Spatial Analysis of the Feasibility of Using Rock Powder as Fertilizer in Agriculture in Mato Grosso in Brazil

Abstract

This study analyzes the potential utilization of rock dust as a sustainable alternative to the use of traditional fertilizers, considering the distance between mining areas and areas where agricultural commodities are produced in the state of Mato Grosso, the largest agricultural producing state in Brazil. To this end, agricultural production by municipality and the position of mining areas in the mining phase related to granite, basalt and kimberlite are analyzed, aiming at developing a map of current potential areas of rock dust fertilizer production, namely for phosphorus (P)- and potassium (K)-based rocks for crops. To analyze the future scenario, areas in the research phase for the same types of rocks mentioned are considered. The results indicate three main potential scenarios: (1) municipalities located in areas that produce agricultural commodities and far from mining areas in production; (2) municipalities located near areas that produce rock dust and with high agricultural production of commodities; (3) municipalities near areas that produce rock dust, but with low production of agricultural commodities. In scenario 1, the use of rock dust may be viable in the event of a supply crisis of traditional fertilizer. In scenario 2, rock dust may fully or partially replace traditional fertilizer. And in scenario 3, rock dust may be used to reduce costs and improve the production of small local producers. Thus, this study indicates that rock dust can be an alternative to traditional fertilizers in the state of Mato Grosso, but it requires registrations in accordance with Brazilian legislation.

1. Introduction

By 2050, the world’s population is expected to exceed 9 billion. This increase of more than 2 billion people, based on current figures, will require an increase in food production. Brazil plays a strategic role in global food production and is currently a major exporter of agricultural commodities. However, this production has required the use of soluble fertilizers to improve soil fertility, introducing nitrogen (N)-, phosphate (P)-, and potassium (K)-based fertilizers. This is the dominant technique in modern agriculture, aiming to ensure the rapid availability of nutrients for plants [1,2].

Brazil is one of the largest fertilizer consumers in the world, accounting for 8% of global consumption. It ranks fourth, behind only China, India, and the United States. Potassium chloride is imported from Canada, Russia, Belarus, and Israel, while phosphate fertilizers originate from the United States, Morocco, Egypt, Israel, Saudi Arabia, Russia, and China. Nitrogen fertilizers originate from Russia, China, Qatar, Belgium, Algeria, Nigeria, and Egypt [3].

Brazilian agriculture depends on the international market to meet domestic fertilizer demand [4,5]. The high cost of acquiring fertilizers, the geopolitical context, and the price indexation to the US dollar can favor the price volatility of this input [6]. In recent years, the devaluation of the real and the Russia–Ukraine conflict have contributed to the increase in fertilizer costs, triggering efforts to find domestic sources of nutrients, including alternatives such as remineralizers [7].

Some rocks are rich in nutrients such as K, P, Fe, Ca, Mg, etc., which are essential for plants [8]. Elements such as K can be obtained from minerals such as micas, feldspar, and nepheline; however, their ability to provide nutrients to plants is associated with the dissolution rate, i.e., the weathering of these minerals [1]. Among the benefits, the use of silicate agrominerals favors cation exchange [4].

The use of rocks with phosphate or potassium concentrations has been studied in several countries around the world as an alternative source to traditional fertilizers. Biswas [9] used rice straw, low-grade rock phosphate (RP), and residual mica along with Aspergillus awamori in India; Bertoldo et al. [10] used algae extract, molybdenum, and rock dust for nitrogen fixation and/or alternative nitrogen supplements; Ajiboye et al. [11] tested the use of phosphate-rich sediments and cashew nut shell residues in Nigeria; Lompo et al. [12] used phosphate rocks in West Africa; Sun et al. [8] used potassium-rich rocks and organic residues in China; Zhao et al. [13] used rocks containing potassium (K) silicate minerals in China; and Luchese et al. [7] used basaltic rock dust in Brazil.

The use of agrominerals is a technology that, in some cases, can benefit not only large-scale farmers, but also family farmers, due to the simplicity of the technique and the results obtained in terms of productivity and low cost. This is due to the widespread availability of rocks and their byproducts in Brazil [14].

However, limitations in the use of agrominerals are primarily related to maximum production costs and the transportation distance from the mine to the agricultural area. This logistical limitation can require transportation distances ranging from 100 to 500 km from the mine depending on the specific characteristics, especially when considering road transportation [15].

