Mechanical practices for the prevention and correction of degraded soils

One of the most important natural resources for man is soil, as it has multiple functions in the nutrient and water cycle and is important for the sustainability of natural systems, such as primary forests and fields (Embrapa, 2003).

The alteration of natural systems by man creates altered zones that can have their production improved, preserved or reduced according to the management adopted.

When the alteration of these systems occurs together with processes that lead to a reduction in the system's productive capacity, it is said that the areas are degraded (Embrapa, 2003), and the practices carried out with the aim of preventing, controlling or correcting this degraded process Soil degradation is divided into three types of practices: vegetative, edaphic and mechanical.

Conservationist practices of a mechanical nature use machines and agricultural implements to intercept and/or conduct surface runoff, thus reducing the loss of water and soil by reducing losses due to erosion. Mechanical practices are divided into preventive practices, which are practices carried out to prevent the emergence of these degradation processes, control practices, which must be carried out when initial problems already exist, to control small sources of degradation, and corrective practices, which aim to correct degradation problems. more advanced.

Preventative mechanical practices

Always using the same working depth with soil preparation equipment (plow, harrow, rotary hoe and scarifier) ​​helps in the formation of compacted layers, which are one of the main causes of surface water runoff, reduced growth and inadequate development of crops among other problems. 

One of the ways to prevent the formation of compacted layers is to carry out agricultural operations at different depths in each agricultural cycle. If possible, a rotating system of agricultural equipment should be carried out, that is, in each agricultural cycle, different equipment should be used with different depths (Table 1).

Ground cover material

The maintenance of vegetation cover material, whether dead matter (crop residues) or live matter (green manure) on the soil surface protects it from the impact caused by raindrops that cause the disintegration of soil particles, followed by the transport and deposition of these particles, these phases constitute the process of water erosion. For the covering material to act as a mechanical soil conservation tool, it must be well distributed throughout the entire area. One of the ways to improve this uniformity is to use the straw chopper and distributor in the harvesters, it allows a more uniform coverage of the area, preventing certain areas of the area from being left without coverage.

Level Cultivation

Level cultivation consists of carrying out all agricultural operations from soil preparation, sowing and other cultural treatments, always following the level curves of the land, so when the rains occur at each curve, the floodwaters lose strength and with this The loss of water and soil through surface runoff is reduced.

Level raking

It consists of the operation of piling up plant remains to form level windrows, so that the force of the floods is contained. These plant remains can be obtained from post-harvest or from planned deforestation. Plant remains that have no economic value and therefore do not justify their removal must be used. To size the windrows at level, the type of equipment used to construct them and the slope of the land must be taken into account, as the greater the slope, the greater the number of windrows to be piled up.

Mechanical control practices

Terracing

Terracing agricultural land is one of the most widespread water erosion control practices among farmers. Its fundamental objective is to reduce erosive processes and consists of splitting ramps, that is, dividing a long ramp (more subject to erosion) into several smaller ones (less subject to erosion), through the construction of terraces. Obstacles are constructed across the slope line, which have the function of intercepting, draining and/or infiltrating excess precipitated water. 

Outflow channels

These are vegetated channels that aim to receive and transport water drained from terraces or other structures. They are formed by shallow, wide depressions and a bed resistant to erosion.

Retention strip crops

These are vegetative barriers that aim to reduce surface runoff, providing partial coverage of the soil surface and dividing the slope.

The crops to be used to form the strips must preferably be fast-growing, with a well-developed root system so that they can be more resistant to floods, crops that allow population density, with a long cycle, with a well-developed aerial part and that are crops of economic interest so that the farmer can also explore them beyond conservation practices.

Rotation strip crops

They are retention strips, but with different crops, these strips have the function of reducing erosion processes by dividing the slope and with the different plant population densities, providing different flow speeds when crossing each strip and the most important thing is that crops are used in that cultural treatments are carried out at different times, so that even when some strips of a given crop are harvested there are still other strips to contain surface runoff, so there have always been strips in the area to contain erosive processes.

Corrective mechanical practices

Scarification

It is an agricultural operation used in the minimum cultivation system, which, according to ASAE (1982), consists of breaking superficial compacted layers of soil up to 40 cm deep with the use of scarifiers, thus enabling soil movement without inverting the tide and maintaining much of the plant residue on the surface that protects the soil from erosion.

Subsoiling

It is a corrective agricultural operation that, according to ASAE (1982), has the function of breaking subsurface soil layers, that is, layers more than 40 cm below the surface, being an operation that must be carried out only when the appearance of layers is detected. compressed.

*Per Viviane Castro dos Santos (CFU), Deivielison Ximenes Siqueira Macedo (Fatene), Leonardo de Almeida Monteiro (UFC) Jefferson Auteliano Carvalho Dutra (CFU), Enio Costa (IFCE), e Daniel Albiero (Unicamp)