The mechanized harvesting of canola crops in Brazil is carried out using different management systems with the support of specific machines or conventional harvesters.
Canola cultivation has become yet another economic alternative to be incorporated into grain production systems in southern Brazil. Due to its characteristics, producers can use the same structure of machines available on their properties, using it in crop rotation schemes, particularly with wheat. Furthermore, the culture promotes the reduction of the inoculum of necrotrophic fungi, which compromise the quality and yield of wheat grains (such as Fusarium graminearum e Septoria nodorum) and provides opportunities for the production of vegetable oil in winter (grains harvested in Brazil contain around 38% oil).
Canola cultivation brings benefits to leguminous crops in succession. Examples include the cultivation of soybeans and beans, and grasses, such as corn, which reduce problems caused by diplody and cercosporiosis, when grown in succession to winter crops. However, in crop rotation systems, canola should preferably precede a monocotyledonous crop, as it is host to the disease known as white mold, caused by the fungus Sclerotinia sclerotiorum.
The uneven maturation and natural dehiscence of the siliques are characteristics of the crop, which determine grain losses before and during harvest. For this reason, when harvesting with direct cutting is used, at the point of natural maturity, significant losses occur. Once the harvesting operation begins, taking into account only the maturation of the first siliques, the remaining ones, which are not yet mature and suitable for harvesting, are harmed, as their grains still have a low dry matter content due to not having been completed. grain filling. On the other hand, if the harvest is carried out late (maturation of the siliques later), losses due to threshing during harvest and pre-harvest will be increased.
To harvest canola, the rural producer has three different alternatives: cutting-rowing and subsequent collection-threshing (implies two mechanized operations), chemical desiccation prior to direct harvesting, and direct cutting at the point of natural maturation.
Previous chemical desiccation (Figure 1) promotes more uniform maturation of the crop, in addition to controlling weeds that could otherwise hinder the grain harvesting process. However, by accelerating the maturation of plants, it makes them more susceptible to losses due to threshing if winds and excessive rainfall occur.
The herbicide must be applied when 60% to 75% of the grains change color (from green to brown) and the interval between spraying and harvesting must be at least one week. Taking into account climatic conditions, in the event of excessive rain or strong winds, losses may be increased compared to direct harvesting without the use of desiccants.
Chemical desiccation in pre-harvest represents an additional cost to the rural producer, but on the other hand it can be seen as an anticipation of weed management in the pre-sowing of the successor crop. With the aim of reducing the effect of desiccant herbicides on pre-harvest and harvest losses of canola grains, the market offers products with adhesion action, which can be added to the herbicide spray mixture.
Grip adhesion agent (latex + surfactant) can be used alone or combined with herbicides in pre-harvest chemical desiccation. The adhesionant works as an adhesive agent, favoring the deposition and retention of the product applied to the siliques, fixing and reducing the flow of the syrup due to the action of rain or any form of irrigation over the crop.
In this type of harvest, it must be started as soon as the water content of the grains reaches the appropriate value (maximum 18%), that is, the operation must be carried out within a maximum of 14 days after spraying the herbicide. Another indicator of the harvest point is that the crop is ready to be harvested, when the majority of the siliques are dry and when shaken they produce a sound similar to a “rattle”.
Harvest management with cutting and raking was carried out for a long time when 30% to 40% of the grains on the main branch (apex) of the plant began to change their color. Based on recent research, the recommended cutting-winding point is when 60% of the grains change from green to brown. As the fertilization, grain filling and maturation processes begin at the base of the plant and progress to the apex of the branches, the grains in the siliques located at the base mature and change color before the grains located in the siliques at the apex.
The ideal point for cutting and raking is when the silique grains located at the tip of the productive branches are still green, but firm enough and do not break when rolled between the thumb and index finger. Most of the time, canola plants will be at the right point for mowing and raking for a period of just three to five days. After cutting and raking, the crop dries and will be ready for harvest in approximately eight days in dry weather, and up to 15 days in periods with greater humidity, due to the occurrence of rain.
