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Haifa Blog

17Oct2011
Practical fertilizers mixing and injection rates calculations

Nutrition data - Haifa Chem Tomatoes Fertilization Guide – Open Field. Fruit fill section – nutrients requirements:

Practical fertilizers mixing and injection rates calculations

• Using Polyfeed fertilizers formulations 

The system on the farm 
1000 litre shuttle, temp 25 C 
Irrigating every day for 3 hours. 15,000 L/h/ha 

Calculate the followings in units per hectare: 
How many bags can we mix in one time into the stock solution tank? 

Suggest injection scheme for the PF and CaN 

What is the max area we can get from one mix of 1000 L stock solution? And what is the required injection rate. 

What is the final rate of fert in the irrigation water and expected EC added. 

Calculations and results 
Stock solution = Fertilizers solubility in water is temp dependence. With Pf we can dissolve 250 -300 Kg into 1000 L of water (10-12, 25 kg bags). See Haifa Brochures. 

The Polyfeed formula has Phosphate in it – so we can’t mix the CaN into the same tank at the same time. Solution – split the PF injection into 3 doses of 25 kg /ha each = 75 kg/ha/week. Inject the CaN in one or two doses of 35 or 17.5 kg/ha respectively. This will allow using one mixing tank and one injection unit for both fertilizers. 

• The stock tank must be clean and empty when changing the fertilizers type. 
1000 L stock solution with 250 -300 kg of PF will cover 10 – 12 ha for one application of 25 kg per ha. 
1000 L stock solution with 2200 kg of CaN will cover 62.8 ha for one application of 35 kg/ha. 
Effective Irrigation time for Nutrigation is 2 hours x 15,000 l/h/hax 12 ha = 360,000 litres – the injection mixing factor is 1:360 or 2.8 L of stock solution per 1000 litres of irrigation water. 
The required injection rate in Litres of stock solution into the flow of irrigation water: 

Total applied water in two hours – 360 m3, the flow is 180 m3/h. For each 1 m3 (1000 L) of irrigation water flow we will need to inject 2.8 L of stock solution (as calculated above). Total injection rate is - 180* 2.8 = 496 L/h of stock solution. 
Added EC – mixing rate 1:360. 
Stock solution has 300 kg of PF in 1000 L (if applying on 12 ha) 
Stock Con = 300/1000 = 0.30 Kg/L = 300 g/L. 
Dilution rate from the Stock solution tank into the irrigation water is 1:360. 
Final concentration in irrigation water is 300 g (fert) into 360 L of irrigation flow = 0.83 g/l. 
Expected EC = about 1.1-1.2dS/m (see tables in the PF booklet or www.haifa-group.com) 

When making a choice of a fertigation system or calculating the capacity we already have in our system to Nutrigate we need to take the following steps: 
1) Know the required nutrients level per application. 
2) Check and decide the area we would like to apply the nutrients in one time. 
3) Choose our fertilizers mix and knowing the expected lowest water temp calculate the fertilizers mixing rate into stock solution. 
4) Calculate or obtain the irrigation system flow rate and the amount of water applied during the Nutrigation process. 
5) Calculate the required injection rate. 
6) Decide on how many application we can or want to apply the above nutrients quantities. 
They are probably few more ways to calculate the above – so this is one example. 

Happy Nutrigation – Shaul Gilan

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