Location of area of study

The State of Mexico is located from 18° 22’ 14” to 20° 17’ 22” north latitude and from 98° 35’ 35” to 100° 36’ 19” west longitude and has a surface area of 2 324 422 ha. It borders with the states of Hidalgo and Querétaro to the North, Puebla and Tlaxcala to the East, Morelos and Guerrero to the South and Michoacán to the West (^{INEGI, 2015}). The climates that occur in the state are: temperate, semi-cold, warm, semi-warm and cold. The annual mean temperature fluctuates from 6 to 28 °C, the annual precipitation ranges from 600 to 1 800 mm, the height above sea level ranges from 340 to 5 100 m (^{INEGI, 1999}; ^{García, 2004}). The dominant soils are: Andosol, Pheozem, Vertisol, Regosol and Arenosol (^{Sotelo et al., 2010}). The State of Mexico is made up of 125 municipalities (Figure 1), for which soils were described (^{INEGI, 2015}).

Figure 1 Location of the State of Mexico and municipalities that comprise it. 

Pheozems distribution

The State of Mexico has 472 718 ha and represents 20.34% of the state surface. Pheozems have potential for most crops and plant species, although climatic conditions limit their adaptation and development. They have potential for species such as corn, wheat, beans, potatoes, carrots, barley, oats, triticale, peas, broad beans, avocados, peaches, plums, raspberries, alfalfa and grasslands (SIAP, 2019). The municipalities with the largest area are: Aculco, Toluca, Axapusco, Acambay and Jilotepec. Due to the surface area of these soils, it can be said that these municipalities have the greatest productive potential for species that adapt to their climatic conditions (Table 1).

Figure 2 Municipalities with the largest area of Pheozem in a) Aculco, Vertisol; in b) Jilotepec; and Cambisol in c) Sultepec. 

Vertisols distribution

The state has 241 485 ha and represents 10.39% of the state's surface. They are located in the central and northern part of the state. They have potential for species such as corn, wheat, beans, triticale, barley, oats, peas, broad beans, alfalfa and grasslands (^{SIAP, 2019}). The municipalities with the largest area are: Jilotepec, Almoloya de Juárez, Ixtlahuaca, Aculco, Acambay and Jocotitlán. These soils are very productive at the state level, although they need irrigation to exploit their full productive potential (Table 1).

Cambisols distribution

The state has 196 047 ha and covers 8.43% of the state surface. They are fertile soils with very good productive potential for plant species that adapt to the climatic conditions of the municipalities, mainly for species such as corn, wheat, beans, potatoes, carrots, barley, oats, peas, broad beans, avocado, peaches, plums, raspberry, alfalfa and grasslands (^{SIAP, 2019}). The municipalities with the largest area are: Sultepec, Zacualpan, Texcoco, Temascaltepec and San Simón de Guerrero (Table 1).

Andosols, Regosols and Luvisols are the next in importance and surface area. They are less fertile, high Al content, medium to coarse textures, slopes >12%, organic matter <2% and acidic pH in the three soils (Figure 3 and Table 2).

Figure 3 Municipalities with the largest Andosol area in a) San José del Rincón, Regosol; in b) Tlatlaya and Luvisol; and in c) Jilotepec. 

Andosols distribution

The State of Mexico has 479 908 ha, covers the largest area and represents 20.65% of the state. They are located in the mountainous parts of the Neovolcanic Axis, Sierra Madre del Sur and in the northern mountains of the state. They are soils of forestry and agricultural vocation. The species that have productive potential in these soils are corn, peas, potatoes, broad beans, carrots, avocados, peaches, plums and raspberries (^{SIAP, 2019}). The municipalities with the largest area are: San José del Rincón, Villa de Allende, Ocuilan, Amanalco, Temascaltepec and Valle de Bravo (Table 2).

Regosols distribution

The state has 265 683 ha and represents 11.43% of the state surface. They have potential for species such as corn, wheat, beans, potatoes, barley, oats, peas, broad beans, avocados, peaches, plums, raspberries, and mangoes (^{SIAP, 2019}). The municipalities with the largest surface area are: Tlatlaya, Tejupilco, Amatepec, Sultepec and Luvianos. These have the largest surface area in the southern part of the State of Mexico, where the predominant climate is tropical (Table 2).

Luvisols distribution

The State of Mexico has 146 905 ha and covers 6.32% of the state surface. They have forestry potential and for fruit trees such as peach, guava, coffee and avocado (^{SIAP, 2019}). The municipalities with the largest area are: Jilotepec, Nicolas Romero, Villa del Carbon, Acambay and Almoloya de Alquisiras (Table 2).

Acrisols, Fluvisols and Leptosols are not very productive, with a forestry vocation, for the production of vegetables and for mining activities. Fluvisols are poorly developed and flat soils; Acrisols are mountain soils with medium texture and acid pH, Leptosols are thin soils 5 to 20 cm, slope> 20 and <2% organic matter, their vocation is mining and forestry (Table 3 and Figure 4).

Figure 4 Municipalities with the largest Acrisol surface in a) Luvianos, Fluvisol; in b) Chalco and Leptosol; and in c) Zumpahuacan. 

Acrisols distribution

The State of Mexico has 46 968 ha and covers 2.02% of the state surface. Acrisols are young, mountain soils and low fertility, if proper fertilization and conservation management is carried out, some species such as avocado, guava, coffee and peach can be planted (^{SIAP, 2019}). The municipalities with the largest Acrisols area are: Luvianos, Valle de Bravo, Villa Victoria, Temascaltepec and Ixtapan del Oro (Table 3).

