University of São Paulo: Method developed at USP calculates the productive potential of agricultural soils in Brazilian municipalities
USP researchers developed a methodology to calculate the productive potential of agricultural soils in Brazil. Based on data on soil characteristics in 70,000 samples collected throughout the country, the method is able to point out, for example, which municipalities are most promising in the production of sugarcane and soybeans. The two crops were analyzed in the research because they have great economic importance, but the method can be applied to other crops. The work was carried out at the Luiz de Queiroz Higher School of Agriculture (Esalq) at USP, in Piracicaba.
“Soil has an inherent ability to meet crop demands in terms of nutrient and water availability, influencing the photosynthetic process of the plant and the production of biomass,” says agronomist Lucas Tadeu Greschuk, who carried out the study. “Therefore, the productive potential of the soil, an indicator known by the acronym SoilPP , refers to its capacity to produce biomass in response to the evaluation of its chemical, physical and biological attributes.”
The researcher developed a strategy to study Brazilian agricultural soils in detail. “Information on land properties, up to 1 meter deep, and multivariate statistical techniques were used to construct a scoring system that ranged from 0 to 100, with the highest values representing high potential of soils for biomass production” , explains Greschuk. “SoilPP has been validated with field information.”
The data analyzed in the work come from the Geotechnologies in Soil Science team (GeoCis) database, organized by Professor José Alexandre Demattê, from Esalq. “About 70,000 samples were used, collected in agricultural areas throughout the Brazilian territory, with information on the levels of clay, sand, silt [a mineral fragment smaller than fine sand and larger than clay] , soil organic carbon, organic matter of the soil, pH [acidity], aluminum saturation, in addition to base saturation, delta pH, terrain slope, weathering index and others”, points out the agronomist. “The attributes of each of them were given a score ranging from 0 to 100, they were all integrated into a weighted index, and finally, each sample had a SoilPP score ranging from 60 to 100.”
productive potential
According to Greschuk, soils with higher SoilPP values are the best in terms of productive potential. “They present greater depth, good drainage, fine texture, rich in nutrients for the plants, the relief can be variable and without the presence of rocky outcrops”, he describes. “On the other hand, those with very low SoilPP have a low capacity to supply nutrients to plants, generally have a coarse texture [sandy] , low water retention and, consequently, low availability for the plant; may have varying depths and, in some cases, a high presence of stones.”
Based on this initial information, further analyzes were carried out in biomes, crops and municipalities. “Based on the map of Brazilian agricultural soils, which covers 205 million hectares [ha] , an estimate was made of the productive potential, the SoilPP, in each of the biomes, divided into areas of 900 square meters [m2] , called pixels [spatial resolution] ,” notes the researcher. Biomes are regions whose vegetation cover and climate have similar characteristics. “The biome with the greatest use for agricultural activities is the Cerrado, occupying around 71 million hectares.”
The municipal average productivity values for soybeans and sugarcane were obtained through the Brazilian Institute of Geography and Statistics (IBGE), and the average was calculated for the 2016 to 2020 harvests. “In total, 2,304 were analyzed. Brazilian municipalities with average soybean yields above 1,500 kilograms per hectare (kg ha-1). Low levels of average municipal productivity were observed in 896 producing cities, which could be increased”, describes the agronomist. “For sugarcane, 2,468 municipalities with average productivity above 35 tons per hectare (ton ha-1) were analyzed, 1,056 had low levels of average municipal productivity”. The research results are detailed in the master’s thesis Productive potential of Brazilian agricultural soils, presented by Greschuk on June 28, at Esalq.
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Greschuk points out that the methodology indicates where the average productivity of sugarcane and soybeans could be improved in places where crops are already being cultivated, minimizing the opening of new agricultural areas. “It is possible to know how much each municipality could increase its average production performance in kilograms or tons per hectare”, he emphasizes. “But this will also require a more in-depth study and also knowing how to investigate which factors are interfering: genetic, soil (pedological), climate or incidence of pests and diseases in the productivity of the respective crops.”
The research was carried out at Esalq’s Department of Soil Science, under the guidance of Professor José Alexandre Demattê. The researchers from Esalq Nélida Silvero, José Lucas Safanelli, Jorge Tadeu Rosas and Nícolas Rosin collaborated with the work. The work was supported by the Fundação de Amparo à Pesquisa do Estado de São Paulo (Fapesp), the Coordination for the Improvement of Higher Education Personnel (Capes) and the Geotechnologies in Soil Science team at Esalq.