Nurseries: technologies for a sector in growth
Plant nurseries are in a production sector which includes sales of ornamental and horticultural plants as well as trees and shrubs. The leading global producer is China. In Europe, the commercial facilities and organiztion in the Netherlands put the country at the top in the globalized market. The regions most active in this sector in Italy are Liguria, Tuscany, Emilia Romagna and Puglia. The sector is of great economic and occupational importance and requires substantial investments and a skilled labor force
The production facilities of plant nurseries are highly organized. The opening phase of the production cycle involves seedbedding, rootstock grafting or cutting and the production of rooted cuttings. Nursuries can grow plants in greenhouses or in open fields. A nursery area is allocated to the development of plants before their sale which are usually growing in pots so that they can be moved. In the micropropagation laboratory plants are produced beginning with cells grown in vitro from a tissue culture using clean stock materials that are free of viruses and fungi. Some nurseries do not feature micropropagation labs. The same is true for areas dedicated to the collection of materials for beginning propogation, seeds, cuttings, grafts, cuttings, offshoots, etc. from mother plants.
The greenhouse is an important structure in the horticulture and floriculture sector for pursuing the various phases of the nursery production cycle. Traditional greenhouses built with glass or rigid plastic materials, including polycarbonate panels, have been joined by tunnel construction in polyester resin or polyethylene film. These latter types are used especially for horticulture and ornamental plants requiring less thermal control.
For protected cultivations a distinction must be made between those grown in the ground and those which are not. For the former, cultivation can be on fixed or mobile benches 1.6 to 2 meters in length in natural or artificial substrates or in the ground. For ground cultivations the seedbeds are well defined to provide service corridors. Cultivations not grown in the ground require a solution of nutritients, a significant innovation now widespread in the Netherlands. The management of these cultivations depends strongly on computer technology with the use of dedicated software which controls the nutritional solution and salinity of the substrate in relation to growth and water consumption.
Greenhouses are heated by hot air blown through openings in suspended polyethylene pipes or by hot water channeled in pipes running under the benches. In the hot months of the year the temperature inside is regulated by various systems, including programmed opening of the greenhouse and covering the structure with a shading net.
Preparation of the substrates and seeding
Substrates can be either natural or artificial. Those of peatmoss and their various mixtures are made by using mills or hammers for crushing the largest materials and rotating sieves as well as humidifying mixers. Potting is performed mechanically with a rate of work at 1,500-2,500 pots per hour. Special cubing machinery equipped with seeders are used for substrates in cubes. In the seedbed seedlings are produced by seeding in boxes, socketed growing trays, on benches or in containers using fully automated machinery with a high work capacity. Precision pneumatic planters are deployed for seeding in the ground. Other than extreme precision in seeding to the required distances and depth, more advanced technology also enables seeding to be performed with the help of satellite systems.
Transplanting, cuttings and herbaceous grafting
Transplanting in pots or cubes is done with fixed transplanters which are mostly automated or with mobile transplanters operating in the greenhouse itself to avoid transporting containers. Their high work capacity makes it possible to reach 2,000 seedlings per hour. In use for cultivations in the ground are tractor mounted transplanters with varying levels of automation, manual transplanters for handling each single seedling or cube or fully automatic transplanters which limit the work of the operator to
controlling the insertion of the growing tray containers on the guide. There are also very versatile transplanters capable of work on seedlings with exposed roots and up to a determined size as are those in use in forestry. Asexual multiplication is often used on cuttings or other materials such as bulbs and rhizomes. To avoid the spread of diseases these clones must be given timely treatment and preserved. For the control of seed-borne pathogens thermal treatment is one application. This can be performed with air and water raised to a determined temperature for a determined time in relation to the crop and method adopted. Branch cuttings can be produced fully automatically beginning with the insertion of a branch with no secondary branches with a system which does not require the operator's control for removing leaves, cutting, handling for hormone dispersion and insertion in growing tray pockets and moving the cutting. To cope with hygenic problems which arise in this sector committed to highly specialized intensive cultivations and to counter resistence to agri-pharmaceutical products a system based on herbaceous grafting has been introduced. This technique is aimed at the elimination of plant treatment products also for cultivars which have no resistence to parasites. This innovation however is not yet widespread.