Mato Grosso is the Brazilian state with the largest agricultural production, generating a total production value of US$ 35.7 billion (BRL 174.8 billion), a 15.2% increase compared to the previous year [16]. This production largely occurs in highly weathered and low-fertility soils, where pH adjustments and significant fertilizer additions are necessary to overcome this limitation.

The state, however, boasts geological diversity, with rocks such as basalts, granites, and kimberlites, which can be used as an alternative source of phosphates, potassium, or other macronutrients for plants. The use of silicate rock powder is favored in areas with high geodiversity, as this resource is widely distributed and can be obtained as a byproduct in mining plants that produce crushed and ground rock [17].

The use of a kind of agrominerals in Brazil is regulated by law no. 12,890/2013, which defined a remineralizer as “material of mineral origin that has undergone only reduction and classification in size by mechanical processes and that alters soil fertility indices through the addition of macro- and micronutrients for plants, as well as promoting the improvement of the physical or physicochemical properties or biological activity of the soil.” The Ministry of Agriculture, Livestock, and Supply regulates and registers remineralizer [18].

Considering the high demand for fertilizers needed for agricultural production in Mato Grosso, as well as the existence of mining and rock mines that can supply rock powder with nutrients such as phosphates and potassium, this paper aims to analyze the potential use of agrominerals by integrating data between municipalities producing agricultural commodities and mining areas for basalt, kimberlite diamonds, and granite. The aim is to identify locations where rock dust can be used as an alternative to traditional fertilizers, based on the distance between the rock-dust-producing area and the area where it will be used.

The article is structured as follows: Section 1 presents Brazil’s and Mato Grosso’s dependence on fertilizer imports, as well as the possibility of using agrominerals as an alternative solution. Section 2 describes how data on the location of mining operations and agricultural production areas were extracted and analyzed. Section 3 presents the interpolation between mining areas that can supply agrominerals and agricultural commodity-producing areas that require fertilizers, as well as future scenario analyses. Furthermore, the results indicate the areas with the greatest feasibility for agrominerals, considering the distance between production and consumption areas. Section 4 demonstrates that, although there are limitations to the use of agrominerals, rocks such as basalt, granite, kimberlite, and others can be used as sources of potassium and phosphorus, alternatives to traditional fertilizers. Section 5 presents the main conclusions of the research.

2. Method

The method used consists of 3 stages: (a) identification and analysis of mining processes related to rocks that can be used for rock extraction; (b) identification of agricultural producing municipalities in Mato Grosso; and (c) analysis and integration of data.

The current scenario is composed of the correlation between active mining operations and current planting areas. In other words, it presents a current feasibility scenario, considering the transportation distance between the consumer and production areas. The future scenario considers areas where mining projects are under consideration, which may or may not come into operation. These projects were correlated with current planting areas to indicate future scenarios.

In the first stage, the SIGMINE database was used, which contains all applications, research permits, and grants of mining titles issued by the National Mining Agency (ANM). Through this platform, data related to mining processes in the state of Mato Grosso until August 2023 were extracted. The collection covered essential information, such as the georeferenced location, the types of minerals explored, and the status of the mining processes of each substance, which were downloaded in shapefile format, to be filtered later. Most of the basalt and granite mines analyzed produce construction materials such as gravel. The areas containing kimberlites are associated with diamond mining. Processes related to gold mining in granites were not considered in the analyses due to the risk of contamination with mercury or other compounds that would make the material unfeasible for use in agriculture. Data on agricultural production in Mato Grosso were obtained based on information available from the Secretariat for Economic Development (SEDEC), which extracted agricultural production per hectare of commodities (soybean, corn, cotton, rice, beans, sorghum, sunflower, coffee, peanuts and wheat) in the state of Mato Grosso during the year 2022 [19]. Based on the production of each municipality, a classification was made on a scale of 1 to 7 (

Table 1. Classification according to agricultural production per hectare.

Class	Description of Classification by Production per Planted Area (ha)
1	0–35,000
2	35,000–75,000
3	75,000–150,000
4	150,000–350,000
5	350,000–550,000
6	550,000–750,000
7	Above 750,000

).

Data integration was performed to create thematic maps using the QGIS geoprocessing software 3.42.0. The areas investigated were properly georeferenced, adopting the SIRGAS2000 datum as the geodetic reference. Cartographic bases from the Brazilian Institute of Geography and Statistics (IBGE) from 2021 were used, including the map of the Brazilian territory, its federative units, and the municipal division of the state of Mato Grosso.

