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Anno 2021 Numero 1 - 2

Technology
January - February 2021

Minimum tillage machinery

The agricultural machinery industry provides effective solutions for carrying out minimum tillage operations. This cultivation technique reduces stress on the soil and keeps the organic substance, with advantages over time in terms of economy and sustainable tillage

Due to experience in the field for several years now, machines' performance for minimum tillage has attained extremely high levels.

Minimum tillage differs from traditional tillage (i.e., plowing + harrowing) in that the soil surface horizon is not overturned, with several positive consequences on work times, diesel consumption and the mineralization of organic matter, because it makes the soil undergo less refinement and leaves more crop residues on the surface.

The best choice of equipment for minimum tillage also depends on soil texture and proper management of stubble or stalks, which in this case are not buried. Moreover, the following crop handling must consider the existence of residues in the first centimeters of soil and the need to manage weeds differently from traditional techniques. From a mechanical point of view, it is necessary to use machinery equipped with working parts (anchors, discs, rollers, springs) suitable to effectively manage the residues, capable of breaking up the soil in a single pass. The best combination of these tools allows the superficial mixing of crop residues (thus a higher concentration of organic matter in the first horizon), a reduction of soil loss due to erosion, less pulverization, less compaction, and less diesel consumption per unit area.

The main disadvantage of minimum tillage is the demand for specific power (i.e., kW per meter of working width), which is usually quite high, depending on the characteristics of the soil worked. The machinery used must, in fact, typically operate at high speeds (7-15 km/h), and to provide a good quality of work, they must have a large mass, as they are made up of many parts, typically 2-3 rows with 10-20 chisel springs each or 6-15 anchors, combined with 40-100 discs, ending with a compactor roller, for working widths ranging from 3-4 up to 6-7 meters. Models with a limited number of discs (and a not excessively large roller) can be coupled to 140-280 Hp (100-200 kW approx.) tractors, while larger models require top of range tractors currently available, even 400 Hp (300 kW) and more.

 

The working parts: The anchors

The placement and sequence of the individual implements are not random, quite the contrary. Careful observation of the actions of the individual elements results in their specific positioning along the forward direction. Typically, on the tiller, anchors are the first tools used for the soil's initial tilling, followed by several rows of discs (of various shapes, sizes, and inclination), and finally by a compactor roller.

For the most difficult and challenging soils to till, the most suitable solution is a tiller built on several rows of corrugated disks, coupled with one or more rows of flexible tines or two-blade chisel springs. This solution provides an effective disruptive action, which is well suited to replace the work of a classic power harrow. The use of anchors is also highly recommended in these cases. The anchors' conformation definitely affects the soil's action because it breaks up the most superficial part more energetically than other tools. This solution allows effective management of crop residues, especially when coupled with one or more sets of discs and a rear roller of the cutting type.

 

Discs

Discs are critical elements of tillage equipment in conservation agriculture, both as main working parts and as supporting parts.

In fact, compared to the discs of the plows, those mounted on the cultivators have a smaller transversal encumbrance because (of course, other things being equal) they are arranged on two or more alternate rows, with a defined angle of inclination, determined by the support of connection to the machine. In fact, each disc is connected by rigid or elastic support. The latter solution is preferred in minimum tillage as, in addition to allowing greater independence of movement, the flexible connection amplifies the typical action of the tool concerning crop residue and impact with stones and rocks, incorporating them into the surface layer, avoiding clogging problems in the following seeding.

The discs are arranged in one or more rows with opposite orientations. Each disc rotates independently on a watertight hub and relative bearing; all elements are then connected to the frame through rubber buffers, which cushion and absorb the stresses resulting from movement in the soil.

Discs can also be flat, with a cutting effect parallel to the forward movement, or convex. The different disc convexity and inclination increase the disruptive action on the soil.

Usually, discs are equipped with a smooth profile on conventional harrows, while in minimum tillage, the most common choice is to use toothed discs, as they have a better breaking action on crop residues.

 

Chisel springs and rollers

Next, a row of reinforced chisel-type springs (which move the residue), followed by a rear roller, complete the residue's surface mixing. Generally speaking, the roller's purpose is to even out and settle the soil profile to ease the subsequent seeding. The most common rollers are cage rollers, which give an orderly shape to the seedbed, sharp or rubber packer rollers, which compact the soil and further crush crop residues, and spring rollers, for a final intervention of aggression on residues.

Kverneland's Actipack roller is equipped with a series of discs with adjustable knives between them for optimal crushing of clods of earth in difficult and heavy soils. On the other hand, for softer soils, the Actiring is offered, equipped with steel rings to reduce the working unit's weight and, therefore, of the entire machine, allowing it to be coupled with medium-power tractors.

 

The “rake effect”

In minimum tillage, it is essential to avoid the so-called "rake effect" i.e., the dragging of crop residues, which causes rapid clogging of the machine. Therefore, the distance between an anchor and an adjacent anchor of the same rank must be quite large, preferably not less than 70-80 cm. This is beneficial in models with several staggered ranks so that the residue that passes can be intercepted by the tool of the next rank. Similarly, the clearance between the ground and the machine frame is also a parameter to be carefully evaluated, again to avoid clogging and dragging.


The benefits of minimum tillage

 

Reduction of soil consumption (i.e., limitation of erosion and, more seriously, of desertification), increase in organic matter content, decrease in soil sealing and compaction, maintenance of biodiversity, etc... Adopting minimum tillage can achieve many benefits.

More generally, a conservative approach to tillage avoids the inversion of layers, leading to minimal changes in the soil's natural composition and structure. It also promotes water infiltration and moisture conservation, counteracts erosion, and helps to improve water quality.

Besides, reduced tillage involves benefits in terms of environmental impact, thanks to reduced CO2 emissions, both for the lower number of passages on the soil of agricultural vehicles and for the possibility of not emitting part of CO2 as a result of the mineralization of organic matter determined by the inversion of the layers produced by plowing. Also, a lower number of passes also results in less soil compaction.

Several studies have found that soil erosion and fertility's negative impact is much lower when minimum tillage techniques are used, including lower operating costs than traditional tillage techniques.

 

 

by Daniela Lovarelli

Keywords: Minimum tillage
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