TOMATO RESEARCH IN ENGLAND

New Zealand Journal of Agriculture, Volume 74, Issue 2, 15 February 1947, Page 145

TOMATO RESEARCH IN ENGLAND

By

SIR THEODORE RIGG,

Director of the C anil iron Institute, Nelson.

THE major centre of tomato research in Great Britain is the Cheshunt Station, in the Lea Valley some 15 miles north-east of London. Other important work on tomatoes is carried out at the John Innes Horticultural Station at Merton, Surrey, and at the Long Ashton Fruit Station, near Bristol.

AT the Cheshunt Station investigations on tomatoes, cucumbers, and flower culture have proceeded for more than 25 years under the able direction of Dr. Bewley. The work has included tests for soil disinfection with both steam and chemicals, the manuring of glasshouse crops, the value of organic and synthetic nitrogenous manures, the breeding of improved varieties of tomatoes, and the study and control of fungous, virus, and insect diseases.

Steam Sterilisation

After many years’ experience of steam and chemical soil disinfectants, Dr. Bewley considers- that steam treatment is the more effective. Steam treatment of glasshouses every other year is now recommended, in contrast to the previous procedure of steaming once in 3 or 4 years. Under Nelson conditions the investigations of the Cawthron Institute have shown the importance of annual steam treatment in maintaining tomato production.

This difference in procedure in the two countries is possibly ' connected with the more effective but more expensive method of steam sterilisation adopted at Cheshunt. In England the top spit of soil is removed, the subsoil forked up, and the steam grid then laid in the trench and covered with 12in. of soil from the next spit. Steam is- passed through the grid at a pressure of not less than 801 b. a square inch for a minimum of 10 minutes. The longer time of steaming under English conditions and the penetration of the steam upward probably ensure more effective sterilisation than under Nelson conditions of . soil steaming.

Manurial Treatment

Early experiments at the Cheshunt Station showed the great importance of all three plant nutrients, nitrogen, phosphate, and potash. Potash appeared to have a special value in reducing blotchy ripening of . the fruit and in safeguarding the plants against certain virus diseases. ,

Present manuring practice at Cheshunt is on a very liberal scale, but a crop of lettuces follows tomatoes and manurial treatment is designed to cover the needs of both crops. About

14 tons of horse manure an acre is used in the first digging of the house, together with Boz. of superphosphate or bone and 4oz. of sulphate of potash to the square yard. After planting of the tomatoes, a topdressing of 2oz. of sulphate of potash to the square yard is used early in the season. Further topdressings of a mixed fertiliser containing superphosphate, sulphate of potash, and dried blood are given during the fruiting of the plants until a total of Boz. of the mixed fertiliser to the square yard has been applied.

Under this manurial programme the plants make heavy growth and as many as 13 trusses of fruit are formed. Top growth is heavy. The plants have less fruit to the truss than in Nelson, but the yield for each plant, 81b., is about the same as the average in tomato houses in Nelson. Though the results obtained in England with this treatment are good, there is some evidence that the very liberal use of potassic fertilisers on the soils of the station is bringing about a magnesium deficiency, symptoms of which were noticed at both the Cheshunt and the John Innes Horticultural Stations. In the tests of organic and synthetic nitrogenous manures carried out at Cheshunt Station little difference in the growth and yield of tomatoes was noticed for the. first .8 years of the experiment, but more recently \ the plots with organic nitrogen have shown to great advantage over those treated with synthetic nitrogen. As superphosphate and sulphate of potash were, used on both series of plots, it seems clear that the use of dried blood on one set of plots has resulted in better soil conditions than has the continued use of synthetic nitrogen in the form of ammonium sulphate.

The reasons for the superiority of the dried blood are not clear, but it is suggested that the bacterial flora is better with dried blood than with ammonium sulphate. Another possible explanation of the poorer growth with synthetic nitrogen is a higher deficiency of magnesium brought about by the liberal use of potassic manures without any replenishment of magnesium.

