Harvesting and preparing the soil for irrigated rice cultivation

The definition of harvesting circuits and the economic preparation of the soil for irrigated rice cultivation are valuable practices for producers who always seek to maximize profitability, without requiring extra investments.

The state of Rio Grande do Sul stands out as the largest national producer of irrigated rice, being responsible for more than 61% of the total produced in Brazil, with an area of ​​1,1 million hectares cultivated. The western border region stands out for being the largest producing region in the state, responsible for 333.680ha (Sosbai, 2014).

Irrigated rice cultivation, when cultivated on uneven surfaces, requires a large number of operations from soil preparation to harvesting. Soil preparation is generally a detailed job, which requires the operation of several implements in order to leave the surface of the soil flat for good leveling, being the crucial step to obtain uniformity in the irrigation depth.

To achieve this, primary preparation operations are carried out, using mainly heavy harrows to remove the ripples left by previous cultivation, such as mud and traffic traces from harvesters and tractors. After this preparation, secondary preparation is carried out, which consists of using lighter leveling harrows, whose function is to partially level the soil, destroying the slopes left by the heavy harrows. These harrows leave the soil looser for the operation of the planers, which aim to correct the microrelief of the soil using their blades, which are loaded with soil in undulations and discharged in depressions, providing a flat relief for leveling.

The marking of contour lines for the construction of rammed earth can be carried out using laser devices where an emitter is installed on a fixed, level base, from which signals are emitted to a receiver installed on a graduated ruler on the tractor. It is the operator's responsibility to guide the tractor, marking the contour lines for subsequent sealing. There is also the possibility of leveling using global positioning equipment (GPS) and automatic pilot, where the area that will be leveled is initially covered with a tractor that has the system, collecting latitude, longitude and altitude data. point to point for subsequent data processing in specific software, redirecting the data to the tractor's GPS and, then, the contour lines are demarcated and blocked using the tractor's automatic guidance (Bisognin et al.

DIFFICULT PREPARATION

However, several difficulties are encountered in putting all these operations into practice, from planning the time to carry out soil preparation, adverse weather conditions, crop/livestock integration, high operational costs, in addition to the lack of qualified labor to operate the system. , which has recently been one of the biggest problems faced by rural producers. In this sense, producing sustainably has been a challenge for producers, where different cultivation techniques and operation of agricultural machinery can be adopted in order to reduce production costs, enabling the operationalization of rice farming. One of the techniques that can be easily applied to any rural property, with the potential to reduce operational costs and soil preparation time, is the choice of the traffic circuit and the harvester unloading location.

HARVEST CIRCUITS

Normally, the harvesting circuits adopted by producers are “circular from outside to inside” (continuous), where the harvester travels around the entire perimeter of the area to be harvested until reaching the center of the field, finishing the operation. This method has the advantage of greater operational efficiency of the harvester, as it performs few headland maneuvers, wasting less time, where grain unloading is often carried out with the harvester in operation.

However, this type of circuit induces the tractor operators that pull the grain tanks to remain “following” the harvesters without knowing the exact moment that they will unload the grains. The disadvantage is the wear and tear of equipment, greater fuel consumption, in addition to forming huge and various tracks within the plots, caused by the set's wheels, which are often in the slope/uphill direction of the terrain, forming a preferential flow channel for the runoff of rainwater favoring the formation of soil erosion.

These tracks, combined with soil erosion caused by water runoff, make the area much more difficult to prepare for successor cultivation, often requiring the landfilling of erosions, searching for soil in a borrow area, consequently increasing the hand of work, the number of operations and the operating cost.

In this context, an alternative is to use the “back and forth” (alternating) circuit and plan the moment of unloading grains from the harvesters. In this system, it is possible to determine a fixed point for unloading the grains, which is always carried out at the ends of the fields, close to roads, edges of fences or irrigation canals, eliminating the tracks caused by tractors in the middle of the field, thus reducing the disadvantages mentioned previously.

To carry out this procedure it is necessary to know which route the harvester can travel to fill its grain reservoir. It is worth remembering that the distance covered by the harvester to fill the reservoir capacity is inversely proportional to the crop productivity and the use of the platform's cutting width, and may vary throughout the field. Once you have these variables, you can use simple mapping tools, such as Google Earth software, to measure possible harvesting circuits.

In reasonably large plots, it is possible to unload grain at both ends. In plots with reduced dimensions, it is possible for the harvester to move 50% of the way in the outward direction and 50% in the return direction, filling its reservoir in the same starting location.

This technique has the disadvantage of reducing the operational capacity of the harvest as unloading with the static harvester becomes mandatory, however, it brings the benefits of reducing damage to the soil.

If the harvest is carried out with the soil slightly moist to dry, which can be achieved by stopping irrigation when the rice reaches the point of physiological maturity, the harvester traffic causes little or no damage to the rammed earth, which can be reused in the next cultivation without the need for primary and secondary soil preparation. In this case, you only need to touch up the rammed earth in some points using a plasterer. After this, the area is desiccated to eliminate the vegetation cover and direct sowing can be carried out on the straw. In this system, the main advantages are the addition of organic matter, reduction of thermal oscillation, nutrient cycling, improvements in structure, greater infiltration and storage of water in the soil, which facilitates seed germination even if there is no precipitation or irrigation after planting. sowing, in addition to not disturbing the weed seed bank, minimizing the problem of red rice.

If due to climatic factors or irrigation management the area is flooded during the harvesting process, the harvesters caused greater damage to the mud, however, it will be much less than the damage caused by tractor traffic. Therefore, when preparing the soil for the successor crop, it will be necessary to completely enclose the area, however, it is possible to adopt the minimum cultivation system, where, in the case of irrigated rice, only light harrowing and enclosing are carried out. , using the same level of rammed earth from the previous cultivation.

SMALL DETAILS AT NO EXTRA COST

Taking into account the high production costs of rice farming, it is observed that there are several techniques for soil preparation, irrigation management and harvest planning that can be adopted by any producer without the disbursement of financial resources, resulting in greater profitability of the crop. activity. Some producers do not take into account small details due to cultural defects or because they are not aware of the damage that could be caused to the soil by poor mechanization management.  

Bruno Pilecco Bisognin, Tiago Gonçalves Lopes, Bruna Flores Batistella, Vilnei de Oliveira Dias, Lamap/Unipampa Alegrete

Article published in issue 151 of Cultivar Máquinas.