Drawbacks of Using Composts

Agricultural use of composts remains low for several reasons:

• The product is weighty and bulky, making it expensive to transport. 
   
• The nutrient value of compost is low compared with that of chemical fertilizers, and the rate of nutrient release is slow so that it cannot usually meet the nutrient requirement of crops in a short time, thus resulting in some nutrient deficiency 
   
• The nutrient composition of compost is highly variable compared to chemical fertilizers. 
   
• Agricultural users might have concerns regarding potential levels of heavy metals and other possible contaminants in compost, particularly mixed municipal solid wastes. The potential for contamination becomes an important issue when compost is used on food crops. 
   
• Long-term and/or heavy application of composts to agricultural soils has been found to result in salt, nutrient, or heavy metal accumulation and may adversely affect plant growth, soil organisms, water quality, and animal and human health 
   
  source : http://agritech.tnau.ac.in/