Manual of techniques for sustainable mountain viticulture Josep Lluís Pérez Verdú

This limitation to the length of the slope has very few repercussions in practice if a slope height of

below 1.5 m is respected. 

•

Maintaining the good condition of terraces at all times is a basic condition for ensuring controlled

water drainage and, ultimately, the stability of all the terracing:

- Any accumulation of sediments or other obstacles on the terraces that hinder or prevent water

from passing must be removed. Water must drain along the length of the terrace without accu-

mulating and jumping sideways towards the valley, which would dangerously increase its erosi-

ve force. 

- Maintenance must be increased on the narrow terraces built by Mas Martinet (1.3-1.5 m), given

that the section available for water to pass is quickly used up in the event of an obstacle. 

- Maintenance is also particularly important on the access paths to the terraces where the gradient

and the length of the slopes and, therefore, the risk of erosion and sediment accumulation are

greater. Furthermore, significant flows from the entire lengthways drainage of different terraces

can accumulate at these points. 

In Mediterranean areas where the episodes of heavy rain are relatively frequent, the controlled runoff

of water is critical point in the construction of terraces. Where the necessary preventative measures

are not strictly observed, extremely serious damage may be caused to the vineyard and adjoining

areas, to the point of risking the survival of operations. The drainage network must be planned before

starting terracing work. 

It can therefore be concluded that the risk of erosion does not depend on the natural gradient of the

land but on the design of the terraces: a badly designed vineyard on a 25% gradient will experience

more erosion than well designed terraces on a 50% gradient. 

Manual of techniques for sustainable mountain viticultur

e - 25

---

2.2.3 Construction technique used for terraces and slope stability

When the construction technique of cutting the top part of the mountain and filling the bottom part is

used, a fragile surface between solid ground and the soil on top is created that often leads to landsli-

des, even during unexceptional episodes of rain (see Section 2.1). Where terraces run perpendicular

to the N-S direction of the general slate units strata of the Priorat unit, the risk of landslides is greater. 

In view of this situation, the constructive solution applied to Mas Martinet terraces has proven to be

effective, even in torrential rain. It consists of ploughing and turning over the soil mass to a depth that

is sufficient to ensure all the terrace rests on a base of solid ground that slopes slightly inwards. The

greater the natural gradient of the land the deeper the ploughed soil must be to ensure that any con-

tact with the solid mountain is almost horizontal. In practice, a minimum depth of 1 m is plough, which

is the average depth reached by the roots of the vine (agronomic criterion).

Even when applying this construction technique, there may be minor problems of landslides, parti-

cularly during episodes of fine rain that penetrates the outside of the soil. If these landslides are

appropriately fixed during the first two years of the terraces, the problem is solved and will not occur

in subsequent years, given that the terracing settles. 

Manual of techniques for sustainable mountain viticultur

e - 26

Slope

Solid gr

ound

Top soil

---

The full sequence of the construction system for a new terrace once the one above it is complete is

as follows:

•

The backhoe excavator opens up a path measuring around 3.5 m wide so that the machine can

move forwards and makes a more or less vertical cut on the inside of the new terrace. Using the

machine, the path is levelled until the height in relation to the upper terrace is kept almost cons-

tant along its entire length. 

•

The soil on the path is ploughed to a sufficient depth so that the new terrace rests entirely on solid

ground. As already indicated, this depth depends on the natural gradient of the land (with a mini-

mum o 1 m).

•

The laser levelling machine is then installed. The backhoe excavator finishes the inner slope of the

upper terrace and levels the inner part of the slope and inside of the terrace being built at the same

time so that the lengthways gradient is 3%. The excess soil is placed on the outside of the same

terrace so that the already levelled inside is higher. 

•

The machine runs along the terrace so that the inside tread marks the exact dividing line with the

slope and the outside tread runs over and compacts the excess soil. The sideways slope of the

terrace is then corrected to around 4-5% towards the inside, placing any excess soil on the outsi-

de of the terrace. 

•

Finally, the width of the terrace is marked (e.g. 1.3 m) and cut by the backhoe excavator as it moves

along the terrace. 

Solid ground

Vertical cut

Machine

path

Finished

terrace

Slope

Manual of techniques for sustainable mountain viticultur

e - 27

---

Once the width has been established, the slope height will depend on its gradient (β) and on the

natural gradient of the land (α). The stable gradient of the slopes is a function of the internal angle

of friction and cohesion of each type of soil ploughed. A direct cutting laboratory test assesses

these basic parameters. In line with the construction technique used on terraces developed by

Mas Martinet, the experiment on the Priorat “Licorella”

1

slate soil shows that slopes with a gradient

of up to 65º - 70º are stable. 

All experiments carried out by Mas Martinet regarding the construction of sustainable terraces

have been undertaken in collaboration with the company Coll de la Teixeta (www.teixeta.cat) loca-

ted in Falset (Priorat, Tarragona).

2.3.4 Effective and safe vineyard operations

•

As already indicated, the terracing land is ploughed to a minimum depth of 1 m so that the roots

of the vine have fewer problems in spreading at any point of the plantation. Furthermore, the earth

retains water more easily, as it increases its fine material content. Where the earth is not turned

over, water in slaty earth such as that of the Priorat region tends to escape through cracks or a

layer of sludge is formed that allows for run-off without infiltration. 

•

The width of the terrace remains constant throughout as, therefore, does the number of rows of

stock in order to avoid non-productive movement or complicated manoeuvres with machinery. 

•

Access to the terraces is zigzagged so that the gradient does not exceed 10-15%. This leads to

the loss of a certain amount of space and the formation of small slope sections with a height or

length above the maximums indicated, although occupational safety when moving with machinery

is gained. With steep gradients, the risk of overturning the tractor is considered inadmissible, par-

ticularly at points where terraces are entered on a bend and where towing a trailer or other machi-

nery. 

1

Licorella: metamorphic slate rock

Terraces with a constant width following level curves

Zigzagged accesses to terraces to improve occupa-

tional safety

---