Question

Why should we prevent overcrowding of plants in a field

Answer 1

If there will be overcrowding of plants in a field then all the plants will not get sufficient amount of nutrients and water as all plants will try to take as much as they require from a limited amount.
Therefore, overcrowding of plants in a field should be prevented.

Answer 2

overcrowding leads to competition amongst the plants. we don't want that to happen. some plants might get the proper nutrition and sunlight required for growth, some might not. which is a hinderance in their growth. so, overcrowding of plants in a field is a bad option to go with