Based on ANM data, mining processes related to granite, basalt, and diamond of kimberlite origin were selected. After identification, the location of the processes was transformed into centroids, with radii of 250 km as a parameter to develop heat maps, considering two distinct analyses: (a) mineral extraction processes in the mining phase, that is, in operation; (b) and which may indicate the future potential for the installation of new mines. Both maps were classified on a scale of 1 to 7 (

Table 2. Classification according to proximity to mining areas.

Class	Description of the Classification Based on the Heat Map of Mining Titles (Pixel Value)
1	0–1.3
2	1.3–2.6
3	2.6–5.2
4	5.2–6.5
5	6.5–7.8
6	7.8–10
7	Greater than 10

), considering the proximity to mining processes, the concentration of processes in the area and the distance of up to 250 km. This chromatic classification provides an intuitive visualization, allowing a quick and comparative analysis of the areas with the highest and lowest density of mining activities.

The interpolation between the data on mining processes and the state’s agricultural production was carried out considering the current scenario and future potential.

For the final mapping of the potential use of agrominerals, the scores obtained from the substance potential map were used, considering only the distribution of mining concession regimes, through the heat map interpolated with the municipal boundaries, as shown in Equation (1).

$$\mathrm{P}{\mathrm{R}}_{\mathrm{Current}}={\displaystyle \frac{\mathrm{MA}+{\mathrm{PS}}_{\mathrm{C}\mathrm{u}\mathrm{r}\mathrm{r}\mathrm{e}\mathrm{n}\mathrm{t}}}{2}}$$

(1)

where

• P${\mathrm{R}}_{\mathrm{Current}}$ = current potential of the rocking technique;
• MA = agricultural map;
• ${\mathrm{PS}}_{\mathrm{Current}}$ = potential of substances according to the mining concession map.

The map of future potential for the use of agrominerals took into account the scores attributed to the map that considers all types of mining requirements, together with the classifications of the agricultural map, as is shown in Equation (2).

$${\mathrm{PR}}_{\mathrm{Future}}={\displaystyle \frac{\mathrm{MA}+{\mathrm{PS}}_{\mathrm{Future}}}{2}}$$

(2)

where

• P${\mathrm{R}}_{\mathrm{Future}}$ = future potential of the rocking technique;
• MA = agricultural map;
• ${\mathrm{P}\mathrm{S}}_{\mathrm{F}\mathrm{u}\mathrm{t}\mathrm{u}\mathrm{r}\mathrm{e}}$ = potential of substances according to the mining concession map.

Both maps were classified according to

Table 3. Potential for the use of agrominerals in Mato Grosso—combined sums of the notes related to current or future agricultural map production and mineral production.

Class	Description of the Classification of Potential Use of Agrominerals Based on the Sum of the Scores on Maps 1 and 2
1	2
2	From 3 to 4
3	From 5 to 6
4	From 7 to 8
5	From 9 to 10
6	From 11 to 12
7	From 13 to 14

on a scale of 1 to 7, providing a clear and comparative view of the potential for the use of agrominerals in different regions of the state.

3. Results

Analysis of the Proximity Between Mining Processes and Production Áreas

Based on analyses of mining concession processes, 2 processes were identified in basalt rocks, in Tangará da Serra and Diamantino; 11 granite extraction processes were identified, located in the municipalities of Cuiabá, Santo Antônio do Leverger, Rondolândia, Nova Lacerda, Juara, and Terra Nova do Norte; and 2 diamond mining processes of kimberlite origin were identified in Juína.

The future scenario indicates the existence of 178 mining processes, 34 of which are basalt, 102 area granite, and 22 are diamonds of kimberlite origin in other phases (

Table 4. Analysis of the municipalities of Mato Grosso, considering the current potential for the use of agrominerals.

Group	Municipalities	Agricultural Production	Proximity to Mining Processes	Average
1	Ipiranga do Norte, Paranatinga, Nova Ubiratã, Sorriso, Campos de Júlio, Lucas do Rio Verde, Nova Maringá, Tabaporã, Diamantino, Nova Mutum, and Sapezal	5 to 7	1 and 2	3 or 4
2	Brasnorte, Primavera do Leste, Dom Aquino, Campo Verde, Juara, Nobres, Poxoréu, Rondonópolis, and Jaciara	3 and 5	3 and 6	3 to 5
3	Rosário Oeste, Juscimeira, Santo Antônio do Leverger, Chapada dos Guimarães, and Cuiabá	1 or 2	5 and 7	3 or 4

); that is, which may come to be consolidated as a future mining enterprise.

