Other questions about APEX crop parameters

[Carlos Alberto Arnillas]

Hello

I continued exploring the different crop parameters and I noticed a few things that I wanted to share. First, I combined crops from ArcAPEX (version downloaded in 2020) and APEXEditor (also downloaded in 2020), so you may find some values related to either of them. I also checked some of the values in the latest downloadable version, and the issues are still there.

1. I found some trees for which HMX > 10 (so tall trees) but for which RDMX = 2, so not very deep roots. These are the trees I found with this pattern: PINE, SGUM, FRSE, FRST, WETF, CTRT.

2. Fallow has RDMX = 10, the deepest one. Is that right?

3. Camelina, safflower, and asparagus has odd WAC2 values. The first two are 0.16 while the latter is 661.22. Other values are larger than 660 but lower than 661. 

4. Not sure if my interpretation is correct, but I believe that according the manual the value after the decimal point in WAC2 should be larger than the value in the WA column. However, I found some crops for which the opposite is true (e.g., peanuts 30/660.25, grain sorghum corn 37/36, stripper and picker cotton 25/20). Are those typos or should I understand that more CO2 will decrease the crop yield for those species? (below a full list of species with unexpected values)

5. JOHNSONGRASS has BN1 == 0.3, while the other crops has BN1 < 0.07. A typo?

6. Is the salinity module working?

7. In the manual, pages 116, 123, and 124, is TB the same as "TOP" and TG the same as "TBS"?

Thanks for all your help!

Carlos Alberto

                          IDC CPNM         CROPNAME CNUM WA   WAC2
 1: Warm season annual legume PNUT          PEANUTS    6 30 660.25
 2: Warm season annual legume CAME         CAMELINA  139 34 660.16
 3: Warm season annual legume SAFF        SAFFLOWER  140 34 660.16
 4:        Warm season annual GRSG    GRAIN SORGHUM    3 37 660.36
 5:        Warm season annual KNAF            KENAF  117 60 660.45
 6:        Cold season annual CRAM           CRAMBE  152 35 660.26
 7:        Cold season annual SEAK         SEA KALE  182 35 660.26
 8:                 Perennial ASPR        ASPARAGUS   51 90 660.22
 9:       Evergreen Tree crop COCO          COCONUT  150 24 660.16
10:       Deciduous Tree crop  OAK         OAK TREE  115 15 660.15
11:       Deciduous Tree crop FRSD FOREST-DECIDUOUS  127 15 660.15
12:       Deciduous Tree crop ALMD          ALMONDS  142 15 660.15
13:       Deciduous Tree crop PCAN           PECANS  171 15 660.15
14:       Deciduous Tree crop PIST        PISTACHIO  174 15 660.15
15:       Deciduous Tree crop WALN          WALNUTS  187 15 660.15
16:                    Cotton COTS  STRIPPER COTTON    4 25 660.20
17:                    Cotton COTP    PICKER COTTON    5 25 660.20

[Luca]

Here are some comments to your questions.

1) Feel free to increase the root depth. Keep in mind that the actual maximum root depth will be influenced also by the depth of the soil profile (with a soil profile of 2 meters and a RDMX of 5 meters, the maximum actual root depth will be 2 meters).

2) It is strange that fallow has such a high value of RDMX. The important thing is that it should have a very low WA to reduce the biomass production. Usually, I set it to 0.01.

3) For asparagus, I have WAC2 equal to 660.22. For camelina and safflower, something happened and you can correct the value into 660.16.

4) Your interpretation of WAC2 is correct. Those numbers (or should I say most of them?) comes from research or literature review, but they can be subject to errors. Feel free to update those values and let us, at the Blackland Research Center, know about it. Collaborations and exchanging information with users around the world is a great way to improve not only the model but also the parameters of plants and implements used in our simulations.

5) A BN1 value of 0.3 looks very high. I would change it into 0.03.

6) Yes, the salt module should be active (I was doing some testing some years ago...).

7) Yes, they are the same as TOP and TBS.

Thanks for pointing these issues out. I will correct the crop table as soon as possible.

Luca