Introduction

The commercial release of GM crops worldwide occur in 1996. Currently, 175 million hectares are cultivated in 27 countries with this technology. Mexico ranks 17th in the adoption of biotech crops with a planted area of 100 000 hectares, mainly from soybeans and insect- resistant cotton and tolerant to the herbicide glyphosate (^{James, 2010}).

The genetically modified plants had their first formal foray into the Mexican countryside in 1988, which was submitted to the government the first application for import and release into insect resistant in tomato field. The first national policy framework for the regulation of genetically modified organisms (GMOs) was established in 1995 by NOM-056-FITO-1995. Since 2005, the Law on Biosafety of Genetically Modified Organisms (LBOGM) constitutes the regulatory framework that allows activities contained use, experimental release, release within a pilot, commercial release, marketing, import and export of GMOs in Mexico program (^{DOF, 2005}).

With the implementation of the regulation on GMOs, the Secretariat of Agriculture, Livestock, Rural Development, Fisheries and Food (SAGARPA), through the National Health Service, Food Safety and Quality (SENASICA) has granted permits for commercial release genetically modified cotton and soybeans; while in the case of maize regulatory progress it has been limited.

One of the strong reasons on which the restriction is based, is the potential environmental risks that cause introgression of genes to local varieties by the adoption of genetically modified maize in a center of origin country of the species (^{Massieu, 2005}; ^{Mercer and Waingwright, 2008}); and secondly, the uncertainty of whether the adoption will represent adaptation strategies to climate change and opportunities to improve maize production in Mexico (^{Mercer et al., 2012}). The area cultivated with genetically modified crops in Mexico, specifically the soybean and cotton crops has not increased in recent years (^{James, 2010}); however, commercial use in production systems in Mexico is fairly widespread, mainly technological, agronomic and economic reasons that have enabled the production units making production processes more efficient.

Success in these crops has boosted private sector interest in the release of genetically modified corn as an alternative technology in agricultural production. However, even if it is argued that it is important to improve the competitiveness of commercial corn farmers there are no studies that show the agronomic and economic reasons that justify their adoption should relax legal restrictions option. Therefore this paper aims to provide information on the agronomic and economic reasons that have corn farmers in different production systems, to use GMOs in Mexico. The central hypothesis is that the technical-productive complex problem that involves corn production; and the diversity of existing production systems in Mexico are restrictive factors limiting the attractiveness of the adoption of genetically modified seeds as an appropriate technology.

Materials and methods

To characterize and define the representative production units (URP) panels’ producers were formed as a means of obtaining direct information, considering producers and experts in the management of production systems in corn and soybeans. In 2013 they were analyzed production systems conventional and genetically modified soybeans. During 2014 and 2015 were studied thirteen production systems conventional maize distributed in the states of Chiapas, Oaxaca, Campeche Durango and Sinaloa (Table 1).

Table 1. Panels and main characteristics of representative production units analyzed soybean and corn in Mexico. 

They settled panels for both crops producers, they were built representative production units, representing the same production system more important in every state analyzed. In this work the URP is considered as one that without representing a specific producer, virtually defines the activities and decisions of producers within it. At the same time, it represents a representative production unit of a scale and the particular production system of a region. Thus, considering some adjustments to the variables used by ^{Bank et al. (1981)} in the characterization of maize production systems in Mexico and in order to have greater coverage analysis of existing production systems; the URP defined, by: i) the technology level, characterized by the use of machinery; ii) the conditions of availability of water used in production; and iii) the destination of production.

The results of each panel in different URP were analyzed in a structure of production costs; comparing, in the case of conventional and genetically modified soy possible agronomic and economic advantages associated with the use of genetically modified seed. Likewise, in URP corn they were analyzed the cost structure of the main agronomic practices performed during production. From this and considering that the seeds of genetically modified maize in Mexico have recently released mainly insect resistance characteristics (Coleopteran and Lepidoptera) and tolerance to the herbicide glyphosate or a combination of both (Commission, 2012); these characteristics were associated with potential agronomic and economic advantages that would result from the adoption of genetically modified corn seeds in the URP analyzed.

To assess the possible agronomic benefits and economic impact on corn production were analyzed in each URP: i) mechanization level; ii) proportion of investment in the control of pests and diseases; iii) proportion of investment in weed control; iv) potential for reducing labor in controlling pests and diseases; v) reduction potential labor weed control; vi) potential for reducing agricultural work in controlling pests and diseases; and vii) reduction potential of farming in weed control, that could represent the use of transgenic seeds from this analysis.

