In this article we aim to provide some clear guidelines on how to ensure the healthy development of the seedling after its planting, as well as some advice regarding the preparation of the plot and the planting properly speaking.

         Prior to planting

       La  The planting properly speaking

         The protector

         The first three years

Prior to planting

A physical-chemical analysis of a soil sample from the plot to be planted is necessary in practically all occasions (see in this section on how to correctly gather a sample in “Previous study. Soil analysis”). Even when certain about the terrain’s validity, knowing the texture of the soil, for example, will enable us to help choose which forest species to use as a support for the truffle. Within the same plot, it is relatively common to find different types of terrain (different chemical compositions and textures). Our many years of experience working in trufficulture has shown us that the holm oak (the most used forest species) is not suitable for clayish soils, which are more or less compact soils where the aeration is not optimal and the holm oak suffers in its development. In such soils, a good option is the Portuguese oak, also known as the gall oak. This tree has a greater plasticity in relation to the possible textures of the soil.

In making an analysis for trufficulture, the following parameters are of interest: pH, organic material, texture, carbonates, active lime, nitrogen, C/N.

Depending on the results of the analysis, some form of intervention in the terrain may be advisable. This isn’t usually the case, but sometimes a somewhat low pH signals the need for making a calcareous addition, or an excessively high C/N ratio means the soil needs to be tilled to favor the evolution of organic material, etc. At present, it has also been noted that a high pH of the soil, above 8.2, can hinder the start of production, even if the truffle is well-installed and forms good brûlées. In this case, a small acidification of the soil (with sulfur, for example) can bring good results. Even better is to dig some holes and introduce a mix of organic material with a pH around 7-7.5 (see “A microclimate for the truffle” in this same section).

If the area to be planted is a forest area, we must respect an appropriate period of one to two years (remove the forest mass, till or plough deeply, and sow one or two cereal harvests). The purpose of doing this is to clean the soil of possible propagators of other fungi (spores, mycorrhizas, mycelium, etc.) that could install themselves in the roots of the mycorrhizal seedling, substituting the mycorrhizas of the truffle.

If the area to be planted is a forest area, we must respect an appropriate period of one to two years (remove the forest mass, till or plough deeply, and sow one or two cereal harvests). The purpose of doing this is to clean the soil of possible propagators of other fungi (spores, mycorrhizas, mycelium, etc.) that could install themselves in the roots of the mycorrhizal seedling, substituting the mycorrhizas of the truffle.

If the area is agricultural (cereals, legumes, fruits, olives, grapevine, etc.), it isn’t necessary to realize an intermediate cultivation to minimize or eliminate as much as possible the fungi from the surroundings.

The preparation prior to the planting involves deeply tilling the soil (plow, disc, subsoiler, etc.). If the subsoiler is used, we can make a second pass over the area. It is best to realize this work some months prior to the planting. For example, if the planting is done in the autumn, a good moment to till is in the previous spring or summer, and if the planting is in early winter or spring, the soil can be tilled in the autumn or winter. Before planting, a pass or two of the cultivator will leave the area prepared to receive the seedlings.

Los primeros años de vida de la plantación de trufa son los más importantes.

Sometimes doubts arise over whether to respect adult trees already existing in the plot; in this case, the answer was clear because the adult holm oak in question produced truffles.

&Una buena preparación del terreno es indispensable para el cultivo de la trufa.

The preparation of the land (deep tilling and passes with the cultivator) is common and advisable prior ti planting.

 

The planting properly speaking.

Prior to planting, we must clearly know what the frame of the plantation will be, that is to say, the distance between seedlings in a row, and between one row and another. The ideal frame doesn’t exist, because no matter the plan, some points will be favorable and others not as much. It is important to be able to pass between the rows with a tractor, or even in both directions, and thus the distance between seedlings must permit this.

