Southwest of Paraná has a rare study on soils with 36 years of data

One of the main difficulties in Brazil when carrying out studies involving soils is the lack of data from a long period of time to draw precise conclusions. With the difficulties in maintaining scientific initiatives in the country, most studies rely on data from a short period of time. On the contrary, a study carried out in Pato Branco, in the Southwest of Paraná, is one of the few in the national territory with data collected in the last 36 years.

Researcher and agronomist Ademir Calegari conducted the study until 2014, when he retired, even before the emergence of the AgroPesquisa Network. At that time, researcher Lutécia Beatriz dos Santos Canalli took over data collection. Later, in 2017, the study was linked to a subproject of the Paraná Network of AgroResearch and Applied Training (Rede AgroParaná) – a partnership between SENAR-PR, Fundação Araucária and the State Secretariat for Science and Technology.

Thus, the decades-long study became the subproject “Long-term effects of soil management systems and cover crops on soil attributes and crop productivity”. Despite this change, which represents resources for the progress of the project, the principle remains the same. The objective of the research is to compare two soil management systems: direct planting and conventional planting. There are 12 different soil cover treatments in winter, made up of different cover plants, grown alone or in intercropping, such as vetch, triticale, ryegrass, among others.

“In this experiment, the physical and chemical parameters of the soil are evaluated to analyze the evolution of soil fertility. Fractionation of soil organic matter is also carried out, to obtain the labile fraction [younger organic matter, coming from fresh vegetable residues – straw] and the fraction associated with soil minerals”, details Lutécia Beatriz dos Santos Canalli.

According to the researcher, the separation of organic matter into the fractions that compose it is an extremely important process in this type of work. “In this way, we can define the contribution of waste [straw] input to the soil through green manures/cover crops and crop residue to increase organic matter. The greater the input of waste [mulch], the greater the increase in organic matter [carbon] in the soil over time”, teaches Lutécia.

Considering the results of the last three decades, which have already generated numerous doctoral, master's and course completion works (TCCs), the data obtained confirm the superiority of the direct planting conservation system in relation to conventional planting. This applies to physical and chemical attributes of the soil and also to crop productivity.

“Direct planting also proved to be more efficient in recovering and maintaining soil organic matter. The results in relation to cover crops vary between years, but fallow treatments, especially clean fallow [soil left completely uncovered], always show the worst results”, he warns.

To overcome the challenge faced by producers who are not always able to give up soybeans, as it is a highly profitable crop, the researcher recommends winter green manure consortiums. “Even if there is soybeans every year, when a consortium of different materials enters in the interim periods, a great diversity is brought into the farming environment. Thus, it improves soil fertility, reduces fertilizer use costs, creates a more favorable environment for natural enemies and less favorable to diseases and pests, leaves a large mass of straw for the direct planting of crops of commercial interest, in addition to other advantages”, he points out.