The search for increased productivity, combined with actions aimed at sustainability and soil conservation, has been the focus of cultivation techniques in agriculture. The use of conventional tillage using disc plows and heavy harrows causes soil losses due to erosion and reduced infiltration capacity, in addition to the compaction of the lower layers, known as harrow footing.
Given this, the Direct Planting System (SPD) has been adopted as an alternative for soil preservation. It is worth highlighting the difference between direct planting and SPD. The first uses only two principles of conservation agriculture, sowing without prior soil mobilization and maintaining vegetation cover on the surface. SPD consists of direct planting associated with crop rotation, runoff management and all other practices that aim to maintain the soil's productive capacity.
According to Embrapa, 32 million hectares are cultivated in direct planting in Brazil, however, among these values, only 2,7 million hectares completely follow the SPD. The state of Paraná stands out, which according to Iapar (Agronomic Institute of Paraná) has around 5,7 million hectares in direct planting, which represents more than 80% of its arable area.
The advantages of SPD are mainly related to the conservation of soil fertility, through erosion control. According to Embrapa, up to 100 million tons of soil are no longer eroded annually, with 18 billion cubic meters of water kept in the soil. The use of vegetation cover reduces the impact of rain and seals the soil surface, allowing water to infiltrate, helping to control erosion processes. Therefore, before sowing, it is necessary to carry out desiccation, keeping the straw as protection and also as a source of nitrogen for the crop to be established.
The presence of plant remains is essential in the SPD, therefore, implements such as plows and harrows, typical of the conventional system, are not used. Only furrowing implements are used for the purpose of uncompacting lower layers. To this end, scarifiers are the most used, working at a depth of up to 30cm, with less soil mobilization. With the reduction in the use of machinery and equipment, diesel oil consumption can be saved by up to 72% (Salton, 1998).
Crop rotation is carried out by alternating between different species in the same area. This process aims to help decompact the soil, reduce the proliferation of agents that cause phytosanitary problems, and reduce the incidence of weeds and pests. Preference should be given to crops with slow decomposition, remaining on the soil surface for longer.
Other practices that complement SPD conservation principles are terracing and level cultivation. According to Denardin et al (2005), terracing aims to control soil erosion on slopes, when the intensity of rainfall exceeds the rate of water infiltration into the soil. To this end, a structure is built across the direction of the steepest slope of the land, consisting of a dike and a channel that retain and allow water to infiltrate or cause water to drain slowly, losing strength and reducing erosion. In the practice of level cultivation, the sowing lines follow the contour lines, that is, planting is carried out according to the unevenness of the land, unlike terracing, in which the unevenness is artificial. Thus, planting lines act as obstacles to reduce the speed of water flow, increasing the rate of infiltration into the soil.
Taking into account that there is no soil preparation prior to sowing, the SPD required the creation of specific seeders, which require a more robust structure and greater weight to apply the necessary force in order to cut cultural residues and the opening of the grooves.
Currently, the Brazilian market, according to Schlosser et al (2016), has 19 companies that assemble and/or manufacture seeders aimed at direct planting, totaling 743 models available, with emphasis on Rio Grande do Sul, with 548 models manufactured (73,76 .XNUMX%).
Seeders for direct planting can be classified into three main types, continuous flow, precision and multiple. Continuous flow ones work with small seeds (wheat, oats, rice), which are continuously deposited in the furrow. Precision seeders distribute seeds in a predetermined number every meter at homogeneous distances. Multiple seeders can be adapted for both continuous and precision flow. Nowadays, models with positive pressure dosing (blowing) are on the market, both for seeds and fertilizers, something relatively innovative in Brazil. In addition, models that promise to dose efficiently at high sowing speeds.
The difference between seeder models is not only linked to their constituent mechanisms, but also to the working width, which will depend on the number of rows. Therefore, larger areas will require seeders with greater working width, thus increasing operational capacity. When purchasing, you must pay attention to the power required by the seeder, which must be in accordance with the power of the tractor.
Without a doubt, the adoption of the SPD accelerated the development of Brazilian agriculture, contributing to the preservation of the soil, the recovery of degraded areas and the reduction of the window between harvesting and sowing, allowing compliance with the agricultural calendar.
In this context, an increase in cultivation areas under this system is projected, especially when talking about strategies to combat global warming, as low soil mobilization, maintenance of vegetation cover and crop rotation increase carbon retention. on the ground. According to the CGE ABC/RS (State Management Committee for Low Carbon Emission Agriculture), by 2020 it is estimated that eight million hectares of SPD will expand in Brazil.
Proper SPD planning is directly related to the success of the system, as well as the conservation and improvement of soil fertility, characterizing itself as a long-term investment for the producer, with a guaranteed return if well implemented.
This technique emerged in 1950 in England, in research with the Paraquat molecule, carried out by Imperial Chemical Industries (ICI), today called Syngenta. It was later taken to the United States, where the research had greater significance, as in 1973 there were already 430 thousand hectares under direct planting in the USA and Canada (Carvalo; Freitas, 2008).
In Brazil, Herbert Bartz, from the city of Rolândia (PR), introduced SPD at the producer level. Concerned about soil degradation on his property due to flooding, in 1972 Bartz traveled to England to the ICI experimental station, where producers were having good results with direct planting. Leaving England, he arrived in the USA to learn about the advances that producer Harry Young was making with direct planting. An Allis-Chalmers seeder was used on the property, which Bartz later imported from the same manufacturer to start planting soybeans. The positive results in productivity, soil conservation and, mainly, related to labor savings with machinery were soon noticed, causing more producers in the region to adopt the new technique.
It is also worth mentioning the introduction of SPD in Brazil, Manoel Henrique “Nonô” Pereira, who in September 1976 used the Rotacaster model seeder, coming from England, adapting a sprayer between the rows. However, with the high soil mobilization caused by Rotacaster and the inefficiency of herbicides, wheat germination occurred. Therefore, in December of the same year, Nonô sowed soybeans on rye straw using the PS6 model seeder from the Semeato brand, achieving better results. He also adapted a tool holder bar to install a cutting disc in front of the seeder to cut straw.
In 1979, the TDA 220 model from Semeato was launched, the first direct planting seeder developed in Brazil. It consisted of a continuous flow type doser and triple disc type furrowers. Later, the brand launched the TDA 300 model, which featured articulated wheelsets, more suitable for uneven terrain and floodplain areas.
At the beginning of the implementation of the SPD in Brazil, many producers were unable to acquire seeders for direct planting due to their high cost, therefore making adaptations to conventional seeders. Cutting discs, depth control wheels, soil pressing wheels and fertilizer placement using narrow knives were added. In small seed seeders, popcorn makers were placed to sow large seeds, a practice that resulted in the multi-seeders we know today.
Sueli Kullmann
Vanessa Bassin Cogo
Vilnei de Oliveira Dias
Lamap/Unipampa Alegrete
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