Defense against telluric parasites and weeds
The high degree of specialization and intensive cultivations favor the proliferation of telluric parasites of various kinds in the soil and substrates which can compromise plant development. As the methyl bromide treatment is now prohibited for disinfestation recourse had been directed to various thermal methods involving solarization and steam treatment with fixed and mobile machinery. Fixed disinfestation plant is used for operations on substrates for cultivations in pots or on benches as well as in the ground. The most widespread system, one which has low energy efficiency, is steam mixed with air injected under tarps but a solution which requires a greater investment and is more efficient involves pipes buried underground for injecting the steam. There are two types of mobile plant, one of which operates continuously and another which aerates in successive cycles and usually feature automatic drive.
Fumigation treatment makes it possible to defend against weed seedbanks. The fight against weeds is in fact increasingly waged with integrated systems, that is, those combining a chemical plus a biological, mechanical and thermal approach. Other than steaming, there are now increasingly more high-performances machines for flame weeding.
Plant protection products
There is a large number of products for pest and disease control in ornamental plants and a wide range of sprayer types, backpack, towed and self-propelled as well as mainly automatic dusters and mist blowers. These former types feature sprayer booms which move at programmed speeds on wheels mounted on frames and are powered by an hydraulic pump. These sprayers are managed by central processing units to make them fully automatic. Considerable savings of plant treatment products compared to traditional treatment can be achieved by using the appropriate nozzles and pressure setting. Generators for thermal sprayers and dusters exploit the pulse reaction principle for generating hot gas at 500°C driven at high speed of 40 m/s to instantly atomize the treatment product mix to droplets smaller than 5 microns. With this method the volume of the product is taken down to as low as 20 l/hr. Also for the defense against parasites efforts are moving ahead for the reduction of chemicals with recourse to integrated systems deploying biological weapons and innovative biotechnologies. Also the agri-pharmaceutical producers are at work in this direction and reducing their marketing of new molecules.
Irrigation
Greenhouse cultivations require a lot of water. On average, cultivations with a continuous cycle need around 2,000-3,000 l/m2 annually. The easiest way to maintain a determined water regime is based on the use of tensiometers measuring the moisture content of the soil inserted in the substrate for signaling the need for irrigation when the humidity level drops below a programmed level.
The use of sprinklers is the system most widely employed with fixed rigid plastic pipes fitted with centrifugal distribution nozzles operating at 10-12 bar. Fertilization and fumigation can also be carried out with this system. Another type is drip irrigation for significant savings in water used. The most suitable type for plants in pots is capillary drip mats. Yet another type is an irrigation system based on plastic tubes with openings buried to the depth of 40-60 cm on a porous material which absorbs water which then rises to the surfact by capillary action.
Robotics and automation
Robotics and automation are the innovative technologies which have increased the competitiveness in a number of production sectors. It has been seen that the automation of protected cultigations has already reached a level of maturity in installations mainly for the control of climate and illumination conditions in greenhouses. It is fairly commonplace to find integrated system installed for winter heating with motorized opening of the greenhouse for ventilation and controlling climate in the summer. Similarily automation has been applied to systems for the control of irrigation, irrigation with fertilization and cultivations not grown in the ground.
The mechanization of plant nurseries and greenhouses, however, are somewhat behind the times as regards the evolution of technologies. Automation is often limited to a single operation, such as grafting and producing cuttings. In this connection, we believe that the introduction of fully automated systems to the production chain of companies which specialize in high value added intensive cultivations is one of the decisive steps to be taken for boosting competitiveness against their traditional competitives in Northern Europe and those emerging in Southern Europe and North Africa enjoying lower labor costs and less severe regulations on safeguarding workers and the environment. What must also be pointed out are the advantages gained with the introduction of robotics and automation amplified by the application of information and communication technologies (ITC) integrated with all the greenhouse production chains for ensuring the processes of product traceability, marketing and planning.
Research and experiments conducted in this sector have led to the construction of robot systems which can replace workers for various operations; the use of a single robot can mount various tools for performing different operations, from grafting to plant treatment, from fertilization to the movement of plants. An important role played by robots is setting up artifical vision for identifying and locating individual cultivations, or parts of them, for carrying out specific operations such as plant treatment, fertilization, pruning and the like. These tasks require the development of special imaging techniques able to utilize electromagnetic and near infrared reaction.
The availability of these new solutions and prototypes and dealings among the businesspeople in the sector are the solid basis for beginning to share and planning joint research projects involving manufacturers of machinery and nursery entrepreneurs and for refining new cultivation practices aimed at increasing the quality of production, reducing impact on the environment and safeguarding the health and safety of workers.
