Agronomic Properties of the Wapiti and Fernie Rock Phosphate

By Lawrence Klusa, P.Ag.

The chemical structure of both the Wapiti and Fernie rock phosphate deposits is similar. Both deposits have approximately 18% to 24% of the rock being phosphoric acid P2O5 (also know as phosphorus pentoxide or diphosphorus pentoxide or phosphorus anhydride). The other major components are 31% to 35% are calcium oxide CaO and 26% to 29% silicon dioxide Si02.

The attached analysis shows a complete list of chemical components of the rock phosphate.

The Wapiti and Fernie deposits are low in heavy metals considered to be of concern in the environment at high levels. A comparison of the chemical structure of the Wapiti rock structure to other North American rock phosphate deposits is attached.

The available phosphate of the Wapiti and Fernie rock phosphate deposits is high relative to most other rock phosphate deposits ranging from 6% to 10% as measure using a standard NAC2 (second sequential extraction procedure with neutral ammonium citrate test). The second sequential extraction procedure is used to eliminate the effects of free carbonates with suppress dissolution of the phosphate rock during the first extraction with NAC. This method has been used by International Fertilizer Development Center for over 25 years. The AOAC method number for this procedure is AOAC 2.3.14 or AOAC 993.31.

Phosphorus is essential nutrient for plant and animal life. As noted by the International Fertilizer Industry Association (IFA):

“All plants and animals require phosphorus (P), an essential macronutrient. The major source of phosphorus is phosphate rock (PR), a phosphate-bearing mineral which is a finite and non-renewable natural resource. Phosphate rock is the primary raw material for producing soluble P fertilizers. It can be applied directly and can solubilize in the soil, making the P available to crops depending on the type of rock, soil properties, climatic conditions, crops/cropping systems, and nutrient management practices. Direct application of phosphate rock (DAPR) is an alternative fertilization option that can contribute to sustainable intensification of agriculture*, particularly in developing countries with suitable PR resources and agro-ecological conditions. (* bold added here for emphasis)

It should be noted that chemically produced phosphate fertilizers such as Monoammonium Phosphate (MAP), Diammonium Phosphate (DAP), Single superphosphate (SSP) Triple Superphosphate (TSP) and all other chemically produced phosphate fertilzers do not qualify as organic crop input and therefore cannot be used for organic crop production. Rock phosphate is the only significant phosphate source allowed for certified organic crop production.

The IFA further note that:

“The potential for applying phosphate rock directly on soils varies in each location. PR dissolution is favoured by soil properties such as increasing soil acidity, high cation exchange capacity (CEC), low levels of calcium and phosphate in the soil solution and high organic matter content. Generally, direct application of phosphate rock is recommended in soils with pH 5.5 or less, such as tropical and subtropical soils which area predominantly acidic and are often deficient in P. Soils of medium phosphate status are considered more suitable for direct application phosphate rock than severely phosphate-deficient soils.

Management practices that can be used to improve rock phosphate efficiency include:

  • Applying rock phosphate close to the roots or incorporating rock phosphate that has been surface spread
  • Severely phosphate deficient soils can bind a significant amount of phosphorus to soild particles. These soils require a much larger application than just the crop requirements to saturate the soil P binding capacity.
  • Direct application phosphate rock should be finely ground and should be incorporated in the soil to promote dissolution. Fine grinding leads to coverage of more surface area and higher solubility.
  • Rock phosphate dissolves more slowly in the soil than chemical fertilizers therefore should be applied in advance of seeding. Slower dissolution has the benefit of providing longer term phosphate availability, i.e., two or more years as identified in the research below.

In a crop trial undertaken by Fertoz in 2016 on a high pH soil with good phosphate availability, results showed that while yields were large, there was only a very small improvement in crop yield versus the control area. This low yield response is likely the result of the high soil pH and slow rock phosphate dissolution and possibily that the phosphate in the soil may not have been limiting (soil tests indicated good phosphate availability). Better results may be seen in subsequent years as the rock phosphate has longer time period to breakdown.

It should be noted that in recent years considerable research has gone into how to make the phosphate in rock phosphate more available for plant growth especially under high pH soil conditions. Much of this research shows very positive results and is reviewed below.

Stanisławska-Glubiak, E., J. Korzeniowska, J. Hoffmann, H. Górecka, W. Jówiak, and G. Wiśniewska. “Effect of Sulphur Added to Phosphate Rock on Solubility and Phytoavailability of Phosphorus.” Polish Journal of Chemical Technology 16, no. 1 (2014): 81–85. doi:10.2478/pjct-2014-0014.

This paper indicates that a granulized rock phosphate and sulfur product mixed at a ratio of 10 to 1 improved crop yield on slightly acid soils and on neutral pH soils.

Naseer, M., and D. Muhammad. “Direct and Residual Effect of Hazara Rock Phosphate (HRP) on Wheat and Succeeding Maize in Alkaline Calcareous Soils.” Pakistan Journal of Botany 46, no. 5 (2014): 1755–61.

This paper indicates that yield improved with the application of rock phosphate over the control and that subsequent crop yields were also better than the control indicating positive long term residual effect of rock phosphate application.

Muhammad Waheed, Muhammad Arshad Khan,Taimur Naseem, Dost Muhammad and Maria Mussarat. Improving effectiveness of rock Phosphate through mixing with Farmyard manure, Humic acid and Effective microbes to enhance yield and Phosphorus uptake by wheat. Pure and Applied Biology. Vol. 4, Issue 4, 2015, pp 480-490.

This paper indicates that rock phosphate effectiveness can be very effectively improved by mixing rock phosphate with farmyard manure, humic acid and/or effective microbes.

Osman, M.A. “Studies on the Possible Use of Rock Phosphate in Agriculture.” International Journal of ChemTech Research 8, no. 10 (2015): 53–68.

This paper indicates that rock phosphate mixed with an acid such sulfur or humic has a very positive effect on crop yield on high pH soils.

M.A. Bustamante, F.G. Ceglie, A. Aly, H.T. Mihreteab, C. Ciaccia, F. Tittarelli “Phosphorus availability from rock phosphate: Combined effect of green waste composting and sulfur addition.” Journal of Environmental Management 182 (2016): 557-563.

This paper indicates that considerable improvement in phosphate availability when green wastes are composted with rock phosphate and elemental sulfur.