Real frames can be used, which are those in which both distances are equal (4×4, 5×5, 6×6, even 7×7). Use of these frames greatly facilitates working the soil with the tractor in a crossed way. Herringbone or symmetrically staggered frames involve planting a row and then placing the first seedling of the next row at the geometric center between the first two seedlings of the first row, thus forming a triangle, and so on. Logically, all of the seedlings of the new row will be placed in the same (intermediate) position in respect to the first row, and then the next row will follow the same pattern in respect to the previous one, etc. An optimal use of the planted area is achieved with the herringbone frame. Lately and with good criteria, use has been made of frames that broaden the aisles and the seedlings are placed closer together within the row, for example, 6×4, 7×3, 7×4, 8×3, etc. The purpose of this distribution is to favor an earlier entry into production and to allow more sunlight into the corridors.

Plantación de árboles micorrizados para el cultivo de la trufa.

Tilling the corridors between the rows of seedlings is recommendable during the first 4-6 years. In this plantation, the distance between the seedlings in the row is about 2 meters, and thus only the corridor between the rows is tilled.

 

To favor exposure to sunlight, we orient the rows in a north-south direction, as long as the shape of the plot allows this. A greater density of seedlings to start with favors a faster implantation of the fungi in the soil, which makes it possible to sooner reach a critical mass of mycelium that in turn leads to an earlier start to production. Thus, starting with a high density of seedlings is always favorable to speeding up production, although the initial cost of the plantation is greater. Suitable pruning must form part of such a plan, and at a certain age we must even consider the possibility of eliminating part of the plantation to maintain open spaces and good sunlight on the soil of the truffle bed, which is necessary for this species. A broad frame involves less initial investment and less pruning, although the initial production will be less and will arrive later.

Densities of between 250 and 400 seedlings / hectare are quite frequent. Higher densities can be very interesting (for example, 400-800 seedlings / hectare) in terms of earlier production and greater initial results, although given the initial costs involved, such densities are not usually realized.

Once the frame of the plantation is decided, the exact location of the seedlings should be marked (stakes, irons, reeds, gesso, spray, etc.) and then we can undertake the planting properly speaking. Although there are exceptions, we present the seedling in a plastic 450 cc case which unfolds without causing any harm to the root ball or the roots. At the moment of planting, it’s enough to dig a hole in the tilled land large enough to introduce the entire root ball and so that it is completely buried. It’s common then to step around the seedling to compact the soil and close any pores in the soil, and to make a small basin to retain water. It’s always best to water the seedling, even if the terrain has good hydric availability, given that watering with about five liters of water per seedling favors the compacting of the soil with the root ball. It’s not necessary to water immediately after planting; we can wait for a reasonable period of eight to ten days and if it rains during this time, the work of watering will have been done for us.

Favorable periods for planting run from October to May, including both months. It should be kept in mind that the seedling has a root ball and that rather than planting, what we are doing is transplanting the seedling from the container to the definitive site in the ground. The appropriate moment will depend on the place (altitude, risks of strong frosts during the dates of the planting, the humidity of the ground, the time we have at our disposal if we are doing the planting ourselves, etc.). Plantings made in early autumn, October and November, are generally best (there are less losses for the same degree of support) than those realized in early spring. In plantations above 1,000-1,100m, however, some people prefer to plant beginning in February because of possible strong frosts in winter; even so, experience has shown us that except for plantations above 1,200 m, the use of a protector (which protects the seedling in winter and generates a more favorable environment in summer), the percentage of rooting is very good in plantings made in the autumn.

In sites of medium altitude (600-1,000 m), plantings made in October with protectors evolve very well. At lesser altitudes with less risk of strong frosts, it is best to plant in autumn. A seedling planted between October 15 and mid-December begins root growth before the arrival of possible strong winter frosts, and thus in the first summer – a critical period for the young plant – it will be more settled in the ground and thus more likely to survive the heat and dry periods of summer.

