This model calculates the percentage of fissured rice kernels as function of a meteorological indicator composed by i) potential evapotranspiration, ii) average thermal and humidity excursion, iii) windy days, iv) consecutive and total dry days, v) total rainy days and vi) total amount of rainfall during the first ten days after heading.

The general equation is given below:

Where:

Cracked (%) is is the percentage occurrence of rice broken kernels;

MI (unitless) is an agro-meteorological indicator accounting for several meteorological variables which can induce the rice grain to adsorb and desorb moisture in the field;

AC (%) is the average percentage of fissured kernels that is usually expected at the end of the season for the simulated rice variety;

IF (unitless) is a parameter accounting for the effect of irrigation management adopted by rice growers on cracking occurrence;

ai (0.4599 for Loto, 0.2072 for Gladio; unitless), bi (3.161 for Loto, 0.653 for Gladio; unitless), ci (0.1116 for Loto, 0.2821 for Gladio; unitless), are coefficients of the equation, specific for Japonica and Indica varieties.

The agro-meteorological indicator (MI) is calculated using the following general equation:

Where:

ΔT10 (°C) is thermal excursion experienced by the rice crop during the first ten days after the heading date;

ET0avg10 (mm d-1) represents the average value of the reference evapotranspiration within the first ten days after heading date;

WD10 (d) is the number of days characterized by wind speed higher than a critical threshold (default value equal to 1.7 m s-1 ) during the first ten days after heading;

DD10 (d) is the number of dry days (complete absence of rain) within the first ten days after heading;

CDD10 (d) represent the number of consecutive dry days in the period considered;

DHH10 (d) are the days with high air humidity, i.e. the number of days characterized by daily humidity excursion lower than a critical threshold (default value equal to 50% ) during the first ten days after heading;

RD10  (d) represent the number of rainy days within the first ten days after heading

TR10 (mm) is the total amount of rain fallen during the first ten days after heading.

It is important to note that in the above equation the divisor is automatically corrected

i)  with the default value of 0.5 when it is equal to 0;

ii) with the default value of 10 when the the nominator and the divisor are respectively higher than 100 and lower than 10.

The Irrigation factor, varies depending on the irrigation management used to grow the rice crop. In Northern-Italian conditions, the default values are:

• continuous flooding (FLD): 1 (Loto) and 1.029 (Gladio);
• dry sowing and postponed flooding at three/fourth leaf stage (DRY): 1.030 (Loto) and 1 (Gladio);
• dry sowing and time-scheduled (IRR): 1.133 (loto) and 1.15 (Gladio).

Once the user edit the string parameter "IrrigationManagement" in the parameter file ("FLD", "DRY" and "IRR" choices are currently possible), the corresponding IF will be automatically calculated.

Created with the Personal Edition of HelpNDoc: iPhone web sites made easy