Author:
Bange M. P.,Hammer G. L.,Rickert K. G.
Abstract
A simple framework was used to analyse the determinants of potential yield of
sunflower (Helianthus annuus L.) in a subtropical
environment. The aim was to investigate the stability of the determinants crop
duration, canopy light interception, radiation use efficiency (RUE), and
harvest index (HI) at 2 sowing times and with 3 genotypes differing in crop
maturity and stature. Crop growth, phenology, light interception, yield,
prevailing temperature, and radiation were recorded and measured throughout
the crop cycle. Significant differences in grain yield were found between the
2 sowings, but not among genotypes within each sowing. Mean yields (0%
moisture) were 6·02 and 2·17 t/ha for the first sowing, on
13 September (S1), and the second sowing, on 5 March (S2), respectively.
Exceptionally high yields in S1 were due to high biomass assimilation
associated with the high radiation environment, high light interception owing
to a greater leaf area index, and high RUE (1·47–1·62
g/MJ) across genotypes. It is proposed that the high RUE was caused by
high levels of available nitrogen maintained during crop growth by frequent
applications of fertiliser and sewage effluent as irrigation. In addition to
differences in the radiation environment, the assimilate partitioned to grain
was reduced in S2 associated with a reduction in the duration of
grain-filling. Harvest index was 0·40 in S1 and 0·25 in S2. It
is hypothesised that low minimum temperatures experienced in S2 reduced
assimilate production and partitioning, causing premature maturation.
Subject
General Agricultural and Biological Sciences
Cited by
24 articles.
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