The rose adapts quite well to different types of soil. Obviously like all plants, it prefers and adapts better to soils with the following characteristics:

• Good permeability.
• Stable structure during cultivation.
• Good drainage.
• A proper balance between clay, silt, sand and organic substance.
• An ideal quantity of nutritious substances.

Regarding this last point, the best soils are said to be of medium texture or of balanced texture. This type of soil can consist of 35 to 55% sand, 25 to 45% silt, 10 to 25% clay and a quantity of organic matter between 2 and 5%. If such balance remains constant throughout the profile of the soil up to 50-60 cm in depth then one can speak of soils of exceptional quality. The word quality, apart from the physic constituents, takes into account properties such as permeability, the ability of not compacting itself much during cultivation and a good balance between air/water in the soil.

If the soil compact itself during cultivation, the available air (oxygen) for the roots will be reduced. Such soils can contain amounts of water that are unfavourable for the plant and can even be lethal.After each watering, a good soil should drain the majority of the water towards the deeper stratums (from the surface to about 60 cm of depth) and leave an ideal volume of air and moisture around the majority of roots for their correct growth. The agricultural soil should consist of many micro and macro capillaries. After each watering, the water with nutrients should remain in the smallest capillaries while the larger ones, have to drain the water due to gravitational force, leaving air to enter.In the majority of the cases, Roses are cultivated on soils that are mainly a combination of clay, sand or organic matter.

To describe in detail the positive and negative characteristics of these types of soils as well as the direct and indirect effects on permeability, root asphyxia, excess or lack of water, excess or lack of nutrients etc, would require a long discussion that is beyond the scope of this book. The principal aspects will be taken into consideration. Clay soil: is hard, stiff and tends to have a high salinity when dry. If it is wet due to large volumes of water, it becomes asphyxiated since it does not drain the water (not even on the surface (photo 1,2). In these cases, the grower has to try to irrigate frequent but with small quantities each time. If possible, sand and organic matter should be added to minimise these short comings.

Additionally 1 2% Lime (CaCO3) should be added to prevent a pH drop and consequently, the loss of soil structure of clay and loam-clay soils.

This quantity of calcium carbonate will also indicate the presence of an adequate buffering ability. In clay soil, the amount of calcium ions present reveals a good soil structure. If the pH decreases to acid levels, the quantity of calcium ions dissolve in the soil solution and would decrease, consequently the soil looses its structure. Calcium ions in the soil also have a ?gluing? function, that is, they unite minute soil particles to create agglomerates which creates a good balance between solid, liquid and gas form in the soil. High quantities of CaCO3 in the soil result in a high pH (Alkaline soils). Sandy soil: It is a type of soil with no or little water retention (holding) capacity and consequently little nutritious substances (compare with for example beach sand). With this kind of soil it crucial to add organic matter.

The quantity of CaCO3, depends on each scenario, it should at least be 0.3-0.4%. The total quantity of organic matter in these soils can be up to 10-12%. Organic soil (high quantities of humus): its principal characteristic is the strong retention of water and possibly, an insufficient drainage with lack of oxygen during cold periods. In the worst cases, a system of drainage with underground perforated tubes is indispensable. Adding sand or other drainage promoting products is useful. A CaCO3 content of about 0.4% is considered adequate. Volumes and frequency of irrigationThe volumes and frequency of the irrigation (cycles) for Roses, and generally all plants cultivated in greenhouses, are regulated by the losses due to percolation or leaching (gravitational water), and evaporation of the plant. By percolation we mean the quantity of water that, due to the effect of gravitational forces, is leached or drained into the deeper layers of the soil. By evaporation we mean, both the quantity of water evaporated from the soil (evaporation), and also through the leaves of the plant (transpiration through the stomata).

The quantity of water that remains stored in the soil represents the level of water holding capacity (the water actually available to the plant). Below the wilting point the water is retained in high quantities by the particles in the soil, and it is therefore not available for use by the plant (fig. 10). In practical terms, the water in the soil can be divided into three categories. 1) Saturation Water the maximum quantity of water that a given type of soil is able to contain.2) Holding Water the quantity of water that a given type of soil is able to retain. Saturation water is quickly lost by the soil, because it cannot be held onto against gravitational forces. Holding water, on the other hand, is the volume of water the soil is able to absorb, because this water holding capacity is stronger than the gravitational forces.

This quantity is absorbed by the roots because the force of the roots taking up the water is more powerful than the soils ability to hold on to the water.3) Wilting Point as the roots slowly absorb the water held by the soil, the water that remains unabsorbed is held on to by the soil more and more strongly, due to its diminishing quantity.

This phenomenon brings the water to its wilting point, below which the little quantities of water that remain, are held so strongly by the soil that the plant is unable to absorb it, for which reason the plant wilts. The volume or quantity of water available depends on the type of soil (sandy or clay) and, as already described, on the quantity of organic matter present. As with fertilization, also in this case absolute and unequivocal values do not exist for every productive situation. These values or factors determine the cycles and volume of irrigation, depending on the following general characteristics: Physical and granulometric characters of the soil.

Size of the plant and the root system. Temperature, R.H., wind, solar radiation and all the climatic parameters that effect the evaporation of the plant. Cultivation density (spacing) and vegetative characteristics of the different varieties available. Presence of impermeable layers, above all in the first 30-50 cm of soil depth. To meet above variables that determine the volume and the frequency of irrigation, it is useful to obtain a Tensiometer (photo 14), that measures the E.C., pH and the tensions or negative pressures to which water is subject in the soil (it measures the strength with which water is held by the soil).

With this instrument, we are able to determine the moment when irrigation should be carried out. To establish this we should first test the soil in order to discover what the real negative pressure values or forces (expressed in Atm. or Bar) are, to which water is subject. When the quantity of water, required by the plant to balance the transpiration, is not absorbed by the plant roots, wilting occurs (the wilting point). This can be caused either by levels of moisture in the soil below the wilting point (dry soil), or by root growth which, relative to the size of the plant mass, is inadequate. In case of the latter (insufficient root development) this imbalance is most evident during hot weather and can be caused by: ? Root damage from parasites (i.e. Nematodes).

High levels of soil salinity. Lack of oxygen in the soil (asphyxiation). Excessive Nitrogen in the feeding program.

(Colombia) Soil cultivation on very clay soil with simple rows. Area north of the Bogota Savana.

(Kenya) The cultivation area near Naivasha Lake is characterized by having poor drainage soil with high percentage of clay (Black Cotton soil)

China (Hangzou). To decrease the high salinity in this soil (EC 6-7 mS) that is situates just a few Km away from the sea, growers tend to wash them out before a rose cultivation is begun.

The water division of clay and sandy soil.

(Ecuador) Before inserting the tensiometre in the soil, all the air inside it must be extracted with a syringe. The depression created this way will facilitate the entering of the water in the tube through the porous bulb.

(Kenya) Drop irrigation in a new greenhouse.

One of the first greenhouse built in Kenya. It is 5.5 m at the highest point and 1.80 m high at the side (low greenhouses have a reduced air exchange).

(Kenya) 5 months old plants grown in 5 litre black plastic bags filled with a mixture of coconut+pumice. At the base of the vases only a litre of pumice is put to increase the drainage. In the base of the bags, holes are done to allow the rooting in the soil.

(Kenya) Elimination of the lateral shoots (suckers)

(Kenya) Cleaning and bending phase on 1 year old plants.