Eliminates Biological Controls
The lack of diversity in a monoculture system eliminates all the functions that nature provides to plants and the soil. It means that there is no range of insect species in a location to ensure that a single population does not get too large and damage too many plants.
Monoculture is bad for soil:: this is an agricultural practice of growing a single crop in the same field at a time..this practice is only to cultivate the same crops in the same fields for several this may lead to the depletion of the minerals and also leads to the many pathogens and soil will be attacked by many diseases.and also by cultivating the same crop in the same fieldĀ  may decrease the rate of production too.and also another point is by this practice we use the same fertilizers etc to cultivate the same crop so by weeds/pests/insects get used to the crop and cause many diseases by that the crop will be damaged and it reduces the mineral wealth,and etc..factors in the field.........

so by these all we can say that monoculture is bad for soil reduces the soil health...

hope this helps.pls mrk as brainliest.........