Glasshouse Tomato Growing

New Zealand Journal of Agriculture, Volume 60, Issue 6, 15 June 1940, Page 458

Glasshouse Tomato Growing

Influence of Management On Prevalence of Disease

F. SYDENHAM,

Assistant Horticulturist, Wellington.

igtll— mi—mi—ini——mi— Uli—-Illi — mt—ini—mi— ?-Illi—!!•$• J It is the aim of all glasshouse I j tomato growers to produce | I abundant and payable crops, j j To produce a plant such as that j I shown in the illustration on the j § left, which matured 121 b. of j i perfect fruit, is not easy, and = I is not achieved by many grow- 1 I ers. To obtain high-producing 1 | plants of good quality in either I j cool or heated houses, very j I careful attention is required to T j be given to details of manage- | j ment. It is with the view of | ! assisting growers who are not = ! meeting with the success de- 1 I sired that this article has been i I written. 1 I * —mi— llli—till-Illi—Illi—Illi——Illi—Illi—Illi—Illi—ll»J«

TXURING the past season many enquiries and specimens of diseased plants were received from growers of glasshouse tomatoes. The cause of the "trouble could invariably be traced to some feature of the management which produced conditions entirely unsuited to the proper development of the tomato plant. The troubles most commonly encountered were leaf-mould caused by the fungus Cladosporium fulvum, and the failure of the blossoms to set, largely due to insufficient soil moisture and unsatisfactory ventilation. The conditions found to be having an important bearing on both the incidence of mould and the non-setting of fruit were watering, ventilation, and manuring.

Watering. Watering was possibly one of the greatest causes of the unsatisfactory condition in the plants. It was common for the surface of the ground to be wet, but the lower strata to be too dry for proper root development. Such a condition occurs in the subsoil when small quantities of water, sufficient only to moisten the surface soil, are given. After this light watering the plant soon shows signs of requiring more, and consequently it is repeated daily or at two- to three-day intervals. This practice increases the humidity of the atmosphere within the house to a degree that is favourable to the development and spread of Cladosporium: Watering Before Planting In general, more attention should be paid to the watering of the house before the plants are set -out. The soil and the sub-soil should be thoroughly wetted, which entails. systematic flooding. Two to three weeks after the flooding, when sufficiently dry, the surface soil should be cultivated in preparation for planting.

Planting To Assist Watering So that the entire surface of . the ground need not be wetted during subsequent watering, it is advisable to set the plants in furrows, as is shown diagramatically. in Fig. 2. It is a good practice to set them in double rows as shown, allowing 18 inches between each row and 36 inches ■ between the double rows. The wider space permits of the handling of the plants with relative ease. During the early stages of growth, water may be concentrated in the furrow. As the plants develop, they may be earthed up as is shown in Fig. 3, and two furrows are then available for watering. - When Is Water Required? If the soil has been thoroughly moistened before planting there should be no need to apply additional water, except possibly a little with each plant at planting time, until the first bunches of fruit have set. This may be two months after planting. The time when this watering should begin is indicated by the condition of the plants. A slight wilting during the hot hours of the day does not necessarily indicate that water is required, but when it is in evidence early in the morning, then additional water should be given. In the early stages of development of the plants the 18 inch wide furrow between the rows should be flooded. The whole area will not require additional moisture until the crop is well advanced. When the plants are small water may not be required for 10. to 20 days, and as they grow it may be necessary to apply water at seven, to 14-day intervals, After watering, the surface layers should be loosened to produce a dry mulch. This serves the double purpose of retaining the moisture in the soil and reducing the humidity of the atmosphere.

It is only when the plants are carrying a large area of leafage and the fruits are developing rapidly that watering should be 'done over the entire space between the ridges. If sufficient water is applied at each watering there should be no further need of additional supplies for at least a week. Time to Apply On no account should water be applied during the afternoon; it should be given early in the morning, and, if possible, a bright day should be selected. If the air becomes saturated with moisture, as occurs with afternoon watering, conditions very favourable for the development and spread of tomato leaf-mould are obtained. Effect on Fruit-set A common sign of both insufficient and over-watering is the non-setting of the fruit. There are a number of causes of the failure of fruit' to set, but this is possibly the most' common. In a number of the houses visited it was the absence of water in the lower levels that contributed to the trouble. Ventilation. The house should be sufficiently ventilated during the day to maintain a reasonably dry - atmosphere. During the cool weather it should be closed at night to retain the heat and opened again early in the following morning. On bright sunny and calm days as much ventilation as possible should be given, but when winds occur only such ventilators as do not permit a cold draught to force its way into the house should be opened. , It is necessary to watch the weather closely and to adjust the ventilators so that the temperature in the house may be maintained within reasonable limits, and to ensure that the humidity of the atmosphere may be kept reasonably low. As the nights become warmer, a little ventilation may be allowed at night, but the temperature should not be allowed to fall below 45 degrees Fahrenheit, and during the daytime it should not exceed 90 degrees Fahrenheit. It is inadvisable to use the side ventilators until the plants are well developed and the fruit has set. Top ventilation is quite sufficient until the plants have made considerable growth, and it is only when the house is well

filled with foliage that additional ventilation is required to remove the large amount of moisture transpired by the plants. Side ventilation should be avoided during the blossoming period, as it is likely to cause a dropping off of the flowers without the fruit setting. ( Manuring. The amount of plant food in the soil and its availability have much to do with the health and . productivity of the crop. Excessive quantities of artificial fertilisers should be avoided. Sufficient, however, should be added to the soil to enable the plants to make healthy growth. An over-supply of nitrogen produces soft, succulent plants which are very liable to disease and which carry only a few blossoms. Insufficient nitrogen, on the other hand, will produce plants of poor colour and plants which are also liable to disease. The optimum amount is available when the soil is adequately supplied with humus; a cover-crop grown in the house after the tomatoes are harvested and dug in when it has made maximum development will assist in maintaining the humus content of the soil. This cover-crop should be allowed to develop until it becomes fibrous, ■. for at earlier stages than this the quantity of humus derived from it is small. In place of the cover-crop, wellrotted turf, leaf-mould, compost, or horse manure may be used. Cow manure is not advised, as it is inclined to consolidate the soil, As an alternative to these materials, rotted straw may be found quite useful. If stacked and exposed to the weather for 6 to

12 months, the fibres break down and a material which breaks readily when twisted is produced. This is very suitable for adding to the soil because of its mechanical action in opening up a soil and its ability to form humus. Manuring Before Planting The supply of phosphate should be maintained, and for general purposes 4oz. of bone-meal and 2oz. of superphosphate per square yard should be applied before planting. Potash has a marked effect on the health and vigour of the crop. Plants which are adequately supplied with this fertiliser are much more able, to resist infection by the organisms causing disease. With this crop, where disease is an important factor in reducing productivity, an application of sulphate of potash at the rate of two ounces per square yard is recommended. ’ Where the supply of available potash is plentiful, the loss of plants through spotted wilt is said to be lessened. Both the, superphosphate and . the potash should be applied two to three weeks before the planting time. Manuring After Planting When harvesting begins a further application should be given. This may be applied as a liquid dressing. Half an ounce each of nitrate of soda and sulphate of potash and 1 ounce of superphosphate dissolved in a gallon of water will be sufficient for four plants, and should be given the day after watering. ‘