Bulb development in onion (Allium cepa L.). IV. Influence on yield of radiation interception, its efficiency of conversion, the duration of growth and dry-matter partitioning
1986
Brewster, J.L. | Mondal, F.M. | Morris, G.E.L.
onion crops were correlated with the total solar radiation intercepted by the leaf canopy. The mean efficiency of conversion of intercepted radiation to dry-matter was 1.58 g MJ−1. However, efficiencies were significantly different between seasons and in two years out of three they were lower for spring-sown crops than for autumn-sown crops. The lower efficiencies coincided with periods of high mean temperature and irradiance. The percentage of the total irradiance intercepted by the canopy during bulbing (1%) was increased by higher plant densities, earlier sowing and in later-maturing cultivars. It was higher in spring-sown than in autumn-sown crops especially at low plant densities. The duration of bulb growth was negatively correlated with 1% and with the mean air temperature during bulb growth. Consequently autumn-sown crops had a longer duration of bulb growth than spring-sown crops and produced exceptionally high bulb yields at high plant densities. Non-irrigated crops had a lower 1% and a shorter duration of bulb growth than irrigated crops, and a lower conversion efficiency in a season of high mean temperature and irradiance.
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