Vegetable Research & Information Center, UC Cooperative Extension

ONION
Leaf Analysis Guide for Diagnosing Crop Nutrient Status

  Nutrient Level
Sampling time and nutrient Deficient Intermediate Sufficient
Early season
(pre-bulbing)
     
Total N, % <3 3-4 >4
PO4-P, ppm <1000 1000-2000 >2000
Soluble K, % <3 3-4 >4
Midseason
(bulbing)


   
Total N, % <2.5 2.5-3 >3
PO4-P, ppm <1000 1000-2000 >2000
Soluble K, % <2.5 2.5-4 >4
Late season
(post-bulbing)

   
Total N, % <2 2-2.5 >2.5
PO4-P, ppm 1000 1000-2000 >2000
Soluble K, % <2 2-3 >3

Plant Part to sample is the tallest leaf blade.

Soil Analysis Guide for Diagnosing Available Nutrient Status

 

Available Soil Nutrient Levels, ppm

Soil Status Phosphorus Potassium Zinc
Very deficient 0-5 <40 <0.3
Deficient 5-9 40-80 0.3-0.5
Intermediate 10-15 80-120 0.5-0.8
Sufficient >15 >120 >0.8

Analytical methods:
Phosphorus - Olsen bicarbonate
Potassium - Ammonium acetate
Zinc

 

 

 

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