Nitrogen deficiency  made worse by
                                    
                                    
                                        
                                                    - Low or high pH soils
 
                                                    -  Sandy or light soils (leaching
 
                                                    - ) Low organic matter
 
                                                    -  Drought conditions
 
                                                    -  High rainfall (leaching) or heavy irrigation
 
                                                    -  Addition or high levels of non-decomposed organic matter/manure (eg straw)
 
                                                    -  Fast growing crops