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Greenhouse, System and Crop Quality Control Checks

A regular and careful programme of daily greenhouse checks avoids problems with the greenhouse and NFT system and gives prompt indications of any developing problems. Most experienced and successful growers have evolved unwritten routines which do this, and this is one of the reasons for their success. However it is worth having a written programme of checks, and a written programme is essential for staff training and management purposes. Good staff will notice problems and report problems seen during the course of their daily work, but not all greenhouses or all parts of the greenhouse will be worked in every day. The manager or supervisor must check all parts of every house at least once and preferably twice every day. These notes provide a written check list for these inspections.

Morning checks when starting work
Walk right through the greenhouse(s) looking at the greenhouse, the NFT system and the crop.

1. Check the greenhouse systems: Vents normal? Heaters normal? Any broken air heating ducts? any obvious leaks in heating pipes?

2. Check NFT systems Any dry rows with wilty plants? check for blocked leader tubes Any wet paths? check for leader tubes out of gully ends, check for gullies which have become unstapled or have developed leaks Any water under or around collecting pipes? check for gully tails which have fallen out of the collecting pipes. If there is any doubt about whether water under collecting pipe is water or nutrient solution, then test it's CF, high CF indicates leaked nutrient solution.

3. Check the crop as you go Any change in crop condition, disease or pest incidence?

4. NFT sump check Is the CF and pH and solution temperature on target? Note all three readings on your daily record sheet. Note water meter reading. Calculate how much water has been used in the last 24 hours. If possible check water usage against 24 hour radiation total. Note levels of A & B solution tanks. There should be either a calibrated sight tube or a dipstick for each stock tank. Are the levels equal? Is usage about what you would expect? Is the solution level in the sump normal? If not check that the Jobe valve is not stuck. Is the solution clear and normal in colour? A very cloudy or foaming solution suggests the presence of organic matter, possibly from rotting roots. Do the pumps sound normal? Abnormal or noisy pumps may indicate incipient bearing failures. Are there any drips from the pumps or their motors? This indicates seal failures.

Afternoon check before finishing work
Do the same checks as in the morning.

Daily checks
1. If you have a greenhouse computer with attached PC examine temperature and humidity graphs to ensure that you are obtaining the environment that you want. Note daily solar integration totals for comparison with water use records. The best comparison is by plotting each days solar radiation and water use on a graph. Once the crop is more than 1m tall, there should be a straight line relationship between solar radiation and water use.

2. If you have a greenhouse computer without attached PC Get the total solar radiation from the computers integrator and clear the integrator. If your computer allows you to obtain mean day and night temperatures and humidities, or maxima and minima then extract and note this information.

3. If you have no computer You should have a maximum and minimum thermometer installed in the same aspirated screen as your temperature sensor for heating and ventilation. Read and record the maximum and minimum temperatures and reset the thermometer. It is still worth having a maximum -minimum thermometer in the aspirated screen even if you have a computer, as these regular checks provide an ongoing continuous check that the computer sensors are properly calibrated.

Once weekly detailed crop check

Tomatoes: collect at least 10 closed flowers at about 5 different places in the greenhouse and count the number of flowers that are bee marked. Note the percentage bee marked. With new hives (except when it is too hot and dry) there should 100% marked, and new hives are required before the percentage falls below 60%.

IPM checks: examine the underneath of leaves working from the head of the plant downwards. Look for adult whitefly, caterpillars, thrips or two spotted mites on the upper leaves and the presence of white fly scales on lower leaves and Encarsia scales (black scales) on leaves immediately below those with light green scale. Watch for russet mite (golden to rusty brown coloured stems, leaf stems and first leaflets) starting from the base of the plants. Staff working on the plants should also be trained to watch for and report any pests.

Disease incidence: look for any leaf or stem disease especially botrytis, blight , leaf mould or powdery mildew.

Root health: If there any wilty plants or plants with stunted growth, examine their roots carefully, if there are no plants like this, then check roots at least five different places within the house. Check that there is new white root under the root mat, and that there is no obvious rotting within the root mat. Check the stems of any wilty plants for stem borer holes or frass (sawdust like excreta from stem borers).

Check gully tails for roots growing into collecting pipes, which may cause overflows and leaks. If necessary schedule root trimming in the work programme.

Revised October 1999. İR.A.J.White. October 1999