The position of the mining processes on the map of the state of Mato Grosso resulted in the heat map, indicating the locations with the highest current concentration of mining (Figure 1A) and another map indicating future potential (Figure 1B).

In general, the analysis of the heat maps reveals a more significant concentration in Baixada Cuiabana and a growing concentration of processes between Juína and Rondolândia, both in the map that covers the mining concession phase (Figure 1C). In the map that includes all phases of the mining project, in addition to the areas mentioned, the regions of Tangará da Serra and Peixoto do Azevedo and Guarantã stood out (Figure 1D).

The agricultural production map (Figure 2) of commodities indicated Sorriso as the location with the largest agricultural production of commodities in the state of Mato Grosso, followed by Diamantino, Nova Mutum, Sapezal, Querência, and Campo Novo do Parecis.

The integration of the mining processes map with the agricultural production map indicated that in both the current and future scenarios (Figure 3A,B), it is possible to identify three main groups (Table 4 and

Table 5. Analysis of the municipalities of Mato Grosso, considering the future potential for the use of agrominerals.

Group	Municipalities	Agricultural Production	Proximity to Mining Processes	Average
1	Comodoro, Gaúcha do Norte, Santa Carmem, Santa Rita do Trivelato, São José do Rio Claro, São José do Xingu, Sinop, Canarana, Ipiranga do Norte, Lucas do Rio Verde, Nova Maringá, Brasnorte, Campos de Júlio, São Félix do Araguaia, Tabaporã, and Querência	4 and 7	1 and 2	3 or 4
2	Alto Garças, Cláudia, Itiquira, Santo Antônio do Leste, Tangará da Serra, Paranatinga, Primavera do Leste, Dom Aquino, Campo Verde, Campo Novo do Parecis, Diamantino, Jaciara, Alto Taquari, Confresa, Guiratinga, Juara, Marcelândia, Matupá, Pedra Preta, Porto Alegre do Norte, Poxoréu, Itaúba, Nobres, Novo Mundo, and Rondonópolis	3 and 6	3 and 7	3 and 5
Acorizal, Jangada, São Pedro da Cipa, Várzea Grande, and Cuiabá		1	5 and 7	3

). Group 1 represents municipalities that have significant agricultural production, but are far from the areas producing agromineralizers. Group 2 consists of those municipalities with significant production and close to areas producing agromineralizers. Group 3 represents municipalities close to areas producing agromineralizers, but located in municipalities where agricultural activity is not so present.

4. Discussions

4.1. Standardization of the Use of Remineralizers

Effectively, remineralizers constitute a legally recognized category of mineral inputs whose purpose is to improve soil fertility through the addition of macro- and micronutrients, in addition to promoting the improvement of the physical, physicochemical, or biological properties of the soil. The guidelines for the definition, classification, specifications, guarantees, tolerances, registration, packaging, labeling, and advertising of remineralizers and plant substrates are established by Normative Instruction no. 5/2016 of the Ministry of Agriculture, Livestock and Food Supply (MAPA), as discussed by Dantas et al. [20].

In the technical context, the term agromineral is often used to designate any rock or mineral of natural origin that contains elements that are beneficial to plants, such as potassium, calcium, magnesium, phosphorus, among others. Although widely used in scientific studies, this term does not have a specific legal definition in Brazilian legislation.

The term rock powder refers generically to any mineral material that has been mechanically ground, regardless of its nutritional content or agronomic efficacy. In other words, it is a raw product that is not necessarily characterized as an agricultural input.

For a rock powder to be officially recognized as a remineralizer, it must meet technical criteria defined by law, including that (a) it must come exclusively from mechanical size reduction (without the addition of chemical compounds); (b) it must have a sum of bases (CaO + MgO + K₂O) equal to or greater than 9% by weight; (c) it must have a minimum content of 1% K₂O; (d) it must meet specific granulometric standards (minimum of 60% < 0.3 mm and 95% < 2 mm); (e) and its agronomic efficacy must be proven by scientific tests.

