Most nutrients needed by plants are supplied solely by soil. Insufficient supply of any of these nutrients may limit plant growth. In natural conditions, nutrients are recycled from plants to soil to meet plant needs. However, agricultural crops may require more nutrients than natural vegetation.
Significant amounts of nutrients are also removed in harvested crops. Optimal crop growth and profitability may require fertilization with inorganic fertilizers, animal manures, green manures, or legume management. This publication concentrates on commonly used inorganic fertilizers important in improving plant growth.
When managing fertilizers, stick to the four Rs: the right amount of the right fertilizer at the right place at the right time.
The four Rs begin with soil testing. Soil tests assess the current nutrient status of the soil and indicate whether these levels are sufficient for crop production. If adequate amounts of nutrients are present in the soil, the right amount to apply is none.
If the laboratory results show response to added fertilizers is likely, there will be a rate recommendation. This is the right amount. The right time and right place depend on site-specific agronomic factors accounting for crop biology and growth stage, and current environmental conditions. Follow the best management practice appropriate for your situation.
Source : msstate.edu