Looking for Citric Solubility

Many traders and users of P fertilizers mistakenly only measure P or P2O5% as an indication of effectiveness. Potash and Phosphate Institute recommends the correct method to measure how effective your phosphate fertilizer. P solubility level (known as citric acid soluble or the effective part of P) will determine how many kg/ton of P will be available to the plants in the near future. Minjingu Organic Hyperphosphate+ is the answer.

Organophosphate passes Potash & Phosphate Institute’s Standards.

“ A large number of Phosphate Fertilizer is available on the market. How does the agronomist select a suitable source?” Here are some points to keep in mind :

Look for Citric Solubility

While we all use P2O5 content as an index of quality it doesn’t mean much in terms of the potential effect of the Phosphate Fertilizer on crops. For example, consider a Phosphate Fertilizer with quite low total P2O5 of 25% and citric acid soluble P of 15%. 1,000kg Phosphate Fertilizer yields 16kg plant available P. By contrast 1,000kg of a material with 30% total P2O5 but citric acid soluble P of 10% yields only 13kg P.


Amount (kg)
2% CA Soluble P (%)
Amount available P (kg)
Amount available P2O5(kg)
Rock / Natural Phosphate P2O5
300      10%
250      10%
250      15%
300      15%

Table Source: Potash and Phosphate Institute (copied from their web page)

Is it fine?
Second quality assessment criteria of Potash & Phosphate Institute:

“ The finer the material the greater the surface of area of the Phosphate Fertilizer exposed to the soil solution for dissolution. Most experts consider grinding so that 80% of the material passes through an 80 mesh (0.18 mm) sieve to be sufficient”.
With Minjingu Organic Phosphate,over 90% of the material will pass 0.15 mm sieve and not more than 10% will pass through 0.25 mm sieve.

Is it dry?
Third quality assessment criteria from of potash & Phosphate Institute:

“ Check moisture content of the Phosphate fertilizer. You get less ‘active’ ingredient (P/US$) if the material is damp/ wet and damp as it is much more difficult to spread in the field.”
Minjingu Organic phosphate is dry; moisture content of only around 5%

What does this mean to you?

In most cases to get the effectiveness of applying 100kg of Minjingu Organophosphate you will need at least 2 times the amount of other P fertilizers. Infact our recent trials in Southern Tanzania comparing the use of 200kg Triple Superphosphate (TSP) vs. about 80kg of Minjingu Organophosphate+ revealed that after 6 months of application, Minjingu Organophosphate yielded 20% more harvest.

First time users of Minjingu Organic phosphate are reminded to take into consideration the soil environment. Depending on the severity of soil conditions, it could take many months before soil environment is improved ( it also takes time to build up the P level in the soil).

Slow Release is Vital to increasing harvest.
Organic phosphate – Much more than just Phosphate Fertilizer

The slow release part of Organophosphate is a vital element that directly affects the quality and quantity of harvest.

Plants require constant supply of P throughout its growth period and if P is not available when needed, harvest quantity will be reduced. This function is not present in chemical phosphate fertilizers. Moreover, plants require a constant supply of P to allow better digestion of nitrogen fertilizer. If nitrogen fertilizer cannot be well absorbed, its remainder known as Nitrate Nitrogen is hazardous. Organic phosphate helps plants digest nitrogen effectively and reduces the unwanted excess of the “Undigested nitrogen.”