According to the Food and Agriculture Organization of the United Nations (FAO), 95 percent of our food is produced directly or indirectly in soils and chemical fertilizers are used indiscriminately to meet the needs of the world's population, which has repercussions on the environment and human health.

Some diseases associated with this practice are celiac disease, goiter, hypertension, and birth defects, as well as various types of cancer. Therefore, it is important to innovate substances that do not imply health risks and meet productivity and nutrition objectives.

To offer sustainable solutions to the problems of agriculture and food security, Martha Elena Domínguez Hernández, a member of the Department of Agricultural Sciences at FES Cuautitlán, is developing the research line "Sustainability, circularity and food security in agroecosystems", which includes the production of organic fertilizers as an agroecological practice.

The objective is to evaluate, through sustainability indicators, the effect of these fertilizers, to use them to improve agroecosystems. Therefore, in addition to producing nejayote and manure fertilizer, it conducts studies with cover crops (these plants cover soils, reducing erosion, regulating moisture content, and attracting pollinators, among other benefits).

Nejayote as fertilizer

Nejayote is the liquid waste obtained from the nixtamalization process (cooking corn with water and lime to make tortilla dough), which is discharged into the drainage system, a situation that represents a problem of water contamination and corrosion in pipes due to its high level of alkalinity.

To reuse this waste generated in large volumes, the researcher, together with María del Carmen Valderrama Bravo, an academic at the first multidisciplinary school, and Rosalba Zepeda Bautista, a researcher at the National Polytechnic Institute (IPN), designed an alternative to use it to fertilize crops, particularly corn, one of the most widely planted grasses in the country as it is fundamental in the Mexican diet and basic for the production of starches, oils, sweeteners, fuels, and various products.

The relevance of this work for the dough and tortilla industry is that compared to other developments that use less than 250 liters of nejayote, up to 150 cubic meters per hectare can be reused in each production cycle, offering a solution for the treatment of larger volumes of this agro-industrial production waste.

Multiple advantages

To make the fertilizer, Domínguez Hernández collects the nejayote and adds manure from livestock species to subject it to aerobic composting, a technique that consists of degradation with bacteria, fungi, and other microorganisms that need oxygen.

This process reduces alkalinity (the result of nixtamalization) from pH levels between 10.5 and 11 to values of 6 or 7; the liquid can then be used as an organic fertilizer and, when combined with manure, increases the content of nutrients such as nitrogen, phosphorous, potassium, calcium, magnesium, iron and boron.

This product offers multiple advantages since by pre-treating it and avoiding disposal down the drain and incorporating it into the soil for corn production, circularity is achieved, that is, closing the nutrient cycle from corn production to agro-industrial processing and, above all, avoiding water contamination.

Furthermore, "the water used in the nixtamalization process is recovered, which allows for auxiliary irrigation of between 7.5 and 15 millimeters to the crops, which favors plant growth in periods without precipitation," explained the professor.

With the use of nejayote manure fertilizer, energy efficiency is increased, since 11.8 mega Joules (MJ) are produced for each MJ consumed, while with synthetic fertilizer 9.1 MJ are generated, which translates into important benefits for the environment, such as a reduction in the emission of polluting gases and more efficient use of resources for production.

At a productive level, the researcher explained that, unlike chemical fertilizers, this fertilizer provides an increase in yields of 1.3 to 3 tons per hectare and also presents an advantage in terms of costs, since 5.9 pesos are obtained for each peso invested, while with other fertilizers a profit of 5.4 pesos is generated.

These data were recorded from the use of the nejayote-manure fertilizer on crops of producers in the state of Puebla, who observed a greater amount of grain, as well as an increase in the content of nutrients and organic matter in the soil, compared to Urea, one of the most widely used chemical fertilizers in Mexico for the production of this cereal.

"This innovation represents an alternative to reduce the use of synthetic fertilizers, which would also imply a reduction in production costs," said the academic.

Collaborations and research goals

Based on this study, collaborations are being carried out with researchers from various academic institutions, including the Instituto Tecnológico y de Estudios Superiores de Monterrey (ITESM), to obtain other agro-inputs from nejayote, such as herbicides or pesticides, and with the IPN, work is being done on the recirculation of nutrients from planting to agro-industrial processing of corn.

Currently, in collaboration with the Universidad Autónoma de Querétaro (UAQ) and the ITESM, the characterization of native varieties of corn and its derivatives is being carried out to identify properties that allow obtaining value-added products.

In this sense, Dominguez Hernandez said that in previous research, nutraceutical properties were found in compounds extracted from nejayote, corn, and tortillas, such as ferulic acid. These qualities refer to the effects that the components have on human health, for example, the reduction in the incidence of some chronic and degenerative diseases, in addition to contributing to the regulation of certain processes related to inflammation.

Another purpose of this project is to evaluate the effectiveness of nejayote manure fertilizers in other corn varieties, to migrate its experimental use to a commercial production system, for which it is in the process of patenting.