So, taking an adult canola plant as an example, and dividing it into three parts (thirds: lower, middle and upper), the plant will be suitable for cutting-rowing when: the upper third presents the majority of green, firm grains with a moisture content of 40% to 45%; and the middle third has 90% of firm, green grains and 10% of yellow to brown grains, with 30% to 40% moisture; the lower third presents grains with more advanced maturation, yellow to gray/black in color, and with 20% to 30% moisture.
Harvesting canola through the cutting-rowing process aims to reduce the risks generated by the occurrence of greenish grains and contributes to the grain quality that is required to obtain the best classifications and prices. To this end, it is necessary to inspect the cultivation field every two or three days so that the color change in the first siliques present in the lower part of the main stem can be observed (twenty to thirty days after the end of flowering). ).
In addition to the consequent reduction in grain losses in the siliques of the lower parts of the plants, and the elimination of weeds in the straw mass, the advantages presented by cutting-rowing are the more uniform maturation of the grains, seven to ten days before harvesting. harvest with direct cutting at the point of natural maturation, with less exposure of the plants to heavy rain, hail and wind, in the period before harvest, where the grain threshing process is more accentuated.
Mowing and raking can be carried out with a number of special header varieties. Currently, platforms for cutting and raking adaptable to self-propelled harvesters are manufactured in the South of Brazil. These use a conveyor belt that operates perpendicular to the direction of travel of the harvester and concentrates the plants in a windrow.
When using cutting-rowing platforms, the cutting knife must begin to act just below the lateral branches present on the main stem. The raked canola must be ready for harvest when the moisture content of the grains approaches 10%, or less, which is verified between 5 and 14 days after cutting and raking.
The harvesting of plants that have been raked (collecting the windrows) must preferably be carried out using a platform equipped with a pick-up mechanism with a conveyor belt, which collects and guides the plants to the harvester's threshing mechanism. After a certain number of days, which will be due to the temperatures and environmental humidity since cutting and raking, the water content of the grains will be very close to 10%, which is the reference water content indicated for commercialization and also the next for short term storage which is around 9 to 10%.
The collection of windrows can also be carried out using self-propelled harvesters, equipped with special platforms for collecting rowed crops or with machines equipped with platforms for harvesting winter cereals and soybeans.
When harvesting occurs on a winter cereal and soybean harvesting platform, the weeds present in the crop and the remaining canola stalks, which are still green, are cut and collected, causing an increase in the water content of the harvested grains. This also causes a reduction in the leaf area of the remaining weeds, impairing the absorption of herbicides used in the management of these plants prior to the sowing of the subsequent crop. The most promising solution is the collection of windrows using the collecting platform, as this has the main advantage of not collecting weeds and green canola stems, which provides drier and cleaner grains.
For harvesting with direct cutting at the point of natural maturity, the predominant color of the grains is the best indicator. The color of the plants themselves and the stems are bad indicators, as the grains dry before the stems and stems of the plants. For this type of harvest, when physiological maturity is reached, the water content of the grains must be determined daily, in order to identify the best time to harvest, as on hot and dry days, drying and dehiscence occur. of grains occurs more quickly, thus increasing threshing losses.
This harvesting method must begin when the water content of the grains is at a maximum of 18%. From this point on, if rain and wind are forecast, the canola must be harvested and the grains go through the pre-cleaning and drying process as quickly as possible. The first areas to be harvested should be those free of weeds, to reduce the spread of seeds from these invaders.
When harvesting begins, and the water content in the grains is above 10%, it is preferable to harvest during the hottest hours of the day, as the high volume of green mass that needs to pass through the harvester makes it more difficult to separate the grains. When harvesting is carried out with low grain and environmental humidity, it is preferable to avoid the hottest and driest hours of the day, to reduce losses due to threshing on the platform.
