W2B-023 Biology matters-1.txt
Producing quality young vegetable plants

VEGETABLE PLANTS grown in glasshouses or polytunnels have increased in popularity since their introduction here in the early 1980s.

The transplants raised in module trays offer an alternative to bare-root and block-raised plants for field vegetable production.

The division of the trays into cells means each plant is a separate unit requiring its own water and feed supply with no buffering reservoir available from its neighbour.

BENEFITS: The main purpose of raising vegetable plants in modules is to produce crops which are uniform and to achieve continuity of market outlets.

In addition, the speed and ease of planting is enhanced by using a module transplanter.

Module plants will also have a small reservoir of water and nutrients on which they survive during the first few days in the field before new roots establish in the soil.

The cost of seed has risen. For example, hybrid cauliflower seed has doubled in price over the last five years.

The use of modules makes better use of high cost seed as better germination is achieved under protection than if sowing the same seed in an outdoor seedbed.

The module trays are usually made of rigid polythene or plastic. After being filled with a module compost they can be seeded using a plate or vacuum seeder.

VEGETABLE CROPS: Modules are used for a range of crops, but especially for brassicas (cabbage, cauliflower, Brussels sprouts and calabrese) and for early leeks.

The size of the module cell varies depending on the plant to be grown and time of sowing. Autumn-sown crops are sown in larger modules as they will not be planted out until the spring, whereas a spring-sown plant will only take about six weeks to produce a plant ready for transplanting.

The larger module will help to extend the season by producing an earlier crop than those sown in a smaller module - for example, a 308 tray. The most common tray used for main crop production contains either 260 or 308 cells.

MANAGEMENT: In the glasshouse of polytunnel, the module trays are raised off the ground to allow air movement under them. This air helps to prune the young roots, keeping them within the cell.

The growth of the plant can then be controlled by the liquid feeding. In a late season when ground conditions are too wet for planting, the young plants can be 'held' by regulating the feeding. Then, prior to planting, they are fed with a higher nitrogen feed to stimulate growth again.

PLANTING: The date of planting has a larger effect on the crop maturity date than the date of seed sowing. This is important when a grower requires continuity of production from crops such as cauliflower and calabrese. Modules are ideal for ease of planting of small areas at regular intervals.

PROPAGATORS: There are specialist plant propagators who produce plants to order as required by their customers. However, it is also possible to grow modules on-farm provided the management of the young plants in modules is very good.

DEVELOPMENTS: The design of trays is changing to allow more plants per unit area of glasshouse and also to be more durable.

In the field, starter solutions applied at planting are now being used to enhance the development of new roots immediately after planting.
