# Pollination Crop model, equations

Hi, folks! I am researching the effect of regenerative farms in Brazil on pollination. Actually i am working with another programming language and the idea is a little different, but i was very inspired by inVEST, especially by the equation part and indices approach. My problem is the interpretation of equations you give in the explanation part.

for instance here: my math knowledge says to me (correct me if i am wrong, please) that exp-part at the top and exp-part at the bottom could mutually elliminate each other, hence we have just resource-abundance left and no deffusion effect. (I forgot to note before, if there is just one season) I was thinking to get it from deviding the upper part (eg., FAfa exp^(distance/R)) by the ammount of the cells ( i am working with Netlogo with the gruid) in the radius of pollination distance? but i am not sure if it is correct. The same question to the equation of pollination abundency. Or in the FP-equation
the bottom part of the friction could be reduced to: h * (1 - PAT). I wanted to know if it should be that way in the given equations, like it is not cleaned up and thatâ€™s it or there is an actual mistake.
One more question is regarding a half-saturation constant. I cannot find the data to that, could you maybe recommened me the possible sources or elaborate a little bit more?

Appreciate your work and thank you very much!

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My appologies! The first part of the question I understood (complex sumâ€¦ cannot be eliminated). The FP-equation (â€¦the bottom part of the friction could be reduced to: h * (1 - PAT) I still wonder.

Hi @Khali1998 ,

Thanks for posting and asking for clarity around the equations for Crop Pollination. I canâ€™t see how the `FP(x)` equation could be factored down to have a bottom term of `h * (1 - PAT(x, j( f(x) ) )`.

I know itâ€™s hard to do on the forum, but if you could show your steps of how that would factor down that would be helpful! Or an uploaded picture of the reduction on paper might be easier than trying to format it here.

• Doug

Hi-hi! Thank you very much for the answer! But I was lost in the brackets, my apologies for the fussâ€¦ everything is fine, the only thing which is left is half saturation constant, is it taken specificly for each farm or are there some generalized data? never seen this index before, neither my superviser. Does it relate to pollination dependancy?

Hi @Khali1998,

Sorry I forgot to touch on the half-saturation constant. Please see the Userâ€™s Guide Data Needs section. Thereâ€™s an optional Farm Vector where half saturation is defined as:

half_sat (ratio, required): The half saturation coefficient for the crop grown in this area. This is the wild pollinator abundance (i.e. the proportion of all pollinators that are wild) needed to reach half of the total potential pollinator-dependent yield.

Hopefully that helps explains what the half saturation is.

Cheers

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