Modern glasshouses in the Lea Valley are similar in design to Nelson houses, but the English houses are always; heated. A temperature of 65 degrees F. is maintained at night and during cold periods, which are frequent in the early English summer. Uniform temperature is considered most important for the satisfactory growth of tomatoes, and both too low temperatures and intense sunlight should be avoided.

Tomatoes in the Lea Valley are planted out in the glasshouses in the third week of March. The plants are stopped in August, but picking of fruit is continued in September and October. As soon as the fruit has been harvested the houses are dug and planted to lettuce, which occupy the houses during the winter. As a rule 16,000 plants are grown to each acre of glasshouse. The plants are spaced 14in. apart in the rows, which are separated by 18 and 27in., alternately, the wider spaces being used for picking the crop.

A noticeable feature of the English houses is the wider central aisle running the full length of the house. The final effect of the English spacing is a somewhat similar number of plants to that grown in Nelson houses.

Developing Varieties

The Cheshunt Station, has always taken a keen interest in testing varieties of tomatoes and in breeding improved strains or varieties. Potentate, which is now • grown' in Nelson, is one of the tomatoes produced at Cheshunt. At present Dr. Bewley is working on a mould-resistant variety which is called E.S. Potentate and Child’s Special are perhaps the best of the glasshouse varieties grown at the station, and Radio and Queen show distinct promise for outside culture. Blotchy Ripening Lack of uniformity in the ripening of tomatoes has always been a difficulty in the English climate. The amount of blotchy ripening may vary in different seasons from 10 to 30 per cent. It is always worse, possibly because of shading, on the bottom two or three trusses than on those higher up the plants. . .

The condition . known as bion v ripening in England includes at least two different types of blotchiness on the skin of the tomato. The most common form is unequal colouring, not accompanied by necrosis in the tissue of the tomato; this form has been controlled to a considerable extent by the use of potassic manures. Another type of blotchy ripening is that associated with necrosis of the fibro-vascular system in the flesh of the tomato, and is similar to “cloud” in Nelson. As far as can be ascertained this type of blotchy ripening is not

controlled by potassic manures. Sometimes necrosis in the tissue of the tomato occurs without the appearance of blotchiness of the fruit.

Dr. Bewley considers that the type of blotchy ripening known as cloud at Nelson is frequently associated with lack of fibrous roots and an undue proportion of deep roots. Though the Cheshunt Station has not made detailed investigations of cloud, he agreed with the results of Cawthron Institute investigations which showed that soil moisture was a factor of great importance in the incidence of the disorder.

Greenback and Hard Core

According to workers in England, hard core is not synonymous with greenback. Tomatoes showing greenback may be affected with hard core, but the latter condition may occur apart from greenback. Little is known in England about the factors which produce hard core, but it is considered to be a nutritional disorder. In England emphasis is placed not only on a correct balance of manures but also on uniform conditions of culture. Intense sunlight, drought, and heavy winds all militate, against good quality of tomato fruits.

In the opinion of plant breeders,

greenback in tomatoes could be eliminated in five years by crossing desirable varieties with Stoner’s Exhibition, which does not show

greenback characteristics.

An interesting feature of experiments at Cheshunt is the testing of calico and transparent plastic materials with a view to the culture of outside tomatoes under semi-glasshouse conditions. It is claimed that in the English climate there would be great advantages, if costs were not too great, in the production in south-east England of early fruit of higher quality than that obtained from outside.

John Innes Horticultural Station

The John Innes Horticultural Station is very widely known for its valuable work on genetics and plant breeding. Of no less importance to the nurserymen and amateur gardeners of England has been the standardisation of potting soil, investigations of compost, and the testing of many well-estab-lished practices in the conduct of nursery work. Though the work of the station covers a wide range of plants, including pip and small fruits, sweet corn, and flowers, considerable attention has been devoted to tomatoes, particularly the breeding of improved bush and dwarf plants and the production of tomatoes resistant to leaf mould.