Results and discussion

The analysis of the results obtained in this research will be presented in different sections for crops of soybeans and corn. In the first case a referential analysis of any comparative way between these species and the fundamental purpose of this is to identify, if there is, those agronomic and economic factors that have affected the adoption of seeds of genetically modified soybeans and from these, to assess whether these factors may be at some agronomically and economically favorable level for the adoption of genetically modified maize, taking into account the characteristics and technological conditions of different production systems.

URP genetically modified soy

The analysis resulting from the structure of production costs obtained panels producers in the URP of genetically modified soybean and its conventional counterpart in both production scales (30 to 100 hectares), show that when genetically engineered seed is used modified in the production process total production costs associated with agricultural management on both scales are lower than those invested in conventional soybeans (Table 2). That is, the use of genetically modified seed decreases production costs particularly in practicing weed control, representing 36.2% decreased and 23.8%, respectively compared to the conventional counterpart in production systems analyzed.

Table 2. Production costs in URP conventional and genetically modified soy in Mexico. 

These differences in production costs found in weed control that represent an economic advantage and that are directly associated with the characteristics of tolerance to the herbicide glyphosate conferred on the seeds of genetically modified soy is the success that favors the adoption of genetically technology modified in the URP, and lies directly on the value it generates in terms of reducing production costs (^{Cotec, 2007}).

These data reaffirm reported by some publications (^{Nelson and Bullock, 2003}; ^{Commission, 2012}). However, as this paper will focus the analysis on the URP corn and commercial adoption of genetically modified seeds not a fact in Mexico, it is necessary to identify those reasons associated with the agronomic and economic success of the adoption of soy genetically modified. Thus, the first reason that favors the adoption genetically modified soy in the URP, is the importance of the problem in economic terms represents weed control in conventional production system (Table 2). Second, the direct relationship between agronomic traits conferred on genetically modified seeds and the problem that seeks to meet with technology and; third, the agronomic benefits resulting from the adoption of technology impacts on favorable economic terms for the production system.

These three factors are observable in soybean production systems in Mexico; therefore, the success of the adoption of genetically modified soybean explains both economically and agronomical (Table 2). On the one hand, the costs of higher production obtained in conventional soybeans are due to selective herbicides used in weed control are more expensive compared to glyphosate that is used in genetically modified soybeans. This higher cost, also adds to the application of a greater number of agricultural activities crop for weed control, it turns out to be more difficult in the conventional system, unlike genetically modified addition to reducing production costs, they represent less investment of labor and cultivation work in the URP of this type.

Corn of URP

Economic importance of controlling pests, diseases and weeds in corn URP

The structure of production costs in the URP corn in Mexico is defined by the production system, which implicitly represents a technological condition. For this reason, the structure of production costs are highly variable for each URP analyzed. However,c ertain specific trends can be seen in the resource management for some systems (^{Montañez and Warman, 1985}). In this regard, if the first factor related to the allocation of financial resources for the realization of agronomic practices to control pests and weeds, associated with the seeds of genetically modified maize is analyzed, it is observed that only two of thirteen URP corn (CHMZT02 and DGMZT05), production costs in weed control are those that represent a greater investment in the overall cost structure with 35.5 and 23%, respectively (Table 3 and 5).

Table 3. Structure of production costs in representative production units’ corn in the state of Chiapas and percentage share of investment in agronomic practices. 

Table 4. Structure of production costs in representative production units’ corn in the state of Oaxaca and percentage share of investment in agronomic practices. 

Table 5. Structure of production costs in representative production units’ corn in the states of Sinaloa, Durango and Campeche and percentage share of investment in agronomic practices 

The level of economic investment in controlling pests and weeds is also variable in irrigated production systems and temporary. The proportion of investment in weed control in URP produced under rainfed conditions is higher than in irrigation, while the control of pests and diseases is more important in the latter URP. This shows that unlike conventional soybeans in the URP corn investments economic intended to control pests, diseases and weeds are not more important than other agronomic practices such as the fertilization and harvest, which in some cases they can reach up to 39.4 and 35.5%, respectively (Table 3, 4 and 5).

Conclusions

Adoption potential seeds of genetically modified maize in Mexico, under current technological conditions agronomic practices in different production systems of corn analyzed, do not represent favorable economic and agronomic benef its for URP by adopting develop transgenic seeds.

A higher level of technology and equipment in production systems does not guarantee greater economic and agronomic benefits that may be associated with the adoption of genetically modified seeds. In fact, they prove to be more suitable in production systems with an advanced technological level, where more labor and reducing agricultural labor is employed may be favored by the traits conferred on genetically modified seeds in the control of pests, diseases and weeds.

The characteristics conferred on genetically modified seeds can contribute to economic solve and agronomically production problems, as long as they are associated and represent an important economic share of investment in production and are tailored to the needs of the production system and derive it agronomic advantages that reduce production costs as in the case of genetically modified soybean.