 

The protector

This is generally a cylindrical plastic tube open at both ends that we place around the seedling once it has been planted in the field. In winter, it protects the seedling from the cold and in summer it lessens the effects of heat, generating a more favorable environment for the seedling in its interior. Not all protectors have the same favorable effect on the mycorrhizal seedling; we believe the protector should be of a specific height, not more than 40 cm, and should be kept in place for one year, maximum a year and a half, after the planting. If we’ve planted in autumn, we can remove it in October of the following year; we want the seedling to go through the next winter without the protector but it’s important to remove it previously so that the seedling can gradually adapt to the cold. If we want to keep it in place, it should then be removed no later than March-April. If we plant in February-April, we can remove it in the following spring, for example in April of the following year, also before the arrival of summer, or at the very latest, in October. The function of the protector, as its name indicates, is to protect the seedling to favor its rooting. There will always be one seedling or other that remains small or that begins its growth later, and in this case it may be suitable to leave the protector for one more year, and if it doesn’t develop suitably after this time, we can consider substituting it.

Protectores utilizados para proteger el árbol micorrizado en los primeros años.

The protector is a good support for the rooting of the young seedling. It protects it from both the cold of winter and the heat of summer; it can be used for one year, or a maximum of two.

The protector we provide with the seedling has specific characteristics, selected after having tried out and observed different models, in which we have judged not only the seedling’s survival and development, but also factors that can affect the maintenance of the truffle mycorrhizas in the roots of the seedling.

 

The first three years of the plantation

The seedlings have been planted and now we face the task of caring for them, initially so that they take root, and then so that they can begin a balanced development and thus produce truffles as soon as possible. We are talking about a first, initial stage of about three years; it is very important to begin caring for the plantation correctly.

The first year, and specifically the first summer, is by far the period when the seedlings need the most attention. Spring rains favor the appearance of weeds, and depending on each case, it will be necessary to hoe around the young seedling to eliminate competition with the seedling. We will carry out this task manually as many times as it is necessary (usually, one to three times), with a small hoe. It is very important to maintain the immediate surroundings of the seedling free of weeds during the first months. When summer arrives, an eye must be kept on the need to irrigate or not; generally, between one and three irrigations are necessary, depending on the rains or storms that may take place. Summer is the most critical period for the plantation we have planted only a few months before; a careful eye must be kept on the need to irrigate from early July to mid-September and irrigating when necessary will be the most important support we can give during this period. Depending on the nature of the soil, after the rain or the irrigation, as the shallow layer dries out, a crust may form that impedes the good ventilation of the soil. We must break up this crust with a hoe or similar implement; this can be done during the days following the rains or irrigation. We will localize the irrigation at the base of the protector, and it’s even common to place the irrigation inside the protector; usually, a small basin is formed around each seedling to retain the irrigation water and even the rain. For each watering, we can use between five and ten liters of water for each seedling. When placing the protector, it’s a good idea to place earth around the outside of the protector, creating a small mound against the protector; if we do this, the basin of each seedling should be a bit larger.

Over the course of these first months, the cultivator is generally passed between the rows in spring to stop the corridors from filling up with weeds; it is a good idea to do this various times, depending on the need in each case. Another interesting option is to cut down the weeds with a scythe, but this is only practical if the soil is free of rocks, which is not very common in trufficulture. Doubts often arise as to whether it’s best to pass the cultivator through the corridors or to cut down the weeds. In the following cases we believe it’s best to cut down the weeds, leaving them to decompose on the soil:

         If there is a deficit of organic material in the soil.

         If the C/N ratio is low, the contribution of organic material will help increase this ratio.

         It’s common to find soils with a pH above 8.2, which implies high rates of carbonates and lime and which, according to the latest research, can hinder the start of truffle production by stopping the truffles from forming primordia in the first stages of their cycle due to a lack of discontinuities in the pH of the soil. In this case, the contribution of cut weeds will favor the incorporation of organic material into the first layers of the soil, a drop in pH and the production of truffles.

         In compacted soils (with clayish textures or very limey) that are poor in edaphic life, it is also advisable to cut down the weeds, allowing for meadow formation, which will favor edaphic life and the ventilation of the upper soil layers.

