Agroecology and its Sustainable Practices/Chapter I. Crop and cover crop associations.

Dear readers, in the previous issue we addressed some aspects related to agroecology and some sustainable practices that can be implemented in agricultural production units, all in order to seek self-sufficiency with the production of agricultural items based on techniques that are friendly to the environment.

Based on these premises, it can be said that a self-sufficient production unit, according to Alvarado (2009), is one that has diversified its production with agricultural, livestock and forestry items and, in addition, seeks to efficiently manage existing resources through correct technology or sustainable practices to improve production.

Therefore, from this issue, we will begin to describe and explain some of the sustainable practices that can be implemented in agricultural ecosystems, such as the association of crops and cover crops that is the subject of this paper.

When we speak of technification in agriculture, we are not referring only to those implemented in conventional agriculture with the use of technological packages that come with the approach of monoculture accompanied by pesticides such as herbicides, insecticides, synthetic fertilizers, among others. There are other alternatives that respect the natural processes of the ecosystem, but it seems that the large agro-input companies offer the producer only one alternative for production as if it were a recipe to produce food.

The establishment of monoculture is an erroneous practice in agro-ecosystems that has been implemented for many years. Some authors, such as Pimavesi (1982), pointed out that the practice of monoculture can damage the soil's biostructure, the plants can be more vulnerable to insect attack and climatic factors, in addition to creating a high dependency on external inputs.

On the other hand, Urbano (2008), indicates that producers who manage a single crop on their farms have stated that they observe soil fatigue because their crop yields decrease; they have associated this behavior with the repetition of the same crop on agricultural surfaces.

Because of the above, those who know the natural processes in the ecosystems have come to the conclusion that such soil fatigue as defined by the producers can be generated by some causes that are mentioned below:

- Loss of the biological activity of the soil, due to the imbalance that can exist in the processes of humification and mineralization by the impoverishment of the vegetal organic matter.

- Depletion of nutrients in the soil horizons, firstly, as mentioned above because of the impoverishment of organic matter and secondly, because of the depth of rooting that the crops may have, since some have deep, superficial or intermediate rooting, then it is logical that if you have a monoculture the nutrients are depleted from some horizons, for example in the forage surfaces when there are trees they extract nutrients from deeper horizons that could become available to plants with superficial roots.

These are some of the causes that generate low production in monocultures, therefore, the producer is forced to incorporate high quantities of synthetic inputs to increase their production.

After delving a little deeper into the consequences of managing an agricultural system based on monoculture, in this section we will address the importance of crop associations and cover crops from a livestock and agricultural perspective.

In the cattle systems the feeding is based on fodder grasses, therefore, in some surfaces it is possible to observe the sowing of monocultures of these species which can bring a nutritional imbalance in the animals, for that reason, it is necessary to use local resources like the fodder leguminous that when associating them with the grasses allows to improve the quality of the available fodders and to diminish the use of external resources.

In this sense, Amesty (2016) points out that the use of grasses and legumes in forage areas favors the conservation of biodiversity and allows for the achievement of quality forage production, in addition to the fact that it could enhance some biogeochemical cycles such as the nitrogen cycle, the leguminous species has the capacity to carry out the fixation of atmospheric nitrogen through the symbiosis carried out by the bacteria of the rhizobium genus with the roots of these plants, that is to say that there would be a contribution of nitrogen to the soil that would allow an adequate growth for the accompanying plant.

To corroborate some of the aspects mentioned above, we will share the results we obtained of raw protein in an experimental trial, where we associated a creeping legume known as fodder peanut whose scientific name is Arachis pintoi with a fodder grass of erect growth known as Guinea Tanzania whose scientific name is Megathyrsus maximus c.v. Tanzania. The results obtained at the end of the experimental period were the following:

As you can see in image 4, the percentages of raw protein in the association improved considerably in the pasture ecosystem compared to the pasture monoculture in a tropical ecosystem, it is necessary to explain to you, appreciated readers, that the adequate values of protein that a pasture must have are between 7 and 12% approximately, The results show that when a creeping legume such as Arachis pintoi is integrated, protein levels can be considerably increased, which will benefit the intake and metabolism of the cattle, which requires this nutrient for production and maintenance.

From the agricultural point of view, in plantations of palm, cacao and banana if we want to preserve the ideal conditions of the ecosystem and control the presence of weeds or arvenses, the creeping leguminous plants fulfill a fundamental function, besides it Cruz, Suarez and Ferguson (1995), indicate that also they present a high potential as for the fixation of atmospheric nitrogen through the symbiosis with bacteria of the genre Rhizobium contributing about 64% of the nitrogen element.

Using this type of species as cover crops is a technique that has a lot of potential to avoid soil degradation, as well as allowing the reduction of herbicides for weed or pest control. On the other hand, Domínguez (1990), carried out an investigation where he used several creeping leguminous plants in the establishment of the cocoa cultivation, among the sowed ones were Pueraria montana and Arachis pintoi, both showed excellent results in the control of arvenses and to maintain the humidity of the ground.

Similarly, the author points out that to establish these species can take about six months and in the first years some expenses must be made in the establishment, but after the first two years the costs are significantly reduced and the use of pesticides is reduced.

Dear readers, this was just some of the benefits we can have if we associate crops and avoid having monocultures in our agricultural ecosystems. It is also important to take into account that some shrub species can be used, but we will talk about them in the next issue.

As it could be observed, some of the quotations made are from several years ago, this was done with the intention that it should be taken into account that these alternatives have been known for many years and in spite of this, in the middle of the year 2020, there are production units that refuse to use them, because they consider that they are not as effective as synthetic products. The problems of conventional agriculture are observed in the long term with degraded soils that will cause crop production to decrease considerably.

- Alvarado, R. (2009). Proposal of the endogenous agro-ecological unit In. Experiences of Lifelong Learning (comp.), Compendium on Agroecology (pp. 59-95). Caracas: Ezequiel Zamora Agroecological School.

- Amesty, J. (2016). Poaceae and fabaceae crawling associations: a sustainable agricultural strategy for the development of fodder agriculture. in. V. Inciarte (comp.), contributions of agrotechnology to sustainable development (pp. 41-71). Maracaibo: Inver-e-Group

- Cruz, R.; Suarez, S. and Ferguson J.E. (1995). Contribution of Arachis pintoi as soil cover in some agricultural systems of Tropical America. In. P. Kerridge (comp.), Biology and agronomy of forage species of Arachis (pp. 110-116). Cali: International Center for Tropical Agriculture.

- Urbano, T. (2008). Phytotechnic Engineering of plant production. Madrid: Mundi-Prensa.