Standardisation of Potting Soil

A mixture of two parts of good —preferably obtained from a

pasture field—one part of friable peat, and one part of coarse sand is recommended for all potting and nursery work. The loam should be prepared 6 months in advance by cutting turves 4in. thick and piling them 4ft. high. The peat should not contain a high percentage of loam, but should be easily broken into pieces up to fin. in size. The sand should be a clean river sand of the coarser grades up to jin. in diameter.

The loam must be sterilised by steam treatment in the usual way, and then the requisite fertilisers should be mixed with the sand. The soil, sand, and peat should then be mixed, resulting in a standard potting soil of wide use in all types of nursery work. The amount of fertilisers added to the sand depends on the purpose for which the soil is to be used. For the sowing of seeds smaller quantities of fertilisers are used than for potting plants.

Nursery Technique

A number of experiments in nursery and garden practice has been carried out. The more important findings from these experiments are: —

The pricking out of young seedlings at the earliest possible time is desirable, and results in better growth and earlier fruiting than with seedlings pricked out late.

Better growth and earlier fruiting are obtained from tomato plants by potting them in 3|in. and sin. pots than with smaller sizes.

Overhead watering of seed boxes and potted plants is superior to dipping the boxes and pots.

If weeds are removed by hand, hoeing of garden crops gives no particular advantage. Weeds in garden crops, particularly carrots and onions, greatly reduce yield. As the hoe is the best tool for removing weeds, hoeing must continue to be an important garden operation.

The composting of tomato plants affected with virus does not destroy the virus. Though infection of tomato plants under outside conditions of culture is unlikely, such compost should not be used for glasshouse work or for potting soil.

Compost suitable for nursery and garden work can be made from wheat straw, using appropriate amounts of ammonium sulphate and water during the process of rotting.

Outdoor Varieties

Though the climate in south-east England is not very favourable for outside tomato culture, considerable success has been achieved at the John Innes Station by choosing varieties suitable for the soil and by timing

seed sowing, potting, and transplanting to avoid any check to growth of the plants. Tomatoes are seldom planted out before late May or early June, resulting in a very short season for the plants. At the John Innes Station, Stoner’s Exhibition, Harbinger, Market King, and Potentate have all given good results, and yields of 4 to 4.61 b. of ripe tomatoes a plant have been obtained.

Other work handled by the station includes the breeding of mould-re-sistant varieties of tomatoes and the classification and improvement of both dwarf and bush tomatoes.

Effect of Deficiencies

Fruit studies comprise the major activities of Long Ashton Fruit Station, an important research centre, but tomatoes have been included in nutritional studies of a large number of crops. By sand culture experiments carried out in pots, the effect on the growth of tomatoes of omitting different plant foods is being closely studied.

Clear-cut deficiencies of nitrogen, phosphate, potash, and magnesium have been obtained in these experiments. Potash deficiency is usually the most serious in its effect and quickly results in the death of the plants. Magnesium deficiency causes a pronounced yellowing of the leaves, resulting finally in the death of tomato plants. In the early stages of magnesium deficiency fair growth of the plant is obtained and yellowing is not marked until fruiting begins. Phosphate deficiency results in a purple colour of the leaves and poor growth of the plants. Nitrogen starvation results in a yellowing and in serious cases complete failure of the tomato plants.

In England repeated sprays of 2 per cent, magnesium sulphate are recommended for tomatoes and other garden crops affected with magnesium deficiency.

Growth-promoting Chemicals

In recent years investigators in both the United States of America and Great Britain have tested several chemicals which have peculiar growthpromoting qualities.

Alpha naphthalene acetic acid has been shown to be valuable in preventing pre-harvest drop of certain varieties of apples. At Long Ashton B-naphthoxy acetic acid and dichlorophenoxy acetic acid have been tested to ascertain their value in promoting set of tomatoes. B-naphthoxy acetic acid used at a concentration of 30 parts a million in water has given very good results, producing effective development of tomatoes even when the stamens of the flowers have been removed. Phenoxy-acetic acid, used in smaller concentrations, has likewise resulted in fruit set, but malformation of the tomatoes frequently occurred.