Plants require nutrients for their growth.
Continuous plantation of crops results in depletion of certain nutrients
like nitrogen, phosphorus, potassium. This results in the decrease of yield.
It is found in healthy soils, and give plants the energy to grow, and produce fruit or vegetables. Nitrogen is part of the chlorophyll molecule, which gives plants their green color and is involved in creating food for the plant through photosynthesis.
It is a constituent of plant cells, which is essential for cell division and development of the growing tip of the plant.
It is an essential element for plant growth and it is important to food crops. Potassium, often called potash, helps the plants to use water and resist drought conditions. It also enhances fruits and vegetables. If soluble potassium is deficient in soil it can result in stunt growth of plants and can also cause other symptomatic issues.
Thus deficiency of any of the nutrient can affect the crop adversely and hence to let the soil replenish its nutrition naturally there should be a gap between crops in order to get a good yield.