Hydroponic Fertiliser for Delphiniums

The following charts show our recipe for an hydroponic fertilizer mix which we found successful for growing our delphiniums as cut flowers.

The recipe is for fertilizers to be mixed into a 20,000 litre tank and watered out as is. No dilution is required. It should be easy for those of you who use concentrated mixes, which are injected into the watering system, to work out your requirements from this chart.

The hydroponic system we used was a "run to waste" system, fertigation being applied until the trays in which the delphinium plants were growing were saturated, and water began to seep out of the drain holes in the trays. Water time obviously varied considerably from day to day and season to season, according to the plant's needs. It should be noted that, in order to keep salts to a level which delphinium will tolerate (relatively low) it is necessary to flush the plants with water for about half an hour at least once a week.

We found scoria, crushed to about 1/4inch diameter, or pumice of a similar size to be an ideal growing medium.

IMPORTANT NOTE: These tables are merely an indication of the fertilizer mixes we used. We accept no responsibility, or liability whatsoever for their efficacy or otherwise. You use this information at your own risk.

TYPICAL SUMMER FEED
Fertilizer per 20,000 Litres Total N P K S Mg Ca
Pot. Nitrate 13-0-46 3kg 0.39   1.38      
Pot. Sulphate 1kg     0.50 0.23    
Cal.Nit. 15.5-(19%C) 15kg 2.33         2.85
Ammonium Nit. 34.5% 4kg 1.38          
Magnesium Sulphate 1kg         0.50  
D.A.P.  21-53-0-2   0.00 0.00   0.00    
Mag. Nitrate 11.0.0.15 3kg   1.53 0.99      
Iron Chelate 450gm            
Borax 20gm            
Zinc Sulphate 10gm            
Manganese Sulphate 10gm            
Sodium Molibdate 0.7gm            
Copper Sulphate 0.5gm            
               
Total Total 4.32 1.53 2.87 0.23 0.80 2.85
  Ratio 2.82 1 1.89 0.15 0.52 1.86
  PPM 216 77 144 12 40 143
               
TYPICAL WINTER FEED
Fertilizer per 20,000 litres Total N P K S Mg Ca
Pot. Nitrate 13-0-46 3kg 0.39   1.38      
Pot. Sulphate 1.5kg     0.75 0.35    
Cal.Nit. 15.5-(19%C) 14kg 2.17         2.85
Ammonium Nit. 34.5% 1kg 0.35          
Magnesium Sulphate 1kg         0.50  
D.A.P.  21-53-0-2   0.00 0.00   0.00    
Mag. Nitrate 11.0.0.15 0 0.00       0.00  
MKP 0-51-33 2kg   1.02 0.66      
Iron Chelate  450gm            
Borax  20gm            
Zinc Sulphate  10gm            
Manganese Sulphate  10gm            
Sodium Molibdate  0.7gm            
Copper Sulphate  0.5gm            
               
Total  Total 2.91 1.02 2.79 0.35 0.50 2.85
   Ratio 2.85 1 2.74 0.34 0.49  
   PPM  145 51 140 17 25  
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Dowdeswell's Delphiniums - Wanganui, New Zealand