Add algorithms to define the percentage of dry matter in the storage roots

[lpmorenoc]

This could be related to the issue https://github.com/lpmorenoc/dssat-csm-os/issues/24 and would require a state variable for the fresh weight with reduced dry matter when there is remobilization of assimilates

[lpmorenoc]

(Comments from James): • Cultivar is the single most important determinant of dry matter, furthermore there is little GxE interaction. This lack of GxE suggests that most varieties respond similarly to variation in growing conditions. This makes life easy for us, although there may actually be more GxE than we think. (Anecdotal evidence suggests that in some varieties the decrease in starch is more marked than in other at the beginning of the rainy season. However, our proposal will likely support this as those varieties that produce a greater flush of new leaves will also have a greater drop in reserves). • As mean temperature increases starch content decreases. • After a drought period there is a flush of new leaf growth when it rains. This flush of new growth is supported by translocation of carbohydrate reserves from the roots and the starch content of the roots decreases.

• [x] With the onset of rains and the flush of new growth the total water content of the tubers does not change when the starch reserves are mobilized. That is the size of the tubers or the receptacle does not change.
• [x] When in spillover mode tubers are filling with starch the starch content is the cultivar value modified by a temperature factor.
• [x] When in reverse spillover the total water content of the tubers does not change, and the starch content reflects the starch translocated to the tops. (Note: based on research in rice translocation of starch from stem reserves to grains we suggest a translocation efficiency of 0.7)
• [x] The temperature factor is determined by the air temperature, if that is available from DSSAT at 10 cm depth. If not, it is determined by the air temperature. A moving average of the temperature for the past ¿20? days will be used to minimize brusque changes. No sure about this change, the model already increase aboveground growth when the temperature increases which should contribute to the reduction of the dry matter.
• [x] When recovering from a trigger event and tubers start filling with starch again, the receptacle size remains constant (ie same total amount of water) and the excess from top needs goes to filling the receptacle. Once the concentration reaches the temperature variety value the concentration of starch is determined by the temperature variety value and the amount of water increases commensurate with the temperature variety starch content.

[lpmorenoc]

New variable with fresh weight of the roots:

[lpmorenoc]

Now we can generate a % of dry matter variable 63485cb:

For this specific experiment/variety there is a reduction of dry matter content during the release of water stress:

[lpmorenoc]

As suggested by @GerritHoogenboom, changes in the dry matter content were done as a rate variable instead of a state variable (whole dry weight):

[lpmorenoc]

Testing with an experiment in Nigeria (allowing retranslocation): Storage dry weight: Percentage of dry matter

[lpmorenoc]

Testing with one of the ACAI trials experiments (Ido, 2017 planting)

[lpmorenoc]

Testing with the ACAI trial using state instead of rate variables. I think the results are better with rate instead of state variables:

[lpmorenoc]

Experiment with different temperatures (Keating, Australia) before adding any effect due to temperature (currently no water or nutrients restrictions):

After adding the effect of temperature with low temperatures increasing the dry matter content up to 5% if the air temperature is 13 C. The 5% could be an ecotype coefficient and would use the cardinal temperatures of 13 as "optimum" or maximum dry matter content and 30 as "minimum" (no reduction of dry matter if the mean temperature is above 30):

Mean temperature:

[lpmorenoc]

Modifying cardinal temperatures (maximum dry matter: 18 C, minimum dry matter 26 C). f74c829

Adding effect of planting age:

[lpmorenoc]

With effect of cardinal temperatures Nigeria trial:

Adding effect of planting age: