Dear DSSATers

While using CERES-Wheat in a class with students with weather data from
Silsoe in England, I found that very unrealistic yields if 1-2 t/ha are
being predicted in drier years (rainfall ~450mm/year as opposed to ~600
mm/year). Wet year yields appear to be OK at around 8-10 t/ha. In reality,
in the dry years, yields of ~5 t/ha were recorded. I have only looked at it
cursorily so far, but there appears to be little to explain this huge
discrepancy - solar radiation is similar for the two years; temperatures
vary a little, but not excessively; rainfall differs as mentioned above,
otherwise nothing else. The difference is not just in the yield but also in
the total biomass produced, and seems to appear about mid-winter in December
(crop planted in September), ruling out summer drought affecting
grain-filling as an explanation. Nitrogen levels are also at an optimum of
around 200 kgN/ha.

I am still trying to track down the problem, but I wondered if anyone else
had experienced similar problems under similar circumstances, and if so,
whether they had corrected the problem?

Robin Matthews.

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Dr Robin Matthews
Institute of Water and Environment
Cranfield University, Silsoe, Bedfordshire MK45 4DT, UK.
Tel: +44 (0)1525 863008; Fax: +44 (0)1525 863384
mailto:[log in to unmask]
http://www.silsoe.cranfield.ac.uk/iwe/people/RobinMatthews.htm
http://ourworld.compuserve.com/homepages/rbmatthews/
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