Soil and additives
Soil is very essential in the growth of the plants and hence its quality is of utmost importance to the farmer. Soil test has to be undertaken if the results from the land are not satisfactory. The soil test gives you the contents of the minerals in it like calcium, sodium, phosphorous, zinc, copper and a lot others. Depending on the chemical composition the quality of the soil can be judged and what kind of plantation can be grown can be estimated as well. The minerals which are missing can be added as nutrients to the land and rotation of crops can help a lot. Again PH of the land is taken 
which is the first step in the soil analysis.
The soil sample must be taken a before a few months before putting anything in the soil and anything can be grown but land has to be prepared for it. The preparation of the land is different for growing flowers, vegetables, fruits and so on. If the soil is proper then disease free and better yield can be obtained. The samples can be taken anytime from the land and should be got tested. It would add up to the testing expenses but would assure you timely and good yield so returns on investment is proper