New Zealand Journal of Crop and Horticultural Science
abstracts
Phenological development and frost risk of ‘Challenger’ sweet corn
(Zea mays) in response to phosphorus
A. L. Fletcher
Agronomy Physiology Laboratory
University of Florida
P.O. Box 110965
Gainesville, FL 326110965
United States
email: alfletch@ufl.edu
D. J. Moot
Agriculture Group
Agricultural and Life Sciences Division
P.O. Box 84, Lincoln University
Canterbury, New Zealand
Abstract Sweet corn (Zea mays) yield responses to phosphorus
(P) are well documented but impacts on development are less defined. For economic,
practical, and environmental reasons sweet corn crops are sometimes grown with
soil P levels below optimal for maximum yields. Any consequent maturity delay
may also affect the risk of the crop failing to mature in the frost-free season.
This research examined the response of sweet corn development to P in two consecutive
field experiments on a low P site (6 µg P ml–1) at Lincoln, New
Zealand. Overall, crops receiving 200 or 240 kg P ha–1 reached canning
maturity 6–7 days earlier than crops receiving no P fertiliser. However,
much of this delay in maturity was overcome by the addition of the smallest amount
of fertiliser (50 kg P ha–1).The differences in maturity resulted from
a change in the duration from emergence to silking. Crops with no added P required
725 and 645 degree-days (°C days) above a base temperature of 8°C to
reach silking in the crops. Crops that received a total of 50 kg P ha–1
required 665 and 590°C days to reach silking. Further additions of P gave
comparatively small increases in development rate towards silking. The difference
was probably because of a limitation of crop growth rate that caused an apparent
delay in development rather than any physiological change in development rate.
In a simulation analysis using these values for development phases and historical
weather data for six locations in New Zealand, the risk of the crops failing
to reach maturity before the first autumn frost was quantified. Sowing date and
location were the dominant factors determining risk, but a limited P supply increased
the risk of crop failure at all locations. The greatest differences in risk were
between the two lowest simulated soil P supplies (6 and 10 µg ml–1);
further increases in soil P supply had less impact on reducing risk. The greatest
differences in risk between the low (6 µg ml–1) and high (30 µg
ml–1) P soils were for late sown crops at southern locations.
Keywords canning maturity; silking; thermal time; Zea mays
New Zealand Journal of Crop and Horticultural Science, 2006, Vol. 34:
393–402
0014–0671/06/3404–0393 © The Royal
Society of New Zealand 2006
H06031; Online publication date 20 November 2006. Received 28 March
2006; accepted 21 September 2006
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