Biogeo chemical cycle:-

Output of Nutrient:-

Output of nutrient from one community may become input of nutrient other community.  

It occurs as follow:-

(a) Soil Erosion:- Loss of calcium and magnesium ion through runoff water.

(b) Biological denitrification:-

Change of NO₃^- to N₂ gas

(c) Crop harvesting   and Transportation

(d) Over grating or deforestation:-

INTERNAL NUTRIENT CYCLING:-