Energy in agricultural systems

Energy is the engine that drives life on our planet and agriculture is no exception.From the photosynthesis that powers plants to the machinery that facilitates harvesting, energy plays a fundamental role in every stage of the productive process. According to Lazarus (2011), all forms of energy can be converted into other forms by certain processes. In the transformation process, one form of energy can be lost or gained, but the total sum remains constant. Therefore, energy is neither created nor destroyed, it is only transformed, a concept that is known as the principle of conservation of energy.

Bioenergetics studies the processes by which living cells use, store and release energy, the main component is the transformation of energy from one form to another, all cells transform energy, for example, Salsbury and Ross, (1992), mention that plant cells use sunlight to obtain carbohydrates (sugars and starch) from biochemical mechanisms, through the process known as photosynthesis, solar energy is converted into chemical reserve energy (biomass). If these carbohydrates are ingested by an animal, their breakdown occurs and their chemical energy is transformed into movement, body heat or new chemical bonds.

In that sense, in this whole series of transformations, there is a loss of energy to the environment, usually in the form of heat, which cannot generate useful work, because it has been released and over time tends to a greater disorder so its entropy increases. The constant influx of solar energy is necessary for the survival of all plants and animals on earth.

Diversified agroecological systems can generate productions with high biological, productive, economic, energy and environmental efficiency, conserving natural resources, without degrading soils, reducing environmental pollution and providing healthy and abundant food for the population. Awareness has been gained of the need to reduce dependence on external inputs and the negative environmental impact of conventional practices. Therefore, more and more sustainable practices are being promoted in the world, being agroecological diversification the most practiced due to the environmental services it provides and its low cost in inputs.

One of these services is the high efficiency it presents in the use of biological factors in the area in question such as the replenishment of trophic activity, replenishing and increasing the level of microorganisms in the active layers of the soil, thereby improving the exchange of it with plants by raising the quality and quantity of nutrients used by them; another is the pest control that occurs through a natural balance by maintaining a high biological diversity which provides greater stability to the system. Integrated livestock–agriculture systems based on agroecological principles have shown that the productivity of the land is higher than that obtained in intensive systems. This is explained by the fact that, as there is a greater richness of species, the earth is kept permanently occupied both with polycultures that offer diverse productions all year round, as well as with animals that also offer stable productions all year round. This situation leads to an increase in the land use index and therefore the productivity of the same by increasing the yields of productions per unit of exploited area.

The energy efficiency indicators should constitute the fundamental tool to design and plan agricultural management strategies, it is key in these agroecosystems to know how to use cultural energy efficiently, leading this to obtaining greater efficiency in the transformation of ecological energy into biomass. According to Gliessman (2006), the energy available for agroecosystems is supplied from two fundamental sources: ecological energy and cultural energy, the first being the one that is taken directly from the sun and is fundamental for the production of biomass through processes of photosynthetic organisms, and cultural is supplied by men in order to optimize the production of this biomass, in turn, cultural energy is divided into biological and industrial, the first is provided by human and animal labor, while the other is the product of non-biological sources such as electricity, fossil fuels and others. The main aspect in the functioning of an agroecosystem is based on how to achieve a greater use of cultural energy in order to transform ecological energy into biomass more efficiently, since the energy supplied by the sun is the sap of agroecosystems and constantly flows in only one direction.

Dear readers, systems with a high level of production are generally based on intensive models that have very low energy efficiency due to the high level of use of energy inputs mainly fuels and others, it is true that production rises, but this is not sustained, due to the cyclical nature of this type of model, bringing as a consequence instability in the efficiency with which energy is used. In polycultures, although the level of production in lower, being varied, allows to maintain the entire period the food supply with less employment of the labor force and therefore the productivity is sustained, this implies that there is a greater richness of species, greater diversity of production and trees, therefore greater energy efficiency.

Something similar happens if you have a large scale in the amount of animals, here the external inputs (concentrates) are used in large proportion for feeding them and as it is known this type of production is energy inefficient since they demand a large amount of energy in relation to the one they deliver. To solve this situation from the energy point of view, it is necessary to integrate this type of production with agricultural ones, achieving a strong interaction between these elements of the system. This results in an increase in agroecological indicators, including energy efficiency.