This model simulates the percentage occurrence of milky white grains on the total dry mass of rice kernels as function of average air temperature occurring in the whole ripening period.

Furthermore the model via two specific parameters takes into account that i) the susceptibility to damage decreases with the progress of the ripening and ii) low seeding density increase the incidence of chalkiness.

The general equation (Naghata et al. 2006) is:

Where:

MW (%) is the percentage incidence of milky white grains on the dry mass of kernels;

k (0.0513 for Loto, 0.0085 for Gladio; unitless) is a coefficient of the equation;

δ (°C) represents the effective temperature daily accumulated over a fixed damage threshold temperature;

ai (11.9867, for Loto, 11.0376 for Gladio; unitless) is a parameter describing the effect of sowing density on chalky incidence: the higher the planting density the lower chalkiness incidence.

In particular the effective temperature (δ) is calculated as follow:

Where:

fi (unitless) is a parameter decreasing the grain susceptibility to chalkiness during the ripening progress. Its values derives from field campaign experiments;

tb (°C) is the average temperature threshold beyond which the damage to grain begins to occurs;

ti (°C) is daily average air temperature occurring during the ripening period of rice.

In the Northern-Italian conditions fi can be valorized using the following default values:

Loto variey:

• fi =1: days from heading ≤ 2;
• fi = 0.5: 2 > days from heading ≤ 8;
• fi = 0.397: 8 > days from heading ≤ 25;
• fi = 0: days from heading >25.

Gladio variety:

• fi = 0.5926: days from heading ≤ 11;

• fi = 0.2977: 11 > days from heading ≤ 29;
• fi = 0: days from heading > 29.

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