Therefore, all remineralizers are rock powder, but not all rock powders can be classified as remineralizers. Likewise, an agromineral may or may not meet the legal requirements to be registered as a remineralizer, depending on its chemical and mineralogical composition and proven agronomic performance.

Although the legislation does not require the presence of all major oxides other than potassium, it is considered technically advantageous for the material to contain significant levels of calcium and magnesium. This is because a greater sum of bases is associated with an increased potential for correction and improvement of soil fertility [21]. In addition to the substances chosen, due to the production potential in the state, a fundamental factor taken into account was the distance between the source of production of agromineral techniques and agricultural production, since the acquisition of conventional fertilizers used in agriculture is a challenge not only due to the high cost, but also to the distance from large production centers [22], which justifies the use of a radius of 250 km to produce the heat maps that were used in the interpolations that resulted in the final maps.

4.2. Basalts, Granites and Kimberlites as Agrominerals

The choice of basalt, kimberlite diamond, and granite was based on the chemical and mineralogical composition of these rocks, which, when used properly, can provide significant benefits in soil remineralization. These substances, rich in macro- and micronutrients, contribute to improving soil fertility, expanding the possibilities of implementing rock dust in sustainable agricultural practices [23]. The use of rock dust by farmers is favored by the low cost and wide availability of these inputs as mining byproducts [17].

4.3. Kimberlites

The study carried out by Fantucci et al. [24] investigated the synergistic effect of co-processing kimberlite rock powder, a byproduct of diamond mining, as a potential catalyst and carbon sink due to its ferrous iron and alkaline earth silicate content, respectively. The results highlighted the significant influence of temperature and kimberlite type on the oxidation efficiency of humic-like substances. Kimberlite was identified as a partial CO₂ sink during advanced oxidation (WAO) through mineral carbonation. The resulting WAO products presented nutrients and beneficial properties, and can serve as soil amendments.

Mato Grosso, with 117 known kimberlite intrusions, grouped into four fields, namely Juína, Paranatinga, Traíra and Jauru [25]. According to Greenwood [26], kimberlite bodies with different compositions are found, with serpentinized pseudomorphs of olivine, garnet megacrystals with kelisite and ilmenite fringes and with perovskite fringes; and other bodies made up of garnet, ilmenite, and phlogopite, with rare zircons and a serpentine and calcite matrix. According to Weska and Svisero [27], the kimberlite intrusions of Piranhas 1, in the Paranatinga region, are composed of megacrysts of 45% serpentinized olivine (Mg₂SiO₄), 25% phlogopite (KMg₃(AlSi₃O₁₀)(F,OH)²), 8% pyrope garnet (Mg₃Al₂(SiO₄)³), 6% magnesian ilmenite (FeTiO₃), 2% diopside (CaMgSi₂O₆), and rarely, perovskite (CaTiO₃) and spinel (MgAl₂O₄).

Kimberlite intrusions can be an alternative source of potassium, which are present in phlogopite, in addition to being able to provide other macronutrients important for plant development.

4.4. Basalt

Previous research with basalts from the Serra Geral Formation, corresponding to the basalts of the Arapey Group, showed positive results as a source of macro- and micronutrients for the soil. Tests with basalt powder in sandy soils revealed improvements in pH and potassium (K), calcium (Ca), magnesium (Mg), and phosphorus (P) levels after the first year of application [28]. Basalt, with its high concentration of silicon oxides (49.35%), when used as a powder in soil fertilization, releases the silicate anion. This substance competes for the same adsorption site as the phosphate anion, resulting in an increase in the availability of phosphorus for plants. This basalt–soil interaction makes a significant contribution to the sustainable and effective supply of essential nutrients to plants [29].

