NB2 function of the "aez.getOptimumCycleStartDateRainfed()"

[WeirdCxychen]

Hi,

The conception of "aez.getOptimumCycleStartDateRainfed()"&"aez.getOptimumCycleStartDateIrrigated()" confused me a lot, the hashtag said in this part we could get the start date of the growing cycle, but I think that the two variables aim to get the start date of rainfed and irrigation, not the start date of the growing cycle. I wonder if the output "maiz_ccd_rain"&"maiz_ccd_irr" in NB2 are the start date of the growing period or the start date of rainfed & irrigation.

Regards,

Xinyue Chang

[NokuzaSezo97]

Hi @WeirdCxychen,

In short, optimum cycle start date means the day of year indicating that if you start plantation on that day, you will obtain the corresponding maximum attainable yield. It is not the starting date of the growing period.

Note that PyAEZ M2 simulates all possible cycles, each with different starting dates, from the given window of user-defined start and end dates, and for output, it only selects the DOY which maximum yield is obtained amongst the cycles as optimum cycle starting data and the corresponding yield is your maximum attainable yield. Both rainfed and irrigated conditions are simulated separately.

Regards,

Swun Wunna Htet

[WeirdCxychen]

Hi,

Could I use this way to interpret your answer?
"maiz_ccd_rain"&"maiz_ccd_irr" are not the exact start date of the growing period, but they could still indicate the optimum start date (sowing date) of the growing period in irrigation and rainfed condition.

And another question:
The two outputs in NB2 are based on the climate data, which I input in "Reading Data" part of NB2. Therefore, could I say that if the climate is really dry around the sowing date, the start date of rainfed would be delayed until the rain is enough to support rainfed? In other words, if there is a serious drought near the planting date, the result tends to show a result which is close to the rainy date after the drought. Is that right?

Regards,

Xinyue Chang

[NokuzaSezo97]

Hello @WeirdCxychen,

For the first question, it is correct.

For question 2, I agree with your interpretation. A small input to consider is the rainfed yield, fc2 factor, fc1 factor and optimum starting date interpreted together. Note that moisture deficit condition is checked for every available cycles for rainfed yield simulation in PyAEZ.

A small example:
If the yield at a location is not much (<500 kg/ha), and fc2 is quite low (<0.3) but fc1 is ok ( value 0.9), this indicates at that sowing date, you will encounter moisture deficit causing maximum yield to be drastically reduced.

Regards,

Swun Wunna Htet

[WeirdCxychen]

Hi, @NokuzaSezo97,

For question 2, in a rain-fed zone, could I say it's normal for the "maiz_ccd_rain" to be later than the actual planting date by about 40 days (the planting date in my study area is about the 120th day of the year if there is a drought during that day and lasts for 40 days without precipitation)?

According to the small example, as for my study area, fc1 and fc2 result in the area which corresponds to my delayed part in "maiz_ccd_rain" result shows that fc1 is quite low (0.68 compared to the other part is about 0.9), fc2 is ok (value 1). Could I say the delayed part encountered a moisture deficit to delay the start date of rainfed?

Here are the illustrations of my results:

[NokuzaSezo97]

@WeirdCxychen,

Fc2 map in green box says there 10% yield reduction which I think not so severe, and fc1 is quite good. What is your obtained yield from that green box?

If you're collecting the evidence of drought before that crop starting date, my only suggestion is checking temperature, solar radiation, and precipitation before the starting date, and see whether either one of the condition has a big setback.

Regards,

Swun Wunna Htet

[WeirdCxychen]

@NokuzaSezo97

Sorry here is a mistake I didn't check out: the green box is about 0.6-0.7. My yeild is about 5200-5300 kg/ha.

Thank you so much for your suggestion!!

[maobw12]

I would like to ask, the ccd in my NB2 comes out to be 365, is this the 365th day of the year before winter wheat starts growing and what is the relationship between ccd and DOY? I am a little confused about the relationship and concepts between LGP of NB1, cycle, maxcycle, mincycle, ccd and DOY of NB2 parameters.

[WeirdCxychen]

@maobw12
LGP is the growing period under water and heat limitation (水热生长期).
ccd is the start date of growing period.
maxcycle & minicycle is the max & min growing length of the crop type you chose (作物可生长的最大最小生长期).

[maobw12]

@maobw12 LGP is the growing period under water and heat limitation (水热生长期). ccd is the start date of growing period. maxcycle & minicycle is the max & min growing length of the crop type you chose (作物可生长的最大最小生长期).

Thank you very much, I have another question, cycle is not DOY, ccd is DOY right? Some of the ccd's I got from NB2 are 365, so what this means is that the growth doesn't start until the last day of the year? My crop is winter wheat. I am confused about this.

[WeirdCxychen]

@maobw12
Infact, the DOY is not a variable in PyAEZ, it's Day Of Year, I'm not sure is the DOY means ccd in this model; you could look up it in User Guide.
As for the ccd over 365, maybe for the principle it means the hole year cliamte is suitable for crop growth, but the exact planting date is not just depends on planting situation.

[maobw12]

Thanks for your answer！

[maobw12]

Hello I have a question I simulated the same values of yield under rainfed and irrigated, I changed the input rainfall data, so in some places the yield data under rainfed and irrigated are different, but there are still a lot of raster data where the yield under rainfed and irrigated are the same, I don't know what the problem is?


Also, in def simulateCropCycle(self, start_doy=1, end_doy=365, step_doy=1, leap_year=False): can start_doy and end_doy be changed to localized crop planting and harvesting doys by themselves?