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The process of using agrominerals starts with crushing rocks into a "rock powder," than using the powder to replenish soil nutrients. The process of replenishing mineral levels in a soil is called soil Remineralisation. While studying alternative ways to replenish ground nutrients, it has been found that agrominerals can also help mitigate other issues such climate change, water preservation and soil management.
At first agrominerals were used to help recreate soil conditions for exotic plants. These were simple practices that occur on a much smaller scale. These include using perlite to enhance the aeration of the soil, using pumice to control evaporation while one can use Vermiculite and Zeolite to store moisture. This soil modification was the start of the agromineral concept and has evolved into looking for alternative sources to obtain the three major nutrient elements. Remineralization has been the term created for implementing rock powders into soils as a source of nutrients. This process has been implemented into bigger operations and has found great success in places like Brazil, Germany, Norway, South Africa, Sri Lanka, and Uganda.
There is a push to move away from chemical fertilizers since it has been connected to groundwater pollution. There has been a shift into looking at grinding rocks into a powder that can be incorporated into the ground as a new way to add nutrients to the soil. The idea behind rock powder originated from the idea that rock weather and is how nutrients were originally put in the soil; the soil is weathered rock. With this concept it has been determined that the rock source is very important because the rock can have unwanted elements that can be toxic for both the plant and the humans ingesting it. Research has been done on rocks such as basalt and dacite; each rock had their pros and cons. The success of the rock powder can be affected by crop cycle. For example, basalt was effective when it came to long-cycle crops, but short-cycle crops it was not as effective as chemical fertilizers. With some rock powders it can take anywhere between 1-5 years to show results. The biggest contributions to rocks being an effective rock powder comes down to mineralogy and chemical composition. Once rock sources that have the proper elements and effectiveness is found, the limitation to rock powders then becomes how it is ground. Grinding a mineral, like olivine, to a particle size that would be effective in the ground (1μm), takes about 1.5 Gigajoule per ton of rock. Research will be needed to find more efficient ways to crush rock for rock-powders to be a sustainable solution for replenishing plant nutrients.
Rocks have become a cheap by-product in many industries and so there is a potential for a massive supply of viables rocks for a cheap price. Remineralization using rock powder can provide up to 5 years' worth of nutrients in a soil. When used in the combination with organic fertilizer, rock powder has proven to be just as effective as chemical fertilizer for a much smaller cost. It has even shown to have higher yields for long term crops. When using rock powder, the plants tended to look healthier, and it was found that the powder helps with holding moisture content. The effectiveness of the remineralization process is dependent on the mineralogy and chemistry of the rock powder, as well as the soil characteristics.
The challenge with rock powders is understanding the solubility rates of the rock powder. Rates are dependent on factors like organic matter, pH levels, secondary clay precipitation. This is a major area of research since their dissolution kinetics are not fully understood. One of the major challenges is recreating the field conditions in the lab, in many cases the solubility rates in the lab are 2-5 magnitudes higher than the ones in the field. It's important to fully understand what the mineralogy and chemical components of a rock. Volcanic rocks were thought to be a good source for rock powder but it was determined that it contains toxic elements as well. Research has been done into phosphate rocks, but these too have the issue of containing heavy and radioactive elements.
The use of rock powder in remineralization has the potential to help mitigate Climate change. When nutrients from certain powders are absorbed, cations are released in the soil which reacts to with carbon dioxide to create carbonate minerals, which can serve as a carbon sink for the carbon cycle. With this discovery there has been a push to further look into remineralizations using rocks powders due to its sustainability potential both from a farming side and a global climate change side.
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