The application of basalt as an agromineral has already been tested by several authors. The use of phosphate and basaltic rocks can be an important source of macronutrients such as P, Na, Ca, and Mg [2]. The same authors indicated that the use of liming provided greater plant development with superior results to soluble fertilizers, probably due to the better ionic balance. For Luchese et al. [7] basaltic rock powder can be used as an alternative source of fertilizers. In the analysis carried out, when applied together with limestone, it caused an increase in the levels of dry matter; elements such as Ca, Mg, and P; and an increase in soil pH. For these authors, the basaltic rock powder evaluated can reduce the use of soluble fertilizers in agriculture, especially phosphates. Among the positive effects is the increase in cation exchange capacity and the increase in net negative charges [4,30,31]. Basalt occurrences in Mato Grosso are associated with different formations, such as Serra Geral, Paredão Grande, and the most representative, the Tapirapuã Formation [32,33]. Barros et al. [34], when analyzing the basalts of the Tapirapuã Formation, identified that the unit is composed of the following content of major elements (%): SiO₂ (between 49.50 and 50.70); Al₂O₃ (between 13.20 and 14.00); Fe₂O₃ (between 12.40 and 12.70); MnO (between 0.20 and 0.19); MgO (between 6.65 and 7.20); CaO (between 10.30 and 10.90); Na2O (between 1.90 and 3.00); K₂O (between 0.51 and 0.65); TiO₂ (1.30); and P2O5 (between 0.14 and 0.17). Thus, in addition to contributing macronutrients, basalt rock powder can be a source of potassium and phosphorus. However, to comply with the regulations on the use of remineralizers, the facies used must have an adequate concentration of these elements. Otherwise, the rock powder only fulfills the role of a source of other macronutrients, which can be beneficial for plants.

4.5. Granite

The effect of granite processing residue on the fertilization of conilon coffee plants in a greenhouse has also been evaluated by Martins and Fanton [35]. The results indicate that the application of the residue increased soil pH and reduced Al³⁺ content in a linear manner, but with a small magnitude. The efficiency of the residue was more notable in soils with greater buffer capacity. For the initial growth of coffee, the residue should be used exclusively as a source of K and Ca, and it is crucial that the soil pH is around 5.0. Doses close to 20 t ha⁻¹ of the residue provided adequate initial growth for coffee. These results suggest that, despite the controversy over its effectiveness, granite processing residue can be a valuable source of nutrients for coffee, especially under specific soil conditions.

Syenite is another rock with a composition similar to granite that is used as an agromineral. Santos et al. [4] used biotite syenite as a nutrient source and obtained an increase in available P and K. In corn leaves, the authors identified an increase in N and K, in addition to increases in plant height, stem diameter, and amount of dry matter in the leaves. However, the authors did not identify an increase in pH, H + Al, total organic carbon, Ca + Mg, T, t, Zn, Cu, Fe, and Mn in the soil.

Although there are several distinct granite intrusions in the state of Mato Grosso, mining processes have the highest concentration in the São Vicente Granite region. This unit is composed of syenogranite; in one of the facies, it consists of potassium feldspar, quartz, plagioclase, and biotite, and occasionally as accessory minerals, zircon, apatite, and titanite. Potassium feldspars account for 46%, and plagioclase corresponds to 18%. The other facies are composed of subhedral phenocrysts of quartz, potassium feldspar, plagioclase, and biotite, immersed in a fine-to-very-fine matrix. Quartz grains represent 40% of the rock, while plagioclase makes up 17% of the phenocrysts, and K-feldspars (orthoclase and microcline) make up 40% of the phenocrysts [36].

The different facies of the São Vicente Granite, in the Águas Quentes State Park region, are composed of the following major elements expressed in percentages: SiO₂ (between 73.47% and 78.14%); Al₂O₃ (between 12.25% and 13.21%); Fe₂O₃ (between 0.72% and 2.27%); MnO (between <0.01% and 0.06%); MgO (between 0.05% and 0.39%); CaO (between 0.04% and 1.03%); Na₂O (between <0.01% and 3.40%); K₂O (between 0.72% and 5.61%); TiO₂ (between 0.11% and 0.24%); and P₂O₅ (between <0.01% and 0.09%) [36]. Thus, granite can be a source of potassium, in addition to contributing other macronutrients.

4.6. Positive Aspects and Limitations

The mineralogical characteristics of the rock, soil pH conditions, climate, and weathering conditions can influence the results related to the application of agrominerals. Studies indicate that more acidic soil conditions can influence the release of K [37]. Several authors have integrated the use of techniques to obtain better results in the availability of nutrients for plants. Ajiboye et al. [11] used the acidification of phosphate rock with liquid from cashew nut shells to obtain a greater quantity of available P. The authors found a general increase in the quantity of P extracted from phosphate rock. Bertoldo et al. [10] used the combination of algae extract, molybdenum, and rock powder, associated with inoculation, and the results indicated a yield similar to conventional methods, but at a lower cost. For Schneider et al. [38], to release phosphate from raw rock, the use of acid-producing microorganisms, such as Aspergillus niger, is an alternative to the use of inorganic acids.

