Ida-Gro Pelletized Phosphate

Not all the phosphate deposits of the world are the same, and few are ideally suited to direct application on your soils. If Mother Nature were as kind to other phosphate deposits as she was to Idaho's mineral deposits, there would be no need to convert the ore into upgraded phosphate products. After all, the only reason for conversion of phosphate rock to single triple superphosphate and mono- or diammonium phosphate is to increase phosphorus availability (neutral ammonium citrate and/or water solubility) to crops. In the case of highly reactive Idaho phosphates, the hydrogen ion activity of the soil is sufficient to provide adequate acidulation and conversion of the phosphate rock to crop-available phosphorus.

Idaho phosphate rock has been evaluated for direct application using a variety of crops on many types of soils. Maize, wheat, barley, beans (soybeans, field), rice root crops (potatoes, cassava), canola and pasture grasses are a few of the crops grown with Idaho ores as the phosphorus source, which have given crop responses approaching superphosphate. Some of the state's phosphate rock is the most reactive apatite known and commercially available for direct soil application. The high reactivity of phosphate is due to the phosphate mineral and molasses.

The reactivity of solubility of different rock suitable for direct application is measured with different extractants in different countries. The most common extractants used for correlation with crop yield are neutral ammonium citrate, 2 percent citric acid, and 2 percent formic acid.

The use of highly reactive rock phosphate versus highly water-soluble sources of phosphorus has significant economical savings at the farm level. There are enormous savings in capital for plant construction and process equipment, plus raw material savings from not having to purchase sulphur for H2SO4 production and application. In the case of phosphoric acid manufacturing for MAP, DAP, and TSP production, the majority of the sulphur burned and converted to H2SO4 is wasted as gypsum, which is stockpiled at the point of phosphoric acid manufacture. The gypsum cannot be used because it has been declared hazardous by the EPA.

The current world production for direct-applied rock is approximately 3.2 million metric tons per year of P2O5. This estimate is based on numbers from the Food and Agriculture Organization of the United Nations. China is the largest direct-applied phosphate rock user in overall area, followed by Eastern Europe. The annual use of direct-applied phosphate rock in Central and South America is estimated at 160,000 metric tons of P2O5. The low application in the United States is due to the current laws which require high neutral ammonium citrate availability, plus poor results received in the past with the Florida and Tennessee rocks when used for direct application.

At one time in the early to mid 1950's, the United States' annual use of direct-applied rock was approaching 1 million tons from Florida and Tennessee, but these two sources of rock are inferior for direct application purposed. Idaho phosphate rock production did not begin until late 1989. The concept of compaction of this phosphate with urea, potash or other materials to produce N-P-K products is currently being given serious consideration.

As a relatively insoluble product, rock phosphate releases its nutrients slowly over a long period of time, while superphosphate dissolves quickly and soon reacts with the soil, usually with aluminum or minerals, and is firmly bound up. Whether superphosphate is more firmly bound than the rock phosphate depends upon the pH. In very acid soils, one might expect that the phosphorus in aluminum phosphate is more firmly bound that the phosphate in rock phosphate, but in neutral or alkaline soil, aluminum is tied up and does not combine with superphosphate. Experimental studies comparing the residual fertilizer value are inconclusive, some favoring rock phosphate and others supporting superphosphate. Whatever differences may exist in a particular situation are reduced considerably with the use of organic residues to stimulate biological activity.

Idaho rock phosphate is a natural product, while superphosphate is chemically processed and often is wasteful. Additionally, naturally mined products contain essential trace elements.

Acidulated phosphates tend to be more energy intensive than rock phosphate. Rock phosphate raises the soil pH, while acidulated phosphates lower the pH. According to one source, triple phosphate can lower the soil pH down to pH 2, with devastating effects on soil life. The sulphur in superphosphte cannot attract soil organisms that attack beneficial fungi. The sulphur in superphospate is in sulfate form, which doesn't attract organisms unless the soil lacks oxygen, in which case fungi cannot survive anyway. Elemental sulfur does attract certain bacteria, which convert it to sulphate. However, an excess of sulfate can lock up molybdenum, so superphosphate may be harmful if used in excess. The more modern and powerful triple phosphate contains no sulphate.

Rock phosphate encourages the growth of certain root-associated fungi which are capable of breaking down insoluble mineral products and transferring the nutrients to the roots, while soluble phosphorus depresses their growth. This is true inasmuch as these fungi seem to proliferate where their usefulness has an advantage. Reliable experiments with them have been difficult, and whether they would supply enough phosphorus from limited reserves to meet the requirements for fast-growing and high-yielding annuals has not been established. Rock phosphate contains phosphorous, which becomes available over a long period of time, while the acidulated phosphates are high concentrated phosphorous carriers. We view the soil as in integrated, living organism that should be treated gently. Those of us who favor a preventive health plan can appreciate the unpleasantness of a strong medicine, whose side effects may be worse than the disease.