  When is it advisable not to cut down weeds but rather till the land? For example, when the plot has a high C/N ratio, above 15-20 and with a high rate of organic material, then it will be best to till the soil to air it, favoring thus the evolution of the organic material to bring the C/N ratio to lower levels favorable to the black truffle.

It has also been observed that in plots where the soil has been tilled, the truffles form at deeper levels, which means it is advisable to till the soil superficially in sites located at higher altitudes to minimize the risk of frosts affecting the truffles. It is also true that in this article we are discussing the first three years of life of the plantation, and that it may also be a good idea to stop tilling the soil after three or four years of the plantation’s life, depending on the physical-chemical analysis of the plot. At any rate, the tilling of the soil will always be superficial, to a maximum of 15-20 cm of depth with a cultivator or harrow, and if we till the truffle bed in later years and we do it over the brûlées, the depth should be even less, a maximum of 10 cm..

As we see once again, a soil analysis is important to help us act with greater precision in terms of whether or not to till the soil, cut down the weeds, etc. Although the soil is commonly tilled during the first three years, after this time, the values provided to us by the analysis of the pH, organic material, C/N and texture should indicate to us whether or not to continue tilling the soil or to cut down the weeds. We still must continue maintaining the base of the truffle seedlings free of weeds and we will continue enlarging this cleared surface, given that the root will occupy more and more space. It may be reasonable to do this for up to five years or until we observe that the seedlings begin to form a brûlée.

Returning now to caring for the seedlings, if there is a significant dry spell towards the end of September or October, we will irrigate for a last time. Mid-October can be a good time to consider what corrections, if any, need to be made to the plantation.

The following spring, we will keep a watch on the immediate surroundings of the seedlings to do any hoeing that may be necessary. Regarding the tilling of the corridors and between the rows, we will act according to our decisions in respect to what we’ve mentioned above.

During the second summer, we will keep a watch on the soil’s humidity. It’s very important to keep the immediate surroundings of the seedling free of weeds and to break the crust that forms after the rains or irrigation. By this time, the seedling can defend itself much better than the previous year and we will only irrigate it in case of a serious dry spell. In respect, however, to the seedlings we’ve had to replace, we will pay special attention to them in terms of watering.

In the third spring, we will follow the guidelines established in the previous years regarding whether to till the soil or not. We will make sure to remove the weeds from around the seedlings; we must increase the area tilled around the seedling, given that the root will continue to expand into new ground; we will break the crust of the soil around the seedlings whenever it forms. Irrigation during the third year, if done at all, should be done on only exceptional occasions; special attention, in terms of irrigation, will be paid to the seedlings replaced the first year.

Plantación de árboles micorrizados para cultivar trufa negra.

A plantation of 2-3 years, appropriately tilled.

 

To sum up in terms of caring for the seedlings during the first three years:

     Irrigation: Careful attention must be paid especially during the first summer, which is a critical moment for the seedling’s survival. Up to three or four irrigations may be necessary from June to October. We will be vigilant the second year to see if irrigation is necessary, but the most important thing will be to remove the weeds from the vicinity of the seedlings and not to irrigate unless absolutely necessary; the third year, the seedlings should be irrigated on only exceptional occasions. Special attention must be paid to the seedlings replaced the first year.

      Protectors: They shouldn’t be kept in place beyond the first year and a half.

    Weeds: The immediate surroundings of the seedlings should be kept free of weeds. Spring and early summer is the period when most care must be paid to this, hoeing when necessary around the young seedling. Crusts must be prevented from forming on the surface of the soil after the rain or irrigation. In respect to the weeds of the corridors, we will decide either to till the soil or cut down the weeds according to what has been discussed above.

Weeds: The immediate surroundings of the seedlings should be kept free of weeds. Spring and early summer is the period when most care must be paid to this, hoeing when necessary around the young seedling. Crusts must be prevented from forming on the surface of the soil after the rain or irrigation. In respect to the weeds of the corridors, we will decide either to till the soil or cut down the weeds according to what has been discussed above.