Engineer achieves promising results by implementing alternative and sustainable practices on a farm in São Paulo
The technological advances incorporated into agriculture following the so-called “Green Revolution” have enabled the expansion of agricultural frontiers and a significant increase in agricultural production in the world, but at the cost of serious socio-environmental consequences. Their practices cause deforestation, drastic changes in hydrological cycles, continuous degradation of soil and its contamination – such as water and food –, global warming, loss of biodiversity, among others.
The State of the Art report on Soil Resources in the World (FAO; ITPS, 2015) points out that near 33% of the soil in world are degraded. Erosion, salinization, compaction, acidification and contamination are among the main problems. Erosion alone eliminates between 25 and 40 billion tons of soil per year, significantly reducing crop productivity and the ability to store carbon, nutrients and water.
Natural processes do not renew or restore soil fertility at the rate of degradation resulting from the conventional agricultural model, resulting in an increase in less fertile soils every day. Added to this is the damage caused to human health by the growing need to use chemical fertilizers and the use of increasingly powerful pesticides to combat progressively resistant pests. All these problems have driven producers themselves to look for alternatives to establish a more sustainable agricultural system.
It is in this direction that forestry engineer Maria Fernanda Magioni Marçal works, who has dedicated herself to studying the recovery and restoration of degraded ecosystems and to work that seeks alternatives to the conventional model of agricultural production through the use of so-called agroforestry systems. As the name suggests, these are agricultural and/or livestock production systems that incorporate the arboreal component in their design and propose management based on the succession of species, following the example of nature. Among the trees, vegetables, cassava, bananas and many other species can be grown, planted and harvested in much shorter periods of time than required for cutting wood. In this way, says Maria Fernanda, “the system does not remain inert over time, but becomes periodically and constantly productive, constituting a source of food and income while the trees develop. The idea is that the soil becomes richer over the years, as management practices seek to optimize resources, just as happens in nature.”
Unlike what occurs in monoculture, the diversification of species provides a more balanced system and the development of healthier plants that are less susceptible to pests and diseases, informs the author. In view of this, agroforestry systems have been used as an alternative technology for the production of healthy foods. Although the results are positive in the recovery of degraded systems, the challenge of using them in larger areas remains.
In her most recent work, which gave rise to her master's thesis supervised by professor Zigomar Menezes de Souza, from the Faculty of Agricultural Engineering (Feagri) at Unicamp, the researcher deals with “Soil quality in agroforestry systems developed for large-scale production scale". The researcher evaluates physical, chemical attributes and carbon and nitrogen stocks in soils in agroforestry systems implemented at Fazenda da Toca, in Itirapina, SP. The great difference of this initiative is to propose systems that can be replicated on a large scale, as they use machines and equipment adapted and developed to meet new management needs.
How it all began
Given the difficulty of eradicating the Greening of organic orchards, Fazenda da Toca adopted agroforestry planting systems in order to invest in the well-being of citrus plants so that they could express greater resistance against the symptoms of the disease. The diversification of the system could also make it difficult for the psyllid to recognize citrus plants.
Given the good results, agroforestry systems on the farm were expanded to other areas on an experimental basis, proposing designs with potential for application on a larger scale. In an area formed by Quartzarenic Neossolo, essentially sandy soil, two different systems were implemented focusing on the recovery of degraded areas, one designed for fruit production and the other for livestock farming. In both cases, windrows were prepared, which are planting strips 1,2 meters wide, separated by rows 5 meters apart. In the case of livestock farming, which requires a more open area for pasture, every three windrows separated by 5 m, a 12 m strip was left for the cattle, followed by three more windrows, and so on. The windrows are covered by a thick layer of plant residues from the management of grasses, shrubs and trees on site, which, in addition to providing nutrients, provide other benefits such as controlling humidity, temperature and promoting the activity of soil microorganisms. Even grass, the great villain of conventional crops, is considered a strong ally for biomass production.
When the researcher began to evaluate the areas at Fazenda da Toca, agroforestry systems had already been implemented two or three years ago and the changes caused to the soil were in the process of development. Cattle had not yet been introduced and productive species were growing. In the pasture areas, intended in the future for cattle, and between the lines, the grass was periodically mowed to serve as cover in the windrows, as well as the material from the pruning of the planted trees and shrubs.
Results
For comparative purposes, the researcher analyzed soil samples from an area of degraded pasture and a forest fragment undergoing natural regeneration for around 35 years, in addition to agroforestry systems. The idea was to know, based on physical and chemical parameters, to what extent the intervention effectively brought results, which served the interests of the farm owners and also academic studies.
The results revealed that agroforestry systems developed for large-scale production contribute to improving the physical and chemical attributes of the soil, which are reflected in its quality, especially in the most superficial layers of the planting rows, far surpassing the natural regeneration process, although no influence has yet been noticed between the lines.
Regarding these results, Maria Fernanda adds: “What can be said now is that the soil inside the windrows is already different from the other sampled points”. As this is a developing system, it is not yet possible to analyze productivity and it is also impossible to predict what will happen in the area reserved for livestock. For now, it has been proven that the soil is improving, but its future behavior is a question to be studied with cattle using pasture and plants in full production. It still remains to evaluate the impact of mechanization between the lines, she explains.
The study also points out that the implementation of agroforestry systems, that is, the change in land use at Fazenda da Toca was considered one of the main factors for the increase in its carbon stock, which also indicates the benefits of this practice.