Construction of terraces with terracing

The construction of terraces is still a necessity in the cultivation of various crops, such as sugar cane, which require specific equipment to carry out the operation.

In the tropics, water erosion is the main way in which the process of degradation of agricultural areas occurs, caused by the detachment and transport of soil particles by the action of water. Erosion results in the degradation of agricultural land, causing considerable damage to the environment. Due to this damage, several conservation techniques have been and are being developed and improved with a view to minimizing them.

Among the practices that reduce surface water runoff, the construction of terraces stands out for its ability to minimize the effect of water action in agricultural areas where there is total or partial suppression of vegetation cover. Terracing basically consists of elevating land transversely to the direction of the land slope in order to intercept the runoff before it reaches a speed capable of causing soil particles to be carried away. The interception structure created by soil movement allows water to infiltrate slowly, maintaining soil moisture and contributing to the replenishment of aquifers.

After the development of a study group in Brazil towards the development of conservation techniques, the practice of building terraces gained strength in the 70s, used both in the conventional tillage system with total soil mobilization, and in systems considered conservationist, citing the Minimum Cultivation with vertical soil movement and the Direct Planting System with practically no movement.

TERRACES

Terraces are made taking into account some characteristics and are classified according to their function and size.

As for its function, it can be classified as a drainage terrace, in which case excess water is intercepted and drained sparingly, which is led to an outlet channel. This type of terrace is recommended for soils with moderate or slow permeability and low infiltration. The movement of earth to build the structure of this terrace is with uneven curves, also called uneven terrace. The infiltration or level terrace has land movement to elevate the structure, it occurs in level curves, therefore, with the function of intercepting water and retaining it, making it slowly infiltrate into the soil profile.

DIMENSION

The size of the terraces refers to the width of the earth movement band, being classified as: narrow base terrace, recommended in high slope conditions; terrace with a medium base, suitable for small and medium-sized areas, using disc or mouldboard plows to move the soil; and wide-based terrace, recommended for large areas with a slope between 6% and 8%, in this case, it requires large machinery called an agricultural terracer.

Despite being a well-known and widespread technique in Brazil, there is still great difficulty regarding its use due to the lack of knowledge of the importance of the technique for preserving agricultural areas and, often, due to the neglect of agricultural producers. One of the biggest problems observed in the field is the incorrect dimensioning for the allocation of terraces, taking into account the characteristics of the production system where it is intended to be introduced, thus reducing its efficiency.

CONSTRUCTION OF AGRICULTURAL TERRACES

Terracing changes the land surface according to the type of terrace previously sized for the area with soil conservation guidelines. Given this characteristic, terraces can be built using various agricultural equipment available on rural properties, from implements pulled by animals or tractors, to ploughs, planers and agricultural terracers.

Using terracing machines, the earth is excavated and disaggregated, accumulating until it forms a raised structure. The terracing machine is the implement that promotes the breakdown, elevation of the earth and finishing in the construction of terraces with greater efficiency and quality. Mobilization is done in two directions, from top to bottom and from bottom to top, transverse to the slope line and, at this point, it is necessary to observe whether the earth mounds are overlapping, forming a uniform elevation after a few passes.

The terraces over the years have undergone transformations caused by external agents, such as the transport of machines, wind, infiltration of rainwater due to the construction of galleries by animals. Another problem that has been observed over the years is the bedding of the terrace, losing its regular shape and, consequently, its functionality. Therefore, periodic evaluation and regular maintenance are important.

STRUCTURE OF AGRICULTURAL TERRACES

The agricultural terracing machine recommended for building terraces is made up of three chassis, one front, one right and one left, and the header with hitch for coupling to the tractor's drawbar or hydraulic lifting system. The front chassis has a set of wheels driven by a hydraulic piston through the remote control used both in transport and operation, participating in regulating the cutting angle of the discs, giving shape to the terrace. The cutting discs are attached to the side chassis, they are also equipped with articulated telescopic arms, which allow the chassis to be closed, facilitating their transport. At the end of the last disc on the side chassis there is the possibility of adding an optional complement with three discs, which allows a better finish on the unevenness left by the terrain. There is also the option of a guide wheel equipped with adjustment for aligning the terracing machine when in use. Each disc has a bearing that regularly needs to be lubricated with oil or grease.

The terracing models available on the market differ mainly in terms of the number of cutting discs, ranging from 14 to 48 discs. The greater the number of discs, the greater the weight of the implement and, consequently, the greater the power required in the tractor to carry out the operation efficiently.

Basic care when building terraces with terracing machines

The practice of terracing must meet the criteria for attenuating or eliminating physical, chemical and biological factors that limit crop development. Among them, the soil moisture status at the time of terrace construction deserves greater importance, as it significantly interferes with its efficiency. It is necessary to pay attention to the correct time to build the terraces. Ideally, the practice should be carried out when the soil is friable, that is, at its field capacity. In soils with high humidity, tractors will not have support to pull the implement and slipping will occur, reducing the efficiency of the practice. Soils with low humidity make it difficult to move the earth, resulting in greater resistance of the discs when penetrating the soil. The construction of terraces in this condition will promote the formation of clods, weakening the structure.

Despite being a technology widespread throughout Brazil, its use is limited by the lack of knowledge about its implementation and cost, especially among small and medium-sized farmers. When sizing, it is necessary to consider essential factors so that the terraces are efficient in controlling erosion. Although the models on the market have similar general characteristics, the choice of terracer must take into account the characteristics of the property for which it will be intended. The operator's ability to understand machine-soil relationships is essential for the success of the operation to ensure the final quality of the terraces, especially regarding the existence of ridge fragility. Agricultural producers, when recognizing how impactful the loss of soil from their agricultural areas is, as if it were the loss of irrecoverable heritage, appropriate knowledge about soil management and conservation, especially about mechanical erosion control techniques, As is the case with terracing, these will perpetuate the production areas from an environmental point of view. And, without a doubt, the terracing machine is an implement that presents the best operational capacity and quality for the construction of terraces when compared to other methods, and depending on the condition of the property and agricultural crop to be explored, it will present a lower operating cost. 

Marcos Roberto da Silva, Fabrício Pedreira Santos, Institution, UFRB/CCAAB/GPESOA

Article published in issue 164 of Cultivar Máquinas.