Estimating a metric of a mixture
However, some of the parameters cannot be added. In our example, such a parameter can be the plantation age, plantation location, cultivar of the fruit, etc


Can you explain why these can't be added? 

There exist many ways to encode categorical information, such as plantation location, such that a ML model can interpret it. In my use-cases, in supply-chain, I deal with thousands of unique location observations, where in I use a geo-encoding API to return latitude/longitude pairs to feed into my models.

In your case, where in you only have 6-factorial observations (that may be wrong), what I would do is to generally categorize your categorical features. So for location, instead of "Florida," I would say "South-East," and then lump all south-eastern locations together. Since you'll have low cardinality in feature size, binary or one-hot encoding may be useful for you.