W.V. (1964). Aust. J. exp. Agric. Ani. Husb. 4: 165.

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