Among the platforms used for grain harvesting found on the national market, the “Draper” platform stands out, in which the feeding auger is replaced by a pair of transverse and one longitudinal conveyors. This provides greater uniformity in the harvesters' feeding and increases the machines' harvesting capacity by between 15% and 20%. With the use of these platforms in the harvesting of canola crops, a considerable reduction in losses is achieved, due to their geometry, their adjustments, and the reduction of friction between the plants and the moving parts of the machine.
In experiments by the authors in 2014, in the municipality of Passo Fundo, RS, four harvest management systems were used, with or without the application of the Grip adhesive, namely: M1: cutting-rowing; M2: chemical desiccation with diquat; M3: chemical desiccation with ammonium glufosinate; M4: direct cut at natural maturity (control). The dose used for both herbicides was 2,0 L/ha and for the Grip® adhesive, 1,0 L/ha.
The accumulation of rain between the previous chemical desiccation until harvesting with direct cutting at the point of natural maturation and the collection of windrows was 49 mm. The rainfall that occurred between the previous chemical desiccation and the harvesting of the desiccated plants totaled 47 mm. There will be an increase in precipitation of 2 mm until harvesting with direct cutting at the point of natural maturity and collection of windrows.
It was observed that canola harvesting management differed from each other. Previous chemical desiccation with the use of the herbicides diquat and glufosinate ammonium and cutting-rowing showed lower pre-harvest and harvest losses than the control. Previous chemical desiccation with ammonium glufosinate + Grip and subsequent harvesting with direct cutting presents lower pre-harvest and harvest losses when compared to other management methods (Table 1).
The use of Grip adhesion agent reduced pre-harvest and harvest losses of the canola crop in harvesting practices in which prior chemical desiccation was carried out, in relation to those operations where the adhesion agent was not applied (Table 1). In these cases, the adhesion agent was mixed with the herbicides diquat or glufosinate ammonium in the application mixture, which was sprayed on the plants. The reduction in pre-harvest and grain harvest losses where the adhesion agent was used confirms the information provided by the manufacturer, that Grip allows better deposition and permanence of agricultural pesticides on the leaf, protecting herbicides from contact action, from losses due to runoff and washing due to rain, significantly reducing grain losses due to threshing.
In relation to grain yield, previous chemical desiccation with ammonium glufosinate, with or without the application of the Grip adhesion agent, presented the best results when compared to the other harvest management adopted (Table 2).
The practice of cutting and raking the plants accelerated and standardized the drying of grains, reducing losses due to threshing and increasing grain yield, even with the occurrence of rain between the cutting and raking and the collection of the climatic windrows, through formation of a compacted mass, half the height of plants that remain standing in conventional crops, which reduces the impact of raindrops.
Chemical desiccation in pre-harvest, at the end of the canola cycle, facilitated harvest management, as it favored drying and leaf fall, in addition to the rapid reduction of water loss in the grains and greater uniformity in the period close to the harvesting point. physiological maturity, reducing losses due to threshing and consequently generating an increase in grain yield.
The use of Grip adhesive reduced harvest losses, increasing grain yield, when compared to treatments that did not receive its application, thus demonstrating the efficiency of using herbicides in conjunction with Grip adhesive in pre-harvest chemical desiccation. of canola contribute to better crop performance.
Harvest management with cutting-rowing or prior chemical desiccation are alternatives that significantly reduce harvest losses and allow for higher grain yields in canola.
Carrying out cutting and windrowing with or without the application of the Grip adhesion agent, at the indicated stage, when 60% of the grains at the top of the plant change from green to brown, reduces pre-harvest and harvest losses and allows for higher yields. of grains, when compared to harvesting management with prior chemical desiccation and harvesting with direct cutting at natural maturity. Cutting-raking also provides a greater reduction in the water content of the harvested grains and a more uniform drying of them, thus reducing drying costs.
Carlos Augusto Pizolotto, Walter Boller, Nadia Canali Lângaro, Gilberto Omar Tomm, UPF
Article published in issue 160 of Cultivar Máquinas.
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