Among the possible positive effects, the application of rock dust can contribute to increasing the soil’s water absorption and storage capacity, the accumulation of biomass in plantations and increasing their photosynthetic capacity; that is, absorbing more atmospheric CO₂, in addition to promoting microbial activities [8]. Thus, in addition to favoring the release of elements into the soil, agrominerals can help reduce global CO₂ levels [17].

The use of agrominerals can fully or partially replace traditional fertilizers. For Luchese et al. [37], the application of rock dust can be an excellent low-cost alternative for nutrient sources and growth media for tropical agriculture. Other authors, such as Biswas [9] suggest the use of low-quality agricultural and mineral residues, such as RP and residual mica, instead of expensive chemical fertilizers. Biswas [9] suggest that the application of agrominerals together with organic fertilizer can replace 50% of chemical fertilizers. The combined application of agrominerals and conventional fertilizers is also suggested as the most promising option by Zhao et al. [13].

In municipalities with large commodity production and located in areas close to sources of agrominerals, such as the municipalities of Brasnorte, Primavera do Leste, Dom Aquino, Campo Verde, Juara, Nobres, Poxoréu, Rondonópolis, and Jaciara, the use of rock dust can represent savings for producers, improved productivity, and an environmental gain, related to the improvement of the provision of soil ecosystem services.

Remineralizers are a good option for farmers with limited resources, as they are cheaper than conventional fertilizers [12]. Therefore, even in municipalities where there is no high production of commodities, such as Rosário Oeste, Juscimeira, Santo Antônio do Leverger, Chapada dos Guimarães, and Cuiabá, rock dust can be a great option to improve the productivity of small farmers who do not have the resources to use conventional fertilizers. Therefore, it is necessary to map local production arrangements that integrate the demand of small producers and the availability of rock dust from mining.

In the case of municipalities located far from mining areas but with large commodity production, although the cost of transportation may make the application of rock dust more expensive in the event of a fertilizer supply crisis, agrominerals may become a viable and important source for maintaining agriculture at full productivity during the crisis.

The future scenario indicates the possibility of expanding the state’s sources of agrominerals. If promising products are identified, there is the possibility of developing mines for the specific production of rock dust, which would enable a production scale capable of meeting a large demand.

However, one of the limitations of the use of agrominerals is their susceptibility to weathering. When they have low reactivity, they are unable to provide the quantity of elements necessary for cultivation [39]. Therefore, all sources of rock dust need to be properly tested, both considering natural weathering and using other techniques that use acids provided by biological activity, or organic materials resulting from alternative sources available locally.

In this scenario, it is possible to state that, although the state of Mato Grosso does not yet have any remineralizers officially recognized by the Ministry of Agriculture, Livestock, and Food Supply (MAPA), it has considerable potential to obtain such recognition. The identification and registration of remineralizers in the state of Mato Grosso means increasing the resilience of the state’s commodity production to fluctuations in international prices, and at the same time making it possible to solve existing challenges in the mining sector, such as the disposal of rock dust, which is common in the activity. However, it is essential to conduct further research to validate the effectiveness of the rock dust produced by local mining companies. This validation is crucial so that this material can eventually be used in a complementary and synergistic manner with fertilizers already used in agriculture, mainly helping small- and medium-sized family farms.

5. Conclusions

This study demonstrated the existence of municipalities where there are active mining operations that could supply rock dust, and, at the same time, there is significant production of commodities; that is, where the logistics scenario favors the use of agrominerals. In areas where there is good availability of rock dust sources, but which are located in municipalities with little or no commodity production, agrominerals can be used as an alternative source for small producers to improve their production at low cost. However, studies need to be carried out to identify whether rock dust can be characterized as a remineralizer, based on the regulations of the Ministry of Agriculture, Livestock and Food Supply. The development of analyses with different types of application is essential to identify, for each type of rock dust and for each type of soil, what the efficiency of the product will be. The literature review indicated that, worldwide, the application of rock dust with other products, or even mixed with traditional fertilizers, can improve efficiency and reduce costs. We suggest that future research conduct case studies in areas with the greatest potential, considering more factors, such as agronomic testing and analyzing transportation costs between mining and planting areas. This study is limited by its regional scale, which does not adequately consider local aspects, such as access roads and soil composition.