Abstract
Different models used for calculating nutrient requirement were compared taking precision farming system as standard. Half of the field area received incorrect amount of fertilizer using conventional method whereas 20% improvement was observed in area correctly fertilized by using average yield and variable soil nutrient index method. Little more improvement in variable soil nutrient index and mean yield for each soil index method was noted than average yield and variable soil nutrient index method. However, even using the gridded (20 m x 20 m grid) precision farming system as standard compared with others, this system is not perfect. For P and K, the result of ignoring within-field variations is that high-yielding parts of the field are inadequately fertilized, while soil nutrients tend to accumulate in low-yielding areas. Key words: Precision farming, Spatial variation, Soil nutrients, Crop yield
