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CSME Research group\u2009\/\u2009UNESP <\/span><\/a> Determining soil composition by X-ray fluorescenceCSME Research group\u2009\/\u2009UNESP <\/span><\/p><\/div>\n \u201cJust as DNA determines the characteristics of humans and other species, different types of minerals affect the agronomic and environmental characteristics of soils in different ways,\u201d says crop scientist Diego Silva Siqueira, who completed his master’s and doctorate degrees as a member of the CSME research group under the supervision of Marques J\u00fanior. \u201cWe provide farmers with what can be thought of as a genetic map of their cropland, which they can use to inform crop management decisions.\u201d CSME\u2019s mapping process collects information about magnetic minerals that make up the soil. Any variation in the soil\u2019s magnetic signature, explains Siqueira, denotes a variation in these minerals and, consequently, in the soil\u2019s agricultural and environmental properties.<\/p>\n \u201cThe technique is suited for tropical and subtropical soils, which are abundant in iron oxides, aluminum and other minerals with strong magnetic fields that act as a sort of nano magnet. But it is not as well suited for temperate climates, where soils have a smaller concentration of these magnetic minerals and a larger amount of silicate clays,\u201d says Marques J\u00fanior. Used for decades in the mining and chemicals industries, by coatings manufacturers, and in materials engineering, magnetic sensing techniques are now being repurposed for use in large-scale agriculture. The solution developed at CSME has been adopted by coffee growers in Minas Gerais and sugarcane farms in S\u00e3o Paulo.<\/p>\n In September 2019, Siqueira and two other crop scientists\u2014Renan Gravena and Gustavo Pollo, a CSME alumnus\u2014joined up to found Quanticum, a startup that provides magnetic mapping services for agricultural applications. They received funding from FAPESP\u2019s Research for Innovation in Small Businesses (RISB, or PIPE in the Portuguese acronym) program for a study on magnetic mapping in tropical coffee farming. \u201cBrazil produces a third of the world\u2019s coffee, but it has yet to fully harness its potential in the market for premium coffee beans,\u201d says Siqueira.<\/p>\n Magnetic mapping has attracted interest from Federa\u00e7\u00e3o dos Cafeicultores do Cerrado Mineiro, a trade association representing around 4,500 coffee farmers in Minas Gerais. \u201cOver the years we have greatly improved our knowledge of the elements that determine a coffee\u2019s terroir<\/em>, such as climate, altitude, and water regime. Magnetic mapping will provide better insight into soil properties, which is crucial in coffee growing,\u201d says Juliano Tarabal, the association\u2019s chief officer. Terroir<\/em> describes the set of regional characteristics that give a coffee its distinctive character. \u201cCoffee from a premium terroir<\/em> can sell for as much as R$100 per kilo in a supermarket, about eight times the price of a conventional coffee brand,\u201d says Tarabal.<\/p>\n Magnetic mapping, he explains, is used to determine the soil properties in each field. When establishing new crops, coffee growers can use this information to choose the variety best suited for each portion of land. \u201cWe can now give buyers assurance of the precise properties and origin of the coffee beans we deliver,\u201d he says. A first-time coffee grower in the municipality of Patroc\u00ednio, Minas Gerais, has recently introduced the technique on his farm. Coffee is a biennial crop and it will take at least two harvest seasons to adequately assess the outcomes from the experiment.<\/p>\n CSME Research group\u2009\/\u2009UNESP <\/span><\/a> Samples with different concentrations of ironCSME Research group\u2009\/\u2009UNESP <\/span><\/p><\/div>\n Three members of Cooxup\u00e9, the world\u2019s largest coffee cooperative, with 15,800 member farms in the states of Minas Gerais and S\u00e3o Paulo, are currently experimenting with the technique. M\u00e1rio Ferraz de Ara\u00fajo, the cooperative’s technical development manager, believes magnetic mapping will help farmers to more precisely apply fertilizers and herbicides depending on each field\u2019s needs.<\/p>\n Total production costs per hectare (ha) for Arabica coffee are currently in the range of R$8,500 to R$10,000, says Ara\u00fajo. Of this amount, around R$4,000 is spent on fertilizers and soil amendments. \u201cUsing these inputs more effectively could significantly improve a farm\u2019s financial performance,\u201d he explains. \u201cEach hectare yields around 30 coffee bags and revenues of about R$15,000 in a good year, or R$10,000 in a bad one. So fertilizers consume 40% of farmers\u2019 revenues,\u201d he notes.<\/p>\n Mineral characterization reduces the requirement for particle size analysis, which indicates the relative content of sand, clay, and silt (mineral fragments of a size between sand and clay), and for chemical analysis, which measures acidity and the availability of nutrients. \u201cSoil mapping can also show which areas are heterogeneous and require more sampling for chemical analysis, reducing the required number of samples,\u201d says crop scientist Alberto Vasconcellos Inda, coordinator of the Graduate Program in Soil Science at the Federal University of Rio Grande do Sul (UFRGS).<\/p>\n CSME Research group\u2009\/\u2009UNESP <\/span><\/a> Taking soil magnetism readings using magnetic susceptibility metersCSME Research group\u2009\/\u2009UNESP <\/span><\/p><\/div>\n Magnetic mapping can also be used to supplement chemical and physical analyses, supporting a more accurate assessment of nutrient requirements when fertilizing a given field. \u201cThe higher the quality of the data, the lower the risk of inputs being applied improperly. Excessive use of soil nutrients, such as nitrogen, can be harmful to groundwater and surface water,\u201d says Inda.<\/p>\n Soil characterization was first introduced in the nineteenth century. The most widely used method, X-ray diffraction (XRD), earned German physicist Max von Laue (1879\u20131960) the Nobel Prize in Physics in 1914. XRD has an accuracy of 95%, and is considered by mineralogists to be the gold standard in analytical chemistry. Other characterization methods include M\u00f6ssbauer spectroscopy, which uses gamma radiation; differential thermal analysis (DTA); and thermal gravimetric analysis (TGA).<\/p>\n These four techniques all have an accuracy greater than 85%. But they all have three drawbacks in common: they are expensive, time consuming, and require highly skilled professionals to operate the equipment. These downsides, says Alberto Inda, have prevented these technologies from being mainstreamed in tropical and subtropical agriculture.<\/p>\n Each X-ray diffraction test analyzes a single mineral at an average cost of R$300 per test, according to market research done by Quanticum. A typical soil sample in Brazil contains more than 10 minerals that, even when present in small quantities, affect the soil\u2019s agronomic properties. Using conventional methods, says Siqueira, a report showing the types and quantities of minerals at a single sampling point would cost more than R$2,000. A survey of 1,000 ha of cropland, assuming one sample is collected per hectare, would cost a minimum of R$2 million.<\/p>\n