All,

Jon Lizaso responded well on the temperature the crop sees, but I wanted to add one more reaction.

I seriously doubt that sowing density reduces PHINT.  If anything, very high sowing density could be sufficiently severe stress that the plant may express leaves more slowly (in fact greater PHINT).  The 95% safe assumption is that sowing density does not affect PHINT.  Fertilization should also not affect PHINT, unless N stress is so very severe that leaves cannot expand and tip appearance is delayed (but very rare).

So, safer to consider that PHINT is not affected by plant density or fertilization.

In fact, here is a "heresy" statement from me.  I don't think anyone has proven that PHINT truely varies among maize hybrids.  So I disagree with Ritchie and Batchelor's introduction of PHINT as a hybrid trait.

Ken Boote

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From: DSSAT - Crop Models and Applications [[log in to unmask]] On Behalf Of Lizaso,Jon I [[log in to unmask]]
Sent: Thursday, June 03, 2010 5:08 AM
To: [log in to unmask]
Subject: Re: Calibration

Maximiano and others interested,
To answer properly your question you should consider that plants in your field sense soil temperature first and later canopy temperature, and based on those temperatures differentiate and expand leaves. What your model "senses" is air temperature input in your weather file. What population densities and N doses are we talking about?

In the field, very high population densities may result in early canopy closure, higher water uptake, and some other changes that may affect the actual soil and/or canopy temperatures plant senses in different population densities. On the other hand, these details are invisible to the model. The only information available to the model are daily values of Tmax, Tmin, and SRAD, and based on that it will calculate thermal time using simulated soil Temp (when leaf number is less than or equal to 10) or air temperature.

Best regards,
Jon

Jon I. Lizaso
Dpto. Producción Vegetal. Fitotecnia
ETS Ingenieros Agrónomos
Senda del Rey s/n
28040 Madrid, SPAIN
email: [log in to unmask]
Tel: 34 91 452 4900 ext 1671
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From: DSSAT - Crop Models and Applications [[log in to unmask]] On Behalf Of Fidel Peña Ramos [[log in to unmask]]
Sent: Wednesday, June 02, 2010 4:38 PM
To: [log in to unmask]
Subject: Calibration

I'm calibrating DSSAT with the cultivation of maize under nine treatments
three densities and three fertilizer levels
it is reasonable that with increasing density decreases PHINT?

Fidel Maximiano Peña Ramos
Ing. En Agrobiologia




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