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A12MClRAIMA MEETING 132.2 Description of nursery techniquesBy the time of the meeting, the sowing process was ending. It started on 2 January1997, then took several weeks because of the control required to ensure goodprogress. The sowing varied according to the number of involved persons available.The coordinator made a presentation of the nursery techniques used, anddescribed the background that led to the decisions taken. The research linedeveloped by Dr G. Falconnet's team (Ecole national du genie rural, des eaux et desfon~ts, France - ENGREF) was proposed and accepted by the participants as aguideline on the nursery operations The following items were discussed in detail:• type of container• substrate• water supply controle fertilization.Plant production relies on the use of plastic containers with 400 cm' volume,chosen according to Falconnet's criteria. Substrate represents a mixture of soil, pinefibre and pine bark. The water supply system used is modern and works well.To ensure performance above common commercial standards, the raising of theplants requires that special measures be taken. Therefore, the following additionaltechnical measures should be introduced into nursery operations:• Maintenance of moisture levels at pF-value of about 1.5 as an average of theminimum and maximum limits of 1-2.7 1 , in order to assure good shape anddevelopment of the root system. Leaching of nutrients must be prevented at thesame time. Irregular watering and subsequent drought lead to inverse rootgrowth and curling. The pF-values cannot be measured accuraJely in the field,yet a practical way was recommended by Falconnet using a fixed course thatallows the weight of 4-6 trays of containers to be monitored simultaneously.Previous calibration allows a scale of weight to be determined whose limitsindicate watering requirements. The device is made up of a dynamometer thatholds the set of trays to be monitored. For the total area of the project seedlings(about 190 x 12 m), at least three such devices are required.e Seedlings should be lightly watered various times a day rather than lessfrequent, heavier watering, because of the problem of nutrient leaching due toexcessive watering.e With regard to the nutrient levels, their supplies should be monitored throughconductivity tests, which must fall within the limits of 250-400 mS.eThere has been no initial fertilization ('osmocote' is usually applied in nurseries);therefore, to achieve good progress in plant production, the nursery systemsrequire systematic v~sits by staff to ensure the following:* control of water quality: measurements of pH* control of watering levels and frequency: appraisal of pF-values* control of nutrient levels: conductivity.The value 1.0 indicates an excess of water, therefore high leaching of nutrients; 2.7 is on thethreshold of causing death from drought.