Fluvisols distribution

The state has 25 216 ha and represents 1.08% of the state. They have high natural fertility, because they have medium texture, they are deep, organic matter content is medium, flat and the crops that adapt to the present climatic conditions are developed; they are located on the banks of rivers, lakes and lagoons. The municipalities with the largest area are: Chalco, Amecameca, Ixtlahuaca, Tlalmanalco and Temamatla (Table 3).

Leptosols distribution

The state has 174 968 ha and covers 7.53% of the state’s surface. The potential of Leptosols is forestry, livestock, recreational and mining; the Rendzico and Umbric subunits have potential for crops such as corn, beans, wheat, barley, oats and rice in the state (^{SIAP, 2019}). The municipalities with the largest surface area are: Zumpahuacan, Luvianos, Malinalco, Tepetlaoxtoc and Tejupilco. In these soils, a quarry is exploited and other minerals that the mining industry demands are extracted (Table 3).

The least productive soils that occur in the state are Solonchaks and Gleysols, due to their high salinity, sodicity, thick textures and irregular slopes, they are soils with little surface and very localized, where only salty grass grows in the case of the former (Table 4 and Figure 5).

Figure 5 Municipalities with the largest area of Solonchak in a) Texcoco and Gleysol; and in b) Valle de Chalco Solidaridad. 

Solonchaks distribution

The State of Mexico is covered by 39 290 ha and represents 1.69% of the state surface. These soils present characteristics of high salinity, electrical conductivity and pH, which is why it is very difficult to grow crops; the potential is for salty grass and for salt exploitation in areas where salinity is very high. The municipalities with these soils are: Texcoco, Nezahualcóyotl, Ecatepec de Morelos and Atenco (Table 4).

Gleysol distribution

The surface in the State of Mexico is 2 765 ha and it only represents 0.12% of the state’s soils. They have a low natural fertility and their vocation is forestry; only a few species can be sown with proper fertilization management. The main municipalities with Gleysols are: Valle de Chalco Solidaridad, Chalco, Temascalcingo and El Oro (Table 4).

Soil information is necessary, because the data is crucial in land use planning, management, environmental studies, erosion studies, conservation and modeling studies, which simulate crop growth and estimate yield in advance (^{Nachtergaele et al., 2000}; ^{Adhikari et al., 2014}; ^{Jafari et al., 2014}). There are very few soil studies and the scales of representation are between 5 and 25 million. FAO has soil studies at the continental level with scales of 1:25 million, 1:15 million and 1:5 million (^{FAO, 1993}; ^{FAO, 1996}; ^{FAO, 2008}).

Soil surveys in the United States of America are scale 1:7.5 to 1:15 million (^{Soil Survey Staff, 1998}). In this sense, ^{Brevik and Hartemink (2013}) use taxonomy and determine that the dominant soils in the USA are: Molisol, Alfisol, Entisol, Inceptisol, Aridisol, Ultisol and Vertisol; furthermore, ^{Lytle (2000}); ^{USDA (2000)}; conducted soil studies and designed a database (NASIS), which facilitated the acquisition, management and location of soils.

At the international level, studies similar to those of this research have been carried out, such as those of the International Center for Reference Information on Soils (CIIRS), where a database with the world's soil information was designed to publicize the studies of soils, which are carried out in different countries (^{ISRIC, 2000}). For their part, ^{Adhikari et al. (2014}) elaborate a national soil map of Denmark, which was based on the FAO-UNESCO legend, using digital soil mapping techniques, with observations of soil profiles and environmental data. This information is the basis for the planning, management, conservation and evaluation of the country’s environmental impact studies.

In the case of Mexico, there are the INEGI soil studies with the scales 1:1 000 000, 1:250 000 and 1:50 000 (^{INEGI, 1970}; ^{INEGI, 1974}) in this regard, the INEGI does not have digital cartography of no scale; for this reason, the results of this work are very important, since they present the digital cartography scale 1:50 000, where the dominant soils are Andosol, Pheozem, Vertisol, Regosol and Cambisol. For its part, the Ministry of the Environment and Natural Resources (SEMARNAT) establishes the bases for conducting and updating soil studies in Mexico (^{SEMARNAT, 1999}).

At the national level, 18 units are reported (^{INEGI, 1974}), of which 11 occur throughout the State of Mexico, the dominant soils being: Andosol, Pheozem, Regosol, Vertisol and Cambisol, which are also the most productive. ^{Sotelo et al. (2010}); ^{Sotelo et al. (2011)} carried out the updating of the soils of the State of Mexico at a scale of 1:50 000, at the level of the Rural Development District (DDR), highlighting that the soil is one of the main natural resources, on which forests are sustained. and food production. In addition, they indicate that having up-to-date information on the type of soil and its distribution facilitates the planning and classification of agricultural activities. ^{Brevik and Hartemink (2013}) mention that in the United States of America soil maps began to be generated at the beginning of the twentieth century, as a need to know the management and conservation of this resource.

Due to the soils present in the municipalities of the State of Mexico, it is recommended that the crop or species to be established be selected, taking into account the climatic conditions and the purpose of production, whether it is for self-consumption or commercial. It is not recommended to establish urban areas in municipalities that have fertile soils and with little slope. There are types of soils that have a vocation for mining exploitation and urban development, such as Leptosols. Urban developments in municipalities must be implemented on these soils and prohibit the construction of subdivisions on soils with agricultural vocation such as: Pheozem, Cambisols, Vertisols and Andosols.

Finally, the information generated is a fundamental tool in the planning of agricultural activities in the municipalities of the State of Mexico, due to the detail of the information, which is at the municipality level. The municipalities of the State of Mexico, with this study, know the types of soils they have and the surface they cover, therefore, they know if the vocation of their soils is: agricultural, livestock, forestry, urban or mining and consequently they can implement better municipal development plans.